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Browsing by Author "Hondzo, M."

Now showing 1 - 5 of 5
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    Comparisons of Actual Fish Observations with Simulated Suitable Fish Habitat in Minnesota Lakes
    (St. Anthony Falls Hydraulic Laboratory, 1993-09) Stefan, H. G.; Hondzo, M.; Eaton, J. G.; McCormick, J. H.
    The purpose of this study is to relate simulated water quality with fish presence observations. The typical seasonal patterns of water temperatures and dissolved oxygen concentrations in twenty-seven classes of Minnesota lakes have been simulated by calibrated models and related to observations of three fish guilds i.e, coldwater, coolwater, and warmwater fishes. Data from 3002 lakes were available in the Minnesota Department of Natural Resources lake database. Water temperature and dissolved oxygen criteria derived from a very large USEP A fish-temperature data base and dissolved oxygen observations were used to define and link simulated water temperatures and dissolved oxygen conditions to suitability of habitats for various species of fish. One-dimensional, dynamic models driven by 25 years of observed weather data were used to model daily water temperature and dissolved oxygen as a function of depth. The lakes are categorized according to surface area, maximum depth, and Secchi depth as a measure of trophic state. Good agreement between fish observations and numerical simulations of fish habitat defined by water temperatures and dissolved oxygen concentrations was found.
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    A Methodology to Estimate Global Climate Change Impacts on Lake and Stream Environmental Conditions and Fishery Resources with Application to Minnesota
    (St. Anthony Falls Hydraulic Laboratory, 1992-03) Stefan, Heinz G.; Hondzo, M.; Sinokrot, Bashar; Fang, Xing
    The effects of global climate were projected on the distribution and growth potential of common freshwater fishes in 5 streams and 27 classes of lakes in Minnesota. The method developed for, this analysis uses laboratory growth and mortality data, and a stream temperature-fish distribution database, to define temperature responses for 32 fish species. Sensitivity to depressed dissolved oxygen concentrations was derived from information presented in the U.S. EPA ambient water quality criteria document on oxygen. Stream and lake water temperatures and lake dissolved oxygen concentrations are simulated by one-dimensional, unsteady heat and oxygen transport models operating on a timestep of one day. Simulations are made for a 25-year historical period (1955.-80) and projected steady-state future climate simulated by general circulation models assuming a doubling of atmospheric CO2• Water temperature and dissolved oxygen (D.O.) concentrations simulated for streams and lakes are then compared to "critical" values for presence (survival ) or "good" growth (time of exposure to temperatures permitting rapid growth) of a fish species or guild. The results project expected impacts on representative Minnesota streams, while the lake results represent a regional analysis for the state as a whole. The following conclusions stand out among the many study results. In wide, essentially unshaded streams, global warming is expected to contribute to elimination of coldwater fishes and some coolwater fishes in many habitats where they were formerly present. Warmwater fishes will gain substantially more potential for good growth than existed previously. Coldwater fishes will have a chance for continued existence only in those streams with adequate shading by riparian trees. Coldwater fishes will have the best chance to survive in deep lakes located in the northern half of the state, but there will be a loss in habitat for good growth. Warmwater fishes will gain habitat for good growth in virtually all types of lakes. Coolwater fishes will gain habitat enabling good growth in most types of lakes. Losses or gains in good growth potential due to global warming are projected to be larger in deep lakes than in shallow ones. The trophic state of the water body will also have an influence on the response of indigenous fishes to climate change. In shallow lakes, trophic state is projected to have little effect on the influence of global warming on habitat suitability for fishes. In deeper, seasonally stratified eutrophic lakes losses or gains of habitat for good growth are projected to be smaller than in oligotrophic lakes of the same size and depth. Lake size and depth are of importance as they affect seasonal stratification of water temperature and dissolved oxygen. Dissolved oxygen limitations are more serious in eutrophic lakes than in oligotrophic lakes. They are also more apparent in deep lakes than in shallow ones. Climate change is projected to worsen availability of habitats for good growth due to oxygen limitations. For the state as a whole, the potentital for good growth of lake dwelling, coolwater fishes is projected to increase by 20 percent and for warmwater fishes by 53 percent. Coldwater species will lose 40 percent of their habitat suitable for good growth. The total habitat for good growth of Minnesota lake fishes, regardless of guild designation, is projected to increase by 6 percent.
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    Predicted Effects of Global Climate Change on Fishes of Minnesota Lakes
    (St. Anthony Falls Hydraulic Laboratory, 1992-09) Stefan, H. G.; Hondzo, M.
    According to global climate change models, e,g. that from the Columbia University Goddard Institute for Space Studies (GISS), Minnesota's mean air temperature will increase by an annual average of approximately 4.0 'C if atmospheric C02 doubles. This is likely to have many environmental consequences, including changes in lake water temperatures and dissolved oxygen concentrations which in turn are likely to affect fish populations. This interaction between climate parameters, lake water quality parameters and fish populations has been investigated through model simulations of Minnesota lakes. Previous results of this study were summarized in September 1991 (Stefan et al., 1991, 1992). Specifically the description of fish habitat is extended herein to include lake benthic area, in addition to lake volume used in the previous report. The findings are as follows: After the projected climate change, good growth habitat bottom area (GGHA) and good growth habitat volume (GGHV) will be reduced for coldwater fish. In contrast, GGHA and GGRV will be increased for coolwater and warmwater fish. Coldwater, coolwater and warmwater fish habitat will change approximately by the same percentage in terms of GGHA or GGHV. The reduction in good growth habitat area or volume for coldwater fishes will be about twice as high for southern Minnesota as it will be for northern Minnesota lakes. The increases for cool water and wa.rmwater fishes will be three times greater for northern Minnesota lakes than for southern Minnesota lakes. The models I and assessment techniques employed to derive these conclusions can serve as templates for analysis of projected climate change impacts in other regions. i
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    Simulated Long-Term Temperature and Dissolved Oxygen Characteristics of Minnesota Lakes and Resulting Habitat Limits for Fishes
    (St. Anthony Falls Hydraulic Laboratory, 1995-08) Stefan, Heinz G.; Hondzo, M.; Fang, Xing
    A lake is exposed to meteorological forcing through the lake surface and hydrologic inputs from the lake basin. Solar radiation and atmospheric long wave radiation heat the water column, while evaporation and back radiation cool the water column. Inflows may heat or cool the water depending on the relative thermal state of the water column at the time of concern. In addition, convective heat transfer driven by the temperature difference between the water temperature and air temperature can also warm or cool a lake. The differential radiative heat absorption throughout the lake depth causes thermal stratification of the water body. The stronger the stratification, the more quiescent i.e. the more stable the water body. The external forcing i.e. wind exerts a drag force on the surface of the lake which, through a variety of external and internal wave motions tends to vertically mix the stratified water column (partially or completely). The external mechanical energy input from the wind is opposed by the potential (buoyant) energy "locked" in the stratification. The stronger the stratification, the more mechanical energy is needed to mix the water column. A schematic representation of a seasonal temperature stratification in a dimictic lake is given in Fig. 1a. The open-water season usually starts some time in April or May in Minnesota lakes depending on the geographical location and the size of the lake. Most lakes are well mixed throughout the entire lake depth in spring. The onset of stratification occurs with the increase of solar radiation intensity and some decrease in the wind activity. The thermal stratification increases in strength from May through July or August. Further water temperature increase in summer is limited by the evaporative heat losses, and by back radiation. In September, solar radiation and air temperature are significantly lower, and wind is often higher, resulting in strong surface cooling, natural convection, and wind-induced mixing. A three layer structure is well defined throughout the summer in many lakes. The surface mixed layer is called 'epilimnion', underneath is a zone of temperature gradient, the 'metalimnion'; and below is the 'hypolimnion'. Surface mixed layer depth increases in the fall until the lake becomes isothermal at a temperature above or equal to 4°C.
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    Year Round Water Temperature and Dissolved Oxygen Simulation Model for Lakes with Winter Ice Cover
    (St. Anthony Falls Hydraulic Laboratory, 1994-12) Stefan, Heinz G.; Hondzo, M.; Fang, Xing; Rasmussen, Anders H.
    The need for predictive water quality modeling has received renewed interest largely because of increased concern over climate change, acid rain, land use practices, toxic wastes, spills and progressive groundwater pollution. Long~term trends in addition to short term responses, are of increased interest. Process~oriented lake water quality models have been developed previously (e.g. Orlob, 1983; USCE 1986; and Riley and Stefan, 1988). These simulation models are calibrated for individual lakes associated with particular climatic conditions. Water quality models which can be used without recalibration for regional lake assemblages and over several years in a continuous mode (during the open water and the winter ice cover season) have not been previously reported in the literature. The purpose of this report is to describe a first attempt to develop a year-round water quality model to simulate vertical water temperature and dissolved oxygen distributions for a wide range of lake morphometries and meteorological conditions. The model is designed to be driven by the meteorological conditions and to operate in a continuous long~term mode. Although the model represents a great over~ simplification, the stratification dynamics of water temperature and dissolved oxygen can be predicted to a reasonable degree.