Assessing Crop Vulnerability and Water-Saving Strategies under Climate Change: Does a Multiscale Analysis Always Add Value?

Abstract

Understanding the impacts of climate change on agriculture is vital for developing effective water-saving strategies (WSS). This study presents a systematic approach to evaluate the performance of WSS at multi-spatial scales from 2020–2099 for the southern Indian state of Andhra Pradesh. Climate data from the EC-Earth3 model under three climate change scenarios: SSP126, SSP245, and SSP370, was used. First, the irrigation water requirements (IWR) were calculated using a soil water balance model at multiple scales. Then, the future vulnerabilities of the selected crops – paddy, groundnut, sugarcane, and maize were quantified by estimating the variability of IWR. Next, groundwater consumption was estimated under a Business-As-Usual (BAU) scenario, following which the water savings in drip irrigation strategy (DIS) and crop shift strategy (CSS) relative to BAU were calculated. Finally, a Water-saving Scale Factor was computed to capture the efficacy of WSS across scales. Findings reveal that groundnut and maize, though drought-resistant, have higher vulnerabilities compared to paddy and sugarcane - a trend that is more pronounced at finer than at coarser scales. Notably, DIS was found to be more effective at water-saving than CSS across scales and climate scenarios. For instance, the state-scale cumulative water savings for DIS is 28% (74.8 BCM), compared to 19% (50.8 BCM) for CSS. In conclusion, multiscale analysis of the efficiency of WSS indicates that a finer scale analysis makes little difference to DIS, but definitely adds value to CSS. Such insights could help policymakers optimize resources spent on devising water-saving strategies for the future.