Rainfall uncertainty and water availability: Elements for planning water allocation to users in irrigation districts of Mexico. Study case: Irrigation District 041, Yaqui River

The aim of this work is to present a protocol for analyzing readily available climatic and hydrological information on watersheds, in order to achieve a rational planning of irrigation water allocation under rainfall uncertainty conditions. We present as case study the Yaqui River watershed and Irrigation District (ID) No. 041 in the state of Sonora, Mexico. The watershed is divided into three sub-watersheds that drain into three reservoirs. Our findings indicate a strong dependence of water availability on the reservoirs, conditioned by El Niño phenomenon. In addition, rainfall-runoff relationships indicate the capability to produce a runoff for each sub-watershed and the differentiated impact of El Niño. The three sub-watersheds require about the same amount of antecedent rainfall for initiating the runoff (5 mm). A standardized precipitation index (SPI) highlights the dynamics of dry and wet spells and the impact on the planted area within the irrigation district. Overall, the functional relationships between El Niño, the SPI, and the planted area in the irrigation district may serve for planning purposes under climate uncertainty scenarios.