ABSTRACT:
The world's water resources and acquatic ecosystems are threatened by the combined effects of humand land use an dclimate change. For example, in response to climate change inducted shifts to ethanol fuels, corn production in the agricultural Midwest will likely increase. The cultivation of corn requires increased irrigation and fertilizer and over-application of agricultural fertilizer results in run-off that greatly increases nutrient levels in the Midwestern streams that drain into the Great Lakes and Mississippi River Watersheds. In addition, agricultural streams are typically channelized in order to increase water conveyance and drainage, but this management strategy results in minimal capacity for biological nutrient processing via stream biota. In the agricultural Midwest, tile drainage rapidly shuttles excess nutrients from fields to streams resulting in high nutrient export compromised water quality, impaired ecosystem function, and reduced biodiversity. In addition, nitrogen-rich water exported downstream can result in algal blooms and subsequent die-offs that reduce dissolved oxygen levels creating periodic “dead zones” like those occurring in Lake Erie and in the Gulf of Mexico.
Biologists at Notre Dame have been partnering with The Nature Conservancy (TNC) to test the efficacy of the novel two-stage ditch management strategy as a means to restore natural floodplains in channelized agricultural streams. The results from these studies will help to inform the Best management Practices for streams used by the USDA- Natural Resources Conservation Service. TNC asked Notre Dame Biologists (Tank) to test whether the restoration of floodplain benches within formerly channelized systems promotes biological nitrogen removal. Laboratory bio-assays on microbes colonizing stream sediments have shown that enhanced surface area in restored floodplain benches increased microbial processing and removal of nitrogen; the two-stage removes more than 5 times as much nitrogen per day as a channelized control reach of stream as a result of microbial N removal on restored floodplains. In short, two-stage management has the potential to remove excess nitrate (N) and decrease N export to downstream waters. Yet, thus far, monitoring efforts to assess two-stage performance can only infer a reduction in nitrate export via a scaling-up of laboratory bio-assays. Until now, we have been unable to explicitly link increased N processing to subsequent water quality benefits due to a gap in our ability to measure streamwater N loads in the field.
The ND-ECI project will employ novel monitoring and treatment technologies to enhance stream N removal, which will translate directly to improved water quality management. For monitoring, we will employ wireless sensor network technologies that enable the real-time tracking of nitrogen loads and relevant measures of stream health. The integration of nitrate sensors into this sensor network will allow us to field test the assumption that two-stage management will reduce nitrogen loads from agricultural streams and improve downstream water quality. The project will build on technologies developed for remote monitoring of sewer systems that were commercialized by our industrial partner, EmNET LLC. This work will deploy and network newly available in-situ nitrate-nitrogen sensors that monitor water quality from the field in real-time. Data from sensor networks will facilitate the identification of large-scale models for agriculturally based nitrogen loading. The development of such models can help balance the maximization of agricultural yields against the need to sustain aquatic ecosystems. This could be achieved by using these sensor networks to provide real-time information required to effectively manage nitrogen cap-and-trade policies aimed at reducing nitrogen loading in our rivers and streams.