A shallow alluvial coastal aquifer in the Batinah area of Oman, with sea-water intrusion that extends several kilometres inland, has been studied experimentally, analytically and numerically. The water table is proved to have a trough caused by intensive pumping from a fresh groundwater zone and evaporation from the saline phreatic surface. Resistivity traverses perpendicular to the shoreline indicated no fresh groundwater recharge into the sea. Using an analytical Dupuit-Forchheimer model, developed for the plain part of the catchment, explicit expressions for the water table, sharp interface location and stored volume of fresh water are obtained. It is shown that by the pumping of salt water from the intruded part of the aquifer, this intrusion can be mitigated. Different catchment sizes, intensities of fresh groundwater pumping, evaporation rates, water densities, sea level, incident fresh water level in the mountains and hydraulic conductivity are considered. SUTRA code is applied to a hypothetical case of a leaky aquifer with line sinks modeling fresh water withdrawal and evaporation. The numerical code also shows that pumping of saline water can pull the dispersion zone back to the shoreline.

A two-dimensional numerical groundwater flow model was established and calibrated for the hyperarid Najd region in southern Oman. The results indicate that recent recharge rates are required to sustain the observed groundwater heads in the Najd. The model was also used to estimate possible ranges of past recharge rates and the effective porosity of the main aquifer unit. Recharge rates during past humid periods were estimated to be no more than 1–3 times modern rates. The effective porosity was estimated to be between 0.06 and 0.093. Insight into the nature of the long-term transport within the aquifer was gained by using transient model runs over the last 350 ka and (1) varying the recharge intensity (from 0.1 to 2.5 times modern), and (2) the timing and duration of humid and dry periods. Finally, results indicate that although recharge rates and the flow conditions have likely changed over time, a steady-state model is capable of reproducing the observed groundwater residence times in the Najd based on carbon-14, helium and chlorine-36 dating.

Hydrochemistry and well hydrographs are coupled to assess groundwater recharge in the regional catchment of Samail, Oman. The complex geology comprises three aquifers: limestones of the Hajar Supergroup (HSG) at the highlands of North Oman Mountains (NOM); fractured/weathered ophiolites; and Quaternary alluvium. Groundwater flows south–north from the NOM to the coast. Samples from groundwater wells and springs (38) were analyzed for isotopes and major ions. Corrected ¹⁴C dating reveals modern groundwater across the entire catchment, while ⁸⁷Sr/⁸⁶Sr (0.70810–0.70895) shows greater homogeneity. Groundwater in the upper catchment is depleted in ²H and ¹⁸O, indicating a high-altitude recharge source (NOM), and becomes enriched downstream, with a slope indicating an evaporation effect. The hydrographs of nested piezometers located in the upper, middle and lower catchment show different recharge responses between deep and shallower depths. Head difference in response to recharge is observed upstream, suggesting a lateral recharge mechanism, contrary to vertical recharge downstream reflected in identical recharge responses. The homogeneous ⁸⁷Sr/⁸⁶Sr ratio, head changes, downstream enrichment of ²H and ¹⁸O, and the presence of modern groundwater throughout the catchment suggest that groundwater recharge takes place across the entire catchment and that the three aquifers are hydraulically connected. The recharge estimated using the chloride mass balance method is in the range of 0–43% of the mean annual rainfall.