Forecasting Great Lakes Basin Responses to Future Change

Dates

Project Start Date: 2010
Project End Date: 2014

Summary

Description of Work USGS scientists are developing science based forecasting tools that capture changes to water flows and discharges of nutrients and sediments to the Great Lakes. The work done by this project provides managers with forecasting tools for predicting the combined effects of climate and land use changes that will help them identify and prioritize the sites best suited for restoration efforts. USGS scientists will use remote-sensing data to establish a baseline understanding of current distributions of invasive wetland plants and then forecast potential invasion corridors. Alterations to the Great Lakes shoreline or water-level patterns associated with global climate change could have significant impacts on the extent [...]

Summary

Description of Work

USGS scientists are developing science based forecasting tools that capture changes to water flows and discharges of nutrients and sediments to the Great Lakes. The work done by this project provides managers with forecasting tools for predicting the combined effects of climate and land use changes that will help them identify and prioritize the sites best suited for restoration efforts. USGS scientists will use remote-sensing data to establish a baseline understanding of current distributions of invasive wetland plants and then forecast potential invasion corridors. Alterations to the Great Lakes shoreline or water-level patterns associated with global climate change could have significant impacts on the extent and composition of coastal habitat. Low lake levels can expose fertile wetland bottomlands to invasive species such as common reed ( Phragmites).

Goals & Objectives

The primary goal is to develop and combine hydrologic models of the Great Lakes Basin suitable for accepting downscaled climate and land-use change inputs, and that produce hydrologic flows suitable for restoration, water quantity, water quality, infrastructure, habitat, and other ecological forecasting. This will facilitate science-based assessments of the impact of climate and land use change on the ecological response at a Great Lakes scale.
Specific objectives are as follows:

Build and calibrate a coarse-scale Precipitation-Runoff Modeling System (PRMS) model of the Lake Michigan Watershed using data from USGS least-impacted stream gages as calibration targets. Develop model calibration methodologies specifically designed to address the ecological and restoration focus of the models.
Evaluate existing evapotranspiration algorithms and develop a new frozen-ground module for the PRMS model.
Simulate impacts of climate change on streams in the Lake Michigan Watershed using down-scaled climate-change predictions from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment report.
Build one fine-scaled PRMS inset model within the framework of the coarse-scale model to investigate local impacts of climate change in areas of interest to stakeholders.
Relate PRMS climate and land-use change flows to SPARROW nutrient loads. Begin work on a TOPMODEL hydrologic flow model of the Great Lakes Basin.
Relate historical wildlife disease data to hydrological indices simulated by the watershed models. Use the relation to forecast changes in disease occurrence and distribution that may result from changes in hydrology due to climate and land-use change.

Questions that will be answered to support restoration in the Great Lakes: The purpose of this project is to answer potential questions about the long-term viability of present day restoration investments given the potential for land use and climate change. Such work helps ensure that public and other funds are not directed to restoration projects that have little likelihood of being self-sufficient and viable over societally relevant time scales. This purpose is important in that it is unlikely future funding will be sufficient to support long-term actively managed restoration activities on the Great Lakes scale.

Approach

Objective 1: The U.S. Geological Survey Precipitation-Runoff Modeling System (PRMS) will be used as the basis for the climate change hydrologic modeling. The PRMS model uses hydrologic response units (HRUs) to partition the watershed into areas with relatively uniform hydrologic response. As a pilot for the National Hydrologic Model (NHM), we will work with the MoWS group to develop the coarse-scale model using the NHM framework. At its coarsest resolution, the NHM will be made up of HRUs based on reference stream gages (1000+ reference gages within the U.S. identified by David Wolock to be free of anthropogenic effects). Additional real-world geographic locations, such as outlets of reservoirs, confluences of rivers, etc. will be used to help ensure consistency when nesting model applications. For the Lake Michigan model, this will include stream locations with previous estimates of loading to provide a calibration baseline for climate-change predictions using the SPARROW framework, and all of the tributary streams that flow into the lake.

The model will be calibrated using the PEST suite of automated calibration software (Doherty, 2010) using a series of least-impacted USGS stream gages as calibration targets. We will also use large-scale datasets of solar radiation and potential evapotranspiration as calibration targets. A step-wise procedure similar to that described in Hay and others (2006) will be used to perform the calibration. The first three steps for calibration (solar radiation, potential ET, annual water balance) will be carried out for the entire model. The final step (monthly water balance, daily flow targets) will be carried out in parts, defined by sub basins in the model. In cases where sub basins are nested, the upstream sub basin will be calibrated first; the parameters in that sub basin will be fixed, and the next downstream sub basin will be calibrated. This procedure will be continued until the confluence with Lake Michigan is reached.

Objective 2: The current version of PRMS has two algorithms for calculating potential evapotranspiration (PET), which may not provide enough spatial variability across large-scale watersheds. Further, both algorithms rely on temperature and solar radiation as inputs, and it is not clear if the parameters calibrated for a particular climate will apply to an altered climate. We will investigate the two PRMS algorithms along with numerous additional algorithms and determine the best approach to be used for current and future climate conditions. The PRMS model will be modified to use the selected algorithm.

The current version of PRMS does not consider frozen ground. This could be simply simulated by adjusting soil-property parameters to reflect the hydrologic response to frozen ground. In reality, frozen ground and the interaction of the surface and subsurface flow paths are much more complicated. A frozen ground module will be developed (Andrew Slater, NSIDC) for incorporation into PRMS using a combination of GLRI and MoWS funds.

Objective 3: Current efforts for the NHM include developing tools for processing spatial datasets and returning values for selected polygons. There will be several datasets developed with down-scaled climate data culled from the IPCC Fourth Assessment (Intergovernmental Panel on Climate Change, 2007). The spatial data processing tool will be used to develop an input data set for PRMS with downscaled climate for each model HRU. The Fourth assessment included results from 15 global climate models (GCMs) run for current conditions and three emissions scenarios. The PRMS model will then be run using the various GCM and emissions scenario combinations, and compared to results for the current climate to determine the impacts of climate change on streamflow in the Lake Michigan watershed. It is anticipated that the coarse-scale model will give representative results at a monthly time scale.

Objective 4: The first order NHM HRUs will be further discretized into a standalone fine-scale hydrologic model for one area of interest. The area of interest will be selected based on input from stakeholders in the watershed. The PRMS model developed at resolutions finer than the coarse resolution Lake Michigan model will begin by initialization from the set of parameters resulting from calibration in Objective 1. This ensures consistency and quality because the finer resolution model will never have more uncertainty in terms of model misfit compared to the coarse scale model.

Anthropogenic factors will be incorporated at the appropriate model resolution. In this manner, the selected higher resolution hydrologic models will be nested within HRUs of coarser resolution hydrologic models. An example of nested scales and model HRUs from the NHM is shown in Figure 2.

Objective 5: Develop HydroSPARROW, to estimate nutrient concentrations in streams throughout the Great Lakes Basin and loading to the Great Lakes from each tributary in response to the changes in climate and land use. HydroSPARROW will be an extension of the existing SPARROW model to accommodate changing hydrologic flow. This extension will link the existing SPARROW model with several water-quantity models, including the GIS spatially interpolated model used to estimate streamflow used in the SPARROW model (D. Wolock, USGS, person. commun.) and stand-alone models WATER (based on TOPMODEL) and the PRMS model developed as part of this project. The GIS spatially interpolated model estimates streamflow throughout the basin using flow measured at existing USGS gages assuming a similar yield throughout each basin. WATER and PRMS estimate streamflow throughout the basin on the basis of meteorological forcing, and specific topographic and land cover features, which enable the models to incorporate the effects of various land-use and climate-change scenarios. The introduction of hydrologic flows, and changes to flows, will allow estimates of future nutrient loading using SPARROW-calculated.

Objective 6: A pilot effort to relate USGS National Wildlife Health Center data to simulated historical and future change flows will be conducted. Indices of hydrologic alteration metrics will be compared to historical spatial and temporal changes in wildlife disease in the Lake Michigan Basin. From these initial relations, preliminary forecasts of how land and climate changed flows affect wildlife disease can be made. Depending on the explanatory power of the relation, additional ecological metrics may be included in future work.

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Contacts

Principal Investigator :: Randall J Hunt
Associate Project Chief :: John F Walker
Cooperator/Partner :: Daniel E Christiansen
Lead Organization :: USGS Wisconsin Water Science Center

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Direct questions and requests to the Principle Investigator.

Purpose

The purpose of this template is to provide insight into the long-term viability of present day restoration investments given expectations of land use and climate change. Such work helps ensure that public and other funds are not directed to restoration projects unlikely to be self-sufficient and viable over societally relevant time scales.

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Forecasting Great Lakes Basin Responses to Future Change

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