ANALYTICAL STUDY OF SELECTED REACH OF THE GANGA RIVER FOR HARNESSING ITS WATER RESOURCES

Abstract

The Ganga River fluvial problem is very complex and multi-disciplinary. The occurrence of braided channel and shoal formation behaviour at different locations due to the sedimentation is the root cause of insufficient navigation. The least available depth (LAD) is less than 1.5 m in many stretches and even less than 1 m at some places. Also Ganga is losing day by day huge prime lands to bank erosion. The effective sediment management of streams, creating the required LAD for navigation, effectively control the predominant channel instability process to achieve concentration of stream flow to generate desired draught is the basic prerequisite for the reasonable and durable navigation channel in the Ganga River. To address this complex technical problem of the Ganga in the location falling between around Varanasi (UP) and downstream around Bhagalpur (Bihar) approximately 700 kms has been selected. The problem relating to depleting stream flows, insufficient navigation channel depth with stream bank erosion, habitat shrinkage of aquatic mega fauna like dolphins, and growing power demand; the innovative application of series of low cost un-gated PK Weir type barrages provided with navigation lock and fish pass is • suggested. As these types of low barrages will invariably be submerged during high floods, it is desirable to provide relatively higher crest levels of PK Weir to sustain its discharging superiority over conventional dams and barrages. Also PK Weir increases the specific flow 3 to 4 times than any other convectional barrage or weir and makes it - more efficient. SRTM DEM data are used as elevation data for terrain analysis & mathematical model investigation is examined in HEC-RAS software. Based on the model developed, six different locations approximately 100 kms apart are identified and a chain or cascade of PK Weir type barrages with varying configuration is simulated in such a way that the creation of back water storage of adjacent PK Weir reaches to successive upstream one. The prime advantage of PK Weir is creation of in-channel storage in the Ganga River is to meet the rising demands for inland Navigation, incidental Hydropower, environmental flow, besides drinking water. Also cost effective channel improvement techniques are suggested to prevent flood water going to habitat lands and help in channclization by controlling river bank erosion and improving navigation depth.