Databases of point sources including combined sewer overflows (CSOs) were acquired from the governmental agencies to map the occurrences and magnitude of the CSOs. Multiple databases of land use, topography, hydrography, soils, and agricultural statistics were used to estimate nonpoint source loading potential in the Saginaw Bay Basin, Michigan. Animal manure production was computed from tabulations of animals by 5-digit zip code area for the census years of 1987, 1992, 1997, and 2002. Fertilizer applications for both urban and agricultural land uses were calculated from county fertilizer estimates for the same periods. Results indicate that point sources from municipalities, industrial sectors and business entities contribute approximately 25% of the total phosphorus load to Saginaw Bay, with the remainder being accounted for by nonpoint source contributions. While the total amount of nutrients (N and P) from animal manure and fertilizer applications and atmospheric deposition declined in the Saginaw Bay Basin, fertilizer applications in non-farmland increased significantly. Estimation of nutrient loading potential at 5-digit zip code level reveals more detailed spatial variation and critical areas of nutrient loading than county level data for implementation of targeted water quality programs.

An analysis of the Iowa City Ralston Creek hourly precipitation record is made prior to construction of data generation models to be used in an urbanization-flooding hazard study. The historical record of hourly precipitation has been constructed from a high density recording gage network within the watershed, with an unbroken length of 33 years (50 years with some discontinuities). A stochastic precipitation model is proposed on phenomenological terms for the time occurrence of storm events. Wet time intervals are scheduled using models for inter-arrival times. Traditional computation difficulties are circumvented in modeling certain time-related persistence effects through the use of independent random variables. The models are presented, described, fit to the data, discussed, and future work is outlined.

In this paper, we define a relatively new concept, resource by the movement of water and materials over specific temporal and spatial scales. Hydrological resource is a geographic area within which water and water-borne materials including nutrients, organic matter, sediments, and pollutants are originated, transported, and deposited to a location, at a specific time over a specific time period. Unlike watershed, the boundary of a hydrological resource shed is delineated by the contributing sources of water and materials to a river or lake during hydrological events and thus more dynamic. It focuses on both temporal and spatial distribution of water and materials within a changing space. We use Distributed Large Basin Runoff Model (DLBRM) to simulate and define the resource sheds and have developed a GIS interface to derive input variables to the DLBRM from multiple databases of land use, soil, DEM, climate, land cover, and hydrography. While relatively new, the concept of hydrological resource sheds provides a new way of displaying, understanding, and discovering the transport and distribution of water and materials and can help resource managers better track and manage source loadings in water quality management. An application example of resource sheds is shown to North America's Lake Erie Watersheds.

The distributed large basin runoff model (DLBRM) was designed to simulate the hydrological processes of the Great Lakes watersheds. As part of its development, the DLBRM was recently applied to 18 watersheds in the Lake Erie basin, where it was first calibrated to reproduce the observed discharge in 1950-1964 and then applied to 1999-2006. Four different calibration objective functions: root mean squared error (RMSE) minimization, mean absolute error (MAE) minimization, correlation maximization, and Nash-Sutcliffe index maximization were tested, revealing RMSE minimization as the most successful method and able to achieve results very close to its global minimum. Further, the distribution of the main DLBRM parameters in the 18 watersheds was consistent with regional patterns, although each watershed was calibrated individually, thus adding credibility to the calibration process. Model performances, while generally good, varied across the basin according to a series of environmental factors, including climate, watershed shape, topography, and land cover and observation factors such as gauging station distribution. Gauging station coverage proved to be extremely important in the ability of the model to track flow variability. The DLBRM proved to be able to replicate well the 1999-2006 hydrologies of most watersheds without recalibration. However, its performance declined in heavily urbanized watersheds, where the landscape changed the most. The results described in this paper will lead to improved model performance and increased practical applications of the DLBRM, providing important information to researchers and decision makers for efficient water management programs in Great Lakes watersheds. DOI: 10.1061/(ASCE) HE.1943-5584.0000304. (C) 2011 American Society of Civil Engineers.

Hydrological resource is defined as a geographic area that contributes material (e.g. water, nutrients, and sediments) over one time interval, passing through a location of interest over another time interval. While similar to the concept of watershed, this relatively new concept has some unique features. First, the boundary of a watershed is delineated by topography and relatively more stable. The boundary of a hydrologic resource shed, however, is delineated by the contributing sources of water and materials to a river or lake during hydrologic events, and changes over both space and time. Second, the concept of watershed emphasizes temporal distribution of water and materials within a given space, and the hydrologic resource shed focuses on both temporal and spatial distribution of water and materials within a changing space. Third, the concept of hydrologic resource shed incorporates the space-time variability in studying watershed patterns and processes. Taking advantage of current tracing, remote sensing, mapping, and modeling technologies, hydrologic resource shed provides a new way of discovering, understanding, and simulating the transport and distribution of water and materials across multiple space and time scales. An example is presented for computing the hydrologic resource shed distributions using a hydrologic model, Distributed Large Basin Runoff Model (DLBRM) in the Maumee River watershed in western Lake Erie Basin of the U.S.

Assessing regional impacts of climate change begins with development of climate projections at relevant temporal and spatial scales. Here, proven statistical downscaling methods are applied to relatively coarse-scale atmosphere–ocean general circulation model (AOGCM) output to improve the simulation and resolution of spatial and temporal variability in temperature and precipitation across the US Great Lakes region. The absolute magnitude of change expected over the coming century depends on the sensitivity of the climate system to human forcing and on the trajectory of anthropogenic greenhouse gas emissions. Annual temperatures in the region are projected to increase 1.4±0.6°C over the near-term (2010–2039), by 2.0±0.7°C under lower and 3±1°C under higher emissions by midcentury (2040–2069), and by 3±1°C under lower and 5.0±1.2°C under higher emissions by end-of-century (2070–2099), relative to the historical reference period 1961–1990. Simulations also highlight seasonal and geographical differences in warming, consistent with recent trends. Increases in winter and spring precipitation of up to 20% under lower and 30% under higher emissions are projected by end-of-century, while projections for summer and fall remain inconsistent. Competing effects of shifting precipitation and warmer temperatures suggest little change in Great Lake levels over much of the century until the end of the century, when net decreases are expected under higher emissions. Overall, these projections suggest the potential for considerable changes to climate in the US Great Lakes region; changes that could be mitigated by reducing global emissions to follow a lower as opposed to a higher emissions trajectory over the coming century.

Water shortage is a chronic problem in arid Northwest China. The rapid population growth and expanding urbanization as well as potential climate change impacts are likely to worsen the situation, threatening domestic, irrigation, and industrial supplies and even the survival of the ecosystems in Northwest China. This paper describes the preliminary work of adapting the Distributed Large Basin Runoff Model (DLBRM) to the Heihe watershed (the second largest inland river in arid Northwestern China, with a drainage area of 128,000 km(2)) for understanding distribution of glacial-snow melt, groundwater, surface runoff, and evapotranspiration, and for assessing hydrological impacts of climate change and glacial recession on water supply in the middle and lower reaches of the watershed. Preliminary simulation results show that the Qilian Mountain in the upper reach area produces most runoff in the Heihe watershed. The simulated daily river flows during the period of 1990-2000 indicate that the Heihe River discharges about 1x10(9)m(3) of water from the middle reach (at Zhengyixia Station) to lower reach, with surface runoff and interflow contributing 51 and 49 percent respectively. The sandy lower soil zone in the middle reach has the highest evapotranspiration rate and also contributes nearly half of the river flow. Work underway focuses on the DLBRM model improvement and incorporation of the climate change and management scenarios to the hydrological simulations in the watershed.

The NOAA Great Lakes Environmental Research Laboratory, Western Michigan University, and the University of Michigan are jointly developing a Distributed Large Basin Runoff Model (DLBRM), a physically based, spatially-distributed hydrology and water quality model, to simulate spatial and temporal point and nonpoint source material distributions in Great Lakes watersheds. We automatically calibrated the DLBRM hydrology to reproduce the 1950-1964 and the 1999-2006 watershed outflows in 18 watersheds throughout the Great Lakes region with excellent results; we are extending it to an additional 16 watersheds. In this paper, we analyze the performance of the DLBRM hydrology components in space and time and its further development.

We apply a concept derived from food web ecology to large-scale spatial patterns of material supply within and between watersheds and coasts by generalizing the definition "resource shed" to source areas for materials supplied to a receptor (e.g., a point location) over a specified time interval. Independent hydrologic and hydrodynamic models, coupled with a particle tracking model, were used to delimit resource shed total spatial extent and relative contributory importance for selected receptors in Lake Erie (North America) over varying time intervals. One resource shed was extended into the Maumee River watershed (OH) by integrating the lake and hydrologic models. Model validation was achieved through comparison with data from the 2005 International Field Years on Lake Erie (IFYLE) study. Resource shed size, orientation, and internal structure varied with receptor location, in-lake circulation, terrestrial precipitation, time interval, and season. River plume extent and interaction were illustrated, and model integration revealed the relative contributory importance of subwatershed catchments to an off-shore receptor.

Recent studies have produced a new understanding of the hydrological history of North America's Great Lakes, showing that water levels fell several meters below lake basin outlets during an early postglacial dry climate in the Holocene (younger than 10,000 radiocarbon years, or about 11,500 calibrated or calendar years before present (B.P.)). Water levels in the Huron basin, for example, fell more than 20 meters below the basin overflow outlet between about 7900 and 7500 radiocarbon (about 8770–8290 calibrated) years B.P. Outlet rivers, including the Niagara River, presently falling 99 meters from Lake Erie to Lake Ontario (and hence Niagara Falls), ran dry. This newly recognized phase of low lake levels in a dry climate provides a case study for evaluating the sensitivity of the Great Lakes to current and future climate change.

When we consider a location with a material (e.g., water, pollutant, sediment) passing through it, we can ask: "Where did the material come from and how long did it take to reach the location?" We can quantify the answer by defining the areas contributing to this location during various time periods as "resource sheds." Various resource sheds and their source material distributions are rigorously defined and properties derived. For watershed hydrology, we compute resource sheds and their source distributions with a spatially distributed hydrology model by tracing water departing from a "cell" (say 1 km(2)) over one time interval, traveling through intermediate cells soil, groundwater, and surface zones, and arriving at the watershed mouth in another time interval. This requires modeling all cells, but only tracing contributions from one at a time. By then combining these simulations for all cell loadings, we construct a map of the contributions over the entire watershed for specific departure and arrival time intervals. We then combine results of several sets of simulations to determine the source distribution for any time period and infer resource sheds from these mappings. We give examples for the Maumee River watershed in northern Ohio, discuss computation reduction, and suggest future extensions to other materials.

The identification of important spawning and nursery habitats for fish stocks can aid fisheries management, but is complicated by various factors, including annual variation in recruitment success. The alewife (Alosa pseudoharengus) is an ecologically important species in Lake Michigan that utilizes a variety of habitats for spawning and early life growth. While productive, warm tributary mouths (connected to Lake Michigan) may contribute disproportionately more recruits (relative to their habitat volume) to the adult alewife population than cooler, less productive nearshore habitats, the extent of interannual variation in the relative contributions of recruits from these two habitat types remains unknown. We used an individual-based bioenergetics simulation model and input data on daily temperatures to estimate alewife recruitment to the adult population by these different habitat types. Simulations suggest that nearshore lake habitats typically produce the vast majority of young alewife recruits. However, tributary habitats may contribute the majority of alewife recruits during years of low recruitment. We suggest that high interannual variation in the relative importance of habitats for recruitment is a common phenomenon, which should be considered when developing habitat management plans for fish populations.

This paper analyzes the application of a spatially distributed large basin runoff model (DLBRM) in the Great Lakes Basin of the United Stats and Canada and discusses four essential components of operational hydrologic model development: model structure, model input, model calibration, and Geographical Information System (GIS)-model interface. The results indicate that large scale operational hydrologic models that are based on mass continuity equations and include land surface, soil zones, and groundwater components require fewer parameters, are less data demanding, and are particularly suitable for solving water resources problems over large spatial and temporal scales than many other models. Use of GIS-model interfaces is essential for utilizing the existing multiple digital databases in defining model input and in facilitating model implementation and applicability.

We can quantify source areas contributing material to a location during various time periods as resource sheds. Various kinds of resource sheds and their source material distributions are defined. For watershed hydrology, we compute resource sheds and their source material distri- butions with a spatially distributed hydrology model by tracing material departing from a cell (say 1 km2) over one time interval and arriving at the watershed mouth in another time interval. This requires modeling all cells, but only tracing contributions from one at a time. By then combining these simulations for all cell loadings, we con- struct a map of the contributions over the entire watershed for specific departure and arrival time intervals. We then combine results of several sets of simulations to deter- mine the source distribution for any time period and infer resource sheds from these mappings. For lake circulation, we discuss the construction of resource sheds and their source distributions in the lake, by using lake circulation models to drive particle tracers in reverse time, and sub- sequent correction. We present Maumee watershed ex- amples, discuss methods of computation reduction and linkage with lake circulation models, construct joint re- source sheds in Lake Erie, and suggest areas of extension.

Because of its size and geometry, the central basin of Lake Erie, one of North America's Great Lakes, is subject to periods in the late summer when dissolved oxygen concentrations are low (hypoxia). An apparent increase in the occurrence of these eutrophic conditions and ‘dead zones’ in recent years has led to increased public concern. The International Field Years for Lake Erie (IFYLE) project of the Great Lakes Environmental Research Laboratory (GLERL, a U.S. National Oceanic and Atmospheric Administration (NOAA) laboratory), was established in 2005 in response to this increase. This project is investigating the causes and consequences of hypoxia in the lake. As part of the effort, scientists from the United States and Canada conducted an extensive field study in 2005 to gather more information on the duration and extent of the hypoxic zone and its effects on the biota in the lake. This article gives a brief history and description of the problem and presents initial results from the field study.

A recent empirical model of glacial-isostatic uplift showed that the Huron and Michigan lake level fell tens of meters below the lowest possible outlet about 7,900 14C years BP when the upper Great Lakes became dependent for water supply on precipitation alone, as at present. The upper Great Lakes thus appear to have been impacted by severe dry climate that may have also affected the lower Great Lakes. While continuing paleoclimate studies are corroborating and quantifying this impacting climate and other evidence of terminal lakes, the Great Lakes Environmental Research Laboratory applied their Advanced Hydrologic Prediction System, modified to use dynamic lake areas, to explore the deviations from present temperatures and precipitation that would force the Great Lakes to become terminal (closed), i.e., for water levels to fall below outlet sills. We modeled the present lakes with pre-development natural outlet and water flow conditions, but considered the upper and lower Great Lakes separately with no river connection, as in the early Holocene basin configuration. By using systematic shifts in precipitation, temperature, and humidity relative to the present base climate, we identified candidate climates that result in terminal lakes. The lakes would close in the order: Erie, Superior, Michigan-Huron, and Ontario for increasingly drier and warmer climates. For a temperature rise of T°C and a precipitation drop of P% relative to the present base climate, conditions for complete lake closure range from 4.7T + P > 51 for Erie to 3.5T + P > 71 for Ontario.

Prediction of Great Lakes ice cover is important for winter operations and planning activities. Current 30day forecasts use accumulated freezing degree-days (AFDDs) to identify similar historical events and associated ice cover. The authors describe statistical models that relate future ice cover to current ice cover, AFDDs, and teleconnection indices, available on the day the forecast is made. These models are evaluated through Monte Carlo simulation and assess the potential of a perfect AFDD forecast in a regression between ice cover and AFDDs between the forecast date (first day of month) and the date for which the forecast is made (first day of next month).

This paper reviews recent developments in hydrologic modeling, and through development of a 2-D large basin runoff model (2-D LBRM), discusses five essential components in the development of operational hydrologic models: model input, model structure, spatial variability, model calibration, and GIS-model interface. Operational hydrologic models should utilize multiple biophysical databases to develop model input parameters over multiple temporal and spatial scales. They should be based on mass continuity equations and include land surface, soil zones, and groundwater components. Spatial heterogeneity of watersheds needs to be taken into consideration using either a hydrological response unit or grid network approach. Simulation results should be calibrated with respect to multiple- objectives for better assessment of model and data errors. GIS-model interfaces need to be developed to facilitate model implementation and applicability.