Assessing irrigation mitigating drought impacts on crop yields with an integrated modeling framework

Abstract

Irrigation is one of the major adaptation strategies to combat the negative impacts of drought on crop yields. However, during droughts, the water resources are limited and determining the exact irrigation amount and its response to crop yields are crucial. Existing crop yield simulation models are data-intensive and a majority of these are point-based. Therefore, this study presents a novel integrated modeling framework by using two parsimonious models (CROPWAT, an irrigation water requirement simulation model; and AquaCrop-GIS, a spatial crop yield simulation model) to simulate corn and soybean yields under different irrigation application rates during drought years at a spatial scale in the Mobile River Basin (MRB), Southeast U.S. To simulate crop yields for drought years, first agricultural drought years are identified using an integrated drought index called the Standardized Precipitation Evapotranspiration Soil Moisture Index (SPESMI). The results indicate that a majority of the basin was affected by mild to extreme droughts during the years 2008, 2011, 2012, 2016. The results of the integrated modeling framework illustrate the potential corn and soybean yields can be increased from 10% to 259% and 20% to 229% respectively under different irrigation water application rates (50%, 75%, and 100% of irrigation water requirement) relative to rainfed crop yields at the counties in the MRB during drought years. These findings demonstrate the importance of overall irrigation and the integrated modeling framework in devising robust irrigation water management plans in drought-affected areas at a spatial scale. Failure in integrating irrigation water requirement models in crop yield simulations will result in erroneous yield simulations, especially during droughts – this is salient given projections for frequent and intense droughts globally. Although the study is focused on MRB, the framework developed is applicable for irrigation planners and water managers in any region that experiences mild to extreme droughts, as long as the farmers have the ability to adapt the irrigation in their practice given socio-economic constraints.