Quantifying the Water-Energy-Land-Food nexus: Data-intensive groundwater models and future scenarios

Abstract:

Declining soil fertility, depleting groundwater (GW) reserves, and increasing energy costs are impacting global agricultural yields. Notably, in South Asia, the need to produce more food will increase in the coming decades, further intensifying the pressure on available resources. To overcome these challenges, understanding the nexus between GW, energy, land, and food (WELF) is imperative. Several studies have looked at these nexus issues, but have predominantly focused on global scales since regional and local dynamics are often missed due to a lack of detailed data. This study evaluates the WELF interactions at a local scale using a data-intensive process-based groundwater modeling approach. We also project into the future the impact of crop-shift strategies to reduce GW and energy consumption. The study area is the Chittoor District in the Indian state of Andhra Pradesh, where groundnut, paddy, and sugarcane are the major crops. The model estimates groundwater pumping required for irrigation by incorporating the FAO CROPWAT model. The models rely on several massive datasets for their inputs – rainfall, crop type and acreage, evapotranspiration (from remotely-sensed MODIS data), land use land cover, elevation, and geology. The groundwater model was calibrated to observed water level time-series from several monitoring wells. The energy required to pump the estimated GW volume was calculated using depth to water level. Results from this study show that water-intensive crops like sugarcane and paddy account for ~80% of both GW and energy consumption. Naturally, hotspots of consumption were concentrated in areas where paddy and sugarcane were most intense. If left unchecked, GW levels may drop as much as 100 m below ground level in these hotspots. The model predicts that the proposed crop-shift strategies can positively impact GW and energy resources. For instance, in less than a decade, moving 50% of paddy crop to groundnut may result in a 10 m rise in water levels and a 15% savings in energy. Process-based models are potent tools in policymaking as they allow the design and evaluation of various interventions using evidence-based analyses. Indeed, these models can help to ensure long-term food, water, and energy security by bringing about sustainability in global, regional, and local food production.