A SAMPLE WATER BUDGET CALCULATION FOR THE STUDY AREA

With the help of the information gathered above an average water budget for the period 1987 – 2002 will be set up. This budget will be later used to set up a steady state flow model. However, due to incomplete data records, the surface flow of the study area has to be estimated from older records (1956-1968; taken from GTZ 1977). A trend line approach will be used to estimate the yearly surface flow from yearly rainfall records. A water budget for the study area can only be set up by making certain assumptions. These assumptions are: (a) the rainfall runoff relationship remains constant from 1956 until 2002, (b)since the completion of the surface dams at the outlets of Wadi Shueib and Wadi Kafrein the whole surface flow of these wadis is used to irrigate the field shown in Fig. 6-5, left, (c) the fields which are irrigated with water from the King Abdullah canal are excluded from the water budget and the classification of the satellite scenes, and (d) the field water requirement of the area represents the water need of the plants, which means, that irrigation return flow has not to be taken into account.

The water balance for the study area consists of the following components: input components into the study area are surface water stored in the Kafrein and Shueib dam, water flowing in Wadi Hisban and in some minor wadis in the southeast of the study area, and infiltrating groundwater from adjacent consolidated aquifers or the deep highly pressurized Ram Group aquifer; output components out of the study area are the water demand of the irrigated fields, which includes irrigation water from the storage dams and pumped groundwater, and outflow through the western border of the study area.

First, the amount of surface water available for irrigation in the study area is estimated. Since yearly rainfall for every period considered exists, the yearly rainfall (Naur Station) versus the available yearly surface flow (from the station in Wadi Shueib, Wadi Kafrein, and Wadi Hisban) were plotted in an x-y diagram. The equation for each wadi derived from trend line through the available points (Fig. 6-12) was used to estimate surface flow for the considered period. An average flow (for the period 1987 – 2002) of 5.5 Mm³ for Wadi Shueib, 5.3 for Wadi Kafrein, 3.93 Mm³ for Wadi Hisban was calculated.

For the remaining small wadis in the study area an average flow of 2 Mm³ was assumed (according to their relative small catchment area). This amounts to a total of 16.8 Mm³ for total available surface flow.

Taking the different planting and harvesting practices under consideration, the yearly field water requirement of the study area was calculated (Tab. 6-12). The calculation revealed that a total of around 31.5 million cubic meter of irrigation water is needed to irrigate the farmland in the model domain. Since no other information regarding planting activities exists for the study area this water demand is taken for the water budgeting.

y = 1.7168Ln(x) - 4.5364

Fig. 6-12: Yearly rainfall values of Naur climatic station versus available surface flow values (Rainfall data taken from Ministry of Water and Irrigation open files, surface flow data taken from GTZ 1977).

The amount of pumped water in the study area can be calculated from the findings above. Since the water stored in the different dams together with the water flowing in Wadi Hisban are exclusively used to irrigated farmland within the study area, the deficit between the estimated field water requirement and the surface water flow represents the amount of groundwater that is necessary to irrigate the farmlands.

If a balanced budget for the study area is assumed, the groundwater inflow into the unconsolidated aquifer can be calculated as the water demand plus the outflow through the western boundary minus amount of available surface water. With the information gathered above a steady state flow model will be constructed.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec [Mm3] [Mm3] [Mm3] [Mm3] [Mm3] [Mm3] [Mm3] [Mm3] [Mm3] [Mm3] [Mm3] [Mm3]

West Vegetable 0,62 0,78 1,26 1,32 1,05 1,05 0,35 0,26 0,11 0,93 0,81 0,61 Well 0,47 0,58 0,95 0,99 1,23 0,20 0,21 0,26 0,19 0,14 0,76 0,46 Hisban 0,18 0,23 0,37 0,39 0,33 0,12 0,12 0,52 0,11 0,08 0,30 0,18 Shueib/Well 0,01 0,01 0,02 0,02 0,05 0,40 0,40 0,51 0,38 0,28 0,02 0,01 KafreinWell 0,36 0,45 0,73 0,76 1,29 1,16 1,16 3,08 1,09 0,80 0,58 0,35

total 1,64 2,04 3,33 3,49 3,94 2,93 2,24 4,62 1,88 2,23 2,48 1,60 Tab. 6-12: Yearly water demand for the irrigated fields (excluding the portion irrigated areas from King

Abdullah Canal).

7. Flow modeling

7. FLOW MODELING

7.1 I

Groundwater systems in semi-arid areas frequently have not been sufficiently characterized hydrogeologically and long term data are generally not available. Long-term time series are necessary however to design future groundwater abstraction scenarios or to predict the influence of future climate change effects on groundwater resources. Fig. 7-1 illustrates how the findings of the different chapters were used to set up the different groundwater flow models and how the results interact with the developed geodatabase.

A conceptual model of flow is set up with the help of geological, hydrochemical, and geophysical methods. The water balance was set up with the help of historical data that were combined with remote sensing methods (chapter 6.7). Afterwards the model is setup and calibrated for steady state flow. The flow model is based on the FEFLOW finite element code (FEFLOW 5.2, WASY Ltd.).

Input parameters were mostly pre-processed by the ArcGIS 9.2 software package (ESRI Ltd.) Afterwards a transient model is developed and applied to two time periods: 1955 – 1970 and 1975 – 2001. Each period has different stress situations placed upon the groundwater system. These stress periods include periods of maximum groundwater extraction, of abandonment of pumping activities, of extreme recharge events, and of drought.

Fig. 7-1: Incorporation of the information of previous chapter into a geodatabase. With the help of the information gathered in the geodatabase a flow model is set up. The results of the flow modeling are stored afterwards in the same geodatabase.

7.2 C

M

F

Only the unconsolidated aquifer is subject to the modeling process (Fig. 7-2). From the geological perspective the study area is characterized by an alternation of alluvial and lacustrine material. The alluvial facies dominates the area close to the East Bank foothills, especially near the outlets of the

major wadis. The lacustrine sediments dominate the western part of the study area and the area between the major alluvial fans (chapter 4.2). The general groundwater flow is from east to west, whereby the groundwater quality, in terms of total dissolved solids, deteriorates along its flow path (chapter 5.2). The groundwater system of the study area has undergone considerable change since its agricultural development (chapter 3). The present-day flow system is in a transient state and is responding to stresses imposed on it. This is manifested in groundwater heads as well as in groundwater quality. The groundwater flow gradient (high groundwater flow velocities) is small in the area dominated by alluvial material and becomes steeper to the west and southwest of the study area.

The steepest gradients (low groundwater flow velocities) can be observed in the vicinity of the Jordan River and the Dead Sea. This behavior was also verified by the direct-push drilling along a north-south profile in the vicinity of the Dead Sea (chapter 5.3.4). This can be attributed to a) a reduction in grain size of the alluvial material in the more distal area and b) to an increase of the lacustrine fraction in the distal fan area.

7.2.2 Aquifer Material

Alluvial fans are semi-circular (assumed for the Wadi Shueib fan), but lateral constrictions, i.e. the influence of neighbouring fans (assumed in the case of Wadi Kafrein and Wadi Hisban fan), lead often to elongated fans perpendicular to the mountain front (Blair 1987). On elongated fans incised channels may transport sediment masses away from the mountain front to the active depositional lobes of their respective fans. Their presence highly influences the form of the fan. Alluvial fans generally have a planconvex geometry and slopes ranging from 2 to 6° in sheetflood dominated environments and up to 30 to 40° in the zone of freefall accumulations (Blissenbach 1954). But slopes within the study area might be lower due to the deposition of the lacustrine facies deposited to a higher extent in the mid basin and to smaller extents near the mountain fronts, thus reducing the general slope of the topography. Larger portion of alluvial material are deposited at the outlets of the major wadis. Along the depositional areas less alluvial and more lacustrine material accumulated. The area between the alluvial fans are dominated by lacustrine sediments. This assumption is undermined by lithological well logs (Appendix), the well water samples (chapter 5.2), and the classification results of the available VES (chapter 5.3). Taking these information together results in an onion shaped geometry around the outlet of the major wadis, where there coarsest material is found close to the apex and the finest distally from the alluvial fan. Consequently, as far as the distribution of hydraulic conductivities are concerned, highest conductivities are expected close to the fan apex of the major wadis. From there the hydraulic conductivity of the unconsolidated material diminishes further towards the west, either circular (Wadi Shueib alluvial fan) or elongated (Wadi Kafrein/Hisban alluvial fan). Lowest hydraulic conductivities are expected distal of the fan apex and in the sedimentary depositional shadow between the major alluvial fans. This proposed behavior is undermined by different well tests (chapter 4.3).

Since the outlet of the major wadis are also geological synclines (chapter 2.2.3.1), the transmissivity in these areas are also higher due to the increased thickness of the unconsolidated material.

7.2.3 System Boundaries

Groundwater flow is from east to west, or east-north-east to west-south-west. The results of the hydrochemical and geophysical investigations indicated that no flow takes place from north to south or from south to north. Therefore the northern and southern boundaries can be regarded as no-flow boundaries. Groundwater inflow from the adjacent consolidated mountain aquifers into the studied unconsolidated aquifer takes place. Therefore a flux from east into the studied aquifer can be assumed.

However, as it was described in the hydrogeological section, the flux is limited to the synclinal structures. The anticlinal structure between the synclines prevent the inflow of groundwater into the studied aquifer. Therefore a flux can only be assumed in the vicinity of the outlet of Wadi Shueib in the north and the outlet areas of Wadi Kafrein and Wadi Hisban and southeast of it. In the southwest and west of the study area (area of the Dead Sea and the Jordan River respectively) two different boundaries can be assumed: either a fixed head boundary or a flux boundary. MERC (2004) estimated a contribution of saline groundwater of around 10% to the Jordan River water. For the study area, this would amount to an average outflow of groundwater of around 3 Mm³ per year in to the Jordan River.

7. Flow modeling

A constant head boundary condition was assigned to the vicinity of the Dead Sea and the Jordan River.

However, the flux out of the model domain was monitored to fit the estimation made by MERC (2004).

7.2.4 Flow Path

The flow path was determined in chapter 6.4, where freshwater is entering the unconsolidated aquifer either from infiltration of surface water streams or from inflow of groundwater from the adjacent consolidated mountain aquifers. The inflow into the unconsolidated aquifer happens only in the area of the Wadi Shueib and the Wadi Kafrein syncline (chapter 2.2.3.1). This area coincide with the infiltration of the surface water streams of the major wadis. From this area groundwater flows towards the west or west-southwest. This could be seen in groundwater salinity maps, where the groundwater salinity increase along its flow path and becomes already brackish in the mid-fan area. Since the salinity of groundwater (in a north-south profile) is higher in the area between the major alluvial fans, the groundwater salinity maps show further, that no flow between the two major alluvial fan flow paths exists. The groundwater flow gradient (high groundwater flow velocities) is small in the area dominated by alluvial material and becomes more and more steep on the way towards the west ad southwest of the study area. The steepest gradients (low groundwater flow velocities) can be observed in the vicinity of the Jordan River and the Dead Sea. This behaviour was also verified by the direct-push drilling along a north-south profile in the vicinity of the Dead Sea. This can be attributed to a) a reduction in grain size of the alluvial material in the more distal area and b) to an increase of the lacustrine fraction in the distal fan area.

7.2.5 Recharge

Recharge to the unconsolidated aquifer in the study area derives from three different sources: inflow of groundwater from the adjacent mountain aquifers, percolation of stream water from intermittent streams and during occasional intensive rainfall events. Since rainfall in the study area is very low (chapter 2.1.2) the amount of recharge from the third source can be neglected for the overall water budget. Different aquifers might contribute to the groundwater inflow into the studied aquifer. In the area of Shuneh the Wadi As Sir Formation (Upper Aquifer) underlies directly the unconsolidated aquifer. Further to the south, in the area of Rama and south of it, the unconsolidated aquifer is underlain by the Naur Formation (Fig. 7-4 left). For the same area even a contribution of the Ram Group aquifer (chapter 2.3) through an open fault system is possible. A large portion of groundwater recharge comes from infiltrating stream water that percolates along the flow course of the major wadis (Wadi Shueib, Wadi Kafrein, and Wadi Hisban). These intermittent streams flow seasonally during the winter rainy season and dry out towards the end of the summer season.

7.2.6 Groundwater abstraction

No water meters were encountered in the agricultural wells during the conducted field campaigns.

Remote sensing data minimum groundwater abstraction rates were calculated for available remote sensing data. Together with information about plant growth, irrigation practises and irrigation water sources, an estimation of minimum groundwater abstraction for different time steps was performed.

These estimations are addressed in the water budget section (chapter 6.7). A second major source of groundwater abstraction is evaporation. The reduction of groundwater transmissivities in the distal fan area leads not only to steeper groundwater flow gradients, but also to ponding of groundwater in the western area. Artesian conditions were reported in the area prior to the development of the area (chapter 3). In some areas the ponding of groundwater leads to steady state evaporation from bare soils of shallow groundwater tables. These wet soils can be observed either directly in the field, on aerial photographs, or in high resolution satellite images. Shallow groundwater under these wet soils were also encountered during direct-push soundings in the study area (chapter 5.3.4). The areas of groundwater evaporation are not steady, but vary with time. The largest area of groundwater evaporation from bare soils can be observed after the rainy season. From this time onwards the area of groundwater evaporation diminishes, but even at the beginning of the rainy season, large areas remain

still under steady-state evaporation conditions. These areas were mapped from available remote sensing data and groundwater discharge of the aquifer system as a result of evaporation was estimated.

However, evaporation losses might have been considerably larger in the past. Ionides (1939) reported many shallow hand dug wells, thus indicating very shallow groundwater conditions. With the beginning of the major development phase of the lower Jordan Valley groundwater levels declined and these hand dug wells fell dry. This can be taken also as an indicator that the area of the so- called

“wet” areas diminished thus reducing the extraction of groundwater by steady-state evaporation.

Another reason may be attributed the drop of the Dead Sea level during the last five decades by about 27 m with the corresponding lowering of the groundwater levels in the surroundings as a result of the readjustment of the salt/ freshwater interface and the lowering of the Jordan River bed along its flow path to the west of the study area.

Fig. 7-2: Conceptual model of flow of the unconsolidated aquifer in the study area.

7.3 F

M

7.3.1 Model set-up and parameter estimation

A considerable amount of input data is required to construct and verify a distributed flow model. The information gathered in the previous sections will be used to set-up this distributed flow model. The numerical flow model is based on the FEFLOW code (FEFLOW 5.2, WASY Ltd.). Input parameters were pre-processed by ArcGIS 9.2 (ESRI Ltd.).

Two different areas were distinguished for the creation of the supermesh elements: areas dominated by the alluvial fan facies and areas dominated by lacustrine facies. The area dominated by the alluvial fan facies was estimated based on the hydrochemical and geophysical sections (Fig. 7-3). Due to the active left lateral motion of the Dead Sea Transform Fault the elongated alluvial fans of Wadi Kafrein and Wadi Hisban experienced a north-south displacement. For the Wadi Shueib alluvial fan a semi circular shape was chosen, since most of the alluvial fan is located away from the main displacement fault. A triangular mesh of 29,438 elements with 14,960 nodes was generated on the base of the

7. Flow modeling

digitized results of the previous sections. In the influence areas of the surface wadis, the triangular nodes were generated and refined along the drainage line of the different surface wadis (Fig. 7-4 right). The mesh was refined in areas of high groundwater in- and output, e.g. along the flow course of the different wadis, and manually altered to avoid numerical problems with obtuse angles.

The following boundary conditions were set: No-flow at the northern, southern borders, and, for reasons stated above, in the middle of the eastern border. Fluxes were applied to the upper and lower part of the eastern boundary to simulate groundwater inflow from the adjacent consolidated mountain aquifers. Fixed-head boundaries were applied to the western boundary of the model domain. The recharge to the aquifer by infiltration of surface water was given by flux boundary conditions along the wadi flow path.

The calibration of a model is always crucial. The main problem is non-uniqueness. In order to reproduce observed values, e.g. groundwater elevation contours, unknown or not sufficiently known transmissivity etc. have to be adjusted. Accordingly, an over-parameterized model is unlikely to predict the impacts of a change in the system correctly, no matter how high the correlation between the calculations and the observations are. Just as crucial as the number of calibration parameters is their selection. Highly dependant parameters can produce identical results with different combinations.

The constraints for the hydrogeological model are subject to the following consideration: the groundwater tables should be reproduced correctly. This comparison between predicted and measured data is an important measure for the reliability of the final model. The verified model can afterwards be used to demonstrate impacts on future water abstraction scenarios and climate changes on the groundwater resources.

Fig. 7-3: Assumed influence area of alluvial fan sediments, depicted from the interpretation of VES and EC contour plots.

The transmissivities have been measured at several locations. Pumping test data revealed changes in transmissivity between the upper fan area and the lacustrine dominated area (in an area that solely is made up of lacustrine formations in the distal fan area, no pumping tests were performed) are more than one order of magnitude. The information gathered for the setup of the conceptual flow model with regard to the flow materials was applied insofar, that the concentric zones of transmissivity (onion layers) were adjusted to the respective alluvial fan shapes (Fig. 7-5 left), where highest transmissivities were applied to the alluvial dominated areas in the upper fan area and lower

The transmissivities have been measured at several locations. Pumping test data revealed changes in transmissivity between the upper fan area and the lacustrine dominated area (in an area that solely is made up of lacustrine formations in the distal fan area, no pumping tests were performed) are more than one order of magnitude. The information gathered for the setup of the conceptual flow model with regard to the flow materials was applied insofar, that the concentric zones of transmissivity (onion layers) were adjusted to the respective alluvial fan shapes (Fig. 7-5 left), where highest transmissivities were applied to the alluvial dominated areas in the upper fan area and lower