An-Najah National University Faculty of Graduate Studies GIS-Based Hydrological Modeling of Semiarid Catchments (The Case of Faria Catchment) By Sameer ‘Mohammad Khairi’ Shhadi Abedel-Kareem Supervisors Dr. Hafez Q. Shaheen Dr. Anan F. Jayyousi Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in Water and Environmental Engineering, Faculty of Graduate Studies, at An-Najah National University, Nablus, Palestine 2005 III بسم هللا الرحمن الرحيم َأنَْزَل ِمَن السََّماِء َماًء فََسالَتْ َأْوِدَيةٌ بِقََدرَِها فَاْحتََمَل السَّْيُل )16(ألرعد .........َزَبًدا َرابًِيا صدق اهللا العظيم IV … Dedicated to My parents, wife and my daughter (Muna) V Acknowledgments First of all, praise is to Allah for making this thesis possible. I would like to express my sincere gratitude to Dr. Hafez Shaheen and Dr. Anan Jayyousi for their supervision, guidance and constructive advice. Special thanks go also to the defense committee members. Thanks also go to those who helped in providing the data used in this study. Water and Environmental Studies Institute or giving me the chance to work on GLOWA project, Palestinian Water Authority (PWA) for producing of water data used in this study. My parents, brothers and sisters, thank you for being a great source of support and encouragement. All my friends and fellow graduate students, thank you. Special thanks to my friend Eng. Rami Qashou’ who’s support will never be forgotten. Finally, thanks to my dear wife Heba for her love, moral support and patience. VI Table of Contents ACKNOWLEDGMENTS ........................................................................................................ V TABLE OF CONTENTS ........................................................................................................ VI LIST OF ABBREVIATIONS .......................................................................................... VIII LIST OF TABLES ....................................................................................................................... IX LIST OF FIGURES ...................................................................................................................... X ABSTRACT .................................................................................................................................... XII CHAPTER ONE INTRODUCTION .................................................................................... 1 1.1 BACKGROUND ............................................................................................................................ 2 1.2 OBJECTIVES ................................................................................................................................. 3 1.3 RESEARCH NEEDS AND MOTIVATIONS ....................................................................... 4 1.4 METHODOLOGY ........................................................................................................................ 7 1.5 DATA COLLECTION ................................................................................................................. 9 CHAPTER TWO LITERATURE REVIEW ............................................................... 11 2.1 HYDROLOGY OF SEMIARID REGIONS ........................................................................ 12 2.1.1 Climate and Rainfall ................................................................................................ 13 2.1.2 Runoff Generation and Channel Flow .......................................................... 16 2.1.3 Storages ............................................................................................................................ 17 2.2 RAINFALL-RUNOFF MODELING .................................................................................... 18 2.2.1 Historical Overview ................................................................................................. 19 2.2.2 Classification of Models and Basic Definitions ..................................... 21 2.3 USE OF GIS IN HYDROLOGY .......................................................................................... 23 2.4 PREVIOUS WORK IN THE STUDY AREA .................................................................... 26 CHAPTER THREE DESCRIPTION OF THE STUDY AREA ...................... 28 3.1 LOCATION AND TOPOGRAPHY ....................................................................................... 29 3.2 CLIMATE .................................................................................................................................... 33 3.2.1 Wind ................................................................................................................................... 33 3.2.2 Temperature ................................................................................................................... 34 3.2.3 Relative Humidity ..................................................................................................... 36 3.2.4 Rainfall ............................................................................................................................. 36 3.2.5 Evaporation .................................................................................................................... 38 3.2.6 Aridity of the Catchment ....................................................................................... 40 3.3 WATER RESOURCES ............................................................................................................ 41 3.3.1 Groundwater Wells ................................................................................................... 41 3.3.2 Springs .............................................................................................................................. 42 3.3.3 Analysis of Springs Discharge .......................................................................... 43 3.4 SURFACE WATER .................................................................................................................. 45 3.4.1 Flow Measurements ................................................................................................. 45 3.4.2 Quality Considerations ........................................................................................... 47 VII 3.5 SOIL .............................................................................................................................................. 49 3.6 GEOLOGY ................................................................................................................................... 51 3.7 LAND USE ................................................................................................................................. 53 CHAPTER FOUR RAINFALL ANALYSIS ................................................................ 58 4.1 RAINFALL STATIONS ........................................................................................................... 59 4.2 CATCHMENT RAINFALL .................................................................................................... 60 4.2.1 Density of Rain Gauges ......................................................................................... 60 4.2.2 Consistency of Rainfall Data .............................................................................. 62 4.2.3 Monthly Rainfall ........................................................................................................ 63 4.2.4 Annual Rainfall ........................................................................................................... 66 4.2.5 Trend Analysis ............................................................................................................. 68 4.3 EXTREME VALUE DISTRIBUTION ................................................................................. 71 4.3.1 Gumbel Distribution ................................................................................................ 72 4.4 AREAL RAINFALL ................................................................................................................. 75 4.5 CORRELATION ANALYSIS BETWEEN STATIONS ................................................... 77 CHAPTER FIVE RUNOFF MODELING ..................................................................... 79 5.1 INTRODUCTION ....................................................................................................................... 80 5.2 GIUH MODEL ......................................................................................................................... 81 5.3 TRAVEL TIME ESTIMATION OF THE KW-GIUH MODEL ............................... 83 5.4 STRUCTURE OF THE KW-GIUH MODEL ................................................................. 87 5.5 KW-GIUH MODEL INPUT PARAMETERS ............................................................... 91 5.5.1 Hydraulic parameters .............................................................................................. 91 5.5.2 Geomorphic parameters ......................................................................................... 91 5.5.3 Parameter Estimation Using GIS ..................................................................... 92 5.6 KW-GIUH UNIT HYDROGRAPH DERIVATION .................................................... 97 5.7 SENSITIVITY ANALYSIS ..................................................................................................... 99 5.8 MODEL APPLICATION FOR HYDROGRAPH SIMULATION ............................. 102 5.8.1 Event 1, 14-2-2004................................................................................................. 103 5.8.2 Event 2, 5-2-2005 ................................................................................................... 106 5.9 ANALYSIS AND DISCUSSION ........................................................................................ 108 CHAPTER SIX CONCLUSIONS AND RECOMMENDATIONS .............. 111 6.1 CONCLUSIONS ...................................................................................................................... 112 6.2 RECOMMENDATIONS ........................................................................................................ 114 REFERENCES ............................................................................................................................. 117 APPENDIX A (TABLES) ..................................................................................................... 125 APPENDIX B (FIGURES) .................................................................................................. 162 APPENDIX C (KW-GIUH OUTPUTS) .................................................................... 171 APPENDIX D (PICTURES) .............................................................................................. 179 ب ......................................................................................................................................................... الملخص VIII List of Abbreviations Symbol The meaning KW-GIUH Kinematic Wave based Geomorphological Instantaneous Unit Hydrograph GIS Geographical Information System DEM Digital Elevation Model EAB Eastern Aquifer Basin PHG Palestinian Hydrology Group PWA Palestinian Water Authority IDF Intensity Duration Frequency Curves MOT Meteorological Office of Transport WESI Water and Environmental Studies Institute N Optimal number of stations Ep Allowable percentage of error Cv Coefficient of variation avP Mean of rainfall 1−nσ Standard deviation P(x) Probability of exceedance oixT Time for the flow to reach equilibrium ioq ith-order overland flow discharge per unit width Lq Lateral flow rate iosh ith-order water depth at equilibrium icsQ ith-order channel discharge at equilibrium rkxT Travel time for the channel storage component ckxT Travel time for the channel translation component iOAP Ratio of the ith-order overland area to the catchment area A Total area of the catchment iN ith-order stream number icL ith-order stream length on Overland flow roughness cn Channel flow roughness Ai ith-order sub catchment contributing area S io ith-order overland slope S ic ith-order channel slope ji xxP Stream network transitional probability ΩB Channel width at catchment outlet Ω Stream network order IX List of Tables Table 1: Abstraction from Wells in the Faria Catchment ........................... 42 Table 2: Spring Groups and Spring Information within Faria catchment .. 43 Table 3: Surface Water Quality Parameters for Badan and Faria Streams . 49 Table 4: Major Soil Types and Characteristics in Faria Catchment ........... 50 Table 5: Total Land use Cover of the Faria Catchment .............................. 56 Table 6: Available Rainfall Stations within the Faria Catchment .............. 60 Table 7: Monthly Rainfall Totals of Nablus Station (mm) ......................... 65 Table 8: Statistical Measurements of the Annual Rainfall of the Six Stations of Faria Catchment .......................................................... 67 Table 9: Trend Equations for the 5-years Moving Average of the Six Stations .......................................................................................... 69 Table 10: t and 1 , 2 2 n t α − − with 90% and 95% Confidence Intervals .............. 71 Table 11: Parameters of Gumbel Distribution for the Six Stations of the Faria Catchment .......................................................................... 74 Table 12: Areal Rainfall Using the Thiessen Polygon Method .................. 76 Table 13: Coordinates, Elevations, Rainfall Averages and Estimated Averages for the Six Stations ...................................................... 79 Table 14: ji xxP For the Three Sub-catchments ............................................ 95 Table 15: KW-GIUH Input Parameters for Al-Badan Sub-catchment ....... 96 Table 16: KW-GIUH Input Parameters for Al-Faria Sub-catchment ......... 96 Table 17: KW-GIUH Input Parameters for Al-Malaqi Sub-catchment ...... 98 X List of Figures Figure 1: A flow Chart Depicting the General Methodology Followed in this Study ....................................................................................... 9 Figure 2: Arid Regions around the World (UNESCO, 1984) ..................... 12 Figure 3: Hydrologic Cycle with Global Annual Average Water Balance (Chow et al., 1988) ...................................................................... 15 Figure 4: Classification of Hydrological Models (Lange, 1999) ................ 23 Figure 5: Location of the Faria Catchment within the West Bank ............. 30 Figure 6: Springs and Wells within the Faria Catchment ........................... 31 Figure 7: Topographic Map of the Faria Catchment .................................. 32 Figure 8: Mean Monthly Temperatures in Nablus and Al-Jiftlik .............. 35 Figure 9: Spatial Distribution of the Mean Annual Temperature in the Faria Catchment .................................................................................... 35 Figure 10: Rainfall Stations and Rainfall Distribution within the Faria Catchment .................................................................................. 37 Figure 11: Monthly Rainfall and Potential Evapotranspiration Rates (ETo) in Nablus and Al-Jiftlik ........................................................... 39 Figure 12: Potential Annual Evapotranspiration Rates in the Faria Catchment ................................................................................. 40 Figure 13: Average, Maximum and Minimum Monthly Discharge of Total Springs within Al-Badan Sub-catchment.................................. 44 Figure 14: Average, Maximum and Minimum Monthly Discharge of Total Springs within Al-Faria Sub-catchment .................................... 45 Figure 15: Soil Types of the Faria Catchment ............................................ 51 Figure 16: Geology Map of the Faria Catchment ....................................... 52 Figure 17: Part of the airphotos of Faria Catchment ................................... 53 Figure 18: The New Land use Map of the Faria Catchment ....................... 57 Figure 19: Double Mass Curve for the Stations of Faria Catchment .......... 63 Figure 20: Mean Monthly Rainfall of the Six Stations of the Faria Catchment ................................................................................. 64 Figure 21: Monthly Average Rainfall of Nablus Station Plotted As Averages of Five Years Intervals.............................................. 66 Figure 22: Yearly Rainfall of Nablus Station ............................................. 67 Figure 23: The 5-year Moving Average of Nablus, Beit Dajan and Al-Faria Stations ...................................................................................... 69 Figure 24: The 5-year Moving Average of Tubas, Taluza and Tammun Stations ...................................................................................... 69 Figure 25: Gumbel Plots of Annual Rainfall for Nablus Station ................ 74 Figure 26: Gumbel Plots of the Standardized Variable of the Six Stations of Faria Catchment ........................................................................ 75 Figure 27: Thiessen Polygon Map for the Faria Catchment ....................... 77 XI Figure 28: Runoff Structure for a second-Order Catchment (Lee and Chang, 2005) ......................................................................................... 84 Figure 29: Surface Flow Paths of A third-Order Catchment (Lee and Chang, 2005) ............................................................................. 90 Figure 30: Digital Elevations Model (DEM) for the Faria Catchment ....... 93 Figure 31: The Three Sub-catchments of the Faria Catchment .................. 94 Figure 32: The Stream Order Networks for the Three Sub-catchments of the Faria Catchment .................................................................. 95 Figure 33: 1mm-GIUH for Al-Faria and Al-Badan Sub-catchments ......... 99 Figure 34: 1mm-GIUH for Al-Malaqi Sub-catchment ............................... 99 Figure 35: Variation of GIUH with Excess Rainfall ................................... 99 Figure 36: Sensitivity Analysis of Channel Width on GIUH ................... 100 Figure 37: Sensitivity Analysis of Overland Roughness Coefficient on GIUH ....................................................................................... 101 Figure 38: Sensitivity Analysis of Channel Roughness Coefficient on GIUH ....................................................................................... 102 Figure 39: Al-Badan Sub-catchment and its Drainage Network .............. 103 Figure 40: Rainfall Depth and Infiltration Capacity Curve of 14/2/2004 Event ........................................................................................ 105 Figure 41: Recorded and Estimated Direct Runoff Hydrograph for Al- Badan Sub-catchment, Event of 14/2/2004 ............................. 106 Figure 42: Rainfall Depth and the Phi-Index of Event of 5/2/2005 .......... 107 Figure 43: Recorded and Estimated Direct Runoff Hydrograph for Al- Badan Sub-catchment, Event of 5/2/2005 ............................... 108 XII GIS-Based Hydrological Modeling of Semiarid Catchments (The Case of Faria Catchment) By Sameer ‘Mohammad Khairi’ Shhadi Abedel-Kareem Supervisors Dr. Hafez Q. Shaheen Dr. Anan F. Jayyousi Abstract Extreme events, such as severe storms, floods, and droughts are the main features characterizing the hydrological system of a region. In the West Bank, which is characterized as semiarid; little work has been carried out about hydrological modeling. This thesis is an attempt to model the rainfall-runoff process in Faria catchment, which is considered as one of the most important catchments of the West Bank. Faria catchment dominating the north eastern slopes of the West Bank is a catchment of about 334 km2 and has the semiarid characteristics of the region. The catchment is gauged by six rainfall stations and two runoff flumes. Statistical analysis including annual average, standard deviation, maximum and minimum rainfall was carried out for the rainfall stations. The internal consistency of rainfall measurements of the six stations was examined by using the double mass curve technique. The results show that all station measurements are internally consistent. Gumbel distribution fits well the annual rainfall and can be used for future estimations. It provides means to understand and evaluate the distribution characteristics of the rainfall in the Faria catchment. Trend analysis of the rainfall has shows an increasing trend for the stations with high elevations and a decreasing trend for low elevated ones. The multiple regression analysis applied to the six rainfall stations proved to be strongly correlated. XIII GIS-based KW-GIUH hydrological model was used to simulate the rainfall-runoff process in the Faria catchment. GIUH unit hydrographs were derived for the three sub-catchments of Faria namely Al-Badan, Al- Faria and Al-Malaqi. The KW-GIUH model is tested by comparing the simulated and observed hydrographs of Al-Badan sub-catchment for two rainstorms with good results. Sensitivity of the KW-GIUH model parameters was also investigated. The simulated runoff hydrographs proved that the GIS-based KW-GIUH model is applicable to semiarid regions and can be used to estimate the unit hydrographs in the West Bank catchments. 1 CHAPTER ONE INTRODUCTION 2 1.1 Background Water is the chief ingredient of life and all ancient civilizations flourished only near the water sources and then probably collapsed when the water supply failed. Water is a finite resource, essential for agriculture, industry and human existence. Without water of adequate quantity and quality, sustainable development is impossible. Water resources management is essential to ensure the availability of water, when and where it is needed, and to safeguard its quality. Hydrologists and water engineers are always concerned with discharge rates resulting from rainfall. Not only measuring rainfall and the resulting runoff are of interest, but also the process of transforming the rainfall hyetograph into runoff hydrograph. Peak flow rate and time to peak are the two important hydrograph characteristics that need to be estimated for any catchment. Unfortunately, the classic problem of predicting these parameters is usually difficult to resolve because many rivers and streams are ungauged, especially those in developing regions or isolated areas. Even in cases where catchments are gauged, the period of record is often too short to allow accurate estimates of the different hydraulic parameters. Flood frequency analysis enables the user to predict flow rates with certain return periods. Historical flow data is necessary to conduct such analysis. Hydrological models that incorporate catchment characteristics to predict flow rates at a given location in the catchment is another tool to be utilized in cases where historical flow records are not available. Hydrological simulation models can take the form of theoretical linkage between the geomorphology and hydrology. The geomorphological instantaneous unit hydrograph (GIUH) is one approach of this kind of 3 model. The GIUH focuses on finding the catchment response given its geomorphological features. The GIUH model is applied in this study to Faria catchment in the northern West Bank. The model uses catchment characteristics to predict flow rates. West Bank is a semiarid region. In arid and semiarid regions storm water drainage and hydrological modeling is important as in humid regions because it is not only a drainage problem but also a water resources management and planning problem. Hydrological modeling in the West Bank has not been given enough care and no intensive studies have been done. In characterizing the catchment, GIS has been applied. Using GIS in hydrology has become an important issue since the beginning of 1980 and up to the present. It enables the user to handle and analyze the hydrological data more efficiently. This thesis concentrates on modeling the rainfall-runoff process in the upper part of the Faria catchment in the northern West Bank. GIS-based KW-GIUH hydrological model was applied as it is available and can model ungauged catchments. The KW-GIUH model can be applied to any excess rainfall through convolution to produce the direct runoff hydrograph. 1.2 Objectives Modeling the runoff in the Faria catchment will provide basic information for the managers to understand runoff generation within the catchment and thus support the decision-making process about future development of the water resources in the area. This will enhance the development of the 4 agricultural sector. It will also support the studies of the Jordan River Basin as Wadi Faria catchment is a major contribution to the Jordan River. The main objective of this research is to model the rainfall runoff process of the Faria catchment and to derive the unit hydrograph for the catchment. The KW-GIUH model that was developed for ungauged catchments is to be used in this research. The geomorphological and topographic characteristics were provided using the GIS system. The other objectives of this study are: 1. Analysis of rainfall data of the Faria catchment. 2. Investigate the rainfall runoff process in semiarid regions. 1.3 Research Needs and Motivations Faria catchment is predominantly arid and semiarid characterized by its natural water resources scarcity, low per capita water allocation and conflicting demands as well as shared water resources. This scarcity leads to the limited availability of water resources and the dire need to manage these resources. Faria catchment, located in the northeastern part of the West Bank, Palestine, is one of the most important agricultural areas in the West Bank. The predominantly rural population in the catchment is growing rapidly, which results in increasing demand for natural water resources. The prolonged drought periods in the catchment and the high population growth rate in addition to other artificial constraints have negatively affected the existing obtainable surface water and groundwater resources. 5 Due to the fact that the available water resources in the Faria catchment are limited and are not sufficient to fulfill the agricultural and residential water demand, reliability assessment of water availability in the Faria catchment is of great importance in order to optimally manage the local water resources. Rural population in the Faria catchment faces a series of problems. These problems are related to different causes including inefficient management, water shortages, environmental pollution, and Israeli occupation. The key problems of the Faria catchment relevant to the water resources can be summarized as follows: 1. Lack of proper management of water resources causes over utilization of the scarce water resources. 2. The water is not properly allocated between upstream and downstream communities and thus water use rights need to be well established and institutionalized. 3. More than 40% of the people in the catchment lacks water supply for drinking purposes. 4. The estimated annual water gap between water needs and obtainable water supply is about 20 millions cubic meters. This gap is increasing rapidly with time. 5. Lack of storage capacity and non existence of small dams to capture the rain floods during the rainy season in order to be used later (As to peace agreements, permits for such projects are required from Israeli occupation authorities, which are almost impossible to obtain). 6 6. Unbalanced utilization of groundwater causes increasing salinity especially in the south eastern part of the catchment in the proximity of the Jordan River. 7. Water losses through evaporation and infiltration from the agricultural canals are high and thus large quantities of water are not fully utilized. 8. Soil erosion in the lower part of the catchment is of great concern. 9. Water pollution is an ongoing problem. For instances surface water originating from the springs mixes with wastewater coming from Nablus City and Faria refugee camp. 10. There is no treatment plant in the catchment. 11. Cesspools are major threats to pollute the groundwater aquifers and springs. 12. The unbalanced use of fertilizers and pesticides has led to the pollution of the scarce water resources. 13. Unmanaged solid waste dumping in some areas adds additional complexity to the pollution problems. 14. Lack of permits to rehabilitate and remediate the deteriorated wells. 15. In contrast to the shallow Palestinian wells, Israeli wells are pumping largely from deep aquifers and thus lowering the water table. From the above it can be inferred that Faria catchment is under a severe problematic conditions that need to be investigated in order to set up proper 7 strategies and management alternatives to address these problems efficiently indemnify. For the aforementioned discussion, this study is of great importance. Due to the fact that the available water resources in the Faria catchment are limited and cannot suffice for increasing water demand to fulfill the agricultural and residential requirements, reliability assessment of water availability in the Faria catchment is of great importance in order to optimally manage the local water resources. This situation has compelled the motivation for conducting a hydrological modeling to better understand and to evaluate the water resources availability in the Faria catchment. This modeling is essential to provide input data for a management system and to enable the development of optimal water allocation policies and management alternatives to bridge the gap between water needs and obtainable water supply under drought conditions. 1.4 Methodology To achieve the above objectives, the available topographic maps of the region were scanned and the catchment was subdivided into sub- catchments. Drainage lines and divides were digitized. The stream paths, possible flow directions and slopes have been determined using the available Digital Elevation Model (DEM) and the base map of the Faria catchment has been prepared. All the information including topography, land use, drainage lines, water divides, soil and geology have been processed using the GIS ArcView 3.2 software. The rainfall data recorded by the different stations of the Faria catchment were analyzed for typical and maximum rainfall intensities and amounts. 8 These were used as a tool to describe the spatial structure of the rain events and to regionalize point station data to catchment rainfall. Rainfall and runoff were measured continuously during the rainstorms of the last two rainy seasons of the hydrological years 2003-2004 and 2004-2005. Accordingly the input parameters to the KW-GIUH model have been estimated. The following summarizes the main steps that were followed: 1. Collect all data and information from national and local institutions. 2. Hydrological measurements and sampling of rainfall-runoff events completed for the two rainy seasons. 3. Analysis of rainfall and runoff data. 4. Set up GIS-based data as input for the model. 5. Model application to the available different rainfall events. 6. Model verification and sensitivity analysis. 7. The final results of the modeling have been formulated. The overall methodology followed in this study is illustrated in Figure 1. 9 Figure 1: A flow Chart Depicting the General Methodology Followed in this Study 1.5 Data Collection Hydrological data in the West Bank is very limited. Difficulties have been faced in collecting the necessary data for this study due to continuous closure of the West Bank cities. Nevertheless the catchment was visited several times to collect further data. Most of the data have been collected from the following sources: KW-GIUH Rainfall Runoff model Geography Topography Geomorphology Climate Geology Soil Springs Wells Rainfall Runoff Quality monitoring Land use development Runoff data GIS Excel Database formatting Characterization of the study area Data collection Flumes construction Site visits Ground truthing Statistics analysis Time series analysis Trend analysis Probability analysis Correlation analysis Unit hydrograph derivation Rainfall analysis Geomorphological data Rainfall data Sensitivity analysis Model application 10 1. Contour Map. The available 1:50000 scale topographic maps have been used to collect elevation data. The maps have been scanned and used within the GIS environment to delineate the catchment and sub- catchments boundaries and divides. The stream paths, possible flow directions and slopes have been determined using the available Digital Elevation Model (DEM). 2. Water resources (springs and wells) data were obtained from the Palestinian Water Authority (PWA) databank. The data included monthly and annual measurements of the abstraction of the wells and yield of springs in addition to the name and coordinates of these resources. The information obtained was in MS Excel format. 3. Rainfall data necessary for the analysis of the rainfall-runoff process have been collected from the PWA and from Nablus Meteorological Station for five different stations (Taluza, Tammun, Tubas, Beit Dajan and Al-Faria). 4. The climatic data for this study was obtained from the Palestine Climate Data Handbook published by the Metrological Office of the Ministry of Transport (MOT), 1998. Climatic data included average monthly values for maximum and minimum temperature, hourly mean wind speed, daily mean sunshine duration, mean relative humidity, pan evaporation and mean monthly rainfall for Nablus and Al-Faria stations. 11 CHAPTER TWO LITERATURE REVIEW 12 2.1 Hydrology of Semiarid Regions One way to define aridity is the moisture deficit, or the aridity index, which is the ratio of mean annual precipitation (P) to mean annual potential evapotranspiration (PET). This index is then reclassified into four main aridity zones and one humid zone and one cold tundra mountains zone, according to the ranges defined by UNESCO (1984). These zones are: hyper-arid (P/PET < 0.05), arid (0.05 <= P/ PET < 0.20), semiarid (0.20 <= P/ PET < 0.50), dry sub-humid (0.50 <= P/ PET < 0.65), humid (P/ PET >=0.65) and cold, which area that have more than six months of an average temperature below 0 degrees and not more than three months where the temperatures reach above 6 degree centigrade. The six arid regions around the world are shown in Figure 2. Figure 2: Arid Regions around the World (UNESCO, 1984) 13 The main hydrological difference between humid areas and arid zones is a high variability in both space and time of all hydrologic parameters (e.g. rainfall intensity, infiltration rates, runoff rates). Floods, although infrequent and rare, appear in arid areas and often cause loss of life and property (Schick et al, 1997, cited by Thormählen, 2003). Many semiarid regions are particularly affected by flash floods, caused mainly by convective storm systems. The main processes that dominate during flashy floods are the generation of Hortonian overland flow on dryland terrain and transmission losses into the dry alluvial beds of ephemeral channels. In dry environments, the hydrological regime is governed by missing baseflow and single episodic flood events traveling on dry river beds, induced by localized, high intensity rainfall (Thormählen, 2003). 2.1.1 Climate and Rainfall The main climatological feature of arid regions is the ephemeral and often localized nature of precipitation usually associated with immense variations in space and time (Thormählen, 2003). The arid zone is characterized by excessive heat and inadequate variable precipitation; however, contrasts in climate occur. In general, these climatic contrasts result from differences in temperature, the season in which rain falls, and in the degree of aridity. Three major types of climate are distinguished when describing the arid zone: the Mediterranean climate, the tropical climate and the continental climate (FAO, 1989). In the Mediterranean climate, the rainy season is during autumn and winter. Summers are hot with no rains; winter temperatures are mild, with a wet season starting in October and ending in April or May, followed by 5 to 6 months of dry season. 14 In the tropical climate, rainfall occurs during the summer. Winters are long and dry. In Sennar, Sudan, an area that is typical of the tropical climate, the wet season extends from the middle of June until the end of September, followed by a dry season of almost 9 months. In the continental climate, the rainfall is distributed evenly throughout the year, although there is a tendency toward greater summer precipitation. In Alice Springs, Australia, each monthly precipitation is less than twice corresponding mean monthly temperature; hence, the dry season extends over the whole year. The rainfall that falls is either intercepted by trees, shrubs, and other vegetation, or it strikes the ground surface and becomes overland flow, subsurface flow, and groundwater flow. Regardless of its deposition, much of the rainfall eventually is returned to the atmosphere by evapotranspiration processes from the vegetation and soil or by evaporation from streams and other bodies of water into which overland, subsurface, and groundwater flow move. These processes are as illustrated by the hydrologic cycle in Figure 3, in which global annual average water balances are given in units relative to a value of 100 for the rate of precipitation on land. Rainfall intensity is another parameter which must be considered when evaluating the rainfall runoff process. Because the soil may not be able to absorb all the water during a heavy rainfall, water may be lost by runoff. Likewise, the water from a rain of low intensity can be lost due to evaporation, particularly if it falls on a dry surface. 15 Figure 3: Hydrologic Cycle with Global Annual Average Water Balance (Chow et al., 1988) A semiarid region is subject to seasonal precipitation, with little or no precipitation in other parts of the years. Rainfall patterns vary widely from region to region and, within a certain region. Temperature is high and annual precipitation amounts are moderate (Ponce, 1989). Evaporation is affected by several climatic elements (e.g. air temperature, relative humidity, net radiation). It is necessary to distinguish between actual rates of evaporation and potential rates. The concept of the potential evaporation assumes that water is not limited and is at all times sufficient to supply the requirements of the dry air and the transpiring cover. Clearly, in semiarid regions, the value for actual evaporation seldom equals the potential evaporation, but is much lower. Generally in semiarid farm lands there is large gap between potential Evapotranspiration and rain depth. 16 2.1.2 Runoff Generation and Channel Flow The high variability of rainfall both in time and space, leads to very high variability of runoff. In humid regions different runoff generation processes (e.g. runoff from saturated areas and slow outflow of large groundwater bodies) deliver more or less permanently water to perennial rivers. In contrast, in arid regions Hortonian overland flow, generated as infiltration excess runoff, is generally assumed to be the dominant mechanism of runoff generation (Abrahams et. al, 1994). The overland flow is described as water that flows over the ground surface heading for the next stream channel and as the initial phase of surface runoff in arid environments (Lange et al., 2003). On plane surfaces a quasi laminar sheet flow may develop, but, more usually, flow is concentrated by topographic irregularities and water flows anatomizing in small gullies and minor rivulets downhill. The main cause of overland flow is the inability of water to infiltrate the surface as a result of high intensity of rainfall or a low value of infiltration capacity or both phenomena (Thormählen, 2003). The difference between rainfall rate and infiltration rate is the concept of calculation the runoff of Hortonian overland flow. Water accumulates on the top of the ground surface, if the infiltration capacity of the soil is exceeded. Surface depressions have to be filled with water, after that runoff generation start to runs down slope. Arid areas with moderate to steep slopes and sparse vegetation cover form the ideal conditions for Hortonian runoff. Streams in the arid and semiarid areas are usually ephemeral, since rainfall events are seldom occurred. Arid and semiarid ephemeral streams flowing only occasionally as a direct response to runoff generating rainstorms and remaining dry for most of the year. Flow in the large streams with their 17 origin outside the arid zone (e.g. Nile River, Indus River or Colorado River) and small spring fed streams are the only exceptions (Thormählen, 2003). Floods in small dryland basins are usually of the flash flood type, either single peak floods or multiple peak events. Flash floods are almost produced by convective rain storm cells and are typical for small scale catchments (<100km²), because most thunderstorm cells are relatively small in diameter. Flash floods are defined as stream flows that increase from zero to a maximum within a few minutes or at most few hours (Graf, 1988). Surface runoff in the eastern slopes of the West Bank where the Faria catchment is located is mostly intermittent and occurs when rainfall exceeds 50 mm in one day or 70 mm in two consecutive days (Forward, 1998, cited by Takruri, 2003). Rofe and Raffety (1965) studied runoff in the West Bank through monitoring and studying runoff data from seventeen flow gauging stations within the boundaries of the West Bank. They concluded that surface runoff constitute nearly 2.2% of its total equivalent rainfall. 2.1.3 Storages Two types of surface flow losses occur in the arid lands, which fill temporal storages (Lange, 1999): 1. Infiltration is a direct loss with Hortonian runoff that governs the volume of storm runoff. Further direct losses occur when water is temporarily stored on route or in the stream system as detention loss or when depression storages retain water in depressions on the surface. 18 2. Linear transmission losses into the riverbed alluvium of the stream channels reduce flood volume as indirect losses, after surface flow has been generated and flows spatially concentrated. The main water storage in dry environments is formed by coarse river bed alluvium. With rainfall events broadly separated in time, the alluvial fill has a large available volume for flood water infiltration practically at all times. The alluvial storages form an infiltration trap for water that flows into them either through the orderly tributary system or directly from adjoining slopes. The alluvial bodies, filled by indirect losses may be relatively permanent and quite deep, serving as important water storage for vegetation or local population. Compared to alluvial fills, the second type of storage is shallower. It is recharged by direct losses and is quickly emptied by evaporation within a few days after the rainfall event. Percolation from rainfall to deep aquifers is generally very small. 2.2 Rainfall-Runoff Modeling The selection, analysis and use of recorded hydrographs for direct simulation purposes are reflected in variation of the unit hydrograph technique. This technique, which assumes a linearity of the transfer function, is computationally attractive and often sufficiently accurate. Unit hydrograph techniques may be applied to synthesize hydrographs either from recorded rainfall events or from specific return period storms extracted from intensity-duration-return period curves and hypothetical time duration patterns (Chow et al., 1988). Hydrological modeling is concerned with the accurate prediction of the partitioning of water among the various pathways of the hydrological cycle (Dooge, 1992 cited by Lange, 1999). Hydrological systems are generally analyzed by using 19 mathematical models. These models may be empirical or statistical, or founded on known physical laws. They may be used for such simple purposes as determining the rate of flow that roadway grate must be designed to handle, or they may be used to guide decisions about the best way to develop a river basin for a multiplicity of objectives. The choice of the model should be tailored to the purpose for which it is to be used. In general, the simplest model capable of producing information adequate to deal with the issue should be chosen (Viessman et al., 2003). Hydrological models are used for several practical purposes. Imagine a flood disaster; during the flood event a model may help to predict when and where there is a risk of flooding (e.g., which areas should be evacuated). After the flood, models may be used to quantify the risk that a flood of similar or larger magnitude will occur during the coming years and to decide what measures of flood protection may be needed for the future. Furthermore, models may help to understand the reasons for the magnitude of flood (e.g., if the flood was enlarged by human activities in the catchment) (Lundin et al., 1998). 2.2.1 Historical Overview The development and application of hydrological models have gone through a long time period. The origins of rainfall-runoff modeling in the broad sense can be found in the middle of the 19th century, when Mulvaney, an Irish engineer who used in the first time the rational equation to give the peak flow from rainfall intensity data and catchment characteristics. A major step forward in hydrological analysis was the concept of the unit hydrograph introduced by Sherman in 1932 on the basis of superposition principle. The use of unit hydrograph made it possible to 20 calculate not only the flood peak discharge (as the rational method does) but also the whole hydrograph (the volume of surface runoff produced by the rainfall event). The real breakthrough came in the 1950s when hydrologists became aware of system engineering approaches used for the analysis of complex dynamic systems (Todini, 1988). This was the period when conceptual linear models originated (Nash, 1958). Many other approaches to rainfall-runoff modeling were considered in the 1960s. A large number of conceptual, lumped, rainfall-runoff models appeared thereafter including the famous Stanford Watershed Model (SWM-IV) (Crawford and Linsley, 1966) and the HBV model (Bergström and Forsman, 1973). A great variety of these conceptual hydrological models has appeared up to the present date. TOPMODEL is one remarkable model developed in the late 1970s (Beven and Kirkby, 1979) that is based on the idea that topography exerts a dominant control on flow routing through upland catchments. To meet the need of forecasting (1) the effects of land use changes, (2) the effects of spatially variable inputs and outputs, (3) the movements of pollutants and sediments, and (4) the hydrological response of ungauged catchments where no data are available for calibration of a lumped model, the physically based distributed parameter models were developed. SHE model is an excellent example of such models (Lange, 1999). Geomorphological Instantaneous Unit Hydrograph (GIUH) (Rodriguez- Iturbe and Valdes 1979) is a recently developed physically based rainfall- runoff approach for the simulation of runoff hydrograph, especially appropriate for ungauged catchments. Lange 1999 mentioned that GIUH model has been used by Allam (1990), Nouh (1990) and Al-Turbak (1996) to develop unit hydrograph for several catchments in the Kingdom of Saudi 21 Arabia. In the semiarid experimental catchment of Walnut Gulch, Arizona, USA, the long history of research provides good runoff records, which facilitated the successful application of calibrated models (Goodrich et al. 1997 and Renard et al.1993 cited by Thormählen, 2003). The long history of research also allowed a non-calibrated model run of KINEROS, a complex distributed model developed for semiarid catchments (Thormählen, 2003). Lange et al. (1999) develop a model not depending on calibration but accounting for the dominant processes of arid zone flood generation. This has been done for the 1400 km² Zin catchment in the Nagab Desert. The ZIN-Model has been developed especially for large arid catchments and has been tested successfully for 250 km² in the semiarid Wadi Natuf (Lange et al. 2001). 2.2.2 Classification of Models and Basic Definitions Two types of mathematical models can be used in hydrology; stochastic and deterministic models. In the stochastic models, the chance of occurrence of the variable is considered thus introducing the concept of probability. In the deterministic models, the chance of occurrence of the variables involved is ignored and the model is considered to follow a definite law of certainty but not any law of probability (Raghunath, 1985). Different classification schemes have been proposed (e.g. Chow et al., 1988, Todini 1988). Figure 4 provide a general overview of the hydrological model using the classification criteria randomness, spatial discretization and model structure. To find the desired hydrological model one should ask the following questions (Lange, 1999): 1- Is there a need to consider randomness? 22 2- Is there a need to consider spatial variations of model input or parameter? 3- To what extent the governing physical laws have to be considered? Randomness is not considered in a deterministic model; a given input rainfall always produces the same output runoff. The outputs of a stochastic model are at least partially random. A deterministic distributed model considers the hydrological process taking place at various points in space. It may either be physically based, i.e. reproducing the rainfall-runoff process only by physical principals on the conservation of mass and momentum, or conceptual reflecting these principals in a simplified approximate manner. In deterministic lumped models hydrological systems are spatially averaged or regarded as a single point in scale without dimensions. Since hydrological processes generally are space dependent, spatial lumping always includes crude conceptualization. Empirical models do not explicitly consider the governing physical laws of the processes involved. They only relate input through some empirical transformed function. Stochastic models are termed space-independent or space- correlated according to whether or not random variables at different points in space influence each other. 23 Figure 4: Classification of Hydrological Models (Lange, 1999) 2.3 Use of GIS in Hydrology Geographic Information Systems (GIS) can be defined as computer based tools that display, store, analyze, retrieve, and process spatial data. GIS is being more and more involved in hydrology and water resources and showing promising results. GIS provides representations of the spatial features of the earth, while hydrological models are concerned with the flow of water and its constituents over the land surface and in the subsurface environment. GIS with its upcoming advanced technology has been a great advantage to hydrological modeling. Hydrological modeling using GIS has been great developed during the last decade when people realized the utility of incorporating GIS with hydrologic modeling. The use of digital terrain models have showed there potential to a number of analysis in hydrology. Lee (1985) cited by Al-Smadi (1998) concluded that GIS is an efficient tool for compiling input data for use in hydrological investigations and best suited distributed hydrologic models. Al-Smadi (1998) mentioned that; Conceptual Deterministic Hydrological Models Stochastic Space -independent Space -correlated Distributed Physically based Lumped Empirical 24 Berry and Sailor (1987) noted some of the advantages of GIS in hydrology and water resources. According to them, GIS provides a powerful tool for expressing complex spatial relationships. It provides an opportunity to fully incorporate spatial conditions into hydrologic inquiries. Different proposed levels of development can be made rapidly and the resulting hydrologic effects easily communicated to decision makers. GIS are highly specialized database management systems for spatially distributed data. GIS provides a digital representation of the catchment characterization used in hydrological modeling. Maidment (1996) summarized the different levels of hydrological modeling in association with GIS as follows: hydrologic assessment; hydrologic parameter determinations; hydrologic modeling inside GIS; and linking GIS and hydrologic models. GIS integrates different elements like automated mapping, facilities management, remote sensing, land information systems and spatial statistics. GIS serves as an input to the management information systems in the corporate domain and modeling. Maidment (1996) tries to focus on the data model which is the key to the GIS modeling in hydrology concluding that “It is probably true that the factor most limiting hydrological modeling is not the ability to characterize hydrological processes mathematically, or to solve the resulting equations, but rather the ability to specify values of the model parameters representing the flow environment accurately”. GIS will help overcome that limitation. Bhaskar et al. (1992) simulated watershed runoff using the Geomorphological Instantaneous Unit Hydrograph (GIUH) with the Arc-Info GIS to compile the required data. In this study GIS has been employed as a tool to determine the hydrologic parameter for the Faria catchment needed to compile the KW-GIUH model. 25 Digital Elevation Model (DEM) is used in number of sub-domains in hydrology. Varied hydrological applications can be driven by different users accessing the same pool of information. As a result, the structure of the database that supports the GIS, quality of the data and the way in which the database is managed lie at the heart of development of many GIS applications. The DEM have proved to be very efficient in extracting the hydrological data from the DEM by analyzing different topographical attributes (elevation, slope, aspect, relief, curvatures) for modeling purposes. DEM has potentially proved to be a valuable tool for the topographic parameterization of hydrological models especially for drainage analysis, hill slope hydrology, watersheds, groundwater flow and contaminant transport etc. The reason of adopting GIS technology in hydrological models is because it allows the spatial information to be displaced in integrative ways that are readily comprehensible and visual. The spatial information collected is further subjected to continuous GIS analysis. The GIS techniques have the potential for widespread application to resource evaluation, planning and management (Grover, 2003). Several of the most popular computer models such as HEC-RAS, HEC-HMS, and Mike SWMM have GIS capabilities that are seldom used. GIS technology has not been used more widely because: • Lack of suitable data. • The technology is too expensive. • The engineering community lack training and education in GIS. 26 2.4 Previous Work in the Study Area Few reports appear in the literature concerning the runoff estimatation and analysis of rainfall data in the West Bank. Rofe and Raffety (1965) have installed special gauging networks which was designed and illustrated for ten wadis. The data were recorded for the year 1962/63 only. The results of this study show that the overall percentage of the rainfall-runoff was 2.2%. Rofe and Raffety (1965) also concluded that runoff was negligible in North West Bank. After the occupation of the West Bank in 1967, the runoff has cautioned to be measured by Israelis from many gauging stations located outside the boundaries of the West Bank. There are some stations located near the Green line (the 1967 cease fire agreement between the Palestinians and Israelis) which may provide reliable historic records on surface runoff. Husary et al., (1995) analyze the rainfall data for the northern west bank. They presented the relationship between rainfall and runoff in Hadera catchment. They found that the ratio of runoff to rainfall ranges from 0.1% to 16.2% with an average of 4.5% for the period of 1982/83-1991/92. Ghanem (1999) conducted a hydrological and hydrochemical investigation of the Faria drainage basin using GIS. According to Ghanem runoff is 2% of rainfall for the upper Faria and about 1% for the lower Faria. Al-Nubani (2000) studied the temporal characteristics of the rainfall data of Nablus meteorological station. By correlating the occurrences of runoff in Rujeeb watershed east of Nablus to the total rainfall values, he concluded that runoff occurs when total rainfall exceeds 48 mm distributed over less that 15 hours duration. As a result of Al-Nubani the runoff is 13.5% of rainfall. Barakat (2000) studied the rainfall runoff process of the upper Soreq catchment in Jerusalem district and developed the unit hydrograph related 27 to four recorded events. Shaheen (2002) has studied the storm water drainage in arid and semiarid regions. He evaluated several rainfall-runoff processes of Soreq watershed. He has also evaluated the application of KW-GIUH model on semiarid watershed. Shadeed and Wahsh (2002) studied the runoff generation in the upper part of the Faria catchment using synthetic models, KW-GIUH model was also used in their study. The annual rainfall recorded at Nablus station for the period 1946-2002 was analyzed including frequency and trend analysis. Intensity-duration- frequency relationships were constructed. Takruri (2003) studied rainfall data in Faria catchment and developed approximate IDF curves for Beit Dajan station. She developed the unit hydrograph for the Faria catchment using traditional methods. From the above it is clear that the ratio of rainfall to runoff in West Bank catchments has a wide range indicating that individual events of different characteristics dominate the rainfall-runoff process. Therefore there is a need for further investigations including detailed and accurate data acquisition of single events and proper modeling in the West Bank catchments. However, the outcomes of the previous studies indicate that the Faria catchment has not been modeled using appropriate rainfall-runoff models. Therefore the obtained results are weak and doubtful. This motivates the study of surface runoff in Faria catchment. This study is an attempt to hydrologically investigate and analyze the Faria catchment as one of the most important catchments of the West Bank, since the catchment has not been modeled using appropriate rainfall runoff models so far. 28 CHAPTER THREE DESCRIPTION OF THE STUDY AREA 29 3.1 Location and Topography The area under consideration is the Faria catchment which is located in the northeastern part of the West Bank and extends from the ridges of Nablus Mountains down the eastern slopes to the Jordan River and the Dead Sea as shown in Figure 5. Faria catchment overlies three districts of the West Bank. Those are: Nablus, Tubas and Jericho district and has a catchment area of about 334 km2 which accounts for about 6% of the total area of the West Bank (5650 km2) (see Figure 5). The Faria catchment lies within the Eastern Aquifer Basin (EAB), which is one of the three major groundwater aquifers forming the West Bank groundwater resources. The Faria catchment borders are: North Jordan and Fassayel-Auja drainage basins from the north and south respectively, Alexander, Yarkon and Al- Khidera drainage basins from the west and Jordan River from the east. The western boundary of the study area lies at the main catchment between the Mediterranean Sea and the Jordan River. The Faria wadi extends from the upper part of the catchment to the Jordan River. Al-Faria and Al-Badan wadis are the two main streams contributing to the Faria catchment. These wadis meet at Al-Malaqi Bridge located 25 km east of Nablus city. The Faria wadi is the major water supply system in the catchment. Springs are located around the stream and discharge water to the stream, through which water is conveyed to irrigation ditches and pipelines that distribute irrigation water to the farms along both sides of the stream. 30 West Bank Districts Salfit Jenin Tubas Nablus Jericho Hebron Tulkarm Qalqiliya Jerusalem Bethlehem Ramallah and Al-Bireh Dead Sea Faria Catchment West Bank Boundary N Prepared by Eng. Sameer Shadeed 0 40 Kilometers $T Nablus # Jordan River Figure 5: Location of the Faria Catchment within the West Bank Irrigation wells are available in the Faria catchment to supply additional water. Within the Faria catchment there exist 13 fresh water springs and 70 groundwater wells as presented in Figure 6. The fertile alluvial soils, the availability of water through a number of springs and the meteorological conditions of the catchment made the catchment one of the most important irrigated agricultural areas in the West Bank. 31 #Y#Y #Y#Y#Y #Y #Y#Y #Y #Y #Y #Y#Y#Y#Y#Y #Y #Y #Y #Y #Y #Y #Y#Y #Y #Y #Y #Y #Y #Y #Y #Y#Y#Y#Y #Y#Y#Y#Y#Y #Y #Y #Y#Y#Y #Y #Y#Y #Y#Y #Y #Y #Y #Y#Y #Y #Y#Y#Y #Y #Y #Y #Y $Z$Z $Z $Z$Z$Z$Z$Z $Z $Z $Z $Z$Z N Layout preparer Eng. Sameer Shadeed 0 3 6 9 Kilometers #Y Wells $Z Springs Catchment Boundary Figure 6: Springs and Wells within the Faria Catchment Topography is a unique factor in the Faria catchment which starts at an elevation of about 900 meters above mean sea level in Nablus Mountains and descends drastically to about 350 meters below mean sea level at the point where the Faria wadi meets the Jordan River. This means that topographic relief changes significantly throughout the catchment. In less than 30 km there is a 1.25 km change in elevation. Such an elevation decline in a relatively short distance has considerable effects on the 32 prevailing meteorological conditions in the area as a whole and, in fact, adds to its importance and uniqueness. Topographic map of the Faria catchment (Figure 7), uploaded into the GIS ArcView system and used in the delineation of flow paths and divides as discussed in section 5.6 of this study. Faria catchment includes about twenty communities within its borders. Most of these communities are rural communities except the eastern part of the city of Nablus, the refugee camps and parts of the town of Tubas and other villages in the upper part of the catchment. N Layou t p re pa re r Eng . S am e er Shadeed Ca tchm ent B oundary To po graph ic M ap o f the Faria C atch m ent 0 3 6 Kilom ete rs Figure 7: Topographic Map of the Faria Catchment 33 3.2 Climate In the West Bank, climatic stations are mainly concentrated in the principal towns and villages. Since the Faria catchment does not contain significantly large built up areas, therefore only two climatic stations are located within the Faria catchment. One of the stations is located in Nablus (570 m elevation) and the other is located in Al-Jiftlik (-237 m elevation). Climatic data for these stations were obtained from the Palestine Climate Data Handbook published by the Meteorological Office of the Ministry of Transport (MOT) (1998). Climatic data included average monthly values for maximum and minimum temperature, mean wind speed, mean sunshine duration, mean relative humidity and pan evaporation. The average values for the climatic conditions prevailing in the catchment area are presented in Appendix A1. The information has been spatially delineated using the GIS ArcView 3.2 software based on data input of temperature and evapotranspiration. 3.2.1 Wind The main wind direction is from west, southwest and northwest. Variation during winter is associated with the pattern of depressions passing from west to east over the Mediterranean (Ghanem, 1999). The prevailing winds in the area are the southwest and northwest winds with an annual average wind speed of 237 km per day in Nablus at a height of 10 meters from ground surface. When this value is adjusted for 2 meters height (the 2 meters height value is used in most of the potential evapotranspiration estimates), average wind velocity drops to 185 km per day. During summer, wind moves with relatively cooler air from the Mediterranean towards the north, with an average wind speed of 288 km per day in June in 34 Nablus at a height of 10 meters. At night the land areas become cooler, causing diurnal fluctuations in wind speed, due to the reduction of the pressure gradient. In winter, the wind moves from west to east over the Mediterranean, bringing westerly rain bearing winds of average wind speed 209 km per day in January. The Khamaseen, desert storm, may occur during the period from April to June. During the Khamaseen, the temperature increases, the humidity decreases and the atmosphere becomes hazy with dust of desert origin. Wind velocities decrease with elevation, thus wind velocities in Al-Jiftlik in the lower part of the catchment are significantly lower than those in Nablus located in the upper part of the catchment. Existing wind data showed that measurements of wind velocities were recorded at a height of 10 meters in Nablus and at a height of 2 meters in Al-Jiftlik. Due to the elevation of Al-Jiftlik which is 237 meters below sea level and the existing mountains surrounding Al-Jiftlik, wind velocities are much lower than those at Nablus. Annual average wind velocity in Al-Jiftlik was estimated at 106 km/day at a height of 2 meters which is much less than the 185 Km/day estimated in Nablus at the same height from ground surface. 3.2.2 Temperature Faria catchment is characterized by high temperature variations over space and over time. Temperatures reduce with increasing elevation in the catchment. The average temperature variation between Nablus and Al- Jiftlik is about 5 oC. The mean annual temperature changes from 18 oC in the western side of the catchment in Nablus to 24 oC in the eastern side of the catchment at Al-Jiftlik. Figure 8 shows the variation in average monthly temperatures in Nablus and Al-Faria stations. Spatial 35 representation of the mean annual temperature in the catchment is presented in Figure 9. 0 5 10 15 20 25 30 35 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months M ea n T em p. (o C ) Nablus Al-Jiftlik Figure 8: Mean Monthly Temperatures in Nablus and Al-Jiftlik 19.0 19.5 18.5 23 .0 21 .5 20 .0 21 .0 20 .5 22 .0 22 .5 18.0 23 .5 23.0 N Prepared by Eng. Sameer Shadeed Mean Annual Temperature (Celsius) Catchment Boundary 0 3 6 9 Kilometers Figure 9: Spatial Distribution of the Mean Annual Temperature in the Faria Catchment 36 3.2.3 Relative Humidity The mean annual relative humidity of Nablus area is 61%. The minimum value of relative humidity is 51% which occurs in May during the Khamaseen weather, while the maximum relative humidity of 67% is usually registered in December, January and February. Relative humidity is in general low in the entire catchment especially in summer months because the catchment is located on the eastern side of the West Bank Mountains. The source of humidity in the region is the Mediterranean Sea, where the western winds bring humidity to the catchment. Eastern winds coming from the desert are usually dry. 3.2.4 Rainfall The West Bank is considered semiarid and has the Mediterranean type climate. Regionally, the winter rainy season is from October to April in the catchment. Rainfall events predominantly occur in autumn and winter and account for 90% of the total annual precipitation events. Although the summer months are dry, some rain events occur occasionally and a high- pressure area governs the weather over the Mediterranean. The continental low-pressure area to the east and south creates a strong pressure gradient across the country, which results in eastward moving sea breezes of relatively cooler air. In winter, the predominately low-pressure area of the Mediterranean centered between two air masses, the north Atlantic high on North Africa and the Euro-Asian winter high located over Russia, is the primary cause of winter weather in the area. The presence of hills in the west of Palestine affects the behavior of the low-pressure area, resulting in westernlies, which force moist air upwards, causing precipitation on the hill ridges. The steep gradient of Jordan Valley produces a lee effect, which 37 greatly reduces the quantity of the rainfall in the Jordan Valley rift area (Husary et al., 1995). The rainfall distribution within the Faria catchment ranges from 640 mm at the headwater to 150 mm at the outlet to the Jordan River. Figure 10 presents the spatial presentation of the rainfall data within the Faria catchment. #Y #Y #Y #Y #Y #Y 450 500 550 400 30 0 25 0 35 0 20 0 150 600 200 600 350 Tubas Nablus Tammun Al-Faria Talluza Beit Dajan N Prepared by Eng. Sameer Shadeed Isohyetal Rainfall Map (mm) #Y Rainfall Stations Catchment Boundary 0 3 6 9 Kilometers Figure 10: Rainfall Stations and Rainfall Distribution within the Faria Catchment 38 3.2.5 Evaporation The Mediterranean climate (hot and dry in the summer, mild and wet in the winter) has six to seven months of dryness in the year. Winter months where moisture is available from rain have low evapotranspiration rates. Summer months with high potential evapotranspiration rates have no rain and thus actual evapotranspiration is limited by the availability of moisture. Evaporation rates in Faria regions are measured from a US Class A pan at Nablus station as shown in the table of Appendix A1. From the table it is noticed that the average annual evaporation measured at Nablus station is about 1682 mm. Evapotranspiration is usually smaller than pan evaporation. Evaporation rates should be multiplied by a pan coefficient (less than 1) to estimate evapotranspiration rates. A more accurate way to estimate evapotranspiration is from climatic data. Monthly potential evapotranspiration rates were estimated according to Penman-Monteith method as modified by FAO using CROPWAT 4 Windows version 4.2 model (FAO, 1998). The maximum potential rate of Evapotranspiration was estimated at 1540 mm/year at Al-Jiftlik and 1408 mm/year in Nablus. Although the temperature variability between Nablus and Al-Jiftlik might indicate a larger difference in evapotranspiration, this difference was reduced as a result of higher wind velocities in dry summer months in Nablus. In the upper part of the Faria catchment, at Nablus, precipitation exceeds potential evapotranspiration in five months of the year (November through March). However, in the lower part of the catchment, at Al-Jiftlik, precipitation exceeds potential evapotranspiration in two months of the year only (December and January). Therefore, irrigation is required during 39 most months of the year in the lower part of the catchment in comparison to the upper part. Figure 11 shows the relation between potential evapotranspiration and rainfall for Nablus and Al-Jiftlik stations. The spatiality of the potential annual evapotranspiration rates in the Faria catchment is presented in Figure 12 as computed using CROPWAT 4 model. From the figure it is noticed that the spatiality of the potential annual evapotranspiration rates is roughly coincide to the spatiality of the mean annual temperature (Figure 9). CROPWAT 4 output results for Nablus and Al-Faria stations are presented in Appendix A2. 0 50 100 150 200 250 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months V al ue (m m ) ETo-Al-Jiftlik ETo-Nablus Rainfall-Al-Jiftlik Rainfall-Nablus Figure 11: Monthly Rainfall and Potential Evapotranspiration Rates (ETo) in Nablus and Al-Jiftlik 40 1440 1430 145 0 1420 1530 1520 14 90 14 60 14 80 14 70 15 00 15 101410 1530 1460 14 40 N Prepared By Eng. Sameer Shadeed Potential Evapotranspiration Rates (mm/year) Catchment Boundary 0 3 6 9 Kilometers Figure 12: Potential Annual Evapotranspiration Rates in the Faria Catchment 3.2.6 Aridity of the Catchment As to UNESCO (1984), aridity can be defined in several different ways and most simply it is a moisture deficit. The moisture deficit, or an aridity index, is determined by the ratio of mean annual precipitation (P) to mean annual potential evapotranspiration (PET). The index ranges for defining arid and semiarid regions are: arid (0.05 <= P/PET < 0.20), semiarid (0.20 <= P/PET < 0.50). 41 Monthly potential evapotranspiration rates were estimated according to Penman-Monteith method as modified by FAO (1998) using CROPWAT 4 Windows version 4.2 model. The results of applying CROPWAT 4 model are presented in the previous section and Appendix A2. It was estimated that the annual potential rate of Evapotranspiration is 1540 mm and 1408 mm at Al-Jiftlik and Nablus stations respectively. For these stations, the long term average annual rainfall is 198 mm and 642 mm respectively. Therefore, the aridity index is 0.13 for Al-Jiftlik and 0.46 for Nablus. This means that arid conditions prevail in Al-Jiftlik, whereas semiarid conditions prevail in Nablus. 3.3 Water Resources 3.3.1 Groundwater Wells There are 69 wells in the Faria catchment; of which 61 are agricultural wells, 3 are domestic and 5 are Israeli wells. These wells are drilled in four sub-aquifers. These sub-aquifers are Eocene, Cenomanian, Neogene and Pleistocene sub-aquifers. All these wells are located in the study area mainly in the areas of Ras Al-Faria, Al-Aqrabanieh, Al-Nasaria, Froush Beit Dajan and Jiftlik along the flexure of wadi Faria. Based on the available data (Table 1), the total utilization of the Palestinian wells ranges from 4.4 to 11.5 MCM/year. Data on the pumping rates from the Israeli wells is available for four wells for only four years from 1997- 2000. The average total abstraction from these four wells was found to be about 8 MCM/year. Average well abstraction from Israeli wells is about 2 MCM/year. Thus, considering the fifth Israeli well without data available, the total abstraction from the five Israeli wells in the Faria catchment is estimated at 10 MCM/year, which is more than the 61 Palestinian 42 agricultural wells combined. Table 1 presents the total annual abstraction from wells in the Faria catchment from 1984 -2003. Wells basic data includes coordinates, well name, location, district, usage, basin, and well depth were obtained from the Palestinian Water Authority (PWA). Appendix A3 gives a summary of these basic data for all wells within the Faria catchment. Table 1: Abstraction from Wells in the Faria Catchment Year Abstraction MCM Agricultural Domestic Total Israeli 1984 4.7 * 4.7 * 1985 5.7 * 5.7 * 1986 5.7 2.2 7.9 * 1987 7.0 2.3 9.2 * 1988 6.8 2.9 9.7 * 1989 6.6 3.3 9.9 * 1990 6.7 3.3 10.0 * 1991 6.3 3.0 9.3 * 1992 4.1 * 4.1 * 1993 5.0 * 5.0 * 1994 5.9 3.0 8.9 * 1995 6.4 3.1 9.5 * 1996 6.6 2.6 9.2 * 1997 5.8 2.8 8.6 6.7 1998 7.6 2.5 10.2 8.3 1999 8.2 3.3 11.5 8.4 2000 7.4 3.9 11.3 8.2 2001 6.1 2.5 8.6 * 2002 6.6 2.7 9.3 * 2003 5.1 2.8 7.9 * * Missing Data 3.3.2 Springs Within the Faria catchment there exists 13 fresh water springs that are divided into four groups. These groups are Faria, Badan, Miska and Nablus. 43 The basic data available on these springs include group name, spring name, coordinates, average annual discharge, minimum annual discharge and maximum annual discharge. Table 2 presents a summary of these basic data. Monthly spring discharge measurements for more than 30 years are available for these springs as presented in Appendix A4. Discharge data of the springs show high spring discharge variability. Annual discharge from these springs varies from 3.8 to 38.3 MCM/year with an average amount of 14.4 MCM/year. The location of the springs and wells within the Faria catchment are shown in Figure 6. Table 2: Spring Groups and Spring Information within Faria catchment Group Spring Name Coordinates Ave. Annual Discharge MCM Min. Annual Discharge MCM Max. Annual Discharge MCM X (km) Y (km) Elevation (m) Faria El Faria El Duleb 182.40 182.00 188.40 187.95 160 155 5.23 1.27 1.71 0.06 10.53 8.60 Badan Asubian Beida & Hammad Sidreh Tabban Qudeira Jiser 180.52 180.12 179.95 180.42 180.13 180.37 184.56 185.32 185.58 184.82 185.28 185.10 130 215 240 160 215 170 0.19 0.81 1.34 1.38 1.33 0.14 0.14 0.10 0.00 0.98 0.00 0.03 0.23 1.75 8.12 1.63 2.33 0.23 Miska Miska Shibli Abu Saleh 187.03 189.90 186.26 182.90 181.28 183.57 -38 -80 -19 1.32 0.95 0.19 0.02 0.71 0.00 2.21 1.15 0.50 Nablus Balata Dafna 176.20 176.20 179.77 179.90 510 560 0.17 0.13 0.05 0.02 0.55 0.49 Total 14.44 3.81 38.31 3.3.3 Analysis of Springs Discharge There are sex springs within Al-Badan sub-catchment, in addition to other two springs that are entirely utilized by the city of Nablus, whereas Al 44 Faria sub-catchment contained two springs in its area. Preliminary analysis on the available monthly discharge measurements including minimum, maximum and average discharge was performed. From the analysis it is concluded that the average annual volume of Al-Badan springs for the 30 years monthly data is about 4 MCM, while the minimum and maximum volumes are about 1.1 MCM and 16 MCM respectively. On the other hand, the average annual volume of Al-Faria springs is about 7 MCM, while the minimum and maximum volumes are 1.4 MCM and 24 MCM. Figures 13 and 14 illustrate the sum of the minimum, maximum and average values of Al-Badan and Al-Faria springs respectively. From figures it is clear that high variability in the spring discharge exists. Results also suggest that the data do not follow a normal distribution and the average value is much closer to the minimum rather than the maximum. 0 200 400 600 800 1000 O ct N ov D ec Ja n Fe b M ar A pr M ay Ju n Ju l A ug Se p Time (Months) D isc ha rg e (L /S ) Maximum Average Minimum Figure 13: Average, Maximum and Minimum Monthly Discharge of Total Springs within Al-Badan Sub-catchment 45 0 200 400 600 800 1000 1200 1400 O ct N ov D ec Ja n Fe b M ar A pr M ay Ju n Ju l A ug Se p Time (Months) D isc ha rg e (L /S ) Maximum Average Minimum Figure 14: Average, Maximum and Minimum Monthly Discharge of Total Springs within Al-Faria Sub-catchment 3.4 Surface Water 3.4.1 Flow Measurements No detailed runoff data were available for Faria catchment. The only hydraulic structure which was constructed in the early 70’s for measuring surface runoff in the Faria catchment is located next to Ein Shibli in the lower central part of the catchment. This hydraulic structure is a wide crested weir which is used as a diversion structure to Al-Faria Irrigation Project. The structure has an upstream stage gage which could be monitored to estimate runoff flows. However, the structure does not have an automatic recorder to register water stage continuously. Therefore, only few sporadic measurements are available for runoff rates from structure. These measurements are not sufficient to estimate the volume of annual runoff through the structure. In August 2003, An-Najah National University in coordination with GLOWA JR project established two 46 Venturi Flumes at Jiser Al-Malaqi to measure runoff rates from both Al- Faria and Al-Badan wadis. GLOWA JR project is an interdisciplinary project that studies the "Impacts of Global Changes on Water Resources in Wadis Contributing to the Lower Jordan Basin". GLOWA project is a German funded project by the German Ministry of Education and Research and is managed by German, Jordanian and Palestinian institutes. Water and Environmental Studies Institute (WESI) of An-Najah University is a counterpartner for Package 2 of GLOWA project researching the water resources in Jordan River. The Flume of Al-Badan wadi was designed to measure 25 m3/s and 0.23 m3/s of maximum and minimum flows respectively. Maximum and minimum flows that can be measured by Al-Faria wadi Flume are 15 m3/s and 0.19 m3/s respectively. In case of low flows the Parshall Flumes are not significantly accurate. There are two reading gauges at each Flume to measure the flow depths at the critical sections, which are converted into flow rates using the designed empirical formulas. The constructed Flumes are still working and the records are available for the two years (2003-2005) since their construction. The Flumes did not have automatic recorders during the first year. The automatic recorders were constructed later and are available since the second year. Photos of the two Flumes are presented in Appendix D1. The recorded runoff data are tabulated as in Appendix A5. Surface runoff of the Faria catchment is considered high compared to other catchments in the West Bank. Within the catchment the runoff decreases from west to east as the slope becomes relatively gentile eastwards down the main stream where rainfall rates reduce also. 47 The city of Nablus discharges untreated industrial and domestic wastewater effluents to Al-Badan wadi while Al-Faria camp discharges untreated domestic wastewater to Al-Faria wadi. Therefore, the stream flow of the Faria catchment is a mix of: 1. Runoff generated from winter storms. This includes urban runoff from the eastern side of the city of Nablus and other built up areas in the catchment. 2. Untreated wastewater of the eastern part of Nablus and of Al-Faria camp. 3. Fresh water from springs which provides the baseflow for the wadi preventing it from drying up during hot summers. Farmers use part of the flowing water for irrigation while the rest discharge into the lower Jordan valley or lost through evaporation. 3.4.2 Quality Considerations No considerable measurements for surface water quality are available for the Faria streams. All the quality measurements conducted in the area are performed for the springs and wells. Since the source of water for the Faria wadi are mostly from springs, then the water quality is dependent on the water quality of these springs. Measurements for spring water quality showed that these springs are generally of good water quality especially chemical quality. The chemical quality data of water from all the springs of the Faria catchment show low concentrations of salts. Therefore, the chemical quality of the Faria streams is good and water is suitable for irrigation (EQA, 2004). A major source of pollution comes from the Nablus 48 municipality. Nablus dumps untreated effluent from its sewage network directly into the Al-Badan wadi, a tributary of the mean wadi of the Faria catchment. The Faria refugee camp disposes of some of its solid waste in pits and the rest by trucking it to a site 1.5 km from the camp to be burned. The effluent is drained into the wadi a few hundred meters away from the camp and wastewater from homes is often dumped directly into the streams or into open ditches. Another source of water contamination is the livestock that use wadis and springs as a drinking water source, and pollute the water with fecal matter. Moreover, local herders bring their sheep and goats to the streams to wash them and to shear the sheep, thereby polluting the surface waters. Finally, an extremely significant pollution factor is the waste disposal and use of agricultural chemicals by the Israeli colonies. However, no information or data are currently available to be considered in this study. However, due to the discharge of untreated wastewater into the wadi its quality has deteriorated significantly. An eye inspection of the wadi and the wastewater entering into it gives an indication of the high deterioration in its quality. Historical data and measurements are not available to quantify such deterioration. Accordingly, samples from the outlet streams (Flumes) of the upper two sub-catchments were collected and analyzed in the context of GLOWA JR project. Samples were taken during different times to study the seasonal variation of the surface water quality. Table 3 shows a summary of the results for the samples collected during the years 2004 and 2005. 49 Table 3: Surface Water Quality Parameters for Badan and Faria Streams Results of the wadi water quality analysis show that runoff during winter as well as peak discharge periods improve the quality of the water in the stream. This is mainly due to the mixing factor. In addition, the microbiological analysis shows that contamination of the water is caused by the untreated wastewater that is flowing from Nablus city and Faria Village and Camp. In general, it is concluded that effluent of untreated wastewater is the main threat to surface water quality of the catchment. This wastewater disposal is causing a major threat not only to the quality of surface water but also to land and soil resources within the catchment. 3.5 Soil The major soil types found in the Faria catchment are as follows (Orthor et al., 2001): 1. Grumusols 2. Loessial Seozems 3. Calcareous Serozems Date Parameters EC μs/cm PO4 Ppm NO3 ppm COD Ppm Turbidity Unit Total.C /100ml Fecal.C /100ml May, 2004 Badan 844 0.30 39.1 32 1.1 1200 700 Faria 571 0.00 15.9 0 5.7 900 600 Aug, 2004 Badan 790 0.40 16.3 120 3.1 3500 2500 Faria 494 0.00 13.6 0.0 3.5 2600 1500 Dec, 2004 Badan 806 0.03 19.8 46.5 5.5 3000 2100 Faria 610 6.00 17.1 0.0 4.1 500 300 Jan, 2005 Badan 732 3.00 16.7 0.0 3.5 2300 1900 Faria 630 0.27 14.0 0.0 18.7 1400 1000 Feb, 2005 Badan 616 0.30 19.8 0.0 3.1 10000 8000 Faria 636 0.22 19.4 0.0 10.5 1000 800 Mar, 2005 Badan 695 0.20 22.4 0.0 1.2 9000 7000 Faria 697 0.01 25.0 0.0 5.4 8000 6500 50 4. Terra Rossas Brown Rendzinas Characteristics of these types are adopted from the document entitled, Environmental Profile for The West Bank, Volume 5, Nablus Profile, ARIJ, 1996. Table 4 shows the characteristics and the areas of the major soil types in Faria catchment. These soil types are spatially distributed over the catchment as illustrated in Figure 15. From the table and the figure it is noticed that Terra Rossas Brown Rendzinas soil and Loessial Seozems cover most of the catchment. These two types; taking up not more less than 70% of the total area. In addition, Loessial Seozems is concentrated in the middle part of the catchment, where Grumusols is distributed over the catchment. Table 4: Major Soil Types and Characteristics in Faria Catchment Soil Type General Characteristics Area (%) Grumusols Parent materials are fine textural alluvial or Aeolian sediments 13 Loessial Seozems Parent rocks are conglomerate and chalk 25 Calcareous Serozems The soil is highly calcareous with grayish-brown color. The texture is medium to fine. Parent rocks are limestone, chalk and marl 19 Terra Rossas Brown Rendzinas The parent materials for this type of soil are originated from mainly dolomite and hard limestone. Soil depth varies from shallow to deep (0.5 to 2 m) 44 Total 100 51 N Layout preparer Eng. Sameer Shadeed Soil Map Grumusols Loessial Seozems Calcareous Serozems Terra Rossas Brown Rendzinas Catchment Boundary 0 3 6 9 Kilometers Figure 15: Soil Types of the Faria Catchment 3.6 Geology Faria catchment is a structurally complex system with Al-Faria Anticline that trends northeast to southwest acting as the primary controlling feature. Additionally, a series of smaller faults and joints perpendicular to this anticline have a significant effect on the surface water drainage area. The geological structure of the Faria catchment is composed form limestone, dolomite and marl. The rocks vary in its thickness, some of them are more than two meters and some of them are intermediate thickness of about 40- 100cm. The rock formations were deposited at the second time Mezosy and 52 mostly refer to the geological Era of Mezosy. The rocks have much intensity of fissures, because of the geological history that the area had faced. The faults and fissures reflect the geological conditions of the area passed and affected the hydrology by a huge infiltration quantity and the appearance of many springs as Badan, Faria, and Miska (Ghanem, 1999). Figure 16 illustrates the geology map of the Faria catchment. Figures 16 and 15 were taken and modified from the data base of the study entitled, A Harmonized Water Data Base for the Lower Jordan Valley (Orthor et al., 2001). N Layout preparer Eng. Sameer Shadeed Geology Map Dead Sea Landslides, Fans Basalt (Lower Cretaceous) Chalk, Limestone, Chert (Ecocene) Calcar. Sandstones, Dolomites, Limestones, Marls Limestone, Dolomite,Marl (Cenomanian, Turonian) Marls, Clays, Gypsum, Sulfur, Clastic Intercalations Marl, Limestone, Sandstone,Conglomerate (Late Ecocene-Miocene) Catchment Boundary 0 3 6 9 Kilometers Figure 16: Geology Map of the Faria Catchment 53 3.7 Land Use The catchment area which has an area of about 334 km2 includes Al-Faria Valley which is one of the most important agricultural areas in the West Bank. A new land use map of the Faria catchment has been developed in the context of GLOWA JR project. The land use images, which are available by Environmental Quality Authority, PHG and Birzeit University, were used in addition to the topographic map and airphotos to shape the new land use map. Part of the airphotos that were used is illustrated in Figure 17. Figure 17: Part of the airphotos of Faria Catchment Ground truthing has been conducted to investigate the actual ground cover. For that purpose, the catchment was visited several times and several 54 photos were snapped that cover the natures of the catchment as presented in Appendix D2. The land use map of the Faria catchment was classified into four classes. These classes are artificial surfaces, agricultural areas, forests and semi natural areas and water bodies. Table 5 presents these classes, the area of each class, its categories and its percent from the whole catchment. The following is a description of these land use classes. 1. Artificial Surfaces The artificial surfaces in the catchment are composed of refugee camps, urban fabrics, Israeli colonies and military camps. The military camps and colonies are used by the Israeli occupation authorities and settlers. The total area of the artificial surfaces is 18047 dunum presenting about 5.5 % of the total area of the catchment. The actual figure is higher due to the fact that most of the roads and associated land were kept out of the scope of the study because of the unit limitations. This percentage is less than that of artificial surfaces in the West Bank (8%) which indicates that the area is not densely populated due to the harsh topography of the nonagricultural area in addition to the political restrictions (EQA, 2004). 2. Agricultural Areas The agricultural land in the catchment is composed of an arable land and heterogeneous agricultural areas. Arable land involves non-irrigated arable land, drip-irrigated arable land, olive groves, palm groves and citrus plantations. The heterogeneous agricultural areas involve irrigated and non- irrigated complex cultivated pattern and land principally occupied by 55 agriculture with significant areas of natural vegetation. The area of the agricultural part of Faria catchment is 115447 dunum which represents about 34.4%. This percentage is lower than that of the West Bank of about 39% (EQA, 2004). 3. Forests and Semi Natural Bodies This group of land use cover is composed of coniferous forests, natural grassland, bare rocks, sparsely vegetated area and halophytes. The forests and semi natural bodies in the Faria catchment occupy an area of about 201087 dunum representing 60% from the total area. It is worth mentioning that most of the Israeli colonies were built at the expense of forests and semi natural areas under the cover of many military laws that consider the forests and vast natural areas as state owned land. 4. Water Bodies No perennial rivers are available in West Bank other than the Jordan River that represents the eastern border of West Bank and Faria wadi. Most of the water courses are seasonal and could be added to the land use maps as linear features of a width less than the threshold of the smallest unit mapped. There are no water bodies controlled by the Palestinians that are large enough to be drawn on the maps of this study. On the other hand there are few water bodies on the Jordan Valley and Faria stream near the Jordan River that are controlled by the Israeli occupation and are utilized for irrigation and fishing (EQA, 2004). One of the artificial water surfaces 56 constructed by the Israeli Authorities is the Tirza reservoir, which has an area of about 250 dunum. Table 5 displays the total land use cover of the Faria catchment. From the table, it is clear that the nonagricultural area is dominant and above the average of the nonagricultural area in the West Bank. The modified land use map is shown in Figure 18. Table 5: Total Land use Cover of the Faria Catchment Land use Cover Area (Dunum) (%) Artificial Surfaces Urban fabrics 13300 4 Refugee camps 972 0.3 Israeli colonies 3107 0.9 Military camps 668 0.2 Sub Total 18047 5.5 Agricultural Areas Olive groves 26506 7.9 Palm groves 394 0.1 Citrus plantations 4650 1.4 Non-irrigated arable land 37289 11.1 Drip-irrigated arable land 6978 2.1 Land principally occupied by agriculture 20458 6.1 Irrigated and non-irrigated complex cultivated patterns 19172 5.7 Sub Total 115447 34.4 Forests and Semi Natural Vegetation Bare rocks 12523 3.7 Halophytes 8757 2.6 Natural grassland 111205 33.2 Coniferous forests 4716 1.4 Sparsely vegetated area 63886 19.1 Sub Total 201087 60 Water bodies/ Artificial surfaces 250 0.1 Total 334831 57 N Modified by Eng. Sameer Shadeed Land Use Map Bare rocks Halophytes Palm groves Olive groves Urban fabrics Military camps Israeli colonies Refugee camps Citrus plantation Natural grassland Coniferous forests Sparsely vegetated area Non-irrigated arable land Drip-irrigated arable land Water bodies/Artificial surfaces Land principally occupied by agriculture Irrigated and non-irrigated complex cultivated patterns Catchment Boundary 0 3 Kilometers Figure 18: The New Land use Map of the Faria Catchment 58 CHAPTER FOUR RAINFALL ANALYSIS 59 4.1 Rainfall Stations The Faria catchment is gauged by six rainfall stations that record rainfall. These stations are: Nablus, Taluza, Tammon, Tubas, Beit Dajan and Al- Faria stations. Before 1994, these stations were controlled by the Israeli Authorities. After the establishment of the Palestinian Authority, the stations except one became under the control of the Palestinians. The Nablus station is a regular weather station in which most climatic data are measured. Monthly and annual precipitation for this station is available for more than 55 years. Al-Faria station is located in Al-Jiftlik village in the lower part of the catchment and is still under Israeli control. This station was established by the Jordanian government as an agricultural experimental station similar to the Deir Alla station on the eastern side of the Jordan River. The station was taken over by the Israeli Occupation Authorities in 1967. The Israeli Authorities neglected the station and therefore its role in serving the Palestinian farmers became insignificant. In 1994, when the Palestinian Authority was established, the Israeli Authorities refused to hand it over to the Palestinians. Therefore, data available from this station is limited to only few years. The other four rainfall stations are located in the schools of Taluza, Tubas, Tammon and Beit Dajan (see Figure 10). These stations are simple rain gages which measure daily precipitation. Data from these stations cover also monthly and annual precipitation for 30 to 40 years. No rainfall intensity charts are available in the catchment except from Nablus station where few years are covered and are available. This is due to lack of continuous measuring instruments for precip