Water demand is outstripping supply in the Colorado River Basin, which supplies water to seven southwestern states and Mexico. An estimated one in 10 Americans get their drinking water from a river system under increasing stress from growing demand and climate change. The U.S. Bureau of Reclamation in conjunction with the Lower Colorado River Basin states developed the 2007 Interim Guidelines (2007-16) to address river operations and diversions. Later, a revised river management structure was developed with the 2019 Drought Contingency Plan. The DCP was essential to address the ongoing historic drought and reduce the risk of Lake Powell reaching critical water levels. While alleviating the effects of long-term drought, the changes implemented with the DCP adversely impact the LCRB states by imposing strict water reductions.
What would water supply levels be without DCP or climate change? In a recent paper “Water Supply in the Lower Colorado River Basin: Effectiveness of the 2019 Drought Contingency Plan,” researchers Luis Huizar, Sarai Díaz, Kevin Lansey, and Robert Arnold explore this question. Their research in the Journal of Environmental Engineering uses four hydrological conditions to evaluate water supply reliability in the LCRB with and without DCP measures and with and without anticipated climate effects. Learn more about their research for mitigating future water shortages at https://doi.org/10.1061/JOEEDU.EEENG-7324. The abstract is below.
Abstract
The Colorado River supplies water to seven southwestern states and Mexico. It is one of the most stressed river systems in the US. To address sustainability in the Lower Colorado River Basin (LCRB), the US Bureau of Reclamation (USBR) organized discussion of river operations and diversions among the LCRB states, eventually leading to the 2007 Interim Guidelines (2007-IG) and then to a revised river management structure, the 2019 Drought Contingency Plan (DCP). Among other features, the DCP increased the severity of reductions, or shortages, in annual water deliveries to the LCRB states (California, Arizona, and Nevada) and Mexico that are triggered by low year-end water levels in Lake Mead. Shortage measures were designed to mitigate the effects of long-term southwestern drought on reservoir levels, perhaps avoiding the worst outcomes for regional water supply while maintaining the energy-generating capability of the Colorado River system. The objective of this study was to evaluate water supply reliability in the LCRB with and without DCP measures and with and without anticipated climate effects. Four combinations of hydrological conditions and management strategies were analyzed. The results show that both 2007-IG and DCP measures will reduce the most severe shortages in Colorado River Water (CRW) supply to the LCRB states and Mexico under historical hydrologic conditions. Neither set of regulating measures insulates the LCRB against drought with anticipated climate change. However, the most distressing low-water projections are predicted to be less frequent and severe with DCP measures in place. The methods used to project the impacts attributable to climate change and the DCP on LCRB water deliveries can be used to anticipate the effects of alternative river management provisions now under consideration for drought mitigation.
Delve into their findings in the ASCE Library: https://doi.org/10.1061/JOEEDU.EEENG-7324.
