Abstract:
In this study basin runoff was simulated using the computer model of the Hydrologic
Engineering Centre-Hydrologic Modeling System, called HEC-HMS for the upper part of
the Halda river basin given rainfall and catchment parameters. The graphical user
interface of the HEC-HMS was used to edit, execute and view model data. Data needed
for this study included soil, land use, digital elevation model, point elevation, contour
line, stream network, rainfall, evaporation, and river discharge. Detailed stream network
was created using topographic maps of 1:50000 scale. Required maps and data were
collected from Water Resources Planning Organisation (WARPO), Institute of Water
Modeling, and Soil Resources Development Institute. The HEC Data Storage System
(DSS) was used for storage and retrieval of time series data. Geographic Information
System (GIS) tools e.g. Arc/Info 8.02 and Spatial Analyst of ArcView 3.2 were used for
delineating watershed and stream network from Digital Elevation Model (DEM).
The chosen basin area was divided into sub-basins and the loss rate parameters such as
interception, infiltration and base flow were estimated. Most of the parameters i.e. canopy
interception and surface storage, soil profile and tension zone depth of Soil Moisture
Accounting (SMA) model were calibrated during simulation. No groundwater zone was
considered in this study region because percolation rate became zero as model suggested.
Flow directions, flow accumulation points, flow path lengths, sub-basin areas were
determined from DEM. Hydrologic modeling parameters (i.e. length of longest flow path,
SCS curve number, lag time, stream velocity, Muskingum X, Muskingum K etc.) and
appropriate rainfall station weightage were estimated using ArcView GIS as input
parameter of the model. The rainfall excess was transformed into direct runoff using Soil
Conservation Service (SCS) unit hydro graph method. Runoffs from subbasins were
combined at the confluences and hydro graphs routed through a channel network using
Muskingum channel routing.
The simulated daily runoff for the entire year was compared with the observed runoff and
that computed using another lumped conceptual model called NAM model of the Danish
Hydraulic Institute.
The peak flow of simulated runoff was 426.08 m3/s on 24th June and observed runoff was
202 m3/s on 24th June. NAM computed peak flow was 405.61 m3/s on 25th June. Thus
HEC-HMS overestimated the peak runoff by 52.3% as compared to observed peak runoff
and by 4.8% as compared to peak runoff by NAM model. HEC-HMS and NAM results
agreed reasonably well.
