Impacts Assessment of Land Use Change on Surface Water Using L-THIA Model in Gorgan Area

Land use changes, mostly relate to great socio - economic benefits, however, many of these changes cause negative effects on the natural environment. One of the important effects is the direct reduction of water resources and water quality. An effective approach in assessing the effects of land use change on water resources is using hydrological models. In the present study, the effects of land use change on surface water in the Gorgan area was evaluated using L-THIA model. The L-THIA model for evaluating long-term effects of land use change on water resources uses available and simple data such as long-term climate data, and land use. In this study we covered 19 years in the period 1988-2007. Land use maps were generated from satellite imagery for the years 1988, 1998 and 2007. The 30-year daily rainfall data were obtained and hydrologic soil groups were also distinguished on soil maps. The model results showed the average amount of runoff depth from 1988 to 2007 changed from 28/55 to the 29/18. Results from the model indicated increased volume and depth of surface runoff in the studied time interval. This shows the necessity of monitoring land use changes in order to control the depth and volume of runoff. The results of this study can assist managers make decisions and monitor land use changes to control changes of depth and volume of runoff in the area. Output maps identified areas high in the mean runoff based on which management programs to control runoff rates can be implemented in the area. Also, the results of this study can be used to prevent increased runoff by controlling land use changes in the area.