Saltwater Intrusion Modeling: Verification and Application to an Agriculturally Used Coastal Arid Region in Oman

This paper deals with numerical modeling of groundwater systems. Ensuring the sustainability of an aquifer’s yield is one of the fundamental tasks for nowadays groundwater management, especially within agriculturally used regions. Within the context of the research project ”International Water Research Alliance Saxony” (Kalbus et al., 2011, submitted), the groundwater quality of near-coastal, agriculturally used areas under the influence of marine salt water intrusion is investigated. In the bounds of the study region’s coastal areas, i.e. the Batinah plains of Northern Oman, an increasing agricultural development and a concurrent lowering of the groundwater level was observed during the last decades. Decreased groundwater levels cause an inversion of the hydraulic gradient which is naturally aligned towards the coast which leads to an intrusion of marine salt water endangering the productivity of farms near the coast. Utilizing the open source modeling software packageOpenGeoSys (OGS, OpenGeoSys (2011)), a three-dimensional, density-dependent model is currently being built up. The model, comprehending a part of three selected ∗Corresponding author Email address: [email protected] (M. Walther) Preprint submitted to Journal of Applied Mathematics July 26, 2011 coastal wadis of interest, will be used to investigate different management scenarios. The modelling’s main focus are the optimization of pumping schemes and, in long-term view, the coupling with a surface run-off model, which is also used for the determination of the groundwater recharge due to wadi run-off downstream of retention dams. Also, the highly uncertain local hydro-geological conditions and scarcity of data are addressed by utilizing an extended inverse-weighted-distance approach for a three-dimensional interpretation of the aquifer’s properties and the model’s calibration. Based on the current simulations’ output, further scenario investigations will be done, assessing various socio-economic targets (e.g. agricultural water demand, industry etc.). Within these scenarios, marine salt water encroachment should be minimized, thus stabilizing the natural equilibrium between the continental freshwater flux and seawater intrusion ensuring a long-term usage of the agricultural areas. Numerical modeling tools are v ery important to develop those scenarios.