Modeling Water Supply and Demand for Effective Water Management in the Sana’a Basin in Yemen

Abstract

Modelling system is the core for the evaluation of water related sectors in the Sana’a Basin. The numerical modelling (MODFLOW) has emerged as an effective tool for managing groundwater resources and predicting future responses, especially when dealing with complex aquifers systems and heterogeneous formations. MODFLOW model has been used herein as a management tool for the targeted sub- basins in Sana’a Basin such (Wadi Bani Hawat, Wadi Dhahr & Al-Ghayl, Wadi Hamdan & As Sabrahand Wadi Ghayman); the most important groundwater resources for domestic and agricultural sectors in Sana’a basin. A conceptual model was designed according to the actual groundwater dynamic flow system in the 2010 Hydrosult Sana’a Basin Model. Also, the governing partial parabolic differential equation was defined, including the vertical conductivity flow between the aquifers. Total groundwater abstraction values from previous studies were compiled, including the 2015 well inventory data of National Water Resources Authority –Sana’a Basin.In this study, three simulations of groundwater development scenarios were distinguished. The first scenario is applied for evaluation of the present status and till 2025. The second and thethird scenarios are focused on the effect of water augmentation i.e. decrease the present rate of groundwater abstraction to 30% and 50% respectively, with considering the highly intervention of IWRM structure of Sana’a basin on the on-going activities related to change land use, change crop pattern, value chain, marketing, modern irrigation techniques, water harvesting techniques, treated waste reuse etc…. Also other Modules were used in calculating the groundwater demand, deficit and unemployment in agricultural sector inSana’a Basin. Scenario 3 gives a remarkable improvement of the water resources system in the four sub-basins within a reasonable period (in the year 2025), thus, it will keep the water resources sustainability; but the unemployment in agricultural sector in Sana’a Basin in scenario 3 will be is the highest value if comparing with the other two scenarios. It will reachin 2025 under scenario 2 and scenario 3 to 10432 and 14762 respectively while in scenario 1 the unemployment will disappeared in 2025. This study is recommended that irrigation systems should be improved, usage of harvesting water methods and treated waste water reuse for agriculture to avoid the depletion of Sana’ Basin aquifer and to reduce unemployment in agricultural sector in Sana’a Basin. Keywords: Groundwater Flow Model, MODFLOW, Management Scenarios, Sana’a Basin, Targeted Sub-Basins.