ISSN:1040-2381    

DOI:10.1080/07438148409354473

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:1040-2381    

DOI:10.1080/07438148409354474

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:1040-2381    

DOI:10.1080/07438148409354475

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:1040-2381    

DOI:10.1080/07438148409354476

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

TVA tributary and mainstem reservoirs show generalized differences in morphometry, hydraulics, nutrient loads, and response to nutrient conditions. Neither type of reservoir is comparable to the natural lakes on which classical eutrophication studies have been based. The majority of published trophic state indices and standards (e.g., hypolimnetc dissolved oxygen depletion, Secchi depth, areal nutrient loading rates, in-reservoir phosphorus concentrations) are inappropriate for evaluation of the trophic status of some or all TVA reservoirs. Relative trophic state indices were developed for mainstem and tributary reservoirs using relevant potentiating and response variables. Ranking of the mainstem reservoirs is based on planktonic chlorophyll, macrophyte coverage, hydraulic retention time, reservoir area less than 5 feet deep, annual pool elevation drawdown, and Secchi depth. Ranking of the tributary reservoirs is based on planktonic chlorophyll, total phosphorus and total nitrogen weighted by the N:P ratio, and bioavailable inorganic carbon levels.

ISSN:1040-2381    

DOI:10.1080/07438148409354477

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A cooperative program between the Wisconsin Department of Natural Resources and the University of Wisconsin–Madison (UW-MSN) has resulted in the assessment of the trophic condition of approximately 3,000 significant inland lakes in Wisconsin. A sophisticated set of computer programs has been developed by the UW-MSN that locates the lakes that are to be classified, extracts the spectral reflectance values from Landsat digital data for those lakes, and then adjusts the lake data for atmospheric effects. The corrected lake statistics from Landsat data are correlated to measured field parameters collected on a limited number of lakes. Finally, the relationships developed are used to predict the trophic condition of the significant lakes in the State.

ISSN:1040-2381    

DOI:10.1080/07438148409354478

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Lake Hefner is a terminal offset reservoir located in Oklahoma City and used as a water supply lake. The lake is eutrophic and customers frequently complain of tastes and odors in finished water. During 1980 to 1981, water and nutrient budgets were constructed to learn the causes of eutrophication of the lake. Most water and nutrients entered the lake via a 11.6 km canal from the North Canadian River. The loadings were regulated so that flow events in the canal coincided with releases of water from Canton Lake, which is located upstream on the North Canadian River, or when rain fell on its watershed. Discharge and nutrient content were monitored during these flow events. Linear regression of concentration of nutrients on discharge showed soluble reactive phosphorus decreased with increasing discharge rate in both North Canadian and Canton flow events. Ammonia, nitrate, and Kjeldahl nitrogen increased as discharge rate increased only in North Canadian flow events. Canal discharge did not have typical features of stream hydrographs. Therefore, canal discharge may not be usable as an infallible predictor of nutrient concentrations. Estimation of nutrient loading of lakes via canals may of necessity remain highly empirical.

ISSN:1040-2381    

DOI:10.1080/07438148409354479

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Numerous indices developed during the last 10 years to quantify the concept of trophic state turned out to be too ambiguous to be useful to lake managers. Based on empirical relationships between various water quality indicators, the most widely used indices use Secchi disk transparency, chlorophyllaconcentration, and total phosphorus as a measure of lake trophic state. Indices based on data from north temperate lakes, however, are not directly applicable to Florida lakes. Many Florida lakes are known to be nitrogen rather than phosphorus limited. Florida lakes also commonly have macrophyte problems which are not accounted for by such indices. A series of indices based on Secchi disk transparency, chlorophyllaconcentration, macrophyte abundance, total phosphorus concentration, and total nitrogen concentration were developed for Florida lakes. The Secchi disk index serves as a physical measure of trophic state. The public perceives water clarity as an important attribute of lakes, and Secchi disk transparency is a good measure of water clarity. The biological measures of trophic state are based on chlorophyllaconcentration and macrophyte coverage. Chlorophyllaconcentration is a good indicator of algal populations and macrophyte coverage is related to potential aquatic weed problems. Since phytoplankton and macrophytes compete for similar habitats, Florida's shallow lakes usually do not experience nuisance conditions of both these autotrophs simultaneously. The chemical measures of the trophic state are total phosphorus and total nitrogen concentrations. These elements are the principal nutrients limiting primary productivity in aquatic systems and therefore provide useful information on the nutritional status of lakes. When the lake is primarily phosphorus limited, based on the ratio of total nitrogen to total phosphorus concentration, the phosphorus trophic index is used. If the lake is nitrogen limited, based on the concentration ratio, the nitrogen index is used. Many Florida lakes are not limited by a single nutrient and are relatively well balanced. In this case an average of the nitrogen and phosphorus indices is used to determine the trophic status. The overall trophic state index for a Florida lake is determined by combining the appropriate values obtained from the physical, chemical, and biological indices. Over 570 lakes in the State were ranked by this method. The relative simplicity of the trophic index, combined with its accuracy and reliability, emphasizes its utility in statewide lake management.

ISSN:1040-2381    

DOI:10.1080/07438148409354480

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Assessment of eutrophication of lakes in watersheds undergoing development is facilitated by estimates of (1) background phosphorus (P) loading and concentration, (2) present-day P concentrations and amounts and sources of P loadings in excess of background levels, (3) the sensitivity of the lakes to future increases in P loading, and (4) relationships between P concentration and other factors that determine lake water quality. Methods have been developed for making such estimates for lakes in the Puget Sound Region based on data already available for most lakes in the region. Background P loadings were computed from P concentration data for 24 undeveloped lakes in the region using a mass balance model, and predictive relationships were developed from these loadings to estimate background loading for other lakes. The standard error of estimate for background loadings and concentrations averages 25 percent for most lakes in the region. Present-day P loadings were then estimated from measured P concentrations for 28 lakes in basins containing residential land. Differences between present-day and background loading were attributed to land use changes. P loadings from septic systems, computed as the difference between total present-day loading and the sum of background and residential runoff loading, were found correlated with the presence of old homes around the lakes (r2= 0.36). The regression relationship expressing this relation can be used to estimate septic-system loading for other lakes. If necessary, P loading from agricultural land can then be estimated on a lake-by-lake basis as the difference between total present-day loading and the sum of background and both types of residential area loading. Methods are presented for estimating the reliability of all estimates, which varies. These empirical relations allow approximations of the cumulative impact that development has had on P loading and the amounts of loading from generalized land use categories. The mass balance P model also estimates lake sensitivity to future increases in P loading. Finally, predictive relationships were developed between P concentrations and Secchi disk transparency and chlorophyllaconcentrations, two key indicators of lake water quality related to eutrophication, based mainly on data for 17 well-studied lakes in the region.

ISSN:1040-2381    

DOI:10.1080/07438148409354481

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

During 1980, as part of its Nationwide Urban Runoff Program (NURP), the U.S. Environmental Protection Agency entered into a cooperative agreement (P002229-01-1) with the New York State Department of Environmental Conservation to study urban runoff at Lake George, N.Y., located in the southeastern Adirondack Mountains. The purpose of the study was to determine the effect of runoff from a developed watershed on the water quality of the lake and its tributaries. More than 40 storm events were sampled during a 2-year period at six tributary sampling stations to assess the loading of plant nutrients and other contaminants from developed and underdeveloped areas to the open waters of the lake. Additionally, the nearshore and open waters of Lake George were sampled during storm and nonstorm periods, to assess the impact of stormwater runoff on the trophic conditions of the lake. Runoff from developed areas accounts for 13.6 percent of the annual phosphorus loading to Lake George, which is 15.1 percent of the load to the South Lake and 6.5 percent of the load to the North Lake. In addition, developed areas contribute 28.9 percent of the annual phosphorus load to the study area at the extreme south end of the lake.

ISSN:1040-2381    

DOI:10.1080/07438148409354482

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor