CONSTRAINTS ON GROUNDWATER RECHARGE IN ARID ENVIRONMENTS FROM FIELD, REMOTE SENSING DATA AND RAINFALL-RUNOFF MODELS: CASE STUDIES FROM KUWAIT

A common perception amongst hydrogeologists working on modeling the partitioning of precipitation in arid and semi arid lands is that modern recharge is minimal. Using the large Raudhatain Watershed (3,696 km²) as our test site occupying 21% the total area of Kuwait, we highlight geologic and hydrologic settings if present will enhance recharge considerably. We estimate the partitioning of precipitation into runoff, recharge, and evapotranspiration over the test site applying a physically-based, semi-distributed Soil Water and Assessment Tool (SWAT) model and taking advantage of spatially distributed remote sensing and GIS datasets. Over the investigated period (1998- 2006), the examined watershed witnessed a few but extensive precipitation events; ~25 events were reported, 5 of which exceeded 20 mm/hr. No flows were reported at the outlet of the watershed throughout the investigated period and no ponding of water in the lowlands or flat areas was detected on ASTER and Landsat thematic mapper images acquired shortly after (1 to 14 days) each of the major precipitation events (>15 mm) suggesting that infiltration is quite high in the examined areas and is widespread across large segments of the examined areas. These conclusions are supported by: (1) examination of NDVI and soil moisture images which show that the observed increases in soil moisture content and vegetation index following a large precipitation events are not restricted to the valley network, instead they are observed across the total area of the examined watershed, and (2) highly porous soil types (e.g., gravel, sand) and high infiltration rates (up to 9m/day). Using the field and remote-sensing based constraints cited we estimate to a first order the average annual precipitation, average annual runoff, and average annual recharge for the Raudhatain Watershed at : 837 x 10⁶m³, 6.9 x 10⁶m³, and 636 x 10⁶m³, respectively. Results demonstrate the enhanced opportunities for groundwater recharge in the examined watersheds and highlight the potential for similar applications in arid areas elsewhere.