Author(s) :

Abu, R. D..

Volume/Issue :

Abstract :

The Galma earth dam was impounded in 1975 to supply Zaria with drinking water and has a maximum storage capacity of 16 million cubic metres, a maximum depth of 14.9m, a dam length of 640m and a total lake length of 40km. The intensification of cultivation, fuel wood harvesting and other landuses within the catchment of the Galma has resulted in increased soil erosion. This study was carried out with the objective of determining the effects of the present landuse/landcover change on the sedimentation rate of the Galma dam. To achieve this objective, Landuse / land cover changes over the catchment of river Galma were assessed from Landsat MSS 50m resolution (resampled) for the 1970s; Landsat TM 30m resolution for the 1980s; SPOT XS 20m resolution for the 1990s and Landsat ETM 15m resolution for the 2000s.The results reveal that cultivated area increased from 2476.25km2 to 3241.36km2 ; built-up area from 4.06km2 to 13.67km2 from 1970s to 2000s respectively while forest and water body show a reduction of 1085.35km2 to 313.52km2 and 7.12km2 to 5.81km2 from 1970s to 2000s respectively. Area statistics of 203.25km2 was uniform for rock outcrop throughout the decades of 1970-2000. Hydrographic survey of the dam was conducted to determine the level of sedimentation by carrying out depth measurement of the dam from the surface to its bed .The result obtained shows that the dam has lost 7.6m depth to sedimentation; indicating 51% loss in installed storage capacity. The results have significant implications for future water supply to the residence of Zaria.

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