The impacts of watershed management on land use and land cover dynamics in Eastern Tigray (Ethiopia)

摘要

Integrated watershed management (IWSM) was implemented to address issues of poverty and land resource degradation in the 14,500 ha upper Agula watershed, in semi-arid Eastern Tigray (Ethiopia), an area known for poverty and resource degradation caused by natural and man-made calamities. The purpose of this study was to assess the impact of IWSM and determine the land use and cover dynamics that it has induced. The change in land use and cover was assessed by integrating remote sensing and geographic information systems (GIS). Two sets of aerial photographs (taken in 1965 and 1994 at scale of 1:50,000) and Landsat ETM+ image (taken in 2000 with 30 m resolution) were used to produce the land use/land cover map and assess land use change. The results reveal significant modification and conversion of land use and cover of the watershed over the last four decades (1965-2005). A significant portion of the watershed was continuously under intensively cultivated (tainted) land. The area under irrigation increased from 7 ha to 222.4 ha post-intervention. The area under dense forest increased from 32.4 ha to 98 ha. The study further shows that IWSM decreased soil erosion. increased soil moisture, reduced sedimentation and run off, set the scene for a number of positive knock-on effects Such as stabilization of gullies and river banks, rehabilitation of degraded lands. IWSM also resulted in increased recharge in the subsurface water. This study reconfirms the importance of IWSM as a key to improve the land cover of watersheds, as a contribution to poverty alleviation and sustainable livelihood.