摘要:

Water quality has been monitored in Lake Phalen (St. Paul, Minn.) from 1981 to 1983. Consistent increases in epilimneticDaphniaabundance have been observed each spring, corresponding to measured Secchi depth maxima. In 1982 and 1983 the increase inDaphniaabundance followed an increase in the density of small algae,principally Cryptomonassp. The increase inDaphniadensity in 1981, when small algal forms were not abundant, suggests another factor, such as predation, may control springDaphniaabundance in Phalen. The impact of the spring increase inDaphniaabundance on summer water quality appears slight. A significant difference in summer mean chlorophyll a concentration between years is not related to a change in epilimneticDaphniaabundance. Summer algal standing crop in Lake Phalen is related to both nutrient and biological factors, including partial nitrogen limitation and changes in phytoplankton community composition.

ISSN:1040-2381    

DOI:10.1080/07438148409354503

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A vertically-segmented, dynamic phosphorus model program was developed for use on a 16 bit microcomputer. The predictive model includes theoretical equations for physical settling, thermocline diffusion, and sediment release of total phosphorus. The model was developed and calibrated using actual data collected from 1980 through 1982. Input loads from combined point and nonpoint sources were entered using a time step equal to 1 day. In the case of Lake Wallen-paupack, discharge occurs from both the epilimnion and hypolimnion during the latter portion of the stratified period. Several discharge scenarios were evaluated to determine if any one would produce a significant reduction in summer epilimnetic phosphorus concentrations.

ISSN:1040-2381    

DOI:10.1080/07438148409354504

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Jordanelle Reservoir, a proposed component of the Bonneville Unit of the Central Utah Project, will be a major source of municipal and industrial water for the Salt Lake Valley. The final environmental impact statement identified the need to evaluate Jordanelle in terms of its downstream impact on Deer Creek Reservoir and the use of the water. To evaluate the impact, a combination of temperature and water quality simulation models, anaerobic simulation of the sediments, empirical nutrient loading models, and estimates of primary productivity were utilized. As a result of these efforts, Jordanelle Reservoir is expected to experience seasonal excesses of eutrophication with resulting low dissolved oxygen levels, potential mobilization of mine tailings, and seasonal recycling of nutrients from the sediments. To restrict the impact of these factors on downstream productivity and to allow efficient routing of nutrients and water through Deer Creek Reservoir, a multiple level withdrawal outlet structure and variable operation scenarios were designed for Jordanelle. The simulation period covered the entire stagnation period with the coefficients defined from previous Deer Creek simulations, the proposed Jordanelle operation plan, and empirical relationships. The procedures defined will be integrated with a watershed management plan to provide for efficient use of Jordanelle water with the resulting least impact to the downstream use of water. This analysis has applications to other impoundments and the determination of efficient operation plans.

ISSN:1040-2381    

DOI:10.1080/07438148409354505

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Time series models of reservoir water quality are water resource management tools and provide insight into reservoir dynamics since they account for autocorrelation, seasonality, and trends present in the data. Autoregressive integrated moving average (ARIMA) models were applied to describe patterns in selected water quality variables of Red Rock Lake, Iowa. Models were generated for total phosphorus, total nitrogen, and suspended solids for an 8-year period (1972–1979). Patterns in lake concentration and the usefulness of time series models to lake and reservoir management are described.

ISSN:1040-2381    

DOI:10.1080/07438148409354506

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Water quality models have been applied to the six University Lakes of Baton Rouge, La., to assist in the analysis of effects of restoration efforts. Phosphorus was identified as the nutrient limiting algal growth in these lakes. A relationship between total phosphorus and fishkills was identified. Initial applications of a modified Vollenweider model indicated that the model was capable of projecting long-term average lake conditions but that it was limited by its inability to represent short-term variations. These variations were crucial for the projection of fishkill episodes. Intensive surveys failed to identify practical modifications to the model within a deterministic format and a stochastic approach was undertaken. Uncertainties were partitioned into terms representing lumped modeling errors and sampling variability. This approach produced results that were suitable for interfacing with objective functions based upon total phosphorus levels. The need for more widespread application of stochastic techniques was evident from experiences associated with this project.

ISSN:1040-2381    

DOI:10.1080/07438148409354507

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Data from 42 lakes and reservoirs in Virginia, North Carolina, South Carolina, and Georgia were used to develop and evaluate cross-sectional regression models for phosphorus. For all models under consideration, the endogenous variable was lakewide average annual phosphorus concentration, and the exogenous variables were phosphorus input to the lake and various geomorphologic and hydrologic variables. A linear model was developed for logarithmically-transformed terms that resulted in a substantially lower prediction sum of squares than did other models under consideration. Among the other models examined were those specified and fitted to north temperate lakes by other investigators. Parameter characteristics and error terms for the proposed model were studied with particular attention directed to the a priori assumption of a strictly linear relation between input and concentration of phosphorus. The calculation of prediction uncertainty is illustrated in an application of the model using an empirical Bayes approach and a prior model based on linearity.

ISSN:1040-2381    

DOI:10.1080/07438148409354508

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Using existing data selected from a large government data base, an analysis of the factors governing algal standing crop in 40 South Carolina reservoirs revealed that chlorophyll a production was considerably lower than that reported for northern temperate lakes. This observation was attributed to the high levels of nonalgal turbidity frequently exhibited by the study reservoirs. The accuracy of eight literature models in predicting chlorophyll was examined and most were found to overestimate actual ambient values. To account for the various moderating factors affecting chlorophyll production in turbid reservoirs, the use of multivariate models is suggested. The results of this study indicate that local conditions should be taken into account when selecting a predictive model for management purposes. One feasible option for government agencies is to develop predictive models using readily available data.

ISSN:1040-2381    

DOI:10.1080/07438148409354509

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The effects on algal productivity of changes in light availability because of suspended materials entering a lake from storm runoff or turbidity generated by wind mixing of sediments are often discussed. The relationships between suspended solids, turbidity, Secchi disk depth, light attenuation, and the resulting photosynthetic response of algae are not well documented. Data from several TVA reservoirs indicate that variations in the available light due to turbidity of the water are large and must be described in more detail before accurate predictions of algal dynamics and macrophyte growth can be achieved. Basic relationships between the various measurements of turbidity, suspended solids, Secchi disk depth, and light attenuation are given. This allows frequent measurements of turbidity or Secchi disk depth to be combined with daily solar radiation and less frequent chlorophyll and C14productivity data to yield a detailed estimate of algal productivity within a reservoir or lake throughout the year. For long lakes and many reservoirs, significant longitudinal gradients in suspended solids will result as the inflowing materials settle and the water column clears. The importance of this gradient of available light for modeling algal dynamics is demonstrated with data from several TVA reservoirs.

ISSN:1040-2381    

DOI:10.1080/07438148409354510

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Emphasis on evaluation techniques where measured versus predicted changes of mass are compared can produce a model that predicts the correct answers for the wrong reasons. The movement of mass between compartments (flux) should be compared to measured flux as part of the model verification. Model verification techniques need to reflect the same level of resolution inherent in the model structure. The U.S. Corps of Engineers water quality model, CE-QUAL-R1, was verified for DeGray Lake, Ark., using this procedure. Several processes important in determining the mass of the constituents were measured for DeGray Lake. Primary production rate and settling rates of algae, total dry weight, and organic matter were compared to predicted fluxes. Results indicated that the model was satisfactory in predicting trends in flux values.

ISSN:1040-2381    

DOI:10.1080/07438148409354511

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In the 1975 National Eutrophication Survey Bear Lake had the best overall water quality of all Utah lakes sampled. However, this oligotrophic state would not be retained because of a mesotrophic level of loading. Because of the unique characteristics of the Bear Lake ecosystem and the present danger of cultural eutrophication, the objectives of this 314 Clean Lakes Study were to: (1) quantify the major nonpoint sources of nitrogen and phosphorus into Bear Lake; (2) quantify the major sources of nitrogen and phosphorus in the Bear River prior to its diversion into Dingle Marsh and Bear Lake; (3) determine the nitrogen, phosphorus, and carbon budgets of Dingle Marsh and define the factors which may regulate the flux of these nutrients into Bear Lake; and (4) if necessary, develop a set of viable cost-effective alternatives for the reduction of the nitrogen and phosphorus loading into Bear Lake. Nutrient loading was determined for each major tributary to Bear Lake and the trophic condition of the lake was determined over an 18-month period. Trophic state determinations were made using TSI values, areal oxygen deficits, and areal phosphorus loadings. Differences in parameters predictions are explained. An historical perspective of the water quality trends is given for Bear Lake (1975–1983). Based upon the observed changes and associated land use alterations, a series of management plans is proposed for maintaining or improving the water quality in Bear Lake.

ISSN:1040-2381    

DOI:10.1080/07438148409354512

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor