A hydro-climatological outlook on the long-term availability of water resources in Cauvery river basin

The past few decades have witnessed massive shifts in land-use patterns, land management practices and water demand in the river basins of peninsular India. Changes in hydrologic regimes of different components of the water cycle pose immense challenge to water security at the catchment scale. This paper provides a comprehensive overview and a quantitative assessment of the long-term availability of water resources in the Cauvery river basin, a major river basin in peninsular India. The Cauvery has been a contentious river for decades regarding water sharing among its riparian states of Karnataka and Tamil Nadu. Moreover, the river basin is characterized by extensive regional variability in both surface water and groundwater distributions and has faced acute water management challenges at multiple space and time scales. A descriptive overview of the major water security challenges faced by the basin is presented along with a detailed synthesis of hydrological modelling approaches and statistical methods to assess the basin’s long-term water availability. The Variable Infiltration Capacity (VIC) model is implemented to evaluate the long-term water balance components at the catchment scale for the period 1951–2016. Decadal Land Use Land Cover (LULC) in the basin for the years 1985, 1995 and 2005 are analysed. The statistical trends in hydrometeorology and extreme climatology of the basin are evaluated at seasonal and annual scales. Seasonal flow behaviour and influence of climate and human activities on streamflow are also assessed. A drought duration analysis is performed to infer about the implications of spatial distribution of water availability across the basin. The results show significant trends in the water balance components and the basin’s hydro-climatology. The LULC analysis shows notable changes in land use patterns due to human activities. Alterations in the predictability and temporal variability of streamflow are observed after the construction of dams which may affect the downstream water availability. This research highlights the importance of comprehensive synthesis of hydrological modelling approaches with hydrological signatures to understand the dynamics of hydrological processes at catchment scale with an objective of providing insights for effective planning and allocation of water resources and judicious management of water demands.