LAUSR

The aim of the work is to present a protocol for analyzing readily available climatic and hydrological information on watersheds for achieving a rational planning of irrigation water allocation under rainfall uncertainty conditions. We present as study case the Rio Yaqui watershed and the irrigation district (ID) No. 041 in the state of Sonora in Mexico. The watershed is divided in three sub watersheds that drain to three reservoirs. Findings indicate the strong dependence of water availability on the reservoirs on El Nino phenomenon. In addition, rainfall runoff relationships indicate the capability to produce runoff of each sub watershed and the differentiated impact of El Nino. The three sub watersheds requires about the same amount of antecedent rainfall for initiating runoff (5mm).  A standardized Precipitation Index (SPI) highlights the dynamics of dry and wet spells and the impact on planted area in the irrigation district. Overall, the functional relationships among El Nino, the SPI and the planted area in the irrigation district may serve for planning purposes under climate uncertainty scenarios.