Predictive Simulation of Flow and Solute Transport for Managing the Salalah Coastal Aquifer, Oman

A three-dimensional numerical model for flow and solute transport was used for the management of the Salalah aquifer. The model calibration procedures consisted of calibrating the aquifer system hydraulic parameters by history matching under steady and transient conditions. The history of input and output of the aquifer were reconstructed in a transient calibration from 1993 to 2005. Predictive simulation of the aquifer was carried out under transient conditions to predict the future demand of groundwater supply for the next 15 years. A baseline scenario was worked out to obtain the piezometric surface and salinity distribution for the “business as usual” conditions of the aquifer. The “business as usual” scenario was predicted and simulated for the period 2006 until 2020. The effectiveness of seven management options was proposed and assessed for comparison with the “business as usual” conditions. The established simulation model was used to predict the distribution of the piezometric surface, salinity distribution, and mass balance under the proposed scenarios for the prediction period 2006–2020. The scenarios were: (1) relocate Garziz and MAF farms far from the freshwater zone, (2) suspend the abstraction of grass production for 4 months a year, (3) changes in agricultural and irrigation system patterns, (4) establish a desalination plant, (5) combined scenario (1 + 4), (6) combined scenario (1 + 3), and (7) combining all scenarios (1 + 2 + 3 + 4). The result of the simulation shows that the best effective option in terms of aquifer groundwater levels is the fifth proposed scenario and the sixth proposed scenario is the best effective option in terms of aquifer groundwater salinity situation during the next 15 years. This project suggested the application of scenario 6 as it is environmentally sound in terms of sustainable management. A prediction has been made which shows that further actions have to be taken within the next two decades to ensure continuity of the municipal water supply. The management scenarios are examined in the case of the Salalah coastal aquifer using groundwater simulation, which can also be applied to other regions with similar conditions. The established model is considered a reasonable representation of the physical conditions of the Salalah plain aquifer, and can be used as a tool by the water and environmental authorities in the management of the groundwater in the region.