Regional flow duration curve for a Himalayan river Chenab

This study is carried out with the objective of examining the effect of altitude on water availability estimates for the various sub-basins of the Chenab river basin (mean elevation of the basin is 3600 m),which is a snow-fed Himalayan river basin located in the western Himalayas. This basin covers all three Himalayan ranges, i.e. outer, middle and greater Himalayas. For this study, the daily flow data of 11 gauging sites varying from 14 years to 23 years in the Chenab river basin are utilised. The other important information related to the physiography, hydrology and meteorology, etc, for the region are derived from the available literature and maps. The daily flow data of nine gauging sites are utilised for developing the regional relationships for water availability computations. These relationships are tested over the remaining two gauging sites. The regional relationships are developed using three different approaches. These approaches include: (i) parameter regionalisation for individual gauged sites of selected probability distribution, (ii) regionalisation of dependable flows and (iii) parameter regionalisation for the region as a whole of the selected probability distribution. The different methods are compared and discussed in detail. It is observed that the flow for a given dependability increases with catchment area and decreases with altitude. The flows of the catchments at higher altitudes exhibit larger variability in comparison to the catchments at lower altitudes. The regional relationships are recommended for the use of field engineers.