The Role of Sediment Removal and Native Plant Community Management for Improving Water Quality in Restored Wetlands

EPA Grant Number: FP917817
Title: The Role of Sediment Removal and Native Plant Community Management for Improving Water Quality in Restored Wetlands
Investigators: Winikoff, Sarah Gillian
Institution: University of Minnesota - Twin Cities
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2015 through August 31, 2018
Project Amount: $132,000
RFA: STAR Graduate Fellowships (2015) RFA Text |  Recipients Lists
Research Category: Academic Fellowships

Objective:

Rising recognition of wetland ecosystem services has led to a substantial increase in the number of wetland restorations. The goal of this research is to better understand how one restoration practice, the removal of accumulated sediment in wetland basins, influences nutrient retention and removal from local and regional groundwater supplies.

Approach:

The fellow will examine surface and subsurface water quality in 50 agricultural wetlands across western Minnesota. In all of the wetlands, hydrology was restored by removing drainage tile, plugging drainage ditches, and re-establishing connectivity to the groundwater supply. In half of the wetlands, accumulated sediment was removed from the basin and redeposited on hills and in the fields that it eroded from. Differences between surface and shallow groundwater nutrient concentrations will be examined in conjunction with measures of soil nutrient concentration, denitrification rate, and vegetative cover estimates to assess whether sediment removal influences nutrient retention and removal in restored agricultural wetlands.

Expected Results:

In agricultural wetlands, topsoil eroded from the surrounding landscape collects in drained wetland basins, burying hydric soils. Hydric soils are often characterized by relatively high concentrations of organic matter compared to upland soils, which generally possess higher mineral content. Thus, accumulated sediment can influence soils chemical properties that have broader impacts on ecosystem function. Soil chemistry influences microbially mediated nitrogen removal (denitrification) by altering the pH and availability of organic carbon, organic and inorganic nitrogen, and metal ions, which enable alternative redox pathways. Therefore, the removal of accumulated sediment should result in higher concentrations of organic matter, lower free metallic ion availability, and increase nitrogen removal rates. In addition, phosphorus retention is influenced by the availability of iron and aluminum ions, which readily bind and sequester phosphate. Therefore, total phosphorus concentrations should be higher in wetland soils with accumulated sediment and elevated mineral content.

Supplemental Keywords:

Wetland restoration, sediment removal, freshwater, denitrification, nutrient sequestration, water quality