An Early Warning System for Riverine Drought Impacts: a National Weather Service Pilot Program

Multi-year drought in the western United States has highlighted a need for the National Weather Service to keep the public informed of the potential impacts of low river levels. Currently, the National Weather Service Advanced Hydrologic Prediction Service (AHPS) provides river flow/stage and forecast information at approximately1,200 forecast points across the United States. Along with this information, AHPS describes potential flood impacts that may occur within the upstream and downstream influence of the forecast points. This type of local impact information allows communities, states, and federal interests to understand their vulnerabilities and make more informed decisions when preparing for and responding to potentially hazardous flood situations. However, similar information is not available for low-flow events.

In order to expand the AHPS river forecast system, the National Weather Service Central Region has undertaken pilot studies to obtain potential low-flow impact information near 21 forecast points in Minnesota's Mississippi River Basin and 17 points in the North Platte River Basin of Nebraska, Wyoming, and Colorado. The National Drought Mitigation Center (NDMC) was contracted to obtain the impact information within the study areas through a review of the literature and surveys of relevant state and federal agencies and local water administrators.

This research has yielded a wide variety of potential low-flow impacts affecting domestic and industrial water supplies, agriculture, hydropower production, navigation, recreation and tourism, and the environment, which will be used to establish critical low flow and stage determinations for each AHPS forecast point. This research also highlights areas where information is lacking. For example, many communities and agencies had difficulty linking impacts to specific river flows and stages. Additional research is needed in these cases to better understand the linkages between water supply and demand. Comparison of the study areas also reveals the unique vulnerabilities of each river basin, which is important for effective regional drought monitoring and planning.

Gaining a better understanding of the impacts caused by low river flows is essential for creating a complete river monitoring system and for fostering appropriate drought mitigation and response strategies. Developing a better understanding of low river impacts at the local scale will also provide more detailed information that can be used in a wide variety of water resources decision making planning at all levels of government. For example, the information would be valuable input for a national web-based drought impact reporting tool being developed at the NDMC. In the face of increasing water demands and inevitable future droughts, expansion of this research is needed across the United States in order to better understand and manage our limited water resources.