International SWAT Conference at IIT Madras in Chennai, India January 8-12, 2018 Assessing Impact of Land use/Land cover Changes on Stream flow in Noyyal River catchment using ArcSWAT model Leelambar Singh 1 , S Saravanan 2 and Jacinth Jennifer 3 1,3 Research Scholar, Civil Engineering Department, NIT Trichy, Tamilnadu, India 2 Assistant Professor, Civil Engineering Department, NIT Trichy, Tamilnadu, India Abstract Water is one of the most important natural resources of any country, which determines all the development activities. Accurate determination of streamflow is required for water resources planning, design and management of all hydrological structures. Catchment hydrology and its local ecosystem are highly affected by the changes in the land use and climate pattern in the catchment. uIn this study, we developed a hydrologic model for Noyyal catchment which is highly urbanized and rapid changes in is land use and land cover (LULC) pattern. The hydrologic model was created using the Geographical Information System (GIS) supported Soil and Water Assessment Tool (SWAT) model for forecasting the streamflow in the river basin. The monthly observed streamflow data at the catchment outlet from 2000 to 2013 were employed for calibration and validation.. Shuttle Radar Topography Mission (SRTM) DEM 30 meter resolution and hydro-meteorological data used for the preparation of the model. Hydrological modelling was conducted for each of the LULC(2003 and 2007) maps in time periods in the Noyyal catchment using Landsat TM and ETM images. Changes in hydrological components between two simulations using LULC maps in 2000 and 2013, respectively, were related to changes of LULC in a multiple regression to quantify the effect of changes in LULC to that of hydrological components at the sub basin scale. From this study, it is concluded that future changes in the LULC are most likely to produce significant impacts on the surface runoff and water yield in the study area. Keywords: Streamflow, SWAT, Noyyal river catchment, hydrological model. Introduction: Urbanization causes the severe problem of LULC changes in the river basin due to rapid population growth. (Fohere et al., 2001, Foley et al., 2005; Silberstein et al., 2012). Without considering the future environmental sustainability of land use changes is increasing the demand of water, soil and agricultural for survival (Lu et al., 2004; Santhiya et al., 2010). In past decades, LULCs changes are the most focused and interested area in research field because, where they changed the runoff, evaporation, sediment yield, groundwater recharge, vegetation, wetland and water yield (DeFries and Eshleman, 2004; Singh and Katpatal 2018). Various countries having limited water resources, rapidly changing underground use and facing several problems related to climate change (Watson et al., 2000; Pielke 2005). In different region of India, rapid urbanization and development have made massive changes in socio-economic aspects, and in future, it is estimated to have further effects (Lambin et al., 2003). Therefore, hydrology is an important step in watershed management strategies water resources planning and conservation measures. Hydrological models gives the advantage of spatial mapping and allows for the consequences and comparisons of the water science generated by the change in land use (Marshall et al., 2005). The most common purpose of most land use models is to simulate the future flexibility of the landscape in different coherent scenarios on many scales (Kok and Verburg, 2007) and the sensitivity of the main processes within the land use has been increased. For proper evaluation of future groundwater improvement effects, there is a need to understand the previous changes in the underground on