Developing a GIS-based Hydrological Model : With special reference to Darfur region

Abstract

This research work concentrated on using Geographic Information Systems (GIS) techniques to produce digital-hydrological maps and to formulate a useful tool for rainfall-runoff estimation. Produced maps were based on elevation data provided by Shuttle Radar Topography Mission, SRTM. Use of such maps enables proper planning of various water-harvesting projects and integrated water resources management in the area. Hydrological mapping was done through several sub-software models. Analysis of produced maps emphasized the use of Digital Elevation Models, DEMs. DEMs generate adequate and better quality maps than manual interpretation from direct satellite imagery. Visual BASIC for Applications (VBA) programming language techniques were used in this work to formulate a computer model to be run under ArcMap software environment. Formulated Curve Number-Runoff Estimation Model (CN-REM) was formulated and tested to read input data in the form of digital maps (soil types, land uses and rainfall) for any study area. This procedure allows determination of the Curve Number (CN) for each polygon according to the Soil Conservation Service (SCS) method. Testing, operation and verification of model was done on large and small scale levels for Greater Darfur area (in western Sudan), and Abu Hamra area (in Darfur) respectively. Estimated values of volumetric water discharge in Wadi Abu Hamra were related to results obtained by Abu Hamra Water Harvesting Project Team (AHWHPT) using the modified rational method. The discrepancy between the two methods emphasizes the need for CN-REM model calibration against measured results for any region before using the software for runoff estimation Analysis of produced maps emphasized the use of formulated CN-REM rather than relying on laborious manual processes. Time loss was dramatically reduced and resultant maps were highly adequate.