PREDICTIVE MODELS FOR GREAT LAKES HYDROLOGY1

ABSTRACT: The individual hydrologic components are assumed to be normally distributed for each month and linear regression equations are estimated for predicting the value of the individual monthly hydrologic components. It is shown that some of the hydrologic components for downwind (in this case downstream) lakes are dependent upon hydrologic events for the upwind lakes. This is particularly so for precipitation in the downwind lake basins which appears to be dependent upon evaporation values for upwind lakes.     

EVALUATION OF GREAT LAKES NET BASIN SUPPLY FORECASTS1

ABSTRACT: Evaluation of the Great Lakes Environmental Research Laboratory's (GLERL's) physically-based monthly net basin supply forecast method reveals component errors and the effects of model improvements for use on the Laurentian Great Lakes. While designed for probabilistic outlooks, it is assessed for giving deterministic outlooks along with other net basin supply forecast methods of the U.S. Army Corps of Engineers and Environment Canada, and with a stochastic approach commissioned by the Corps. The methods are compared to a simple clima-tological forecast and to actual time series of net basin supplies. Aetual net basin supplies are currently determined by estimating all components directly, instead of as water-balance residuals. This is judged more accurate and appropriate for both forecasting and simulation. GLERL's physically-based method forecasts component supplies while the other methods are based on residual supplies. These other methods should be rederived to be based on component supplies. For each of these other methods, differences between their outlooks and residual supplies are used as error estimates for the rederived methods and component supplies. The evaluations are made over a recent period of record high levels followed by a record drought. Net basin supply outlooks are better than climatology, and GLERL's physically-based method performs best with regard to either component or residual net basin supplies. Until advances are made in long-range climate outlooks, deterministic supply outlooks cannot be improved significantly.     

Ohio's Balanced Growth Program: a case study of collaboration for planning and policy design

This paper describes the collaborative planning process for a new landscape planning programme in Ohio that seeks to influence land urbanisation patterns through joint local land use decision making on a watershed basis. The programme was developed through a collaborative process by a state agency-appointed task force that included agency staff and a wide range of stakeholders. The paper describes the process in terms of the collaborative mechanisms, the participants, the programmatic outputs, and the social and organisational outcomes that set the foundation for enhanced watershed quality through better land use decision-making practices. Key collaborations formed during the process were inter-agency collaborations, a non-profit organisation that partnered with the agencies, and that of state agencies with local governments to develop watershed-based land use plans. A most critical outcome was creation of a learning community, through an exploratory research process that used multiple methods of data gathering and consensus-building deliberation. The paper is based on a review of published documents and plans, meeting minutes, participant observation of committee and workgroup meetings and interactive research.     

Of Small Streams and Great Lakes: Integrating Tributaries to Understand the Ecology and Biogeochemistry of Lake Superior

Lake Superior receives inputs from approximately 2,800 tributaries that provide nutrients and dissolved organic matter (DOM) to the nearshore zone of this oligotrophic lake. Here, we review the magnitude and timing of tributary export and plume formation in Lake Superior, how these patterns and interactions may shift with global change, and how emerging technologies can be used to better characterize tributary–lake linkages. Peak tributary export occurs during snowmelt‐driven spring freshets, with additional pulses during rain‐driven storms. Instream processing and transformation of nitrogen, phosphorus, and dissolved organic carbon (DOC) can be rapid but varies seasonally in magnitude. Tributary plumes with elevated DOC concentration, higher turbidity, and distinct DOM character can be detected in the nearshore during times of high runoff, but plumes can be quickly transported and diluted by in‐lake currents and mixing. Understanding the variability in size and load of these tributary plumes, how they are transported within the lake, and how long they persist may be best addressed with environmental sensors and remote sensing using autonomous and unmanned vehicles. The connections between Lake Superior and its tributaries are vulnerable to climate change, and understanding and predicting future changes to these valuable freshwater resources will require a nuanced and detailed consideration of tributary inputs and interactions in time and space.     

A Probabilistic,Parcel‐Level Inundation Prediction Tool for Medium‐Range Flood Forecasting in Large Lake Systems

This study contributes a bathtub‐style inundation prediction model with abstractions of coastal processes (i.e., storm surge and wave runup) for flood forecasting at medium‐range (weekly to monthly) timescales along the coastline of large lakes. Uncertainty from multiple data sources are propagated through the model to establish probabilistic bounds of inundation, providing a conservative measure of risk. The model is developed in a case study of the New York Lake Ontario shoreline, which has experienced two record‐setting floods over the course of three years (2017–2019). Predictions are developed at a parcel‐level and are validated using inundation accounts from an online survey and flyover imagery taken during the recent flood events. Model predictions are compared against a baseline, deterministic model that accounts for the same processes but does not propagate forward data uncertainties. Results suggest that a probabilistic approach helps capture observed instances of inundation that would otherwise be missed by a deterministic inundation model. However, downward biases are still present in probabilistic predictions, especially for parcels impacted by wave runup. The goal of the tool is to provide community planners and property owners with a conservative, parcel‐level assessment of flood risk to help inform short‐term emergency response and better prepare for future flood events.     

Environmentally stratified sampling design for the development of Great Lakes environmental indicators

Understanding the relationship between human disturbance and ecological response is essential to the process of indicator development. For large-scale observational studies, sites should be selected across gradients of anthropogenic stress, but such gradients are often unknown for a population of sites prior to site selection. Stress data available from public sources can be used in a geographic information system (GIS) to partially characterize environmental conditions for large geographic areas without visiting the sites. We divided the U.S. Great Lakes coastal region into 762 units consisting of a shoreline reach and drainage-shed and then summarized over 200 environmental variables in seven categories for the units using a GIS. Redundancy within the categories of environmental variables was reduced using principal components analysis. Environmental strata were generated from cluster analysis using principal component scores as input. To protect against site selection bias, sites were selected in random order from clusters. The site selection process allowed us to exclude sites that were inaccessible and was shown to successfully distribute sites across the range of environmental variation in our GIS data. This design has broad applicability when the goal is to develop ecological indicators using observational data from large-scale surveys.     

PCBs in sediments of the Great Lakes--distribution and trends, homolog and chlorine patterns, and in situ degradation

A region-wide data analysis on polychlorinated biphenyls (PCBs) in the sediment of the Great Lakes reveals a total accumulation of approximately 300 ± 50 tonnes, representing a >30% reduction from the 1980s. Evidence of in situ degradation of sediment PCB was found, with estimated t_1/2 of 11 and 17 years, at two open water locations in Lake Ontario. The relative abundance of heavy homologs as well as para-chlorines decreases with increasing depth, while the opposite is true for medium and light homologs and ortho-chlorines. In Lake Michigan, the vertical pattern features enrichment of heavier congeners and reduction of ortho-chlorines in deeper sediment layers, opposite to the trend in Lake Ontario. PCBs decrease log-linearly with increasing latitude and longitude. Air deposition of PCBs to lake sediment decreases at about 0.077 ng cm⁻² yr⁻¹ per degree latitude (N) for the geographic region extending from the Great Lakes to within the Arctic Circle.     

Zinc and lead sequestration in an impacted wetland system

The fate and bioavailability of pollutant metals is important to the long-term health of freshwater wetland systems, particularly in areas with elevated background levels of trace metals. Precipitation of some authigenic mineral phases in wetland sediments can potentially limit metal bioavailability through sequestration in low-solubility compounds, such as metal sulfides. Zinc and Pb concentrations were analyzed in water, plant and sediment samples taken from a metal-contaminated wetland in Chicago, IL, USA in order to assess metal fate and bioavailability, while X-ray absorption spectroscopy (XAS) studies were conducted to determine zinc speciation in the wetland sediments. The results showed sequestration of metal into the pond sediments, most likely in iron precipitate phases. In surface sediments, re-release of Zn and Pb into pore waters was correlated with microbial iron reduction, while the presence of sulfide in anoxic pore waters corresponded to decreased dissolved concentrations of both elements. Analysis of extended X-ray absorption fine structure (EXAFS) data confirmed that sulfide compounds dominated zinc speciation throughout the sediment. Uptake of trace metals in Phragmites plants was limited primarily to plant roots, while concentrations of both Pb and Zn in aquatic vegetation were significantly elevated, representing a potential bioaccumulation hazard.     

湖泊健康评价指标体系及评价方法初探

湖泊健康评价是进行湖泊监测和管理的基础。丰富了湖泊生态系统健康的概念,指出其应当考虑湖泊的各种服务功能。以湖泊生态系统健康概念为基础,构建了湖泊健康评价指标体系,给出16个综合评价指标及各指标评分方法。以四川大学明远湖为例,采用层次分析法（AHP）计算各指标权重,对其进行健康评价,得出健康综合指数为3.55,表明整个湖泊处于＂较健康＂状态,分析了影响湖泊健康状态的疾病因子及湖泊的生态修复方法。     

巢湖水资源开发和水环境保护

巢湖是我国五大淡水湖之一,也是安徽省最大淡水湖,对安徽省的工农业生产和人民生活起着举足轻重的作用。本文分析了对巢湖水资源开发中产生的主要环境问题,并提出了在保护生态环境的前提下开发巢湖水资源的战略措施。