Modeling Irrigation Efficiency Paradox From Farmers' Behaviors

Abstract

Agricultural irrigation accounts for 70% of global freshwater withdrawals, highlighting its critical role in water conservation. However, numerous studies have presented the irrigation efficiency paradox, whereby increased efficiency rarely reduces water consumption. This study explores this paradox by deriving the elasticity of total water use to efficiency to provide theoretical criteria for paradox emergence. Moreover, an agent‐based model that incorporates farmers' irrigation decision with a physically‐based hydrological‐crop model is employed to create a detailed simulation of water‐land use dynamics and hydrological process in response to irrigation efficiency improvements. Both approaches are applied to the Hedong Irrigation District, Ningxia, China. The results show that higher irrigation efficiency decreases the total water use of rice but increases that of wheat and maize. The total water use of the entire irrigation district exhibits a “first increasing then decreasing” pattern. Under the land redline constraint, total water use peaks at 9.32 (IQR: 9.26–9.40) ×10 ⁸  m ³ when irrigation efficiency reaches 0.60, whereas deactivating this constraint delays the critical threshold to 0.80 and drives total water use to a higher theoretical value of 9.53 (IQR: 9.48–9.83) ×10 ⁸  m ³ . While wetter conditions delay the threshold, drier conditions forward it. To manage this paradox, this study proposes an adaptive pricing regulation scheme that dynamically adjusts water, crop, and land costs with efficiency changes. From the perspective of farmers' irrigation behavior, the study findings provide both theoretical foundations and simulation approaches to predict and mitigate the irrigation efficiency paradox, offering valuable insights for sustainable agricultural water management.