TR-58 : Hydrological network design for Narmada basin

Abstract

Hydrological and hydraulic design of water resources projects depend to a considerable extent on the information about hydrological processes obtained through observations at measurement sites/stations. In spite of its importance, studies for determining optimum density of hydrometric network in general and stream-gauging network in particular are not extensive in many countries, and particularly so in India. Two basic scientific problems in network design are; how many data acquisition points are required and where to locate them.

In this study, methodology and computation steps of physical-statistical method to determine representative catchment area per stream gauging station have been explained in detail. Guidelines for selection of stream-gauging sites have been highlighted. This methodology has been applied for Narmada basin using available annual flow data for five sites namely; Jamtara, Barmanghat, Mandleshwar, Rajghat and Garudeshwar. For reach Jamtara-Garudeshwar 36 years of data was available, while for Jamtara-Mandleshwar, Jamtara-Rajghat, Barmanghat-Mandleshwar, Bramanghat-Rajghat and Barmanghat-Garudeshwar reaches only 9 years data was available.

Variation of stream gauging area per station with catchment area between the various considered reaches has been studied for the available data. The effect of variation in sample length on stream gauging area per station has also been studied.

It is seen that as sample length increases from 9 to 36 years, the catchment area per station decreases from 4, 183 km² to 2,411 km², following a linear pattern. In case of variability with river basin area covered by river reach, there is no systematic pattern, but there is general decrease of catchment area per station from 3,928 km² to 1 ,221 km² as basin area covered by the river reaches increases from 47,693 km² to 72,395 km².

On the basis of this study, with somewhat limited data a basic network density of one station per 2,41 1 km² area for developing relationships of hydrological parameters of the basin could be recommended for Narmada basin upto Garudeshwar. This does not include secondary and special purpose stations.