Tropical river basin development- a case study in selection of sites for vented dams

Abstract

Scarcity of water in various parts of the country is of major concern in the recent years. Even places with very high annual rainfall face the water shortage during the non-monsoon months. This indicates scope for the improvement in planning, development and management of water resources. Dakshina Kannada, a coastal district of Karnataka, on an average receives more than 3000 mm of annual rainfall and still faces acute shortage of drinking water during the summer months. The river Netravathi which is a tropical, seasonal river of the district is the major source of water for the region including rapidly progressing Mangalore city with a population of more than 5 lakhs. Due to the hydro-geological characteristics of the area, construction of major dams across the rivers is not feasible. Under these circumstances, construction of small structures such as vented dams may be appropriate in conserving the river water. To achieve the required storage and to conserve the river water, a series of such dams is proposed. The average annual yield of the river is about 11,502 Mm3. At present, the amount of utilized is less than 1% and there is large scope for conserving river water. This paper highlights the site selection criterion for the construction of such vented dams across the river Netravathi. These dams when constructed will allow optimal river basin development without causing inundation. The total capacity of the dams is about 101.91 Mm3 with further scope to increase the height of the dams by providing proper bank protection works. The vented dam at the downstream end of the river nearest to the sea also serves the purpose of salt water exclusion, protecting the adjoining aquifers from salt water intrusion during the summer months. � 2008 Taylor & Francis Group, LLC.