International Journal of Agriculture: Research and Review. Vol., 2 (S), 942-948, 2012 Available online at http://www.ecisi.com ISSN 2228-7973 ©2012 ECISI Journals EVALUATING HYDROLOGICAL RESPONSE TO LAND USE CHANGE USING THE AGWA-GIS BASED HYDROLOGIC MODELING TOOLS HABIB NAZARNEJAD 1* ,KARIM SOLAIMANI 2 ,KAKA SHAHEDI 2 AND VAHEDBERDI SHEIKH 3 1- PhD student, Faculty of Natural Resources, Sari Agriculture and Natural Resources University, Sari, Iran 2- Faculty of Natural Resources, Sari Agriculture and Natural Resources University, Sari, Iran 3- Watershed Management Department, Gorgan University of Agricultural Science and Natural Resources, Gorgan, Iran *Corresponding Author Email: hnazarnejad2000@yahoo.com ABSTRACT: Planning and assessment in land and water resource management are evolving from simple, local-scale problems toward complex, watershed-wide regional ones. Such problems are addressed with numerical models that can compute runoff in large watersheds with varying soils, land use and management conditions. The GIS-based tools, such as the Automated Geospatial Watershed Assessment - Soil and Water Assessment Tool (AGWA - SWAT), can be used to illustrate the effects of land use practices on runoff, and to support watershed-wide land use management decisions. This paper illustrates how AGWA acts as a powerful and flexible tool for managing watershed resources and understanding as well as predicting complex and changing system of watersheds. AGWA has been applied to automates the process of converting commonly available GIS data to input parameter files compatible with the SWAT hydrologic model in the Bustan Dam watershed in northeast of Iran. Input parameters were processed using AGWA in conjunction with available topographic, soil and landcover data in the study area. Key words: AGWA, Bustan dam Watershed, GIS technology, Hydrologic modeling, Runoff, SWAT INTRODUCTION In developing countries where resources are scarce and ever increasing population pressures create stress on available resources, methods are needed to examine the effects of human induced pressures and resulting land cover changes. Understanding such effects through spatially explicit watershed modeling opens the door for monitoring and correlating environmental change with socio- economic and health changes (Cirone et al., 2000; King et al., 1999; Patz, 2001; Troyer, 2002). The primary objective in this study was to determine the suitability of the Automated Geospatial Watershed Assessment (AGWA) tool in assessing hydrologic change in the Bustan Dam Watershed in northeast of Iran where floods and soil erosion over deep and fertile loess soils are major environmental issues. The Automated Geospatial Watershed Assessment (AGWA) tool is a multipurpose hydrologic analysis system to use by watershed, water resource, land use, and biological resource managers and scientists in performing watershed and basin-scale studies (Burns et al., 2004). It has been developed by the U.S.D.A. Agricultural Research Service’s Southwest Watershed Research Center. AGWA provides the functionality to conduct all phases of a watershed assessment for two widely used watershed hydrologic models: the Soil and Water Assessment Tool (SWAT); and the KINematic Runoff and Erosion model, KINEROS2. SWAT (Arnold et al., 1994) was developed by the USDA Agricultural Research Service (ARS) to predict the effect of alternative land management decisions on water, sediment and chemical yields with reasonable accuracy for ungagged rural watersheds. It is a distributed, lumped-parameter model that