Project Number: 8070-13000-015-013-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Apr 15, 2020
End Date: Feb 14, 2023
The objectives of the project are fivefold: 1. Characterize the variability of nitrate concentration-discharge relationships at diel, storm event, and seasonal time scales. 2. Examine the effects of biophysical processes and hydroclimatic conditions on nitrate concentration-discharge patterns from headwater to small watershed scales. 3. Select one stream reach and use nutrient injection experiments to ascertain the effects of in-stream processes on nitrate concentration-discharge patterns over a range of flow conditions. 4. Synthesize findings from objectives 1-3 in Mahantango Creek and apply foundational knowledge to guide sensor-based concentration-discharge monitoring approaches in Conewago Creek. 5. Leverage findings from concentration-discharge studies to better inform conservation and planning recommendations from the Agricultural Conservation Planning Framework (ACPF).
The proposed project will take place within the research domain of the Upper Chesapeake Bay Long-Term Agroecosystem Research (LTAR), which is part of a broader network of 18 LTAR sites across the US focused on the sustainable intensification of agriculture. Research in the Upper Chesapeake Bay LTAR focuses on four experimental watersheds – Anderson Creek, Spring Creek, Mahantango Creek, and Conewago Creek – that represent the diverse physiography and farming practices of the Upper Chesapeake Bay region. For this project, we propose to focus our experimental work in Mahantango Creek and Conewago Creek. Small watersheds (< 10 km2) in Mahantango Creek and Conewago Creek will serve as the experimental unit in which detailed assessments of concentration-discharge relationships will be conducted. At the outset of the project, we will deploy up to five s::can sensors in the stream network of WE-38, a 7.3 km2 subwatershed of Mahantango Creek. The sensors will be installed in representative stream reaches that bracket a range of spatial scales from headwater to small watershed. Data from the initial s::can monitoring campaigns will provide important insight into the key biophysical processes and hydroclimatic conditions that affect nitrate concentration-discharge patterns at diel, storm event, and seasonal time scales. To better understand the role of in-stream processes on nitrate concentration-discharge relationships, we will select one representative stream reach and carry out several steady-state nutrient injections over a range of flow conditions. Each injection will span a three- to five-day period that encompasses pre-storm baseflow and the complete stormflow hydrograph. Data from the pre-storm injection period will be used to quantify nitrate uptake and release processes during baseflow, whereas data from the stormflow period will be used to provide insight into the relative roles of distal (i.e., upstream of the experimental reach) versus proximal (i.e., the injected nitrate source within the reach) nitrate sources on nitrate concentration-discharge patterns. In year three of the project, we will transfer three of the s::can sensors from Mahantango Creek to a similarly-sized subwatershed of Conewago Creek and repeat the s::can monitoring and injection experiments. Doing so will enable us to test whether the foundational knowledge concerning nitrate concentration-discharge patterns and the factors that affect them is readily transferred from one agricultural watershed to another. In the final year of the project, we will synthesize the findings from both watersheds and use the results to better inform conservation and planning recommendations made by decision support tools such as the Agricultural Conservation Planning Framework (ACPF), which is currently being assessed for potential application in the Upper Chesapeake Bay region.