MODELING OF RUNOFF AND SEDIMENT OUTFLOW FROM A BASIN USING HEC-HMS

Abstract

For sustainable management of natural resources for a watershed area, analysis of resources is compulsory. The analysis of water resource can be achieved with the support of appropriate calibrated and validated hydrologic model. Hydrologic Engineering Center Hydrological Modeling System (HEC-HMS) is a widely used hydrological model used worldwide to simulate rainfall-runoff modeling and surface erosion. The present study has been undertaken to model rainfall-runoff and sediment outflow on Vamsadhara river basin in south part of India using HEC-HMS model. This watershed is located between Mahanadi and Godavari river catchment in India draining a total catchment area of 7927.55 km2. Surface runoff and sediment yield have been found to have large variability in the basin due to spatial variation of precipitation and catchment heterogeneity. In this study, the HEC-GeoHMS 10.4 have been used to prepare the basin model, meteorological model, and control specifications to account spatial heterogeneities of basin characteristics. The developed model was exported in HEC-HMS to model runoff and sediment yield from the basin. Soil Moisture Accounting (SMA) method has been used for continuous simulation of hydrological modeling in the HEC-HMS model on the study area. The model was calibrated using observed independent data from 1994-2002 To compute the surface soil erosion, Modified Universal Soil Loss Equation (MUSLE) was used in HEC-HMS model on Vamsadhara River basin. GIS is used for generating topography factor (LS), soil erodibility factor (K), crop management factor (C) and conservation practice factor (P) using DEM, soil map and Land use cover map of the study area. The model has been calibrated using observed data from time period (1994-97) and validated using independed data from years (1998-02) to estimate the runoff and sediment load on daily basis. The performance of the model during runoff calibration ranges from good to best model with NSE=0.75, coefficient of determination R^2=0.80, PEP=10.6%, PEV=4.65%. Similarly, for runoff validation, the model performance could be rated as very good with NSE=0.775, PEP=2.4%, PEV= 8.5%. On the statistical Evaluation, the maximum sediment load generated from the Vamsadhara river basin was 304564589.24 tons in 2000-time year. The Calibrated sediment yield NSE efficiency was 72.56, co-efficient of correlation R^2=0.78 during 1994 to 1997. Similarly, The NSE efficiency was 69.34 and co-efficient of correlation R^2=0.68 was found during validation periods from 1998 to 2002. iii Sensitivity analysis has been completed on the 11 parameters of the SMA model to check the sensitivity of parameters to rainfall-runoff modeling. The sensitivity of the model parameter varies from -40% to +40% in stage of 20% possession another parameters constant. It is found that soil storage is the maximum sensitive parameter trailed by soil percolation, maximum infiltration, tension storage and impervious layer. Remaining constraints have been found to be less sensitive with soil (%) to be the least sensitive. Overall the model performance has been satisfactory in simulating rainfall-runoff and sediment outflow from the Vamsadhara river basin using HEC-HMS model and developed model could be used for hydrological simulation in the basin.