Analysis of Cauvery water-sharing award using an analytical framework model

Abstract

The award finalized by the Cauvery Water Disputes Tribunal CWDT (2007a,b) [Final order of the Cauvery Water Disputes Tribunal. Ministry of Water Resources, Govt. of India, New Delhi] for water sharing among the co-basin states of the Cauvery river basin in India was analyzed and compared with the results obtained by using a model proposed by Garg and Azad (2018) [J. Hydrol., 560, pp. 289–300] by analyzing the same data that was used by the Tribunal. The comparison of the model results for a real basin, with the results of the altogether different approach like the tribunal award, was made to serve two purposes (i) establishing confidence in the applicability of the model, which otherwise might be considered as some mathematical jargons by the authors without having adequate connect with the realities (ii) analyse the Tribunal award for its rationality and to draw general inferences. The analysis of the Tribunal award led to some new insights on the water sharing among co-basin states, namely (i) it is demonstrated that it would not be proper to reduce the allocation of water to a co-basin states for distress year in proportion to its’ allocation for the normal year to ensure an equitable distribution among co–basin states (ii) it is also revealed that the static allocation even for normal yield of the basin as a whole, should not be made among co-basin states, because it is possible that the normal yield of the basin as a whole may not synchronize with the normal yield of co–basin states (iii) the study defied the general perception that the inclusion of groundwater in overall water availability of the basin will lead to reduction in share of the surface water for co–basin states having relatively more groundwater potential as compared to other co-basin states. The study indicated that the CWDT (2007a,b) award failed to ensure an equitable water-sharing among co-basin states even for a year with normal yield in the Cauvery basin as a whole. The results of the model demonstrated different allocations to different co-basin states depending upon the hydrological conditions of the individual co-basin states for the normal yield of the Cauvery basin as a whole against the static allocation of water recommended by the Tribunal. The model recommended that the water allocation be varied from 380 thousand million cubic feet (TMC) to 399.4 TMC for Tamil Nadu, from 278.1 TMC to 315.2 TMC for Karnataka, from 42.5 TMC to 45.2 TMC for Kerala, and from 5.6 TMC to 6.2 TMC for Pondicherry depending upon the hydrological conditions of the co-basin states during a normal yield of the Cauvery basin, against the static values of water allocation proposed by the Tribunal of 419 TMC for Tamil Nadu, 270 TMC for Karnataka, 30 TMC for Kerala, and 7 TMC for Pondicherry for the normal yield of the Cauvery basin. Further, the study showed that if groundwater is also included along with surface water for water allocation among co-basin states, then the model allocated 3.5TMC more surface water to Tamil Nadu under the normal hydrologic condition of the Cauvery basin. Prima facie, it is against general perception that the surface water allocation to Tamil Nadu would be significantly reduced if the groundwater is also considered along with the surface water as groundwater potential of Tamil Nadu co-basin state is relatively higher than other co-basin states. It can be safely concluded from the study that the model proposed by Garg and Azad (2018) has the potential to resolve the transboundary water allocation problems and the model is flexible to include any number of demand and supply-side variables along with their weights in a rational manner.