The WEAP estimated results for the current base year 2013 and for the future years reaching 2095 show the river in poor conditions, especially in case no actions are taken to improve the situation. The estimated scenarios result by WEAP show the benefits and the drawbacks of each scenario.
4.1. Current Results:
The current 2013 WEAP estimated results mentioned in Table 11, show a total water demand equal to 381.9 MCM/yr, and a total water requirement equal to 597.91 MCM/year at the ULRB which matches with the studies done on this area concerning this topic. Alameddine et al. compute a total water demand 390 MCM by the year 2010 (Alameddine et al., 2018). Moreover, a study assesses a domestic water demand 83.3 MCM/yr, an industrial water demand 33.4 MCM/yr, an agricultural water demand 250 MCM/yr and an agricultural water requirement 415 MCM/yr with 60% efficiency corresponding for 35,500 ha of irrigated crops (H. Jaafar et al., 2017). These estimated values give a total water demand of 367.7 MCM and a total water requirement of 531.7 MCM/yr, thus matches the results in the Table 11. Whereas in a study done by the USAID, and before the Syrian crisis, total water demand was less, especially the domestic one. USAID researchers compute a total domestic demand 21 MCM/year corresponding to 380,000 capita, an industrial demand 5 MCM/year and an agricultural demand 249 MCM/year corresponding to a 45,700 ha of irrigated area (USAID-LRA, 2012c).
Concerning the water supply, the current WEAP estimated results show a surface water withdrawal equal to 266.6 MCM/year which approximately matches with Alameddine et al. and Jaafar et al. who computed a surface water supply 200 MCM/year at the year 2010 and 206 MCM/year at the year 2016, respectively (Alameddine et al., 2018; H. Jaafar et al., 2017). Regarding groundwater supply, the WEAP estimated result show a 329.2 MCM/year, in match with Jaafar et al. who mentioned a 320 MCM/year groundwater abstraction for agriculture only at the year 2016 (H. H. Jaafar & Ahmad, 2020). In contrast, a groundwater withdrawal was estimated at 190 MCM/year at the year 2010 and 156 MCM/year (Alameddine et al., 2018; USAID-LRA, 2012c). Moreover, a groundwater withdrawal for irrigation sector only was found to vary between 130 MCM/year and 200 MCM/year (Nassif, 2016). Besides, Molle et al. mentioned a 415 MCM/year groundwater withdrawal considering the irrigation efficiency at the year 2017 (Molle et al., 2017). Differences in groundwater extractions estimations mainly are due to the efficiency in water networks. Some studies take in account this efficiency and others mention the need of water which is the demand of sites from the groundwater, regardless the efficiency of water networks.
Concerning the river’s water quality, the current results estimated by WEAP are discussed in the section (3.2.) and compared with other studies. Having a look on those results shown in table 8 and comparing them with the limitations shown in table 6, illustrates the problem. All of the nitrates, the total dissolved solids, biochemical oxygen demand and the phosphates represent concentrations higher than permissible.
4.2.Future Results:
4.2.1. Scenario 1 results: Reference scenario:
The WEAP estimated results show that the unmet demand begins at the year 2023 and reach about 225 MCM at the year 2050 as shown in Fig. 6a which approximately matches the prediction done by Alameddine et al. that is equal to 200 MCM at the year 2050 (Alameddine et al., 2018). Jaafar et al. mentioned an unmet demand of 114 MCM at the year 2016 (H. Jaafar et al., 2017), however, in this study, this unmet is covered by the groundwater. The WEAP estimated groundwater result shows a decline in its volume estimated to be 103.76 MCM at the year 2013 which is lower than that estimated by Ministry Of Environment (MOE) at a value of 221 MCM at the year 2011 (UNDP, Ministry Of Environment, 2011). Other studies estimated much lower groundwater volume depletion at the values 45.7 MCM/year at the year 2013 (Nassif, 2016), 65 at 2014 (UNDP, 2014), 87 MCM/year at , 2016 (H. Jaafar et al., 2017), 70 MCM/year at 2017 (Stokvis, 2017), and 57.5 MCM/year between 2010 and 2016 (FAO-IHE DELFT, 2019). The WEAP groundwater volume results continue by declining its initial storage which is 8.19 BCM at the year 2013 to reach a storage of 4.43 BCM and 3.57 BCM at the year 2050 and 2095, respectively, as shown in Fig. 6b. Concerning the WEAP results related to the river flow, it represents a decline in its volume from 529 MCM at the year 2013 to reach 460 MCM and 367 MCM at the year 2050 and 2095, respectively, as shown by Fig. 6c. This decline is a result of a higher future water volume’s withdrawal that is causing a drop of about 1.8 MCM/year in the river volume. This drop is almost matching that mentioned by Jaafar et al. who estimated an average rate decreasing volume 1 MCM/year between the years 1966 and 2011 (H. Jaafar et al., 2017). Moving to the WEAP estimated results concerning the river’s water quality, it shows a huge increase in pollutant’s concentrations in the river by time as shown by Fig. 7. The nitrates, TDS, BOD, and phosphates average yearly concentrations are increasing from 6.25 mg/L, 494.44 mg/L, 48 mg/L, and 6.3 mg/L at the year 2013 to 8.48 mg/L, 574.6 mg/L, 56.26 mg/L, and 8.14 mg/L at the year 2095, respectively, as shown in Fig. 7. These results combining the increased unmet demand with the decreased river and groundwater volumes, associating with the morbidly deteriorated water quality makes clear that solutions must be found. For this purpose, the scenarios results are discussed in the section below, in order to get to an optimum solution that saves the water resources of the Bekaa valley.
4.2.2. Suggested Scenarios results:
Scenario 2 results: (GWR)
The groundwater abstraction restrictions (GWR) scenario shows a huge increase in the unmet demand caused by the limited supply from groundwater. The unmet demand reaches 427.46 MCM at the year 2050 and 791.12 MCM at the year 2095 as shown by the Fig. 6a. Although the groundwater storage volume witnesses a huge increase in its storage volume that reaches 12.82 BCM and 17.33 BCM by the year 2050 and 2095, respectively as shown by the Fig. 6b. This limitation caused a stress on the litani river which in result cause a decline in its flow volume to reach 438.65 MCM and 356 MCM by the year 2050 and 2095, respectively as shown by the Fig. 6c. Regarding the river’s water quality results in this scenario, the nitrates, TDS, BOD, and phosphates average yearly concentrations witness a drop from 6.25 mg/L, 494.44 mg/l, 48 mg/L, 6.3 mg/L going from the year 2013 to the year 2030 to reach 5.71 mg/L, 279.15 mg/L, 37.7 mg/L, 5.04 mg/L, respectively. After this drop these pollutants return to increase to reach 8.7 mg/L, 358.8 mg/L, 57.6 mg/L, 7.43 mg/L, respectively, by reaching the year 2095 as shown in Fig. 7. This drop in the pollutant’s concentrations is due to the limited available water for use, that in its turn limits the quantity of polluted water released into the river. Besides, it increases again as a result of the accumulation of pollutants by time in the river. This scenario is rejected although it maintains the groundwater volume; it magnifies the unmet demand and doesn’t improve the river’s water quality which prevents achieving the main objectives of the study.
Scenario 3 results: (WQI)
The water quality improvements scenario shows a decrease in the unmet demand caused by the increase in the availability of adequate river water for use. The unmet demand reaches 3.35 MCM and 253.31 MCM by the year 2050 and 2095, respectively as shown by the Fig. 6a. Although the groundwater storage maintains its volume over several years to reach 8.21 BCM at the year 2050 then it returns to decline to reach 5.83 BCM at 2095 as shown by the Fig. 6b. This improvement stressed the litani river which in result cause a decline in its flow volume to reach 324.97 MCM and 197.2 MCM at the year 2050 and 2095, respectively as shown by the Fig. 6c. Moving on to the river’s water quality WEAP results; the nitrates, TDS, BOD, and phosphates average yearly concentrations show a huge continued decrease from 6.25 mg/L, 494.44 mg/L, 48 mg/L, 6.3 mg/L, at the year 2013 to 3.48 mg/L, 284.08 mg/L, 17.73 mg/L, 2.1 mg/L at the year 2095, respectively, as shown in Fig. 7. This scenario can be accepted since it achieves almost all the goals of this research; it maintains the groundwater volume over several years, decreases the unmet demand and saves river water from the pollution.
Scenario 4 results: (EFFI)
The efficiency improvements scenario shows a decrease in the unmet demand, besides the supply requirement also decreases, a result of the decline in the losses throughout the water networks. The unmet demand reaches 166 MCM and 469 MCM by the year 2050 and 2095, respectively as shown by the Fig. 6a. Despite the groundwater storage volume that declines throughout the years, but still better than the one of the reference scenario, it reaches 5.17 BCM and 4.65 BCM by the year 2050 and 2095, respectively as shown in Fig. 6b. This improvement almost shows a result like the reference scenario results. Concerning the litani river volume, it declines to reach 466 MCM and 377 MCM by the year 2050 and 2095, respectively as shown by the Fig. 6c. In the other hand, the WEAP estimated water quality results show an increasing average yearly concentration of the nitrates, TDS, BOD and phosphates going from the year 2013 that records 6.25 mg/L, 494.44 mg/L, 48 mg/L, 6.3 mg/L, to the year 2095 that records 7.5 mg/L, 517.8 mg/L, 49.26 mg/L, 7.26 mg/L, respectively as shown in Fig. 7. This scenario is rejected since it is similar to the reference one, it doesn’t present any remarkable advantages.
Scenario 5 results: (WQI & EFFI)
The combining improvements scenario shows a huge decrease in the unmet demand caused by the increase in the availability of adequate river water for use and by the decline in supply requirement. The unmet demand reaches 2 MCM and 114 MCM by the year 2050 and 2095, respectively as shown by the Fig. 6a. Although the groundwater storage shows an increase in its volume over several years then it decreases to reach 9.1 BCM and 5.81 BCM by the year 2050 and 2095, respectively as shown by the Fig. 6b. These improvements caused a huge stress on the litani river which in result cause a decline in its flow volume to reach 340.9 MCM and 235 MCM by the year 2050 and 2095, respectively as shown by the Fig. 6c. Besides, the WEAP estimated results concerning the water quality of the Upper Litani River was found to be better. The nitrates, TDS, BOD and phosphates average yearly concentrations are decreasing from 6.25 mg/L, 494.44 mg/L, 48 mg/L, 6.3 mg/L at the year 2013 to reach 2.94 mg/L, 207.58 mg/L, 14.87 mg/L, 1.53 mg/L, respectively, at the year 2095 as shown by Fig. 7. This scenario is accepted since it conserves the groundwater volume, decreases the water loss and the unmet demand and saves river’s water from pollution.
Scenario 6 results: (GWR & WQI & EFFI)
The combining improvements and groundwater abstraction restrictions scenario shows an increase in the water unmet demand caused by the restrictions on the groundwater withdrawals. The unmet demand reaches 253 MCM and 389 MCM by the year 2050 and 2095, respectively as shown in Fig. 6a. This scenario is almost like the groundwater abstraction scenario. Although the groundwater storage witnesses a huge increase in its volume to reach 15.33 BCM and 23.32 BCM by the year 2050 and 2095, respectively as shown in Fig. 6b. The Litani river is under a stress caused by the availability of adequate water for supply and the limitations on groundwater supply. The litani river volume reach 340 MCM and 232 MCM by the year 2050 and 2095, respectively as shown in Fig. 6c. Regarding the WEAP estimated water quality results, this scenario shows an improvement in pollutants concentration. Hence, the average yearly concentration of the nitrates, TDS, BOD and phosphates is decreasing from 6.25 mg/L, 494.44 mg/L, 48 mg/L, 6.3 mg/L at the year 2013, to reach 2.8 mg/L, 144.24 mg/L, 13.8 mg/L, 1.1 mg/L, respectively, at the year 2095 as shown by Fig. 7. This scenario is rejected although it increases the groundwater volume, saves the river’s water from pollution; it increases the unmet demand which conflicts with the research objectives.
The scenarios results estimated by WEAP shows that the best scenario which represents sustainability in the water resources accompanied by the lowest water unmet demand is the scenario 5 which includes both improvements WQI&EffI scenario. This sustainability is assessed by the maintenance of the groundwater volume and the good river’s water quality. Those results show the need of policy-makers to really take an action to beat the upcoming severe climate conditions and growing population. The necessary actions will be represented by some technical and political improvements, which transform the wastewater from burden to benefit, and will create a smart water management plan. To reach this end, a set of wastewater treatment plants must be planted and designed to treat an additional 200 MCM/year effluent volume by the year 2095, equivalent to a total capacity of 265 MCM/year. Moreover, the water and wastewater networks must be tested and renewed if necessary; focusing on the separate sewer systems instead of the combined one.