Climate change and human interventions have triggered hydrological changes in four major river basins in Kerala, indicating a potential risk for water resources, a study conducted by K.Sreelash, scientist at the National Centre for Earth Science Studies (NCESS) here, has revealed.
The study, which bagged the best paper award at the 29th Kerala Science Congress held at Thiruvalla, found that all the four rivers, namely the Chaliyar, Bharathapuzha, Periyar, and Pamba, showed a decline in discharge more predominantly after the mid-90s, implying a decrease in per capita water availability. Between 1995 and 2010, the flow of the Periyar declined by 700 million cubic metres.
Pointing to the unprecedented drought situation in Kerala, the paper maintains that this was the result of a long-term degradation of the hydrological system, coupled with the effect of climate change.
An analysis of the rainfall pattern revealed that the number of small rainfall events (between 5 to 25 mm) declined after the mid 90s while the number of high intensity rainfall events showed a sharp rise. There was a considerable decline in the annual rainfall of the Chaliyar river basin followed by the Bharathapuzha, whereas the Periyar and the Pamba showed less significant changes in rainfall.
The increase in temperature, coupled with changes in cropping patterns, was found to trigger the loss of more water through evapotranspiration (ET). The paper observed that the increase in built-up area and plantations and the decrease in forest cover and paddy fields had posed immense stress on the river hydrology.
During 2001, 22% of the total water input to the Periyar was lost through ET. This rose to 30% in 2009 and 34% in 2012. The loss of surface water was compensated from groundwater resources, leading to overexploitation and subsequent decline of the water table across Kerala.
The paper calls for establishing a network of critical zone observatories to monitor the river hydrology. It also stresses the need for rainwater harvesting and groundwater recharge mechanisms and adaptive cropping systems to build resilience to climate change and mitigate the impact of human interventions on river basins.
