Anatomy of an interrupted irrigation season: Micro-drought at the Wind River Indian Reservation

Water shortages during the growing season have become increasingly common at the Wind River Indian Reservation (WRIR) in Wyoming since the turn of the 21st century. In a new study published online in Climate Risk Management, CIRES researchers at the ESRL Physical Sciences Division and collaborators examine the causes for a micro-drought during the 2015 irrigation season, which occurred within a water year that was characterized by wetter-than-normal conditions and remained drought-free, according to the U.S Drought Monitor. The researchers combined a social science assessment with analyses of the region’s hydroclimatic observations to deconstruct how this shortage manifested at WRIR. This study illustrates how micro-droughts can result from social and environmental factors unique to a local system, and how a collaborative project can support drought preparedness at a tribal reservation.

In the hydroclimate analyses, CIRES researchers found that although precipitation at the WRIR and the surrounding mountains during the 2015 water year was about 120 percent of normal, snowfall was significantly below normal, particularly at higher elevations, meaning the surplus in precipitation fell as rain. This lead to a diminished snowpack in the Wind River Mountain Range, where the bulk of the reservation’s water comes from. Abnormally high temperatures were the cause: wintertime average temperatures over the Wind River range were as much as 7.2 degrees Fahrenheit above normal. The diminished snowpack melted out much faster and earlier than expected, and the early spring runoff was augmented by an extremely wet May. Reservoirs in the southwest of the reservation were overflowing, and water managers did not have the capacity to hold back the water. June brought back abnormally high temperatures, and the atmospheric evaporative demand increased quickly thereafter. In the peak of the growing season, farmers and ranchers were hit with a rapidly drying landscape, and found themselves with little water in the reservoirs to fulfill their needs. As a consequence, the irrigation season was terminated about six weeks earlier than normal.

This study shows that a collaborative approach to drought preparedness can be successful, through the co-production of an early warning system and monitoring infrastructure, capacity building, and conducting a community-driven social-ecological system vulnerability assessment. These insights will be used to directly inform drought planning and help identify short- and long-term adaptation strategies that can be implemented at the Wind River Indian Reservation. While this assessment is particular to this reservation, the insights gleaned from this integrated research framework can serve as a model elsewhere in the Intermountain West region and beyond.

Posted: November 7, 2017

Authors of Anatomy of an interrupted irrigation season: Micro-drought at the Wind River Indian Reservation are Shannon McNeeley of the North Central Climate Science Center, Candida Dewes, Imtiaz Rangwala, and Mike Hobbins of the ESRL Physical Sciences Laboratory, Crystal Stiles of the High Plains Regional Climate Center, and Cody Knutson of the National Drought Mitigation Center.