Simulation of Moisture and Recharge in Sand Dune using 'SWIM' Model

S.A. AlHassoun (Saudi Arabia)


Mathematical Modeling, Soil Moisture, Sand dune,Recharge .


Recharge to aquifers is considered as the main source of groundwater, while moisture in the soil has a big role on the plant growth and evapotranspiration processes and on the quantity of recharge of groundwater to aquifers. Thus, prediction of soil moisture content and aquifer recharge has an important impact on water resources management especially in arid and semi-arid countries like Saudi Arabia where vast areas are covered with sand dunes underlaid by groundwater aquifers. In this study, a numerical model named 'SWIM' or 'Soil Water-Infiltration and Movement Model' is used to simulate soil moisture distribution and to estimate aquifer recharge in sand dune in Qassim region in Saudi Arabia. The model is based on finite difference method which solves Richard’s equation for unsaturated flow. Input data to the model such as rainfall rate, evaporation, capillary head, hydraulic conductivity…etc, are obtained from the measurements in the laboratory and from field data using different instruments normally used for moisture content determination. Model results of moisture evolution in sand dune proved the powerful and effectiveness of 'SWIM' model in prediction of moisture in dune areas. Results also showed that the recharge to aquifer below 'Qassim' dunes, during study period, is about 11% of precipitation.

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