GIUH models based on uniform and non uniform stream flow velocities
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Date
2006-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present study was carried out with the objective to develop mathematical models for Geomorphologic Instantaneous Unit Hydrograph by considering uniform stream flow velocity as well spatial distributed (non uniform) stream flow velocity along the stream network. In this approach, a unifying synthesis of the hydrological response of a catchment to surface runoff is attempted by deriving equations of general characteristics which express IUH as a function of Horton‟s numbers i.e. area ratio (RA), bifurcation ratio (RB) length ratio (RL), an internal scale parameter (LW) denoting the length of the highest order stream; and the peak velocity of the stream flow (v). In the present study, these geomorphologic properties of the watershed were determined by using Horton‟s stream order laws.
GIUH model formulation was attempted considering the uniform and non uniform stream flow velocities in the watershed network. In case of uniform flow velocity, the stream flow is assumed to be constant throughout the watershed network and the flow velocity was determined from the geomorphological quantities of the network and the intensity of the effective rainfall, while in case of variable velocity model the flow velocity was considered to vary according to the slope pattern of the network of various order of streams. The conceived models were developed by using the geomorphological and hydrological data of a small hilly watershed known as “Arki watershed” comprising an area of 2460 ha in Solan district of Himachal Pradesh (India).
The performance of both the models viz., GIUH with uniform and non uniform flow velocities has been evaluated for the study area considering sixteen storm events by employing various statistical error indices. Based on qualitative and quantitative comparison it was observed that both the GIUH models based on uniform and non uniform flow velocities are applicable for the study area. However, on the basis of the calculated values of statistical indices it was found that the GIUH-UV model performed better in comparison to the GIUH-VV model except in the computation of peak rate of runoff where the GIUH-VV was found to be better performing than GIUH-UV model.
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