Interannual to Decadal Climate Variability and Urban Water Security in the Missouri River Basin: Case Studies of Kansas City, Lincoln, and Great Falls Urban Areas

The Missouri River Basin (MRB) is the largest river basin in the U.S. and is one of the most important crop and livestock-producing regions in the world. The MRB contains some of the country's most sparsely-populated agrarian counties, as well as 2344 urban communities.

In a study of associations between decadal climate variability (DCV) phenomena and hydro-meteorological (HM) variability in the MRB, we found that positive and negative phases of the Pacific Decadal Oscillation (PDO), the tropical Atlantic sea-surface temperature gradient variability (TAG), and the west Pacific warm pool (WPWP) temperature variability were significantly associated with decadal variability in precipitation and air temperature in the MRB, with combinations of various phases of these DCV phenomena associated with drought, flood, or neutral HM conditions. We will report on a methodology developed and applied to assess whether the aforementioned DCV phenomena directly affect the hydrology of the MRB. The Soil and Water Analysis Tool (SWAT) was used to simulate water yields in response to realistic values of the PDO, TAG, and WPWP at 75 widely distributed, eight-digit hydrologic unit areas within the MRB. SWAT driven by HM anomalies in both the positive and negative phases of the PDO and TAG resulted in major impacts on water yields, as much as ±20% of average water yield in some locations. Impacts of the WPWP were smaller. Thus, our results show that the combined and cumulative effects of these DCV phenomena on the MRB HM and water availability can be dramatic with important consequences for the MRB.

We will also report on the application of the SWAT system to simulate and predict DCV impacts on water supply and demand in the Great Falls, Montana; Lincoln, Nebraska; and Kansas City urban areas in the MRB. In this study, we find that simulation of water yield, ground water, and evapotranspiration by the SWAT system, driven by observed HM variables in the Great Falls and Lincoln urban areas, correlate highly with independently measured water supply and demand by the two urban water systems, thus validating the SWAT system for prediction application in these urban areas.

Our report will also include our interactions with officials in the three urban water systems about their possible use of DCV-based probabilistic forecasts of precipitation, temperature, and water demand in their decision-support systems.