UBC Theses and Dissertations
Flow routing model for upper Indus river (Pakistan) Hashmi, Danial
For the flow forecasting of the Upper Indus Basin (UIB) Pakistan, it is observed that large quantities of ungauged lateral flows enter many sections of the Indus River system during the monsoon and the snow melt season. The river is steep, flow travel times are short, and the data are currently available only on a mean daily flow basis. There are very few gauging stations and the travel time between them is less than a day, so that standard routing procedures such as the Muskingum method was difficult to apply because of the large amount of ungauged lateral flows entering the main channel. Calibrating the Muskingum model was therefore difficult because of the ungauged lateral flows, and also because the coefficients used in the Muskingum method are a function of routing period and vary considerably when the routing period is less or greater than the travel time. There was a need for a model which could not only route the flows through the Upper Indus reaches but also could link all the sub basins contributing to the Indus flows. The whole UIB is divided into reaches, and a digital computer Link Model is developed which links these reaches and routes the flows through these reaches using the flow routing method developed by Quick and Pipes. The Link Model adds the known lateral flows to the main channel flows and also calculates the ungauged lateral flows if the stream gauging data for the downstream station is known. This Model can easily be interfaced with the UBC Watershed Model, which forecasts the land phase of the flow and the total system of models can be used for flow forecasting of UIB. The routing method adopted is very flexible and easy to calibrate, because the principal feature of the routing method is that the routing coefficients are determined directly from the stage-discharge and area-discharge measurements at the gauging stations, so the method is pre-calibrated before commencing routing, and therefore avoids the problem of accounting for ungauged lateral inflows. The model has been tested on a 400 km segment of the main stem Upper Indus River, which lies above Tarbela dam i.e, between Besham Qila and Kachura gauging stations Fig (5.1). and was found satisfactory. Given the required data the Model can be used in any similar system.
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