Modern records of gaged flow for major rivers are limited to the last 120 years, at most. These records, which reflect average annual flows as well as periods of drought, have been used to allocate water resources and plan for future uses. Tree-ring based reconstructions of streamflow have been used to extend records back in time. The most well-known of these, for the Colorado River, showed that the period of flow used to allocate the basin's water supplies in the 1920s was one of the wettest period of flow in the past five centuries. Reconstructions of flow for other basins, such as the Sacramento River, have shown that drought much longer than any in the gage records have occurred over past centuries.
This research will use centuries-long tree ring records to reconstruct streamflow for the Missouri River Basin for gages from the headwaters to the confluence with the Mississippi River. This will be done using innovative statistical techniques based on Bayesian methodologies. To date, The Missouri River Basin is the only major river headwaters in the western US for which reconstructions from tree rings have not been generated. This knowledge gap is critical given that the region is facing an array of water resources issues that are challenged by hydrologic variability-- both floods and droughts-- over just the past decades. Providing a longer context for understanding past variability of flow and climatic controls on it, particularly at decadal and longer time scales, is critical for anticipating and managing water supplies in the future. The Missouri River system is the life-blood of the American Midwest. The research team will collaborate with the US Army Corps of Engineers Institute of Water Resources and their Upper Missouri Basin Offices to develop and test scenarios of past tree-ring reconstructed river discharge that can be used for different aspects of the Corps' operations on the river system, leading to better multi-stakeholder discussions on how best to manage climate induced risk in the region. This direct engagement will enhance the application of the research products, as well as provide guidance for their design. To engage Montana water users in the headwaters region of the Missouri River Basin, the research team will convene a workshop for local, state, tribal, and national management agency personnel with the goal to build capacity to incorporate scientific information into planning and management. The research team will also partner with a new NSF EPSCoR project with a focus on Montana's vulnerability to climate change to produce a K-12 science module on water resources.