Browsing by Author "Riley, Michael J."
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Item Dynamic Lake water quality simulation model "Minlake"(1987-08) Riley, Michael J.; Stefan, Heinz G.Lakes are in a continuous state of change. Some changes occur over very short periods of time on the order of hours and minutes. Other changes mark long-term trends in the biological and physical condition of a lake. Among the long-term trends in many lakes are a decrease in depth and an increasing productivity in a process called eutrophication. Typically, eutrophication occurs over a time scale of centuries. However, man-made changes to the watershed of a lake may result in a rapid acceleration of eutrophication such that significant changes in the water quality of the lake are noticed in a time span of a few years. Anthropogenic acceleration of eutrophication, known as cultural eutrophication, is due to agricultural, urban, and recreational development in the watershed of a lake which causes an increase in the nutrient loading to a lake. In response to the concern for the water quality of an eutrophic lake, many lake treatment practices have been developed. Treatment processes can be divided into watershed practice methods, inflow-outflow methods, and intake treatment methods. A partial list of these practices is provided in Table I. In some instances, treatment methods have been implemented without significantly improving the quality of a lake. The failure of a treatment method is often a result of a poor understanding of the short term dynamics of a lake which affect the rate and extent of cycling of nutrients within the water column, sediment, and biological components of a lake. To evaluate the effectiveness of lake treatment methods on Minnesota lakes, the Minnesota Lake Model (MINLAKE) has been proposed to model the principal dynamic relationships in a lake on a daily time scale. Treatment methods can then be modeled by modifying those components of the model which will be directly affected by the treatment process. The model can then predict the indirect and direct effects over a period of several months.Item Dynamic Lake Water Quality Simulation Model "Minlake"(St. Anthony Falls Hydraulic Laboratory, 1987-08) Riley, Michael J.; Stefan, Heinz G.Lakes are in a continuous state of change. Some changes occur over very short periods of time on the order of hours and minutes. Other changes mark long-term trends in the biological and physical condition of a lake. Among the long-term trends in many lakes are a decrease in depth and an increasing productivity in a process called eutrophication. Typically, eutrophication occurs over a time scale of centuries. However, man-made changes to the watershed of a lake may result in a rapid acceleration of eutrophication such that significant changes in the water quality of the lake are noticed in a time span of a few years. Anthropogenic acceleration of eutrophication, known as cultural eutrophication, is due to agricultural, urban, and recreational development in the watershed of a lake which causes an increase in the nutrient loading to a lake.Item An Introduction To Mathematical Modeling Of Lake Processes For Management Decisions(St. Anthony Falls Laboratory, 1987-02) Hanson, Mark J.; Riley, Michael J.; Stefan, Heinz G.Use of Minnesota takes has increased, placing demands on lake managers to maintain or to improve water quality. Although many different management and lake rehabilitation techniques have proven effective, the complex nature of the in-lake processes makes selection of a technique and prediction of effectiveness very difficult. Lake managers are often confronted with expensive projects that must actually be tried to determine their effectiveness.Item Mixing of the Seneca and Blue Lake waste water treatment plant effluents with the Minnesota River(1984-11) Stefan, Heinz G.; Farrell, Gerard J.; Riley, Michael J.; Lindquist, Katherine F.; Horsch, George M.Eight field surveys, forty five laboratory experiments, and several types of analyses have produced information to understand and predict the mixing of the Seneca and Blue Lake WWTP effluents with the Minnesota River to a reasonable degree. Both discharges are from submerged pipes, 7 ft and 6.5 ft in diameter, respectively. The mean annual discharge rates are at present on the order of 23 to 25 cfs and at velocities on the order of .6 to .8 fps.