The Impact of Land Use/Land Cover Change on Hydrological Components due to Resettlement Activity: SWAT Model Approach

Abstract

Modification of land use systems constitute use/land cover and hydrology. Though the qualitative impact of disappearance of forest, agricultural expansion, and modifications of other land use systems is well understood, quantified results are necessary to understand the magnitude of the effect of a proposed action plan and make informed decisions based on them. Recent advances in distributed hydrological models integrated with Geographic Information Systems (GIS) are of great help in this regard since they overcome temporal and spatial limitations helping in quantifying these impacts for big watersheds for longer time periods. The results from the studied watersheds studied revealed that agricultural and forest covered areas significantly differed between years 1972 and 2007. A distributed hydrological model Soil and Water Assessment Tool (SWAT) is used in this study to quantify changes in land use/land cover that impacted hydrology of Anger Gutin resettlement area. Application of statistical analysis for fitness of observed and simulated flow values using the Nash- Sutcliffe coefficient (ENS) and correlation coefficient (R2 ) resulted 0.725 and 0.81 respectively while validation results for the two statistical measurements were 0.62 and 0.68 respectively. Land use land cover maps of 1972, 1986, and 2007 were used as input to quantify changes that occurred as result of land use changes. Analysis of Variance (ANOVA) carried out to assess significance of differences for means (p # 0.05) for outputs of SWAT in watersheds studied revealed that there is a significant difference within sub watersheds for all hydrological variables and sediment simulated except for potential evapotranspiration and sediment concentration. Sediment concentration in sub watersheds that are found in or around urban areas is found to be higher than other sub watersheds. Water yield also increased during wet seasons (May - September) by 42.61% and 40.18% in watershed one and two respectively while declined during the dry season (October – April) by 20.61 % and 24.18 % for watersheds one and two, respectively. Simulated results for both watersheds supported the qualitative truth that modified land use/land cover affect hydrology. From the results of the analysis of SWAT, it is concluded that the model can be used as a decision support tool before such big schemes like resettlement projects commence.