GEOMORPHOLOGICAL ANALYSIS AND HYDROLOGICAL MODELING OF THREE HIMALAYAN CATCHMENTS OF NEPAL AND INDIA

Abstract

In the present study the hydrological response of three Himalayan catchments namely Bhagirathi at Maneri Bhali-I (India), Bhilangna at Ghansali (India) and Madi at Sishaghat (Nepal), have been critically examined in terms of geomorphological characteristics. Hydrological modeling using HEC-HMS semi-distributed model has also been carried out for the three basins. The twenty five numbers of geomorphological features namely basin length, basin order, bifurcation ratio, channel length ratio, channel area ratio, stream frequency, drainage density, drainage texture, infiltration number, constant of channel maintenance, channel gradient, basin relief, relief ratio, length of overland flow, rho coefficient, ruggedness number, sinuosity index, elongation ratio, circularity ratio, form factor, shape factor, compactness coefficient, and drainage basin similarity have been derived for three basins using ASTER DEM (30m×30m) downloaded from the website www.earthexplorer.usgs.gov by analyzing in GIS environment. HEC-HMS with the help of HEC Geo-HMS extension in ArcGIS environment has been used to set up using DEM, soil and LULC information, hydro-meteorological data etc. for the basins and the performance of the model has been evaluated for all the basins. The geomorphological analysis of the study basins shows that the Madi basin of Nepal and Bhilangna basin of India have some similar geomorphological features, viz. areal extent, topography, elongation ratio, drainage density, drainage texture etc. while that of MB1 is different in most of the geomorphological aspects. Also, the hydrologic responses deduced from the geomorphological characteristics showed that the Bhilangna basin is closer to the Madi basin. The overall HEC-HMS model results show that the efficiency for the MB1 and Bhilangna are ranging from NSE=0.60 to 0.70 and R2 = 0.65 to 0.75 for calibration and validation periods. The NSE and R2 for the Madi basin are 0.79 and 0.80 respectively. Finally, it was found that the Madi and Bhilangna basins are geomorphologically similar in most of the geomorphological attributes and the HEC-HMS model performance is good for MB1 and Bhilangna and very good for the Madi basin. However, the HEC-HMS model performance for the Bhagirathi and Bhilangna basins can be improved using either fine resolution grid data or the station data. The results of the geomorphological characteristics should be linked with the flow characteristics.