Performing Department
Forest & Natural Resources Management
Non Technical Summary
This research is being conducted in the Piedmont region of the Southeastern US, specifically in Surry County, NC. We are using a comparative study approach with three stream reaches all agricultural lands with a mix of row crop and pasture: (1) a stream restored in 2012, (2) a channelized ditch with little riparian vegetation and (3) an impacted stream with a forested riparian buffer. Our study also includes a reference reach that flows through a forested section but also includes agricultural land uses in the watershed. We established well/piezometer transects at representative cross sections in the streambed and riparian areas to calculate water and solute fluxes. In the restored reaches, transects are located in the vicinity of engineered instream geomorphic features. At the remaining sites, we have targeted naturally occurring debris dams and riffle/pool sequences to capture variability in stream flow and hyporheic exchange. Vertical hydraulic gradients and hydraulic conductivity are being measured seasonally in each riparian piezometer to calculate hydraulic flux via Darcy's Law. Water chemistry is also being measured seasonally to characterize patterns of pore water chemistry and the extent of reducing conditions which will be used to calculate mass flux of key solutes (e.g. nitrogen, phosphorus, sulfate, iron and carbon). We are also measuring surface water quality and instream hydraulic gradients to characterize hyporheic flow and nutrient export seasonally. To quantify greenhouse gas fluxes (CO2, N2O, CH4) and relate measurements to hydrologic and water quality observations, dissolved gas concentrations (using silicone tubing) and fluxes at the soil-atmosphere interface (using statics chambers) are also being measured seasonal sampling periods.The restoration approaches in the study streams fit within the context of Natural Channel Design with the primary goal to implement structures or modify stream channel morphology that mimic natural channel behavior. This implies that the restored sites should present hydrologic and biogeochemical characteristics most similar to the reference site while departing from the impacted reaches. However, little evidence in the literature suggests that restored streams are more similar (hydrologically and biogeochemically) to reference sites than control sites. In order to test this hypothesis, we are using established statistical techniques to assess inter-site variability and similarities among the studied sites.Awarded Start Date: 9/1/14Sponsor: Purdue University
Animal Health Component
0%
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
The primary objective of this research is to understand and predict the impact of river restoration in agroecosystems on surface water-groundwater (SW-GW) interactions and biogeochemical processes in the near-stream zone (hyporheic and riparian zones). Restoration approaches that aim to improve water quality by enhancing retention time and promoting reducing conditions may increase nitrogen removal via denitrification, but be achieved at the expense of phosphorus desorption and emission of greenhouse gases (e.g N2O, CO2, CH4). Through this project, we will test the hypotheses that (1) restored streams will have elevated water tables and prolonged, more extensive areas of reducing conditions compared to unrestored streams, (2) instream channel complexity will lead to higher denitrification rates, higher phosphorus concentrations in pore water via desorption, and increases in N2O and CH4 fluxes in restored compared to unrestored reaches, and (3) restoration approaches closely aligned with reference channel geomorphology will have greater SW-GW interactions and biogeochemical transformations.
Project Methods
We propose to use a comparative approach whereby we use an unrestored restored reach, a minimally impacted reach, and 3 restored reaches to investigate the impact of stream restoration type on the hydrological and biogeochemical functioning of stream hyporheic and riparian zones.