Impacts of climate change on hydrology and water quality: Future proofing management strategies in the Lake Simcoe watershed,Canada

The impacts of climate change on hydrology and water quality of the Black River, a tributary of Lake Simcoe, Canada, were assessed for the period 2001–2100, by integrating two models, HBV and INCA-P, and using statistically downscaled data from the Global Circulation Model CGCM3 for two IPCC scenarios (A1b and A2). The effectiveness of catchment management strategies was assessed across the 21st century by simulating controls on sewage treatment works and fertiliser applications, and implementing buffer strips and bank erosion controls.     

Extreme water level rise across the upper Laurentian Great Lakes region: Citizen science documentation 2010–2020

As the global water balance accelerates in a warming climate, extreme fluctuations in the water levels of lakes and aquifers are anticipated, with biogeochemical, ecological and water supply consequences. However, it is unclear how site-specific factors, such as location, morphometry and hydrology, will modulate these impacts on regional spatial scales. Here, we report water level time series collected by citizen scientists for 15 diverse inland lakes in the upper Laurentian Great Lakes region from 2010 to 2020, and we compare these time series with those for the two largest Great Lakes, Lake Superior and Lake Michigan-Huron. Combined with historical data (1942–2010), the findings indicate that lakes spanning seven orders of magnitude in size (10^?2 to 10⁵ km²) all rebounded from record low to record high water levels during the recent decade. They suggest coherent water level oscillations among regional lakes (large and small) implying a common, near-decadal, climatic driver that may be changing.     

Forecasting impacts of climate change on Great Lakes surface water temperatures

Temperature influences the rates of many ecosystem processes. A number of recent studies have found evidence of systematic increases in Great Lakes surface water temperatures. Our study aims to construct empirical relationships between surface water temperatures and local air temperatures that can be used to estimate future water temperatures using future air temperatures generated by global climate models. Remotely sensed data were used to model lake-wide average surface water temperature patterns during the open-water period in Lakes Superior, Huron, Erie, and Ontario. Surface water temperatures typically exhibit linear warming through the spring, form a plateau in mid-summer and then exhibit linear cooling in fall. Lake-specific warming and cooling rates vary little from year to year while plateau values vary substantially across years. These findings were used to construct a set of lake-specific empirical models linking surface water temperatures to local air temperatures for the period 1995–2006. Hindcasted whole-lake water temperatures from these models compare favourably to independently collected offshore water temperatures for the period 1968–2002. Relationships linking offshore water temperatures to inshore water temperatures at specific sites are also described. Predictions of future climates generated by the Canadian Global Climate Model Version 2 (CGCM2) under two future greenhouse gas emission scenarios are used to scope future Great Lakes surface water temperatures: substantial increases are expected, along with increases in the duration of summer stratification.     

The 2017 African Great Lakes Conference: Conservation and development in a changing climate

In May 2017, the African Great Lakes community convened for a region-wide conference in Entebbe, Uganda. The African Great Lakes Conference (AGLC) focused on 6 regionally-important themes, and 300+ attendees presented over 100 talks and posters. The AGLC culminated in the adoption of a set of Conference Resolutions designed to direct the future of African Great Lakes conservation and management. As an Introduction to this Journal of Great Lakes Research special section on African Great Lakes, we report on the impetus for the African Great Lakes Conference as well as discuss three major advances and investments that were a direct result of conference resolutions adopted at the meeting. First, we present the AGLC Resolutions, a set of management issues and solutions developed at the conference. Second, we discuss the African Great Lakes Conference Fund, a conservation fund that has awarded $500,000 USD to launch four new initiatives. Finally, we describe African Great Lakes Inform, a knowledge management platform designed to promote collaboration in the region. The AGLC in general, and these three major conference outcomes specifically, provide a set of basic building blocks to advance partnerships, research and capacity in the African Great Lakes region.     

Changes in mid-summer water temperature and clarity across the Great Lakes between 1968 and 2002

In recent decades, three important events have likely played a role in changing the water temperature and clarity of the Laurentian Great Lakes: 1) warmer climate, 2) reduced phosphorus loading, and 3) invasion by European Dreissenid mussels. This paper compiled environmental data from government agencies monitoring the middle and lower portions of the Great Lakes basin (lakes Huron, Erie and Ontario) to document changes in aquatic environments between 1968 and 2002. Over this 34-year period, mean annual air temperature increased at an average rate of 0.037 °C/y, resulting in a 1.3 °C increase. Surface water temperature during August has been rising at annual rates of 0.084 °C (Lake Huron) and 0.048 °C (Lake Ontario) resulting in increases of 2.9 °C and 1.6 °C, respectively. In Lake Erie, the trend was also positive, but it was smaller and not significant. Water clarity, measured here by August Secchi depth, increased in all lakes. Secchi depth increased 1.7 m in Lake Huron, 3.1 m in Lake Ontario and 2.4 m in Lake Erie. Prior to the invasion of Dreissenid mussels, increases in Secchi depth were significant (p < 0.05) in lakes Erie and Ontario, suggesting that phosphorus abatement aided water clarity. After Dreissenid mussel invasion, significant increases in Secchi depth were detected in lakes Ontario and Huron.     

Tributary phosphorus monitoring in the U.S. portion of the Laurentian Great Lake Basin: Drivers and challenges

This paper examines the tributary monitoring network currently in place for sampling the amount of phosphorus entering the U.S. Great Lakes, focusing on the challenges faced by the agencies and organizations responsible for maintaining the network. The tributaries that are monitored vary in terms of flow, the size and terrain of the watershed being drained, and patterns of land use. Data generated by this network are used by researchers to compute lake-wide phosphorus loads. In this work, the primary drivers and challenges associated with operating an effective phosphorus tributary monitoring program were investigated through interviews with stakeholders responsible for managing a portion of the existing network. Based on these interviews, the authors identify three recommendations that policy makers interested in maintaining an effective phosphorus monitoring network in the Great Lakes should consider. The first is to provide states with incentives to support the long-term monitoring that is required to estimate phosphorus loads in tributaries to the Great Lakes; currently, most states design their programs to meet the requirements of the Clean Water Act, which results in patterns of sampling that are not necessarily useful for computing loads. The second recommendation is to facilitate the creation of a monitoring protocol that generates enough samples to identify trends and quantify loads at a level of certainty necessary for use in statistical models and load control programs. Finally, funding mechanisms capable of supporting long-term monitoring programs need to be established, with programs in Michigan and Minnesota serving as potential models.     

Revisiting the Great Lakes Water Quality Agreement phosphorus targets and predicting the trophic status of Lake Michigan

LM3-Eutro is a high-resolution eutrophication model with several improved features lacking in historical Great Lakes models. We calibrated LM3-Eutro using a 2-year (1994-1995) dataset and performed a hindcast simulation from 1976 to 1995 to evaluate the model's ability to make predictions over an extended period of time. Results show a reasonable agreement between model output and field data over this time period. The model predicted that an annual loading of 5600 metric tons (MT) would result in a lake-wide annual total phosphorus (TP) concentration of 7.5 μg L^− 1. Using best estimates of future TP loadings, LM3-Eutro forecasts suggest that Lake Michigan will remain oligotrophic and will continue to meet the 7 μg L^− 1 spring TP concentration Great Lakes Water Quality Agreement objective.     

Dominant glacial landforms of the lower Great Lakes region exhibit different soil phosphorus chemistry and potential risk for phosphorus loss

Phosphorus (P) losses from agricultural soils are a growing economic and water-quality concern in the Lake Erie watershed. While recent studies have explored edge-of-field and watershed P losses related to land-use and agricultural management, the potential for soils developed from contrasting parent materials to retain or release P to runoff has not been examined. A field-based study comparing eight agricultural fields in contrasting glacial landscapes (hummocky coarse-textured till-plain, lacustrine and fine-textured till-plain) showed distinct physical and geochemical soil properties influencing inorganic P (P_i) partitioning throughout the soil profile between the two regions. Fields located on the coarse-textured till-plain in mid-western Ontario, Canada had alkaline calcareous soils with the highest Total-P_i concentrations and the majority of soil P_i stored in an acid-soluble pool (up to 91%). In contrast, loosely to moderately soluble P_i concentrations were higher in soils of the lacustrine and fine-textured till-plain in southwestern Ontario, northeast Indiana and northwestern Ohio, US. Overall, soils on the lacustrine and fine-textured till-plain had a greater shrink swell-capacity, likely creating preferential flow to minimize P_i interaction with the more acidic, lower carbonate and lower sorption capacity soils. These differences in soil P_i retention and transport pathways demonstrate that in addition to management, the natural landscape may exert a significant control on how P_i is mobilized throughout the Lake Erie watershed. Further, results indicate that careful consideration of region-specific hydrology and soil biogeochemistry may be required when designing appropriate management strategies to minimize P_i losses across the lower Great Lakes region.     

The past is a key to the future: Lessons paleoecological data can provide for management of the African Great Lakes

Rapid ecological changes in the African Great Lakes (AGL) present lake managers with extraordinary challenges to understand the changes' underlying causes and forecast what they portend for the future. Monitoring and experimental data from the AGL are essential but are limited in duration and continuity. The magnitude of change suggests that a centennial-millennial timescale perspective is needed to identify drivers of change and prepare for changes yet to come. In this review I propose that paleoecological and paleolimnological approaches can provide this perspective.AGL paleorecords have documented the impacts of excess sedimentation, external nutrient loading, and climate change, and can demonstrate the specific ecosystem responses associated with these various drivers. Paleorecords can help us understand how multiple stressors interact and in some cases can falsify specific cause-and-effect hypotheses when the putative causes can be shown to have occurred after the effect started.The number of useful AGL paleorecords is still quite small. Replication is needed to test if patterns seen and hypotheses inferred from single localities are robust for an entire lake, and to understand regional variability within and between lakes. Because many paleorecord methods are quite inexpensive it would be highly desirable if these approaches were incorporated into the routine tool kit of local AGL scientists working in tandem with fisheries and water-quality scientists. Training African lake scientists and conservation biologists to analyze paleorecords should be a high priority for AGL stakeholders interested in the long-term prognoses for the economic and biodiversity resources that they oversee.     

Reducing current and future risks: Using climate change scenarios to test an agricultural conservation framework

Evaluating the potential effects of changes in climate on conservation practices can help inform strategies to protect freshwater biodiversity that are robust, even as conditions change. Here we apply a climate change “test” to a framework for estimating the amount of agricultural conservation practices needed to achieve desired fish conservation outcomes for four watersheds in the Saginaw Bay region of Michigan, USA. We developed three climate scenarios from global climate model outputs (high emissions scenario, “2080s” timeframe) to provide insight on potential impacts of a climate driver that represents a key uncertainty for this management system, the amount and timing of spring and summer precipitation. These scenarios were used as inputs to agricultural watershed models, which produced water quality outputs that we compared to thresholds in fish biodiversity metrics at the subwatershed scale. Our results suggest that impacts of climate change on evaporation rates and other aspects of hydrology will shift the relative importance of key stressors for fish (i.e., sediment loadings vs. nutrient concentrations) across these different watersheds, highlighting the need to design resilient implementation plans and policies. Overall, we found that changes in climate are likely to increase the need for agricultural conservation practices, but that increasing the implementation rate above current levels will likely remain a good investment under current and future climate conditions.     

Hydroclimatic variability across the international Lake of the Woods watershed: Implications for nutrient export and climate sensitivity

Characterizing streamflow and relationships with climate and watershed characteristics is an essential first step in the design of any monitoring program to assess basin response to changes in land use or climate. This is especially true for the international Lake of the Woods watershed, where recurrent algae blooms have been associated with nutrient inputs from the watershed and climate warming. Here, we present a basin-wide hydroclimatic analysis within the sparsely monitored Canadian portion of the basin. Spatial and temporal patterns in climate and runoff were assessed across the two major geo-zones: the Precambrian ‘Shield zone’, dominated by bedrock, forests and lakes, and the poorly drained ‘Agassiz zone’ where ditching and drainage for agriculture have substantially enhanced the hydrologic connectivity. While climate conditions were consistent across the watershed, Agassiz basins were flashy, highly variable, and more seasonal compared with Shield rivers, likely due to the moderating effect of lake storage in the Shield region. Temperatures increased across the basin (1910–2010), and there was more rainfall and runoff during the ice-covered months (Nov-Mar), suggesting a shift toward earlier snowmelt. Marked seasonality and large swings in flow extremes at the Agassiz rivers suggest this region is particularly sensitive to hydroclimatic change and that frequent monitoring is needed to capture important periods of nutrient export like spring runoff and storm events. In contrast, substantial storage within the Shield landscape suggests this zone is more hydrologically ‘resilient’ to climate extremes and that water quality and quantity measurements can be less frequent.