Water Resources Research Act Program

Details for Project ID 2019ID087B

Watershed scale assessment of water quality and nutrient retention in conservation agriculture

Institute: Idaho
Year Established: 2019 Start Date: 2019-06-01 End Date: 2020-05-31
Total Federal Funds: $15,000 Total Non-Federal Funds: $30,000

Principal Investigators: Zachary Kayler

Abstract: Regional water quality depends on the actions of multiple landowners and stakeholders. Nutrients, in the form of carbon, nitrogen and phosphorus species, in agricultural lands can leave fields and contribute to downstream water quality issues such as eutrophication, denitrification of N2O (green house gas), and nitrate levels that threaten biological systems. Land managers have developed prescriptions to address nutrient losses from fields, but implementation is not necessarily coordinated. Thus, while one or more fields may be managed optimally in a watershed, others may not be. To understand nutrient flows and subsequent management for water quality, the impact of land and water management needs to be quantified at the watershed scale. This study proposes to quantify nutrient retention and water quality in two watersheds that contrast with each other in respect to the predominate agricultural management. The Palouse Conservation District (PCD) has established water quality monitoring program in two watersheds, one under predominately no-till management and the other under predominately conventional till. No-till management is a means to increase soil health in the field, but it has also been associated with increased nutrient losses to nearby streams. We will use the sediment record from different positions in the watershed to assess the overall impact of no-till on water quality, determine catchment wide erosion rates, and quantify watershed level nutrient turnover times. There are two project tasks for the first phase, 1) use two years of water quality data to estimate carbon, nitrogen, and phosphorus mean residence times using a steady-state model, 2) use stable (δ13C, δ 15N, δ P18O) and radio isotopes (14C,10Be) from stream sediments and cores to calculate nutrient turnover within different points in each watershed. The study is set in two watersheds currently monitored by the PCD. The field work will consist of collecting sediments cores at specific sites within the two watersheds where discrete samples are currently monitored. A series of isotope analysis will be performed on sediment samples collected in the stream and from sediment cores. The isotope analysis has two purposes, 1) to help in validating the model output, and 2) to indicate the degree to which the material has been processed by microbial activity or held within the watershed via geochemical mechanisms (e.g., sorption). We anticipate the approach we develop here can be broadly used as tool in other areas practicing conservation agriculture as no-till is increasingly adopted across the country. The project is led by established researchers in their field. Kayler is new faculty to the University of Idaho and this is his first application to the USGS 104b. He has extensive experience in using stable isotopes and working in agricultural, forest, and aquatic systems. Hidy is an expert in Beryllium analysis and modeling. The facilities at Lawrence Livermore National Lab (LLNL) represent the cutting edge in accelerator mass spectrometry. By collaborating with the Boylan and the PCD, we are taking advantage of their history of farmer and land owner network development as well as outreach opportunities they operate. This proposal for seed funding represents the first phase of this research and we intend to submit to future funding opportunities (NSF, DOE-LLNL) using the data developed from this project.