Effects of Alternate Wetting and Drying on Water Savings and Rice Yields in The Philippines

Abstract

Water scarcity is a significant challenge for farmers in major rice-producing countries, as traditional rice production typically requires rice fields to remain flooded throughout the growing season. Alternate Wetting and Drying (AWD) is a water management technique developed for rice cultivation where rice fields are allowed to dry intermittently. This paper evaluated the causal impact of the AWD irrigation technique on water savings and rice yields in a large-scale gravity-based irrigation system in the Philippines. Using a 2-year panel data set from a trial based on a random encouragement design, we employ a difference-in-differences empirical strategy and conduct a number of robustness checks (e.g., propensity score matching, changes-in-changes and Kinky least squares) to achieve the study objective. We find strong positive impacts on water savings and no penalty in terms of rice yields when farmers are randomly encouraged to adopt AWD. Results from the heterogeneity analysis indicate that midstream farmers save the most amount of water and upstream and midstream farmers typically experience larger yield impacts. Findings highlight AWD's potential to address water scarcity and adapt to climate change, suggesting that water stress in major rice-producing regions can be mitigated through broader adoption of AWD. The study also points to the need for more targeted promotion efforts and policy strategies to ensure more equitable water distribution in gravity irrigation systems.