International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 – 8958 (Online), Volume-9 Issue-6, August 2020 183 Retrieval Number: F1309089620/2020©BEIESP DOI: 10.35940/ijeat.F1309.089620 Journal Website: www.ijeat.org Published By: Blue Eyes Intelligence Engineering and Sciences Publication © Copyright: All rights reserved. Abstract: Runoff is a very important phenomenon of hydrological cycle and it is relevant for the watershed management programme for conservation and development or natural resources and its management. However, In India the availability of accurate information on runoff is very scarce and needs to be calculated empirically for further developments. The Soil and Water Assessment Tool (SWAT) is a physical parameter model which has been developed to estimate values for the runoff, sediment and nutrient carry off from the agricultural watersheds under various distinct land management practices. For the present study, a small agricultural watershed has been selected for runoff assessment. Watershed is considered to be the ideal unit for management of the natural resources. Extraction of watershed parameters using Remote Sensing and Geographical Information System (GIS) and use of mathematical models is one of the current trends for hydrologic evaluation of these watersheds monitored. The Soil and Water Assessment Tool (SWAT) having an interface with Quantum GIS (QGIS) software (QSWAT version 1.3) was selected for the estimation of surface runoff from an area of Punpun basin near Patna an intermediate watershed of Punpun river, located in southern Bihar region. Maps of the region obtained from the Bihar Remote Sensing Application Centre (BIRSAC) were used for computation. The model was run and validated with the observed runoff and for the years 2005-2010. The performance of the model was evaluated using statistical and graphical methods to assess the capability of the model in simulating the surface runoff from the study area. According to the model estimates, the value for the surface runoff was maximum for the year 2007 as 710 mm and was minimum for the year 2005 with about 185 mm. As per the observed values of discharge from the Central Water Commission (CWC), the values for surface runoff for these years were different by about 10 to 11%. Keywords: Surface Runoff, QGIS, DEM, SWAT. I. INTRODUCTION Surface runoff is a crucial to be estimated for a better resource management and to promote a sustainable environment. It’s one of the main reasons for soil erosion and hence its simulation becomes important to help making some Revised Manuscript Received on July 20, 2020. * Correspondence Author Aditya Shekhar, Department of Civil Engineering, IIT Kanpur, U.P., India. E-mail: sardi@iitk.ac.in Subha Sinha*, Department of Civil Engineering, Department, M.I.T. Muzaffarpur, Bihar, India. E-mail: starsubha@gamil.com © The Authors. Published by Blue Eyes Intelligence Engineering and Sciences Publication (BEIESP). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/ ) reliable land use and land management practices [1]. Floods have been common occurrence in the Punpun basin situated in Bihar, India that makes it vital to have a close estimation of hydrological parameters that are the main cause [2]. Today, Mathematical models are being used to evaluate parameters like Runoff, Soil erosion, Sediment yield, prompt overflow and other important values that defines the area in terms of its water intake or release. Interpretation with GIS technology helps to generate accurate runoff models. Various models like Water Erosion Prediction Project (WEPP), Limberg Soil Erosion model (LISEM) etc. have been commonly used nowadays like researchers to simulate values for these parameters. The SWAT (Soil and water assessment tool) model has been checked by many different authors and validation have been published for various basins. SWAT 2005 was selected for the present study and a 5-year simulation was performed for a small watershed inside the huge Punpun basin, situated in the state of Bihar. II. STUDY AREA AND DATA COLLECTION 1. Study Area a) Description of location Punpun River is one of the important river bank tributaries of the Ganga River. It originates from the Chottanagpur hills of Palamau district at an elevation of 300 m in Bihar. The length of the river is 200 km and it is mostly rain fed and carries minimal discharge during non-monsoon period. It often causes heavy flood damages on the eastwards side of the Patna city. Roughly trapezoid in shape, the catchment length is about 180 km and average widths in the upper and lower reaches are 60 km and 25 km respectively. The catchment area of the basin is about 8,500 km 2 . This is 1% of the total area of Ganga basin in the country. A watershed has been selected near the Patna district and the surface runoff modeling has been done for the same. The figure 2 shows the watershed area selected. The watershed number 24 as per the nomenclature done in boundary generation was selected for SWAT modeling. The area of the watershed is 720 sq kilometers and extension is: South Latitude: 25.28464 degrees; NWest Longitude: 84.76438 degrees E; North Latitude: 25.559372 degrees; NEast Longitude: 85.304751 degrees E. b) Hydrology of the Region The Lower Ganga plain system consists of the tributaries as well as the distributaries of the main Ganga. Bhagirathi and Padma comprise of the important ones. Hydrological Simulation of Runoff for a Watershed in Punpun Basin using SWAT Aditya Shekhar, Subha Sinha