GREAT LAKES WATER RESOURCES: CLIMATE CHANGE IMPACT ANALYSIS WITH TRANSIENT GCM SCENARIOS1

ABSTRACT: The U.S. Army Corps of Engineers conducted an assessment of Great Lakes water resources impacts under transient climate change scenarios. The integrated model linked empirical regional climate downscaling, hydrologic and hydraulic models, and water resource use sub-models. The water resource uses include hydropower, navigation, shoreline damages, and wetland area. The study is unique in that both steady-state 2°CO₂ and transient global circulation model (GCM) scenarios were used and compared to each other. The results are consistent with other impact studies in that high scatter in regional climate among the GCM scenarios lead to high uncertainty in impacts. Nevertheless, the transient scenarios show that in the near-term (approximately 20 years) significant changes could occur. This result only adds to the urgency of creating more flexible and robust management of water resources uses.     

LAKE ONTARIO REGULATION UNDER TRANSPOSED CLIMATES1

ABSTRACT: The implications of Lake Ontario regulation under transposed climates with changed means and variability are presented for seasonal and annual time scales. The current regulation plan is evaluated with climates other than the climate for which it was developed and tested. This provides insight into potential conflicts and management issues, development of regulation criteria for extreme conditions, and potential modification of the regulation plan. Transposed climates from the southeastern and south central continental United States are applied to thermodynamic models of the Great Lakes and hydrologic models of their watersheds; these climates provide four alternative scenarios of water supplies to Lake Ontario. The scenarios are analyzed with reference to the present Great Lakes climate. The responses of the Lake Ontario regulation plan to the transposed climate scenarios illustrate several key issues: (1) historical water supplies should no longer be the sole basis for testing and developing lake regulation plans; (2) during extreme supply conditions, none of the regulation criteria can be met simultaneously, priority of interests may change, and new interests may need to be considered, potentially requiring substantial revision to the Boundary Waters Treaty of 1909; (3) revised regulation criteria should be based on ecosystem health and socio-economic benefits for a wider spectrum of interests and not on frequencies and ranges of levels and flows of the historical climate; and (4) operational management of the lake should be improved under the present climate, and under any future climate with more variability, through the use of improved water supply forecasts and monitoring of current hydrologic conditions.     

PROJECTED INCREASES IN MUNICIPAL WATER USE IN THE GREAT LAKES DUE TO CO2-INDUCED CLIMATIC CHANGE1

ABSTRACT: Two scenarios of CO₂-induced climatic change are used to estimate changes in water use for a number of municipalities in the Great Lakes region of Canada and the United States. Both scenarios, based on General Circulation Models produced by the Goddard Institute for Space Studies (GISS) and Geophysical Fluid Dynamics Lab (GFDL), project warmer temperatures for the region. Using regression models based on monthly potential evapotranspiration for individual cities, it is projected that annual per capita water use will increase by a small amount, which will probably have only a marginal effect on water supplies in the Great Lakes basin. This method could also be used to assess the potential impacts of CO₂-induced climatic change on water use by the agriculture and power sectors, as well as the effectiveness of water policy initiatives, such as price changes. More work is needed to project water use during peak periods (warm dry spells), which may occur more frequently in a 2 × CO₂ climate in this region.     

Flooding and erosion hazards on the ontario great lakes shoreline: a human ecological approach to planning and management

Understanding flood and erosion hazards in the context of developing coastal management plans requires an appreciation for variations in climate, geology, vegetation, land uses, human activities and institutional arrangements. On the Great Lakes, fluctuating water levels are characterized by temporal variations in their magnitude and frequency and their impact on flooding and erosion also differ from site to site. The traditional planning and management mechanisms in Ontario, through the use of emergency responses and land use setbacks, have been insufficient in resolving the rising costs of damage to property due to flooding and erosion along the Great Lakes shoreline. There is a need to develop an alternative management model with a focus on understanding hazards in the context of their natural and human components. A case study of the preparation of a resource survey for the Saugeen Valley Conservation Authority illustrates the development of a human ecological approach and its applicability in developing shoreline management plans for the Great Lakes.     

Urban water demand and climate change

This paper presents a methodology for improved understanding of options for managing urban water demands under the uncertainties associated with climate change. It combines a sensitivity analysis of water supply with forecasts of water demand and examines how conservation efforts may offset deficits which result from climate change. It presents a case study of Nassau County, New York State, USA, that concludes that deficits projected for warmer climate scenarios can probably be alleviated by increased conservation. For scenarios of decreased precipitation, more extreme measures (eg rationing) may be necessary, illustrating the prudence of considering climate change in planning studies for communities which already experience water supply problems.     

An evaluation of the impact of persistent water level changes on the areal extent of Georgian Bay/North Channel marshlands

A conceptual mathematical model has recently been devised to assist environmental managers in predicting the impact on coastal marsh areas of long-term changes in water levels. The model considers such impact solely in terms of the geometry of the confining basin, the change in ambient water level, and the maximum depth for which bottom-rooted emergent vegetation is present. This model is applied to 17 shoreline marshes of various shapes in the Georgian Bay/North Channel region of the Great Lakes.Model outputs of predicted maximum and minimum marsh area subsequent to changes in long-term levels are compared to marsh areas measured from available historical air photos dating from 1935 to 1985. The results of such comparisons indicate that such a geometric model, despite its neglect of the biological complexities of marsh ecology, can serve as a valuable tool for assessing the range of impacts of both natural and man-made changes in long-term ambient water levels on shoreline marshes.     

A Rapid Response Survey to Characterize the Impacts of the 2017 High Water Event on Lake Ontario

In the spring and summer of 2017, communities along the Lake Ontario shoreline suffered from the worst flood event on record. In late May, daily water levels reached their highest point in over 100 years, and flooding continued throughout much of the summer as lake levels slowly declined, with inundation and erosion significantly impacting shoreline homes and businesses. In this work, we present results from a rapid response online survey of property owners along the New York Lake Ontario shoreline to quantify the perceived flood impacts of the 2017 extended high water event. The survey focused on the degree and spatial distribution of inundation and erosion; the duration and drivers of inundation; the associated damages to different property features, with an emphasis on shoreline protection; and the degree of disruption to business and other activities and services. Photographic documentation of inundation extent and property damage also was provided by survey respondents. We demonstrate the potential utility of this dataset by characterizing key features of inundation and erosion impacts across the shoreline, and by using classification and regression trees to explore the predictability of inundation and erosion based on property characteristics. This work is part of a larger effort to develop models of inundation and erosion that can support flood impact assessments across the shoreline and help communities better prepare for future extended high water events.     

Impact of Climate and Land Use Change on Streamflow and Sediment Yield in a Snow‐Dominated Semiarid Mountainous Watershed

This study investigates the impact of climate and land use change on the magnitude and timing of streamflow and sediment yield in a snow‐dominated mountainous watershed in Salt Lake County, Utah using a scenario approach and the Hydrological Simulation Program — FORTRAN model for the 2040s (year 2035–2044) and 2090s (year 2085–2094). The climate scenarios were statistically and dynamically downscaled from global climate models. Land use and land cover (LULC) changes were estimated in two ways — from a regional planning scenario and from a deterministic model. Results indicate the mean daily streamflow in the Jordan River watershed will increase by an amount ranging from 11.2% to 14.5% in the 2040s and from 6.8% to 15.3% in the 2090s. The respective increases in sediment load in the 2040s and 2090s is projected to be 6.7% and 39.7% in the canyons and about 7.4% to 14.2% in the Jordan valley. The historical 50th percentile timing of streamflow and sediment load is projected to be shifted earlier by three to four weeks by mid‐century and four to eight weeks by late‐century. The projected streamflow and sediment load results establish a nonlinear relationship with each other and are highly sensitive to projected climate change. The predicted changes in streamflow and sediment yield will have implications for water supply, flood control and stormwater management.     

MODELING HYDROLOGIC IMPACT OF WITHDRAWING THE GREAT LAKES WATER FOR AGRICULTURAL IRRIGATION1

ABSTRACT: Growing interest in agricultural irrigation in the Great Lakes basin presents an increasing competition to other uses of Great Lakes water. This paper, through a case study of the Mud Creek Irrigation District in the Saginaw Bay basin, Michigan, evaluates the potential hydrologic effects of withdrawing water for agricultural irrigation to the Great Lakes. Crop growth simulation models for corn, soybeans, dry beans, and the FAO Penman method were used to estimate the difference in evapotranspiration rates between irrigated and nonirrigated identical crops, based on climate, soil, and management data. The simulated results indicate that an additional 70–120 mm of water would be evapotranspirated during the growing season from irrigated crop fields as compared to nonirrigated identical plantings. Dependent upon the magnitude of irrigation expansion, an equivalent of about 1 to 5 mm of water from Lakes Huron-Michigan could be lost to the atmosphere. If agricultural irrigation further expands in the entire Great Lakes basin, the aggregated potential of water loss to the atmosphere through ET from all five Great Lakes would be even greater.     

POTENTIAL EFFECTS OF CLIMATE CHANGE ON GROUND WATER IN LANSING,MICHIGAN1

ABSTRACT: Computer simulations involving general circulation models, a hydrologic modeling system, and a ground water flow model indicate potential impacts of selected climate change projections on ground water levels in the Lansing, Michigan, area. General circulation models developed by the Canadian Climate Centre and the Hadley Centre generated meteorology estimates for 1961 through 1990 (as a reference condition) and for the 20 years centered on 2030 (as a changed climate condition). Using these meteorology estimates, the Great Lakes Environmental Research Laboratory's hydrologic modeling system produced corresponding period streamflow simulations. Ground water recharge was estimated from the streamflow simulations and from variables derived from the general circulation models. The U.S. Geological Survey developed a numerical ground water flow model of the Saginaw and glacial aquifers in the Tri‐County region surrounding Lansing, Michigan. Model simulations, using the ground water recharge estimates, indicate changes in ground water levels. Within the Lansing area, simulated ground water levels in the Saginaw aquifer declined under the Canadian predictions and increased under the Hadley.     

Water Quality and Plankton in the United States Nearshore Waters of Lake Huron

Our goal in the development of a nearshore monitoring method has been to evaluate and refine an in situ mapping approach to assess the nearshore waters across the Great Lakes. The report here for Lake Huron is part of a broader effort being conducted across all five Great Lakes. We conducted an intensive survey for the United States nearshore of Lake Huron along a continuous shoreline transect (523?km) from Port Huron, Michigan, to Detour Passage. A depth contour of 20?m was towed with a conductivity-temperature depth profiler, fluorometer, transmissometer, and laser optical plankton counter. Multiple cross-contour tows (10-30?m) on the cruise dates were used to characterize the variability across a broader range of the nearshore. The cross-contour tows were comparable with the alongshore contour indicating that the 20-m contour does a good job of representing the nearshore region (10-30?m). Strong correlations were observed between water quality and spatially associated watershed land use. A repeat tow separated by several weeks investigated temporal variability in spatial patterns within a summer season. Strong correlations were observed across each variable for the temporal repeat across broad- and fine-scale spatial dimensions. The survey results for Lake Huron nearshore are briefly compared with a similar nearshore survey in Lake Superior. The biomass concentrations of lower food web components of Lake Huron were notably approximately 54-59?% of those in Lake Superior. The towed instrumentation survey supported the recent view of a change in Lake Huron to an ultra-oligotrophic state, which has been uncharacteristic in recent history.     

HOW CLIMATE UNCERTAINTY SHOULD BE INCLUDED IN GREAT LAKES MANAGEMENT: MODELING WORKSHOP RESULTS1

ABSTRACT: In two workshops, we evaluated decision analysis methods for comparing Lake Erie levels management alternatives under climate change uncertainty. In particular, we wanted to see how acceptable and effective those methods could be in a public planning setting. The methods evaluated included simulation modeling, scenario analysis, decision trees and structured group discussions. We evaluated the methods by interviewing the workshop participants before and after the workshops. The participants, who were experienced Great Lakes water resources managers, concluded that simulation modeling is user-friendly enough to enable scenario analysis even in workshop settings for large public planning studies. They felt that simulation modeling can improve not only understanding of the system, but also of the options for managing it. Scenario analysis revealed that the decision for the case study, Lake Erie water level regulation, could be altered by the likelihood of climate change. The participants also recommended that structured group discussions be used in public planning settings to elicit ideas and opinions. On the other hand, the participants were less optimistic about decision trees because they felt that the public might view subjective probabilities as difficult to understand and subject to manipulation.     

Assessing Risk in Operational Decisions Using Great Lakes Probabilistic Water Level Forecasts

/ A method adapted from the National Weather Service's Extended Streamflow Prediction technique is applied retrospectively to three Great Lakes case studies to show how risk assessment using probabilistic monthly water level forecasts could have contributed to the decision-mak-ing process. The first case study examines the 1985 International Joint Commission (IJC) decision to store water in Lake Superior to reduce high levels on the downstream lakes. Probabilistic forecasts are generated for Lake Superior and Lakes Michigan-Huron and used with riparian inundation value functions to assess the relative impacts of the IJC's decision on riparian interests for both lakes. The second case study evaluates the risk of flooding at Milwaukee, Wisconsin, and the need to implement flood-control projects if Lake Michigan levels were to continue to rise above the October 1986 record. The third case study quantifies the risks of impaired municipal water works operation during the 1964-1965 period of extreme low water levels on Lakes Huron, St. Clair, Erie, and Ontario. Further refinements and other potential applications of the probabilistic forecast technique are discussed.KEY WORDS: Great Lakes; Water levels; Forecasting; Risk; Decision making     

Water Stress Projections for the Northeastern and Midwestern United States in 2060: Anthropogenic and Ecological Consequences

Future climate and land‐use changes and growing human populations may reduce the abundance of water resources relative to anthropogenic and ecological needs in the Northeast and Midwest (U.S.). We used output from WaSSI, a water accounting model, to assess potential changes between 2010 and 2060 in (1) anthropogenic water stress for watersheds throughout the Northeast and Midwest and (2) native fish species richness (i.e., number of species) for the Upper Mississippi water resource region (UMWRR). Six alternative scenarios of climate change, land‐use change, and human population growth indicated future water supplies will, on average across the region, be adequate to meet anthropogenic demands. Nevertheless, the number of individual watersheds experiencing severe stress (demand > supplies) was projected to increase for most scenarios, and some watersheds were projected to experience severe stress under multiple scenarios. Similarly, we projected declines in fish species richness for UMWRR watersheds and found the number of watersheds with projected declines and the average magnitude of declines varied across scenarios. All watersheds in the UMWRR were projected to experience declines in richness for at least two future scenarios. Many watersheds projected to experience declines in fish species richness were not projected to experience severe anthropogenic water stress, emphasizing the need for multidimensional impact assessments of changing water resources.     

MATHEMATICAL MODELS: PLANNING TOOLS FOR THE GREAT LAKES1

The Great Lakes Basin Commission has initiated a Framework Study to assess the present and projected water- and related land-resource problems and demands in the Great Lakes Basin. Poorly defined objectives; incomplete and inconsistent data arrays; unknown air, biota, water, and sediment interactions; and multiple planning considerations for interconnected, large lake systems hinder objective planning. To incorporate mathematical modeling as a planning tool for the Great Lakes, a two-phase program, comprising a feasibility and design study followed by contracted and in-house modeling, data assembly, and plan development, has been initiated. The models will be used to identify sensitivities of the lakes to planning and management alternatives, insufficiencies in the data base, and inadequately understood ecosystem interactions. For the first time objective testing of resource-utilization plans to identify potential conflicts will provide a rational and cost-effective approach to Great Lakes management. Because disciplines will be interrelated, the long-term effects of planning alternatives and their impacts on neighboring lakes and states can be evaluated. Testing of the consequences of environmental accidents and increased pollution levels can be evaluated, and risks to the resource determined. Examples are cited to demonstrate the use of such planning tools.     

Climate and Land Use Effects on Hydrologic Processes in a Primarily Rain‐Fed,Agricultural Watershed

Anticipating changes in hydrologic variables is essential for making socioeconomic water resource decisions. This study aims to assess the potential impact of land use and climate change on the hydrologic processes of a primarily rain‐fed, agriculturally based watershed in Missouri. A detailed evaluation was performed using the Soil and Water Assessment Tool for the near future (2020–2039) and mid‐century (2040–2059). Land use scenarios were mapped using the Conversion of Land Use and its Effects model. Ensemble results, based on 19 climate models, indicated a temperature increase of about 1.0°C in near future and 2.0°C in mid‐century. Combined climate and land use change scenarios showed distinct annual and seasonal hydrologic variations. Annual precipitation was projected to increase from 6% to 7%, which resulted in 14% more spring days with soil water content equal to or exceeding field capacity in mid‐century. However, summer precipitation was projected to decrease, a critical factor for crop growth. Higher temperatures led to increased potential evapotranspiration during the growing season. Combined with changes in precipitation patterns, this resulted in an increased need for irrigation by 38 mm representing a 10% increase in total irrigation water use. Analysis from multiple land use scenarios indicated converting agriculture to forest land can potentially mitigate the effects of climate change on streamflow, thus ensuring future water availability.     

Forest environmental investments and implications for climate change mitigation

Forest environmental conditions are affected by climate change, but investments in forest environmental quality can be used as part of the climate change mitigation strategy. A key question involving the potential use of forests to store more carbon as part of climate change mitigation is the impact of forest investments on the timing and quantity of forest volumes that affect carbon storage. Using an economic optimization model, we project levels of U.S. forest volumes as indicators of carbon storage for a wide range of private forest investment scenarios. Results show that economic opportunities exist to further intensify timber management on some hectares and reduce the average timber rotation length such that the national volume of standing timber stocks could be reduced relative to projections reflecting historical trends. The national amount of timber volume is projected to increase over the next 50 yr, but then is projected to decline if private owners follow an economic optimization path, such as with more forest type conversions and shorter timber rotations. With perfect foresight, future forest investments can affect current timber harvest levels, with intertemporal linkages based on adjustments through markets. Forest investments that boost regenerated timber yields per hectare would act to enhance ecosystem services (e.g., forest carbon storage) if they are related to the rate of growth and extent of growing stock inventory.     

A Decision‐Analytic Approach to Managing Climate Risks: Application to the Upper Great Lakes1

Brown, Casey, William Werick, Wendy Leger, and David Fay, 2011. A Decision‐Analytic Approach to Managing Climate Risks: Application to the Upper Great Lakes. Journal of the American Water Resources Association (JAWRA) 47(3):524‐534. DOI: 10.1111/j.1752‐1688.2011.00552.x Abstract: In this paper, we present a risk analysis and management process designed for use in water resources planning and management under climate change. The process incorporates climate information through a method called decision‐scaling, whereby information related to climate projections is tailored for use in a decision‐analytic framework. The climate risk management process begins with the identification of vulnerabilities by asking stakeholders and resource experts what water conditions they could cope with and which would require substantial policy or investment shifts. The identified vulnerabilities and thresholds are formalized with a water resources systems model that relates changes in the physical climate conditions to the performance metrics corresponding to vulnerabilities. The irreducible uncertainty of climate change projections is addressed through a dynamic management plan embedded within an adaptive management process. Implementation of the process is described as applied in the ongoing International Upper Great Lakes Study.     

EFFECT OF INFLUENT PHOSPHORUS REDUCTIONS ON GREAT LAKES SEWAGE TREATMENT COSTS1

ABSTRACT: Controlling phosphorus sources, such as laundry detergents, for eutrophication control has been the aim of water resources management in many areas. However, the advisability of limiting phosphorus in raw wastewater continues to be debated. One aspect that has received little attention is the cost savings at sewage treatment plants practing phosphorus removal. It is estimated, based on available data and observations where detergent phosphorus has been reduced, that cost savings could range from about $0.20 to $1.70 per capita per year for an influent reduction of about 1.5 mg/L of phosphorus. These savings result mostly from a decrease in the amount of chemicals needed to remove phosphorus at the plant as well as a decrease in sludge production. For the U.S. Great Lakes basin, total annual savings amounting to several million dollars are projected given a basin-wide ban. Although estimates of cost savings are presented for the Great Lakes basin, the results are applicable to other areas where phosphorus controls are being considered.     

CLIMATIC VARIATION AND SURFACE WATER RESOURCES IN THE GREAT BASIN REGION1

ABSTRACT: There is mounting evidence that increasing amounts of atmospheric carbon dioxide may lead to significant changes in global climate during the next century. The possible effects of such climatic changes on surface runoff in the Great Basin Region of the western United States has been investigated by applying water balance models to four watersheds in Nevada and Utah. The most probable change, a 2°C increase in average annual temperature coupled with a 10 percent decrease in precipitation, would reduce runoff from 17 to 28 percent of the present mean, with drier basins showing the greatest change. Decreasing precipitation by 25 percent causes runoff reductions of 33 to 51 percent. Equivalent changes to a cooler and wetter climate show corresponding increases in runoff of approximately the same magnitude, but such a shift is not considered likely. Based on projected water requirements for the year 2000, a change to a warmer and drier climate would cause severe water shortages in many parts of the Great Basin.