Land-use changes and erosion on some highland soils of Ethiopia.
2003
Selamyihun Kidanu and Tekalign Mamo(Researchers)
The study evaluated changes in land use and the associated gully erosion incidence in the past three and half decades at Ginchi watershed in the central highlands of Ethiopia using two panchromatic aerial photo sets (1957 and 1994) as an input to produce GIS-based cover maps and digital elevation models. The results showed that in the watershed area, cropping expanded at a rate of 3 ha per annum into traditional grasslands, and compared to 1957, cropping has increased by 118%. During the same period the area under woodland and riverine trees declined by 18-20%. Close examination of the land-use change further revealed that 81% of cropland in the base year was maintained as cropland in 1994, while 17% was converted back to grassland. Out of the total grassland in the base year only 33% continued to be under the grass in 1994 while 63%was converted in to cropland. Gully formation was a striking phenomenon, and the total length of the gullies in 1994 was about 12 km (3.8 km km-2) in 1957. Over the same period, the surface area of t he gullies increased from 16.6 ha to 36.2 ha. At a constant rate of expansion, this would present an increment of 5% per year of which 75% came from new gullies. Over t he years, the gullied area under cropland declined by 36% while those under grassland particularly in the upper part of the watershed increased tenfold. This calls for alternative grazing management especially during wet seas9on in order to release pressure on the upper slopes where the risk of environmental degradation and detrimental impact down the slopes remain highest.
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