Analysis of land use and land cover changes and their effects on the water balance of Insiza dam catchment

Abstract

Land-use and land-cover changes have an effect on the water balance as well as water yield of catchments in Zimbabwe. Most of these changes can be attributed to economic activities undertaken by communities within the catchments in an effort to improve their standards of living. The research was carried out in Insiza dam-catchment to investigate the effects of temporal land-use and land-cover changes on Insiza dam-catchment water balance. GIS and Remote sensing techniques were used in ENVI 4.2 and ArcGIS 10 to compute and analyse LULC changes in the study area. Three Landsat images for 1989, 1998 and 2008 (path and row of 170 and 74) were downloaded from the USGS website and classified through maximum likelihood to create thematic maps. Change detection techniques were used to compute class statistics as well as accuracy assessment. The LULC changes were then related to the water balance by computing water use and runoff for each land-cover class. The results showed that there were notable changes in LULC in the Insiza dam-catchment from 1989 to 2008 where cropland and grassland had the greatest increase and decrease respectively. Cropland increased by 81.30% following the FTLRP whilst grassland decreased by 154.48%. Although the annual runoff generated increased from 1989 to 2008 by 48.30%, the increase was not significant because of a suspected increase in sediment load due to the increase in bare soil by 56.56%. There is therefore a need for regulation of LULC activities in dam catchments as changes in land-use have an effect on the water balance.