Water Resources Research Act Program

Details for Project ID 2013NV195B

Estimation of Atmospheric Wet and Dry Deposition of Nutrients to Lake Tahoe Snowpack

Institute: Nevada
Year Established: 2013 Start Date: 2013-03-01 End Date: 2016-02-28
Total Federal Funds: $39,779 Total Non-Federal Funds: $94,643

Principal Investigators: Rina Schumer

Abstract: Eutrophication of Lake Tahoe through inputs of atmospheric and terrestrial nitrogen (N) and phosphorus (P) are considered the main reasons { along with increased light scattering by particulate inputs { for declining water clarity during the last 40 years. Most current atmospheric deposition estimates for nutrients (N and P) in the Basin only consider direct deposition loads to the lake surface, while atmospheric deposition to terrestrial areas surrounding the lake remains a major missing component in a comprehensive nutrient balance of the Lake Tahoe Basin. Measurement of wet (via precipitation) deposition of nutrients are limited in the Basin, and even more limited are studies that have addressed nutrient loads in snowpack and snow deposition, which accounts for over 70% of precipitation inputs in the Lake Tahoe basin. For the development of successful mitigation strategies, it is important to assess the respective nutrient inputs and sources to watersheds and identify the degree to which they are mobilized within the watershed. The goal of this study is to fill the gap in Tahoe Basin terrestrial atmospheric deposition estimates using an integrated approach that includes experimental measurements to directly quantify { on an integrated bi-weekly basis { of wet deposition loads by snow and snowpack accumulation of N and P in Lake Tahoe watersheds; basin-wide peak-snowpack sampling to assess N and P loads available in the basin prior to the onset of snowmelt; and spatial extrapolation of wet deposition and snowpack loads to the entire watershed area using refined modeling. Snow-related wet deposition loads in the Basin will be directly quantified using wet deposition samplers deployed at two sites in the basin for two full years; and wet deposition sampling will be compared to bi-weekly snowpack core sampling at seven sites in the basin, allowing for assessment of how snow-related deposition is modulated (for example, enhanced by dry deposition or decreased by mobility) in the snowpack. Peak snowpack loads of nutrients in the entire basin will be further constrained using high-resolution assessments (50 sampling locations) of snowpack N and P concentrations prior to the onset of snowmelt and to calculate the total loads of nutrients available for runoff. Finally, all field measurements describe above will be spatially extrapolated using the Parameter-elevation Regressions on Independent Slopes Model (PRISM) climate mapping system. This work will train one Masters student in the Graduate Program of Hydrologic Sciences at the University of Nevada, Reno. Data generated by this study will be made publically available through the Tahoe Climate Information Management System. Dissemination of research results will occur through a minimum of one-peer reviewed scientific publication and presentation at the NIWR/UCOWR annual meetings as well as the American Geophysical Union Fall meetings. Since the Lake Tahoe Basin straddles the boundary of Nevada and California, field work will occur in both states. Lake Tahoe tourism, which depends on the beauty and natural resources of the watershed, is a large economic engine for the State of Nevada. Finally, this work will create a new regional collaboration between the PIs and the UC Davis Tahoe Environmental Research Center.