RAINFALL-RUNOFF MODELLING OF BHAGIRATHI CATCHMENT USING MIKE 11

Abstract

This study presents a rainfall runoff modeling of Bhagirathi catchment using the MIKE 11 NAM model from the Danish Hydraulic Institute (DHI). The study case applied to the model is the Bhagirathi catchment above Uttarakashi. Open source data rainfall, temperature and evaporation are used. This report describes the application of a conceptual rainfall runoff model to investigate the peak and monthly flows at the Bhagirathi River Basin in Uttarakhand. Observed discharge data at maneri bhali is used for calibration and validation of model. There are seven rainfall and temperature grid stations in this catchment. The evaporation grid station are two because of having resolution of 0.50 xO.50 but rainfall and temperature having resolution of 0.25°xO.25°.The catchments comprising of seven sub catchments were delineated using l-IEC-GeoHMS 10.2.The catchment was delineated using Shuttle Radar Topographic Mission digital elevation model (SRTM DEM) of 3-arc second resolution. Again with the help of ArcGIS 10.2.2 the thiessen gage weights were determined. MIKE 11 NAM uses these gage weight to determine weighted rainfall. 10 The time series observed flow data was divided into four seasons monsoon, post monsoon, winter and summer. The model was calibrated using observed one year daily stream flow data (1989) season wise and then validated for next five years (1990-1995). The simulated peak flow occurred in 1989 with approximate values of 76.1285m3/s on I9' May. The reliability of MIKEI 1 NAM was evaluated based on the Nash Sutcliffe efficiency Index (El) and water balance error (WBL). For summer season the El and WBL obtained during the calibration is .737 and 5.7%. The El and WBL obtained during the validation periods (1990, 1993, 1994, 1995) are 0.137 and 3.5%, 0.495 and 2.8%, 0.607 and 5.7%, 0.579 and 7.4%. The NAM model is good for the catchment for the summer season with the used input time series data.