Morphometric Analysis, for Surface Irrigation Assessment by Using GIS and Remote Sensing. A Case Study of Gilgel Gibe Watershed, Oromia, Ethiopia.

Abstract

Morphometric analysis of watersheds has a vigorous protagonist in predicting sites for surface irrigation assessment. Morphometric analysis is the measurement and mathematical examination of the arrangement of the earth’s surface, shape, and dimension of its landform. The present study analyzed the morphometric parameters (liner, areal, and relief parameters) of the Gilgel Gibe watershed for surface irrigation assessment using GIS and remote sensing. DEM with a 30-meter spatial resolution of the study area was used for the morphometric parameters analysis. The results revealed that the stream orders of the watershed vary from first order to fifth order with a total of 1961 stream numbers measuring a total length of 1741.95kms. The analyzed areal aspects such as circularity ratio, elongation ratio, and form factor show the shape of the watershed is elongated, contains moderate value of bifurcation ratio, low value of drainage density, low stream frequency, generated slopes map shows larger areas of this watershed near flat. Overall, the morphometric analysis reflects that the watershed is favorable for surface irrigation development and it can benefit the local community to meet the food demand. Based on evaluated compound values of all morphometric parameters those sub-watersheds are ranked from 1st to 7th. By considering those ranks of all sub-watersheds, priority for suitability was given. SW-1 and SW-5 are classified under high-priority classes. Whereas SW-2, SW-3, SW-4, SW-6 and SW-7 are under medium priority classes. For a more proper evaluation of the watershed for surface irrigation development, further investigation on the physical land suitability analysis of the watershed is needed.