Forecast/Nowcast Great Lakes Nutrient and Sediment Loadings
USGS scientists will collect real-time, near-real-time, and synoptic flow and water-quality data from tributaries to the Great Lakes. The work would be aligned with the proposed National Monitoring Network Design for the Great Lakes. There are currently a number of streamflow gages operating at many of the proposed sites and water quality samples being collected at a number of the proposed sites. There is also real time water quality data being collected at several sites.
Tributary Monitoring Sites Automated samplers, water quality multi sensor probes, and gage house and stage equipment were deployed at 30 of the Great Lakes National Monitoring Network sites. These sites are being monitored to:
- provide baseline information,
- provide support for measuring restoration progress,
- and demonstrate the ability to reduce monitoring costs through the use of real-time sensors.
Water samples collected at the 30 tributary monitoring sites include suspended sediment; nutrients (incl. nitrogen, nitrite, nitrite + nitrate, total nitrogen, ortho-phosphorus, and total phosphorus); chloride, and bacteria. One sample per storm event is analyzed for major ions. At each site, monthly base flow samples are being collected, plus up to eight storms, with 6 samples submitted per storm (60 environmental samples per site). Samples will be used to develop statistical relations between continuously measured parameters and lab analyzed parameters. In-situ water-quality sensors deployed at each site measure turbidity, temperature, conductivity, dissolved oxygen, and pH every 15 minutes.
The work proposed in this work plan will build on current USGS monitoring efforts and those of other entities in the Great Lakes. The results of this effort will support the Lakewide Management Plans, Remedial Action Plans, and State management plans.
The USGS will expand tributary monitoring according to the National Monitoring Network for Coastal Waters design. This project will include:
- Nutrients and Sediment using automated and manual sampling;
- The development of watershed models throughout the Great Lakes.
The monitoring effort will help to make progress towards more complete implementation of the Great Lakes National Monitoring Network (NMN) for Coastal Waters tributary design and will include sampling in some embayments and drowned river mouths where tributaries discharge. This effort will be built on the ongoing USGS monitoring of these components and coordinated with proposals submitted to the EPA as part of the GLRI granting process.
To determine the current status of the nutrient loading to each Great Lake and forecast potential future changes in loading, a GIS regional model is proposed to be developed which links results of two existing types of models. We propose to link results of the water-quality watershed model, SPARROW (SPAtially Referenced Regression On Watershed attributes model) with the results from water-quantity models, WATER and PRMS. SPARROW will provide an estimate of the long-term average loading and average nutrient concentrations for streams throughout the basin for present conditions and for various future land-use-change scenarios. Output from WATER and PRMS will be used to estimate the current flow in streams throughout the basin and their response to climate change. The water-quality results (from SPARROW) will then be combined with the estimated flows throughout a study area (WATER and PRMS) in a GIS framework to estimate basinwide loading for current conditions (2008/9) and for various future projections (changes in climate and land use). This model can then be integrated into a decision support tool that can be used to estimate the impact of potential land management decisions and climate change.
Additional models will be evaluated to design a modeling project to simulate flows and loads of sediment, phosphorus, nitrogen, and emerging contaminants and pathogens (if possible) in up to three “representative” tributaries of the Great Lakes Basin. These watershed models for three representative subbasins will be used throughout the Great Lakes Basin to estimate flow, contaminant loads, and the effects of individual basins on the ecological well-being of the Great Lakes. The focus of this modeling effort would be to (a) provide a more detailed understanding of the hydrologic and water-quality processes in the basin at a scale not possible with a large-scale or non-process oriented model, and (b) identify sets of runoff and water-quality parameter values for the modeled subbasins that can be transferred to and used in subbasins with similar geological and hydrologic characteristics.
This information will provide baseline information, provide support for measuring restoration progress, and model potential load changes throughout the Great Lakes. This effort will be coordinated with the EPA, COE, FWS, States and other monitoring and modeling entities.