摘要:

A mathematical model of Lake Ashtabula Reservoir, Valley City, N. Dak., was developed based on the one-dimensional reservoir thermal model, CE-THERM-R1. The major assumption employed in CE-THERM-R1 is that the reservoir is represented as a vertical series of completely mixed horizontal layers (one-dimensional assumption). Longitudinal and lateral variations of constituent concentrations cannot be predicted. Lake Ashtabula, whose pool is long, narrow and largely confined to the run-of-the-river, exhibits both vertical and longitudinal water quality gradients. To represent this two-dimensional aspect of the system, the model was organized using three CE-THERM-R1 pools coupled in series in which the simulated outflow constituent quantities for the first and second pools became the inflows for their respective downstream pools. By using this model configuration it was possible to simulate longitudinal as well as vertical temperature variation and the concentration of total dissolved solids, thus reducing the severity of the one-dimensional assumption.

ISSN:1040-2381    

DOI:10.1080/07438148609354607

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The CE-THERM-R1 model was used to simulate the depths of mixing and frequencies of short-term, non-seasonal hydrodynamic behaviors for a small (1.5 ha) pond in western South Carolina. Two years of data were used to calibrate the system coefficients and to assess the adequacy of the simulations. Mixing depths and frequencies were then used to assess the effects of nonseasonal allogenic forces on the planktonic succession and distribution. The results demonstrate that the intensities and frequencies of allogenic forces are directly related to the plankton periodicity and the development and persistence of accumulations of organisms and particulate material. The calibrated model is now being tested for predictions of system responses to real-time meteorological data collected from a local meteorological tower.

ISSN:1040-2381    

DOI:10.1080/07438148609354608

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The U.S. Army Corps of Engineers has developed one-and two-dimensional models as tools for water resources management. CE-QUAL-R1 is a variable-layer, horizontally averaged water quality model. CE-QUAL-W2 is a two-dimensional (laterally averaged) finite-difference hydro-dynamic and transport water quality model. The water quality algorithms in both models are similar and both have been applied to DeGray Lake, Ark., a reservoir that has been extensively studied by the Corps of Engineers. The reservoir is of particular interest because of dissolved oxygen declines in the metalimnion of the main pool during summer and fall months. Both models successfully predict spatial and temporal variations in dissolved oxygen concentrations in their respective dimensions. Evaluations were made of all flux values contributing to simulated oxygen dynamics.

ISSN:1040-2381    

DOI:10.1080/07438148609354609

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Using mean basin slope and watershed area to lake surface area ratios, 58 Iowa lakes were classified into four distinct groups. Physical factors that can be altered very little once a lake is constructed may drastically affect sport fishing and the cost of maintaining quality fishing. Mean basin slope ([Sbar]) and watershed to lake area ratios (WA) can be determined prior to lake construction, and should ultimately influence lake site and construction plans. The exact relationship between the physical parameters, lake quality, and quality of the fishery in Iowa is unknown. Understanding these relationships will assist in developing fish management programs for existing lakes and describing the fisheries potential of proposed lakes. The lake groups formed used the following criteria: Group A, WA 0/–30:1 and [Sbar] greater than 8 percent; Group B, WA 30/–80:1 and [Sbar] greater than 4 percent; Group C, WA 0/–30:1 and [Sbar] below 8 percent; Group D, WA greater than 40:1 and [Sbar] below 8 percent. A lake with WA greater than 80:1 or with [Sbar] below 2 percent would also be classified as Group D. Angler acceptable standing stock was composed of bluegill,Lepomis macrochirus, and redear sunfish,Lepomis microlophus, TL 152 mm (6 in.) or larger; crappie,Pomoxis sp., TL 203 mm (8 in.) or larger, largemouth bass,Micropterus salmoides, TL 254 mm (10 in.) or larger, channel catfish,Ictalurus punctatus, TL 305 mm (12 in.) or larger, and black bullhead,Ictalurus melas, TL 203 mm (8 in.) or larger. Mean standing of fish varied among lake groups, ranging from 652 kg/ha (583 lbs/acre) to 808 g/ha (722 lbs/acre). Mean standing stock acceptable to anglers was 309 kg/ha (276 lbs/acre) in Group A lakes, 464 kg/ha (415 lbs/acre) in Group B lakes, 478 kg/ha (427 lbs/acre) in Group C lakes, and 132 kg/ha (118 lbs/acre) in Group D lakes. Statistical analysis revealed that mean standing stock of angler acceptable fish was significantly greater in Groups A and B lakes than in Group D. Group B lakes produced a significantly higher mean standing stock of angler acceptable fish than Group A. These data suggest that lakes with basin and watershed characteristics similar to those in Group B produce maximum angler acceptable fish standing stocks.

ISSN:1040-2381    

DOI:10.1080/07438148609354610

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A methodology has been developed to help protect lake water quality from degradation by nutrients. Criteria have been established which are keyed to protect the most sensitive water use of the lake. The categories of water use include aquatic life (including fisheries), recreation and aesthetics, drinking water, agricultural use, and industrial use. These criteria are the basis for more specific water quality objectives that are tailored to individual sites—either lakes or portions of lakes. Phosphorus concentration was chosen as the primary means of quantifying water quality, although nitrogen also can be used where it is the limiting nutrient. For phosphorus-limited lakes, the criteria used to protect drinking water and recreation are 10 μg/L total phosphorus. Criteria for fisheries and aquatic life differ according to important species. For example, for lakes with important salmonid fish resources, the criterion is a phosphorus concentration between 5 and 15 μg/L. For stratified lakes with important warmwater fisheries, a phosphorus concentration of 10–40 μg/L has been proposed. These criteria have been proposed specifically for British Columbia and may not be directly applicable to other areas.

ISSN:1040-2381    

DOI:10.1080/07438148609354611

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Although the contribution of sediment-generated methane to dissolved oxygen demand has been well documented in a number of stratified lakes throughout the world, little work on the subject has been performed in shallow, un-stratified lakes. To quantify the role of methane in carbon and oxygen cycling in such environments, carbon and methane budgets were prepared for Carlisle Lake, a small, shallow, unstratified, hypereutrophic lake. The budgets reveal that about 10 percent of the summer oxygen demand is exerted by the bacterial oxidation of methane. Methane production accounts for recycling of about 5 percent of the carbon produced by primary production and about 10 percent of the carbon reaching the sediments. Methanogenesis may indicate the degree of heterotrophic activity in sediments. This work supports such a conclusion and also suggests that methanogenesis may be indicative of the intensity of nutrient regeneration from sediments.

ISSN:1040-2381    

DOI:10.1080/07438148609354612

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A technique was developed for determining the sediment oxygen demand (SOD) and iron and manganese release rates under laboratory conditions. Site-specific comparisons of this method with the EPAin situtechnique, indicated a consistently lower SOD rate but improved reliability. Manganese release began as the dissolved oxygen concentration approached 1 mg/L and below. Iron release did not begin until –100 to –150 mv oxidation reduction potential was reached. A high degree of consistency was indicated between replicates. Laboratory andin situSOD rates yielded a two-dimensional model of reservoir oxygen budgets. The laboratory rate compared favorably to the assumed SOD rate of the model. As a result, TVA has incorporated the laboratory-determined rates and iron and manganese release rates into the reservoir management planning process. Specific measured and modeled rates determine waste load allocations for several reservoirs.

ISSN:1040-2381    

DOI:10.1080/07438148609354613

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Twenty-three softwater lakes in British Columbia, Canada, were sampled before fall overturn to assess thein situconditions associated with internal phosphorus loading. Hypolimnetic sediment and water results were correlated with physical and morphological characteristics of each lake. The concentration of soluble reactive phosphorus (SRP) measured 1 m above the sediment–water interface was strongly correlated with the oxidation reduction potential (ORP) measured at the same depth. Above 0 mV, soluble reactive phosphorus was below 3 μgL−1at 1 m above the sediment–water interface. Below 0 mV, soluble reactive phosphorus concentrations increased exponentially with decreasing oxidation reduction potential. A model using sediment loss on ignition (LOI) and spring overturn phosphorus (SOP) can predict the hypolimnetic oxidation reduction potential. Lakes with areal water loading values < 10 m yr−1typically had higher loss on ignition and spring overturn phosphorus concentrations. High loss on ignition and spring overturn phosphorus concentrations will cause anoxic conditions in the hypolimnion and internal phosphorus loading if the oxidation reduction potential drops below 0 mV at the sediment–water interface. Using the relationships presented, the impact of watershed development and lake restoration projects on internal phosphorus loading can be predicted.

ISSN:1040-2381    

DOI:10.1080/07438148609354614

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The water quality of the south basin of Long Lake, Minn. was monitored following Ca(NO3)2application in May 1984. The NO2+NO3−Nconcentration was elevated throughout the water column in 1984, but declined to pretreatment levels by 1985. Growing season mean total phosphorus and chlorophyll a concentrations were similar to pretreatment years. The impact of sediment Ca(NO3)2treatment on midsummer water quality in Long Lake was slight because of external loading. Sediment composition and residual NO3−Nmay limit the usefulness of this technique in many lakes.

ISSN:1040-2381    

DOI:10.1080/07438148609354615

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Budget calculations in the shallow lakes Dümmer and Schlei, F.R.G., and in limnocorral experiments carried out in Lake Schlei between 1981 and 1983 showed large seasonal fluctuations of internal phosphorus loading. These fluctuations were related to the load of the electron acceptors nitrate and sulfate from the tributaries and the internal metabolic processes. Based on lake budget studies, phosphorus release occurs predominantly during late spring and early summer (two months with maximum release rates of up to 200 mgP/m2·d).In siturelease rates correlated poorly with water column pH and with results of laboratory experiments carried out on those sediments. The phosphorus released was correlated with iron-bound phosphorus in the sediment (phosphorus measured as extractable by hydrogen sulfate treatment); however, down to a depth of microbial activation in the sediment. Algal development and nitrate depletion in the water had a strong triggering effect on phosphorus release from sediment. The mechanisms of internal phosphorus recycling became evident by monitoring the concentrations of iron, phosphorus, sulfate, and nitrate in the interstitial solutions. Management implications were derived from these results.

ISSN:1040-2381    

DOI:10.1080/07438148609354616

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor