The water resource utilized for social activities in Djibouti is almost exclusively groundwater which is abstracted by shallow wells from the porous sediments in wadis with estimated thickness of several meters to around 20 meters, and by deeper wells from the fractured zone of basaltic base rock. Because of small annual precipitation and high geological ambiguity associated with wadis and fractures, to find out new good groundwater locations is not an easy task in Djibouti.
In this project, utilizing collected various field data, we try to construct numerical hydrologic models for estimating groundwater movement through wadis and fractures. A terrestrial fluid flow simulator GETFLOWS is used for this purpose, in which surface/subsurface coupled flows under precipitation/evapotranspiration are dealt. It might be able to reproduce and visualize occasional flooding through wadis at rainfalls, infiltration into the wadi sediments, and flow/retention of groundwater in wadi networks.
For the first modeling site, we deal Ali Faren catchment, a small part of large Ambouli watershed which spreads in the south-west of Djibouti City.
Using the satellite image of Google Earth and high-resolution DSM (AW3D supplied by RESTEC), the target area including wadi networks and base rock surface were discretized three-dimensionally into around 35,000 horizontally and 15 vertically, with corner-pointed structured grid system.
In the symposium, we will present the modeling procedures, settings of geological conditions and hydraulic parameters, and results of simulation including model equilibration, calibration and prospecting case studies.