Understanding Trends in Snow Accumulation and Streamflow Using Snow Telemetry and Streamgage Observations in the Missouri River Headwaters

The Missouri River headwaters are located in the mountains of southwestern Montana and drain the eastern side of the continental divide. These headwaters serve as a water source for the Missouri River basin, which covers 10 states with an approximate population of 12 million people. A key component of the annual water budget in the headwaters is from snowfall, accounting for around 70% of the total annual flow in this region. The Western U.S. is generally comprised of semi-arid to arid regions that exhibit a high degree of inter-annual to multi-decadal variability. Changing trends in water availability due to climate change and yearly variations must be understood and quantified for proper allocation and forecasting of water resources. Here we use snow, temperature and precipitation records from the Natural Resource Conservation Service (NRCS) and streamflow records from the U.S. Geological Survey (USGS) in a coupled analysis designed to assess recent changes in these temperature sensitive high alpine headwaters over the last 40 years of record. Snow water equivalence, streamflow and temperature are key metrics that are indicative of changes in these headwater regions and are useful in determining the amount, timing and duration of hydrologically important snow-driven events. These data are being examined to determine what role inter annual and decadal drivers such as the El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the Pacific/North American Pattern (PNA) play in controlling the amount and timing of water availability in this catchment. Metadata from the weather stations used in this study are being analyzed to determine how changes in station characteristics, such as vegetation growth or equipment updates, can help explain variances in trends or relationships seen in the data beyond large-scale climate variations.