Water Availability Assessment in a River with Complex Water Transfer System

Abstract

The water availability in a river influence significantly due to change in flow regime because of water transfer from external sources or regulated operations like river diversion, construction of dam, on-stream uses, etc. The assessment of impact of water transfer on water availability in the river is imperative for the planning of water allocation scheme of the river system to meet its on-stream demands. If the water transfer system is complex, then it need capable simulation tool to simulate runoff and assess the water availability in the river at given point of time at a desired location. The flow regime in Kharun river of Chhattisgarh state has been found strongly influenced by regulation operations associated with the water transfer from Ravishankarsagar reservoir to Kharun river and its supply through the series of anicuts to meet various water user demands. Present paper deals with the water availability assessment of Kharun river and estimation of dependable flow at various probability levels at different time periods and analysis of flow regime under virgin and regulated condition using Mike Basin software and Flow Duration Curve technique. The study indicated that the Kharun river is originally an intermittent river having average 1802 MCM flow during monsoon season and 2-3 months thereafter. The river receive average 116 MCM of water from Ravishankarsagar reservoir through direct link and in the form of irrigation return flow, thus river experiences significant rise in dependable flow throughout the lean period which is being used to meet various user demands. The river which runs dry during summer season under virgin condition has found significant rise in stream flow due to water transfer in to the river and dependable flow even at 90% probability of exceedance is observed between 2.83 to 3.26 m3/s.