Modeling Wastewater Management Options with a Water Evaluation and Planning Tool (weap) for Wadi Nar Watershed, West Bank, Palestine

Water supply is a critical issue in the Middle East, particularly in the West Bank and Gaza Strip (Palestine). Water resources are scarce due to the arid climate and the population growth while water resources management and development is complicated by the ongoing Israeli occupation. There is a critical lack of sanitation in the West Bank. Only 45% of the Palestinian population is connected to a sewer network; the majority of households dispose of domestic sewage into unlined cesspits. There is currently only one operational wastewater treatment plant (WWTP) in the West Bank, so most of the sewage is directly discharged to the environment without treatment. Reuse of treated wastewater has great potential to alleviate this problem and improve crop yield. This paper presents a case study in the Wadi Nar Watershed (WNW) in the West Bank. The Water Evaluation and Planning Tool (WEAP) was used for mapping the management options related to wastewater reuse in WNW. Results show that WEAP is a sound management tool that can visualize the impact of key factors on the treated wastewater quantities and corresponding total area of wastewater reuse. INTRODUCTION The Middle East region including West Bank suffers from a chronic shortage in water resources accessibility. One of the most potential and promising alternative solutions is to reuse the treated wastewater for irrigation in agriculture. Wastewater management challenges are increasingly common. In water scarce regions, treated wastewater becomes a valuable alternative water resource for agricultural use. The identification and evaluation of different wastewater management options requires the integration of manifold issues to meet the needs of all stakeholders involved in the decision making process. This paper aims at documenting the development of a Water Evaluation and Planning (WEAP) tool for mapping the management options related to wastewater reuse in Wadi Nar Watershed (WNW), West Bank, Palestine. WNW is a watershed that extends from the eastern hills of Jerusalem and drains into the Dead Sea as shown in Figure 1. Twelfth International Water Technology Conference, IWTC12 2008 Alexandria, Egypt 2 Figure 1. Location of WNW in the West Bank The watershed lies entirely within the eastern groundwater basin of the Mountain Aquifer and is contained within Jerusalem and Bethlehem governorates. Figure 2 depicts a multitude of general properties of the watershed. Apparently, WNW is of great heterogeneities in terms of ground surface elevation, head contours of groundwater, evapotranspiration, rainfall distribution, subsurface formations, and aridity. For a detailed elaboration of these issues, see Mutlak et al. (2006) and HWE (2007a). Twelfth International Water Technology Conference, IWTC12 2008 Alexandria, Egypt 3 Figure 2. General properties of Wadi Nar catchment PROBLEM IDENTIFICATION WNW witnesses the disposal of untreated wastewater into the main wadi course. Wastewater originates from the major Palestinian cities and local communities in the area, including East-Jerusalem that are inhabited by a total of approximately 135,000 residents. The on-going practice of the disposal of untreated wastewater into the Wadi course forms a health hazard, does not comply with the environmental requirements, and may potentially contaminate the underlying aquifer. Management options proposed for WNW would imply the reuse of the generated wastewater by installing wastewater treatment plants in the area. Based on the work of HWE (2007a) and Klawitter et al. (2007), Figure 3 shows the expected population size of the study area by year 2035, the corresponding water consumption, wastewater generation, and the area of land needed to implement an economically-sound wastewater reuse scheme. Twelfth International Water Technology Conference, IWTC12 2008 Alexandria, Egypt 4 Figure 3. Current and expected future population, water consumption and wastewater production, and proposed land to be equipped for potential wastewater reuse in the study area SCOPE AND OBJECTIVES This paper aims at documenting the development of a Water Evaluation and Planning (WEAP) tool for mapping the management options related to wastewater treatment and reuse in WNW. Scope of work includes the following:  To map the recent wastewater collection situation;  To visualize and describe different wastewater management scenarios taking into account increasing wastewater quantity caused by population growth and increasing central water supply;  To build up the WEAP model allowing for the simulation and analysis of various treated wastewater use scenarios in relation to the availability of land fit for irrigation in WNW. The WEAP model developed for WNW takes into account the following management options (Klawitter et al., 2007): Option I: Reuse of wastewater from all Palestinian communities including East Jerusalem. This option connotes the construction of a centralized treatment plant for wastewater generated from all the Palestinian communities (including East Jerusalem) linked to WNW. Option II: Under the second option, there are two alternatives:  (IIa) reuse of wastewater from all Palestinian communities excluding East Jerusalem. This implies the construction of one separate treatment plant for the wastewater from all the Palestinian communities (excluding East Jerusalem) linked to WNW; Twelfth International Water Technology Conference, IWTC12 2008 Alexandria, Egypt 5  (IIb) Reuse of wastewater from all Palestinian communities in East Jerusalem through a separate wastewater treatment plant for the wastewater originated from these communities. Therewith, WEAP visualizes the following planning output spatially and temporarily (among others):  Amount of water consumed by each community in the study area based on the activity level (population size and per capita water consumption on daily basis);  Amount of wastewater generated from each community in the study area;  Amount of wastewater treated by each proposed wastewater treatment plant; and  Total agricultural area that can be irrigated adequately. METHODOLOGY AND IMPLEMENTATION In order to achieve the research objectives, we implemented the methodology depicted in Figure 4 and outlined in the subsequent sections. Figure 4. A pictorial representation of the methodology We started by gathering the available relevant information mainly from the discussion papers developed within the overall study. In addition, information was obtained through meetings and workshops. This important step facilitated the conceptualization of the WEAP model. In addition, this is a guarantee that the data used and the options mapped are in full concordant with the other team members. After collecting relevant data, work objectives were developed and existing problems were comprehended such that the objectives address these problems. Twelfth International Water Technology Conference, IWTC12 2008 Alexandria, Egypt 6 Conceptualization was a crucial step since it precedes the development of the WEAP model. The conceptualization rotated around the design of the management options that were agreed upon earlier. We relied largely on the study of Abu-Madi (2006) in mapping the management options and in creating the WEAP model. After determining the options and the designation of the related input parameters, WEAP models that address the different options were developed and tested accordingly. WEAP results were verified for the different options by comparing them with the results presented by Abu Madi (2006). The outcomes from running the WEAP models developed to map the above-mentioned options are presented and analyzed in the following sections. CONCEPTUALIZATION OF MANAGEMENT OPTIONS Existing conditions – status quo This scenario considers the existing conditions. Conceptually, Figure 5 depicts this scenario. Almost 2 million cubic meters (mcm) of raw wastewater are recently being dumped in the Wadi untreated. Figure 5. Conceptual representation of the status-quo scenario Twelfth International Water Technology Conference, IWTC12 2008 Alexandria, Egypt 7 Option I: Reuse of wastewater from all Palestinian communities including East Jerusalem This option connotes the construction of a centralized treatment plant for the wastewater generated from all the Palestinian communities (including East Jerusalem) linked to WNW. Figure 6 depicts the conceptual representation of this option. The location of the WWTP is next to Ubeidiya located within WNW. Figure 6. Conceptual representation of the first management option (Option – I) Option IIa: Reuse of wastewater from all Palestinian communities excluding East Jerusalem This implies the construction of one separate treatment plant for the wastewater from all Palestinian communities (excluding East Jerusalem) linked to WNW. Figure 7 depicts the conceptual representation of this option. Option IIb: Reuse of wastewater from all Palestinian communities in East Jerusalem through a separate wastewater treatment plant for the wastewater originated from these communities This implies the construction of one separate treatment plant for the wastewater generated from the Palestinian communities in East Jerusalem. Figure 8 depicts the conceptual representation of this option. Twelfth International Water Technology Conference, IWTC12 2008 Alexandria, Egypt 8 Figure 7. Conceptual representation of the Option – IIa Figure 8. Conceptual representation of the Option – IIb DEVELOPMENT OF WEAP MODELS General description of WEAP WEAP stands for Water Evaluation And Planning System (see Figure 9). Twelfth International Water Technology Conference, IWTC12 2008 Alexandria, Egypt 9 Figure 9. The opening window of WEAP WEAP is developed by the Stockholm Environment Institute (SEI) based in Boston, MA, US. WEAP Can be downloaded from www.weap21.org. WEAP is a tool for integrated water resources planning and provides a comprehensive, flexible and user friendly framework for policy analysis and impact assessment. WEAP is comprehensive, straightforward, easy to use, and attempts to assist rather than substitute for the skilled planner. As a database, WEAP provides a system for maintaining water demand and supply information. As a forecasting tool, WEAP simulates water demand, supply, flows, storage, pollution generation, treatment and discharge, etc. As a policy analysis tool, WEAP evaluates a full range of water development and management options. WEAP operates on the basic principle of water balance where it places the demands (water use patterns, equipment efficiencies, reuse, prices and allocation) on an equal footing with the supply (streamflow, groundwater, reservoirs and water transfers). WEAP is applicable to municipal and agricultural systems and single catchments or complex transboundary water systems. Additional information about WEAP is available at www.weap21.org.