Groundwater Potentials in Arid Land of Chad

Interpretation of Recent Space Images and Field Surveys

Landsat_Mosaic

In July 2015, the Center for Remote Sensing began a two-year research project to map potential groundwater resources for use in urban and agricultural development in the landlocked Republic of Chad in north Africa.

The terrain of Chad in central Africa is dominated by the low-lying Chad Basin (elevation about 250 m). It rises gradually to mountains and plateaus on the north, east, and south. In the east heights of approximately 1,000 m are attained in the Ennedi Plateau. The greatest elevations are reached in the Tibesti massif in the north, with a maximum height of 3,415 m at Emi Koussi. The northern half of the republic lies in the Sahara. The Bodélé Depression, with the Grand Erg de Bilma, is a low sand-covered region in the southern Sahara that is surrounded by volcanic highlands. Permanent streams do not exist in northern or central Chad as infrequent rain falls on the Tebesti Mountain and Ennedi Plateau. The result is often flash floods, and the streams usually dry out within a few days as rainwater seeps into the subsurface.

The project relies on the processing and analysis of all recent satellite image data to recommend additional groundwater sites that are presently required to satisfy urgent needs. This is important because the landscapes of Chad have not yet been adequately mapped using recent space images, particularly radar and thermal data. Satellite images represent excellent tools for the proposed activity as they have been used in desert regions for groundwater exploration. These include optical images that display surface features, radar data that penetrate sand to reveal underlying topography, Shuttle Radar Topography Mission (SRTM) data that allow three-dimensional viewing of the land features and ASTER and MODIS data that allow mapping thermal anomalies.

Upon the analysis of the most recent satellite images, these will be grouped in a Geographic Information System (GIS) to allow superposition and correlation of notable features. The satellite image analysis and interpretation will be followed by hydro-geophysical surveys in the field. It is further proposed to construct digital maps of all physical features that relate to sites of potential groundwater concentration.