This project has done for the estimation of surface runoff for the Tarbela reservoir. The Rational Formula Method was used to determine the surface runoff. The different weighted maps were generated to estimate the overall runoff in a watershed. The weighted soil map, Landcover map and slope maps were generated. Then these maps were overlaid based on the relative weights to the different map types. The weights were assigned proportional to the surface runoff capability of the specific group in each map. Surface Runoff a weights The drainage area was calculated from the flow accumulation. The flow accumulation was gained through the Arc Hydro utility, by terrain processing. The outlet of the flow accumulation provided the high accumulated cell for the whole drainage area. The precipitation data for the year of 2002 in the drainage area was interpolated by the IDW (Inverse distance weighted) to generate the rainfall surface. The rainfall surface was used in the resultant ‘C map’ (weighted overlaid map of (LC+Soil+Slope) and drainage area to calculate the total surface runoff (Q). There are different models to calculate the surface run off, as a literature review during this study. The CN (curve number) and SCS models can also perform the same estimations.
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