M. Alisa Mast
Science and Products
Paradox Valley Total Dissolved Solids (TDS) Regression Equations
The primary objective of the project is to evaluate and update previous regression equations, developed for the USGS streamgages and continuous water-quality records,that describe the relation between specific conductance measured in the Dolores River and calculated total dissolved solids TDS. A secondary objective is to evaluate brine discharge to the river using a previously developed...
Selenium Mobilization from Shales
Selenium (Se) and salinity (total dissolved solids) are water-quality concerns in much of the arid western US where agricultural and urban irrigation overlie Cretaceous-age shale. Leaching of Se and salinity from shale can degrade water quality and negatively affect aquatic biota in receiving water bodies. In the upper Colorado River Basin, programs since 1985 have worked to reduce Se and...
Water, Energy, and Biogeochemical Budgets (WEBB): Loch Vale Watershed
Loch Vale is an alpine/subalpine watershed in Rocky Mountain National Park where the U.S. Geological Survey has been conducting research since the 1980s. Our research has focused on the effects of climate change and atmospheric pollutants on water, soil, vegetation, and aquatic life. The alpine/subalpine ecosystem in Loch Vale is sensitive to changes in climate and air pollution. Our long-term...
Water-Quality Sampling at Five Hydrologic Benchmark Stations in the Western United States
The Hydrologic Benchmark Network (HBN) was established in 1963 to provide Swiftwater Creek, MT long-term measurements of streamflow and water quality in areas of the United States that are minimally affected by human activities. Historically, the HBN has used a fixed-interval sampling strategy, however other more robust sampling strategies are now available. Trend networks, for example, can...
Preferential elution of ionic solutes in melting snowpacks: Improving process understanding through field observations and modeling in the Rocky Mountains
The preferential elution of ions from melting snowpacks is a complex problem that has been linked to temporary acidification of water bodies. However, the understanding of these processes in snowpacks around the world, including the polar regions that are experiencing unprecedented warming and melting, remains limited despite being instrumental in...
Costa, Diogo; Sexstone, Graham A.; Pomeroy, J.W.; Campbell, Donald H.; Clow, David W.; Mast, Alisa 2017 Monitoring and tracking wet nitrogen deposition at Rocky Mountain National Park
The Colorado Department of Public Health and Environment (CDPHE), the National Park Service (NPS), and the U.S. Environmental Protection Agency (EPA) issued the Nitrogen Deposition Reduction Plan (NDRP) in 2007 to address the effects and trends of nitrogen deposition at Rocky Mountain National Park (RMNP). The agencies chose a glidepath approach...
Kristi Morris; Mast, M. Alisa; Wetherbee, Gregory; Baron, Jill; Cheatham, Jim; Bromberg, Jim; Devore, Lisa; Hou, James; Gebhart, Kristi; Bell, Mike; Gay, David; Olson, Michael; Weinmann, Timothy; Bowker, Daniel
Controls on spatial and temporal variations of brine discharge to the Dolores River in the Paradox Valley, Colorado, 2016–18
The Paradox Valley in southwestern Colorado is a collapsed anticline formed by movement of the salt-rich Paradox Formation at the core of the anticline. The salinity of the Dolores River, a tributary of the Colorado River, increases substantially as it crosses the valley because of discharge of brine-rich groundwater derived from the underlying...
Mast, Alisa; Terry, Neil Science needs for continued development of total nitrogen deposition budgets in the United States
The objectives of this white paper are to describe the state of the science with respect to total Nr deposition budgets in North America and the research needed to improve these budgets from both a measurement and modeling standpoint. The document is intended to serve as a plan for TDep research activities but also, more broadly, to provide...
Wetherbee, Gregory A.; Pamela H. Templar; Richard V. Pouyat; Stephen M. Decina; Brian M. Kerschner; Thomas H. Whitlow; Pamela E. Padgett; Donna B. Schwede; Baron, Jill S.; Clow, David; Mast, Alisa; Sexstone, Graham A.; Kristi H. Morris
Estimating metal concentrations with regression analysis and water-quality surrogates at nine sites on the Animas and San Juan Rivers, Colorado, New Mexico, and Utah
The purpose of this report is to evaluate the use of site-specific regression models to estimate metal concentrations at nine U.S. Geological Survey streamflow-gaging stations on the Animas and San Juan Rivers in Colorado, New Mexico, and Utah. Downstream users could use these regression models to determine if metal concentrations are elevated and...
Mast, Alisa Linking transit times to catchment sensitivity to atmospheric deposition of acidity and nitrogen in mountains of the western United States
Transit times are hypothesized to influence catchment sensitivity to atmospheric deposition of acidity and nitrogen (N) because they help determine the amount of time available for infiltrating precipitation to interact with catchment soil and biota. Transit time metrics, including fraction of young water (Fyw) and mean transit time (MTT), were...
Clow, David W.; Mast, Alisa; Sickman, James O. Spatial and temporal variation in sources of atmospheric nitrogen deposition in the Rocky Mountains using nitrogen isotopes
Variation in source areas and source types of atmospheric nitrogen (N) deposition to high-elevation ecosystems in the Rocky Mountains were evaluated using spatially and temporally distributed N isotope data from atmospheric deposition networks for 1995-2016. This unique dataset links N in wet deposition and snowpack to mobile and stationary...
Nanus, Leora; Campbell, Donald H.; Lehmann, Christopher M.B.; Mast, Alisa
Estimation of salt loads for the Dolores River in the Paradox Valley, Colorado, 1980–2015
Regression models that relate total dissolved solids (TDS) concentrations to specific conductance were used to estimate salt loads for two sites on the Dolores River in the Paradox Valley in western Colorado. The salt-load estimates will be used by the Bureau of Reclamation to evaluate salt loading to the river coming from the Paradox Valley and...
Mast, Alisa Climate-change signals in national atmospheric deposition program precipitation data
National Atmospheric Deposition Program (NADP)/National Trends Network precipitation type, snow-season duration, and annual timing of selected chemical wet-deposition maxima vary with latitude and longitude within a 35-year (1979–2013) data record for the contiguous United States and Alaska. From the NADP data collected within the region bounded...
Wetherbee, Gregory A.; Mast, Alisa Controls on selenium distribution and mobilization in an irrigated shallow groundwater system underlain by Mancos Shale, Uncompahgre River Basin, Colorado, USA
Elevated selenium (Se) concentrations in surface water and groundwater have become a concern in areas of the Western United States due to the deleterious effects of Se on aquatic ecosystems. Elevated Se concentrations are most prevalent in irrigated alluvial valleys underlain by Se-bearing marine shales where Se can be leached from geologic...
Mills, Taylor J.; Mast, Alisa; Thomas, Judith C.; Keith, Gabrielle L. Spatiotemporal patterns of mercury accumulation in lake sediments of western North America
For the Western North America Mercury Synthesis, we compiled mercury records from 165 dated sediment cores from 138 natural lakes across western North America. Lake sediments are accepted as faithful recorders of historical mercury accumulation rates, and regional and sub-regional temporal and spatial trends were analyzed with descriptive and...
Drevnick, Paul; Cooke, Colin A.; Barraza, Daniella; Blais, Jules M.; Coale, Kenneth; Cumming, Brian F.; Curtis, Chris; Das, Biplob; Donahue, William F.; Eagles-Smith, Collin A.; Engstrom, Daniel R.; Fitzgerald, William F.; Furl, Chad V.; Gray, John R.; Hall, Roland I.; Jackson, Togwell A.; Laird, Kathleen R.; Lockhart, W. Lyle; Macdonald, Robie W.; Mast, Alisa; Mathieu, Callie; Muir, Derek C.G.; Outridge, Peter; Reinemann, Scott; Rothenberg, Sarah E.; Ruiz-Fernandex, Ana Carolina; St. Louis, V.L.; Sanders, Rhea; Sanei, Hamed; Skierszkan, Elliott; Van Metre, Peter C.; Veverica, Timothy; Wiklund, Johan A.; Wolfe, Brent B. Water-quality response to a high-elevation wildfire in the Colorado Front Range
Water quality of the Big Thompson River in the Front Range of Colorado was studied for 2 years following a high-elevation wildfire that started in October 2012 and burned 15% of the watershed. A combination of fixed-interval sampling and continuous water-quality monitors was used to examine the timing and magnitude of water-quality changes...
Mast, Alisa; Murphy, Sheila F.; Clow, David W.; Penn, Colin A.; Sexstone, Graham A.