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981.
Model simulations of dissolved oxygen characteristics of Minnesota lakes: Past and future 总被引:1,自引:0,他引:1
A deterministic, one-dimensional, unsteady numerical model has been developed, tested, and applied to simulate mean daily
dissolved oxygen (DO) characteristics in 27 lake classes in the state of Minnesota. Reaeration and photosynthesis are the
oxygen sources, while respiration, sedimentary, and biochemical water column oxygen demand are the sinks of oxygen in the
model. The lake classes are differentiated by surface area (A
s), maximum depth (H
max), and trophic status expressed as Secchi depth (Z
s). Because lake stratification is most important to lake oxygen dynamics, simulated DO characteristics are plotted in terms
of a stratification parameterA
s/H
max
0.25
and Secchi depthZ
s. Simulations provide DO profiles on a daily time scale. Specific DO characteristics of ecological and environmental interest
are epilimnetic DO, hypolimnetic DO, DO gradient from surface to bottom, and DO minima and maxima. Specific results are as
follows: Simulated mean daily and weekly DO values in the epilimnion of all lakes for both past and future climate scenarios
are near saturation over the summer season. Hypolimnetic DO values depend strongly on lake morphometry, trophic status, and
time throughout the summer season. Future climate conditions are specified as the historical records from 1955 to 1979, adjusted
(monthly) by the 2 × CO2 GISS model output to account for doubling of atmospheric CO2. With this climate change, weekly averaged epilimnetic DO is projected to drop by less than 2 mg/liter, and will remain above
7 mg/liter throughout the open water season. The hypolimnetic DO reductions after climate change are on the order of 2–8 mg/liter.
Periods of anoxia are longer by as much as 80 days. Those changes would alter water quality dynamics in lakes and have a profound
effect on lake ecosystems including indigenous fishes. The results presented are useful for evaluating environmental management
options. 相似文献
982.
Trends and issues in land and water resources management: Setting the agenda for change 总被引:1,自引:0,他引:1
The classical model of a paradigm shift is used to explore changes that are occurring in public lands and water resources
management. Recent policy developments suggest that the traditional paradigm, which is characterized by sustained yield, is
in the process of being invalidated. While no new paradigm has been fully accepted, the emerging paradigm does appear to be
based on two principles: ecosystem management and collaborative decision making. Implementation of these two principles is
likely to require extensive revision of traditional management practices and institutions. Failure to address these issues
could result in adoption of the rhetoric of change without any lasting shift in management practices or professional attitudes. 相似文献
983.
In Hawaii, trace concentrations of pesticides used in the production of pineapple were found in the groundwater supplies of
Mililani Town in the Pearl Harbor Basin on the island of Oahu. Groundwater serves as the major source of drinking water and
residents pay for wellhead treatment of the contaminated water, via their monthly water bill. The agricultural chemical users
within the Pearl Harbor Basin do not include these wellhead treatment costs in their production costs. The agricultural industry
benefits from using pesticides but does not pay the entire societal cost of using these chemicals. In this study we evaluate
the specific financial cost of wellhead treatment, and not the economic value of groundwater. While wellhead treatment costs
could conceivably be shared by several parties, this study focuses on the financial impact of the pineapple industry alone.
This study factors annual wellhead treatment costs into annual pineapple production costs to measure the effect on annual
financial return from pineapple production. Wellhead treatment costs are calculated from the existing granulated activated
carbon (GAC) water treatment facility for Millilani Wells I and II. Pineapple production costs are estimated from previous
cost of production studies. The inclusion of wellhead treatment costs produces different production-cost results, depending
on the scale of analysis. At the local scale, the Mililani wellhead treatment costs can be factored into the production costs
of the pineapple fields, which were probably responsible for contamination of the Mililani Wells, without causing a deficit
in economic return. At the larger regional scale, however, the return from all of the pineapple grown in the Pearl Harbor
Basin can not sustain the cost of wellhead treatmentfor the entire water supply of the basin. Recommendations point to the
prevention of groundwater contamination as more cost-effective measure than wellhead treatment. 相似文献
984.
985.
986.
Peter Wathern Stephen N. Young Ian W. Brown Dawn A. Roberts 《Environmental management》1987,11(1):7-12
The EEC Shellfish Directive is a policy designed to protect and, where necessary, improve the quality of designated shellfish waters. Its implementation within the UK, however, has had no effect upon water quality for two reasons. First, the policy has important defects, having ambiguities concerning public health provisions and lacking designation criteria. Second, UK government has sought to achieve formal compliance, while at the same time ensuring that its full financial impact on public expenditure has been contained. Consequently, only those fisheries which already comply with water quality standards have been designated. Within Wales, one fishery has been designated, while other, commercially more important, but grossly contaminated shellfisheries have not. 相似文献
987.
A multivariate statistical method for analyzing spatial patterns of water quality in Georgia and Kansas was tested using data in the US Environmental Protection Agency's STORET data system. Water quality data for Georgia and Kansas were organized by watersheds. We evaluated three questions: (a) can distinctive regional water quality patterns be detected and predicted using only a few water quality variables, (b) are regional water quality patterns correlated with terrestrial biotic regions, and (c) are regional water quality patterns correlated with fish distributions? Using existing data, this method can distinguish regions with water quality very different from the average conditions (as in Georgia), but it does not discriminate well between regions that do not have diverse water quality conditions (as in Kansas). Data that are spatially and temporally adequate for representing large regions and for multivariate statistical analysis are available for only a few common water quality parameters. Regional climate, lithology, and biotic regimes all have the potential to affect water quality, and terrestrial biotic regions and fish distributions do compare with regional water quality patterns, especially in a state like Georgia, where watershed characteristics are diverse. Thus, identifiable relationships between watershed characteristics and water quality should allow the development of an integrated landaquatic classification system that would be a valuable tool for resource management. Because geographical distributions of species may be limited by Zoogeographic and environmental factors, the recognition of patterns in fish distributions that correlate with regional water quality patterns could influence management strategies and aid regional assessments. 相似文献
988.
Y. Dubuc P. Janneteau R. Labont C. Roy F. Brire 《Journal of the American Water Resources Association》1986,22(2):297-303
ABSTRACT: The use of peatlands as the main form of wastewater treatment in a northern climate was studied for the James Bay Energy Society. The Fontanges campsite (70° 17′ 30″ W; 54° 34′ 00″ N) was chosen as the study site. In less than 1.5 km from the point of discharge BOD5, COD, total hardness, inorganic carbon, orthophosphates, total phosphorus, ammonia and total nitrogen were reduced by at least 90 percent. The peatland treatment system studied is divided into four components, each having a specific function. The first part combines the action of microorganisms and adsorption on peat, thus reducing the organic content while increasing the inorganic constituents. The second part uses peat to adsorb the inorganic elements already present in the wastewater and those produced in the first part of the system. The third component acts as an aerator, increasing the dissolved oxygen and decreasing the BOD5 levels of the water. The fourth part removes most of the remaining nutrients, thus acting like a tertiary treatment. Overall, peatlands seemed to be effective in treating domestic settled wastewater in a cold climate. 相似文献
989.
M. Hossein Sabet James Q. Coe 《Journal of the American Water Resources Association》1986,22(4):587-596
ABSTRACT: A large-scale simulation/optimization model provides schedules for operation of water and power for the California State Water Project (SWP). The SWP consists of a series of reservoirs linked by rivers, pumping plants, canals, tunnels, and generating plants and is operated by the California Department of Water Resources. The Department provides water to municipal and agricultural users, and manages its electrical loads and resources. The model, therefore, performs hydraulic and electrical computations leading to optimal operation of the entire system. It consists of hydraulic network programming components to meet the storage objectives at all the reservoirs, a linear programming component to determine the schedules at pumping and generating plants, an electrical network programming component to balance electrical loads and resources, and a number of other simulation components. It operates on yearly, weekly, and daily bases. It is primarily used for real-time operation of the SWP and can provide hourly detail schedules which are implemented by the SWP staff via a computerized system. 相似文献
990.
Andrew Charles Gross 《Environmental management》1986,10(1):25-39
This article analyzes water quality on a global scale. An overview of the global water supply and demand situation is presented first, including regional and country information, as well as data on selected water use patterns. The focus then shifts to a discussion of water pollution, its various causes, impact, and remedies, with emphasis on legal and administrative solutions. Water pollution control expenditures and the resultant achievements are dealt with in the final third of the article, with projections to 1995. A wide variety of published sources was dovetailed to obtain a composite picture and most likely scenario; this was supplemented with primary interviews by the author conducted in North America, Western and Eastern Europe, and Oceania at the start of the 1980s. 相似文献