Analyses of Land Use/Land Cover Change Dynamics in the Upland Watersheds of Upper Blue Nile Basin

Abstract

Investigating land use/land cover (LULC) change is important for effective sustainable land resource management and for understanding the changes in hydrological processes. In this chapter, we investigated LULC dynamics in three experimental watersheds: Mizewa (27 km2), Debre Mawi (5.23 km2) and Enchilala (4.14 km2) of upper Blue Nile Basin, Ethiopia. These watersheds are experimental watersheds for investigating runoff processes, erosion, and soil conservation practices. The LULC changes were measured through interpretation of Landsat images of 1973, 1986, 2000, and 2013 supported by repeated field visits. Based on the image analysis and field survey, cultivated, forest, shrub/bush land, and grazing land are the major LULC classes during the study periods. The result showed an increase in cultivated land mainly at the expense of shrub/bush, forest, and grazing land for all three watersheds. The cultivated land increased from 30 to 68 % in Mizewa, from 67 to 80 % in Debre Mawi, and from 55 to 86 % in Enchilala within the past 40 years. This is likely associated with the population that has been steadily increasing at a growth rate of 2–3 % per year during the past five decades. However, the rate of change of cultivated land of Mizewa (27 ha/year) is greater than Debre Mawi (1.5 ha/year) and Enchilala (3.2 ha/year) watersheds. The higher rate of change is the same for the other land uses. This is likely because the rate of expansion of cultivated land into steep slope, degraded, and marginal lands was found to be much more in Mizewa, which is located on the main road from Bahir Dar to Debre Tabor. The expansion of cultivated land and the decrease of vegetative covers through forest will cause a decrease in evapotranspiration and increase in overland and subsurface flow and will increase soil erosion. This leads to growth of numerous gullies as observed in Debre Mawi and Enchilala. Therefore, the current trends in LULC must be improved, toward the resource management and conservation of the existing vegetation and other natural resources in all the three watersheds. These should be done in collaboration with all stakeholders including local communities, government, and NGOs for effective management of natural resources.