The Combined Effect of Vegetation and Soil Erosion in the Water Resource Management

Water has always played a vital role in human societies. In order to manage the water resources, many countries have built water reservoirs, for example, dams for sustainable development, growth and poverty reduction. Vegetation, in the watershed region of a dam, plays a very vital role on soil erosion and consequently on the sediments deposition in the water reservoir. This study intends to analyze the impact of vegetation cover on soil erosion and thereby the sediments deposition in the watershed region of a dam by using satellite remote sensing technique. For this, Mangla dam which is one of the most important water reservoirs in Pakistan and its capacity has been reduced by more than 20% since its construction, is selected as the study area. Shuttle Radar Topographic Mission (SRTM) data, onboard the space shuttle Endeavor, was used to calculate the total drainage area for the Mangla watershed. Landsat images for the years 1979, 1980, 1992, 1998 and 2002 were used to estimate the total area of vegetation in the Mangla watershed region. In order to estimate the vegetation area, two vegetation indices, that is, Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) were applied on Landsat MSS, TM, and ETM+ images. The comparison of sedimentation and vegetation data indicates that except for the year 1992, the load of sedimentation in Mangla dam decreases with an increase in the vegetation area in the Mangla watershed region. The maximum vegetation in the Mangla watershed region is estimated in the year 2002, and subsequently, the load of sediments in the same year in Mangla dam is minimum. The current study thus indicates that the soil erosion which is the main reason of sedimentation in water reservoir can be controlled with the help of plantation of various species of vegetation in the watershed region of the reservoir.