Hydrological Modeling of Burhi Gandak River Catchment, Bihar using HEC-HMS
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Date
2022
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DRPCAU, PUSA
Abstract
Hydrologic simulation has become essential tools for understanding
environment and human influences on river flows and designing ecologically
sustainable water management approaches. The present study was carried out in the
Burhi Gandak catchment having an area of about 10913.1 sq. km up to Samastipur
gauging site (outlet) using SRTM DEM. This flat and elongated watershed had a
mains stream of 6th order and experiences less discharge in a short period. The length
of overland flow and the constant of channel maintenance had high values, which
suggests that the river catchment streams experienced delayed discharges. Due to a
high percolation rate, a high chance of groundwater recharge is anticipated on
mountainous terrain with a low drainage density (0.57 km-1). In the HEC-HMS, under
the loss method, SCS-CN method was chosen, while in the transform method clark’s
unit hydrograph and SCS unit hydrograph were chosen. For the flood routing method,
the lag method was applied in the HEC-HMS model. The calibration of the model
was done with Monsoon data -2020 and the validation was done with Monsoon data -
2021. During the years 2017 and 2020 Waterbodies, flooded vegetation, agricultural
land and rangeland increased by 30.02%, 7.96%, 6.88% and 27.7%, respectively.
There was a 16.33%, 4.6%, and 21.34% decline in the built-up area, forest land and
barren land, respectively. The computed peak discharge was 1683.3, 1910, and 2292
m3/sec and the RMSE was found 0.5 in all cases – calibration, optimization and
validation periods, respectively. The NSE value was 0.70, 0.78, and 0.765, the percent
bias was 14.01%, 3.74%, and -3.13%, and R2 was 0.77, 0.79, 0.77, respectively for
Calibration, optimization and validation. The maximum discharges of five extreme
events predicted for monsoon season-2017 were found to be 1.68%, 1.98%, 2.48%,
5.05%, and 4.23% higher for monsoon season-2020, respectively. While the fiveminimum
simulated discharges (2020) were higher than the minimum simulated
discharge (2017) by 20%, 240%, 225%, 245.16%, and 296.23%, respectively. Due to
changes in both land use and land cover during 2017 and 2020, there was an increase
in the catchment's flow and a noticeable difference between the discharge in 2017 and
2020. The amount of runoff increased by 18.58% between 2017 and 2020.