Hydrological Feasibility Of Chandragiri Estuary Towards Augmenting Drinking Water Supply In Kasaragod Municipal Area During Drought Period: A Case Study

摘要

The utilisation of estuaries as a source of fresh water is limited because of sea water intrusion and high salinity especially during summer months. This paper deals with how seawater intrusion can be checked at appropriate place and time in Chandragiri estuary of North Kerala towards using the stored estuarine fresh water to augment the drinking water supply in Kasaragod township during the drought periods. The Chandragiri river discharge data indicates that there is enough water to meet the water supply demand for Kasaragod Municipal area only for the monsoon period and postmonsoon period upto March. It is understood that the leanflow during the last phase of summer is almost nil. The availability of ground water as well as the subsurface flow in the river course during the dry period has already been assed quite insufficient to meet the Kasaragod Water Supply. Scheme. The drinking water requirement for Kasaragod Municipal area has been assed for the present and future. The projected demand assuming a population growth of 2% per annum has been calculated at a consumption rate of 1001pcd as 7 MLD. The worst dry period considered here based on available data is 77 days during March-May. The water demand for this period is 0.54 Mm~3 The hydro environment situation of estuarine reach of Chandragiri river has been studied with special reference to the river flow pattern, estuarine channel storage, sear water intrusion pattern etc and based on this the location of temporary bunding and its time of erection, completion etc are decided. The location of bunding is near Thekkil bridge of NH and time of bunding is second half of December. The storage created by the temporary bund nearer to the Thekkil bridge is worked out as 1.3 Mm~3 against the demand of 0.54 Mm~3. Necessary suggestions has been made regarding the size of bunding, size of opening and its time of closing. The bunding with the help of sand bags will get flushed off during the initial stage of monsoon floods and hence it will not create any flooding upstream. The proposed bund and creation of pool of fresh water upstream may not cause any negative environmental impact or otherwise the entire 20 km of estuarine reach will be saline due to seawater intrusion. Temporary bunding and arresting seawater intrusion into estuaries will be a successful technique to fight the drought situation in coastal Kerala.