Abstract:
Many methods e.g. empirical formulae, SCS curve number method etc. are used in design discharge computations/ continuous runoff modelling. Using the SCS curve number method, certain empirical relationship of catchment hydrological variables and dimensional unit hydrograph, design hydrograph/ continuous runoff modelling is done. The computations are done for a watershed in Narmada basin for 25, 50 and 100 years return period and the 1- day design storm. The 1- day duration rainfall depths are, respectively, for the above return period are 143, 161 and 181 mm.
Land use mapping is done for a part of Narmada basin from Jabalpur to Hoshangabad. The catchment area is 27900 sq km. The mapping is done using satellite data of sensors WIFS and LISS-3 onboard IRS. WIFS data for September 1997 and February 1997 are used. The LISS-3 data for September 1997 is used.
GIS softwares namely ILWIS and ERDAS are used here. ERDAS (ver. 7.5) is used for the digital image processing. Sequential clustering technique is used. ILWIS is used for computing of watershed physical properties namely length, area and slope.
Curve numbers are assigned to land use cover classes using land use cover map and collateral data on soils. Average curve number is computed for a watershed for design runoff hydrograph computations. The watershed lies in Umar catchment. The areal extent of the watershed is 17.2 sq km. Peak discharge computed for 25, 50 and 100 year return periods using land use map prepared from WIFS and LISS-3 data are respectively 52, 59 and 67; 58, 66 and75 cumec. The design discharge is useful for irrigation/ water resources structures in the watershed.
