Cauvery river dispute: A management Perspective

Abstract

The river Cauvery rises in the Brahmagiri range of the Western Ghats in the Coorg district of Karnataka at an elevation of about 1340 m. Harangi, Hemavathi, Shimsha, Arkavathi, Lakshmanathirtha and Swarnavathi are the major tributaries joining the river Cauvery in the Karnataka territory. Kabini which drains the eastern slopes of the Western Ghats in the north Malabar district of Kerala State flows through Karnataka and joins the river Cauvery. At the place where Cauvery enters the Tamil Nadu State limits the Mettur Reservoir has been formed. Bhavani, Amaravathi and Noyil are the tributaries to the river in the Tamil Nadu State. Cauvery is thus an interstate river with an unique characteristic geographical layout in that its upper hilly catchment lying in the Karnataka and Kerala States is influenced by the dependable south-west monsoon during the months June to September, while its lower part lies in the plains of the Tamil Nadu State served by the not so dependable north-east monsoon during the months October to December. The two parts of the catchment may be taken as meeting at the Hogenekal falls just above the Mettur Reservoir, where the river narrows down to form a single defined neck. The yield of a river system is the annual virgin flows at its terminal site. The yield or the total available quantum of water in a river system depends upon rainfall pattern, catchment area characteristics including soil and vegetal cover, and various climatic parameters affecting evaporation and evapotranspiration in the basin. The annual yield of a given basin varies from year to year depending upon the occurrence of the rainfall, its intensity and distribution in time and space. In a virgin-river system, i.e., a river basin where the natural river flows have not been withdrawn for any use, the assessment of the total yield becomes easy, based on the gauge and discharge observations. However, such a situation is hard to come across, because practically in every river system, there have been withdrawals of water for different uses by man. Therefore, to assess the available yield in a river system, the observed flows at different gauge and discharge sites have to be considered along with the withdrawals of water for different uses like irrigation, hydro-power generation, domestic and industrial water use etc. above each such gauging station. The computation of total annual flow including upstream withdrawals at the terminal site is termed as yield of the river system. Since the annual yield of a river varies from year to year depending upon the rainfall distribution, consequent run-off and withdrawals etc., such data is collected for a number of years to assess the reliable yield. In order to take care of wet and dry cycles, and to even out their effect, it is preferred that data for as many years as is available should be considered, provided that data is homogeneous and reliable. For more than a century disputes are being raised between the then States of Madras and Mysore now the States of Tamil Nadu and Karnataka in respect of sharing of the waters of river Cauvery. Such disputes are often raised when an inter-State river or international river passes through different States or nations. Courts are faced with the situation as to how to sort out the claim of each State or the nation, as the case may be, on some reasonable and rational basis.