摘要:

The history, objectives, and operation of the Michigan Lake & Stream Associations, Inc., is reviewed. This paper details the steps in forming a State association, including the original motivation and the legal problems involved.

ISSN:1040-2381    

DOI:10.1080/07438148409354563

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Dilution water has entered Moses Lake since 1977, usually in amounts exceeding 100 106m3, which has amounted to exchange rates of around 10 percent day−1in 8 percent of the lake volume nearest the input. The principal cause for the marked reduction in algal biomass and increased transparency, prior to the Mount St. Helen's ashfall, was the dilution of inflow concentrations of NO3. Average summer chlorophyll a was closely correlated with flow-weighted mean inflow NO3. Increased NO3–N:SRP in undiluted inflow water following the ashfall caused P limit growth in the lake. Increased dilution water input in 1982, compared to the 2 post-ash years, reduced inflow NO3to biomass-controlling levels in spite of continued high ratios of soluble N:P in the lake. Dilution water was pumped to previously undiluted Pelican Horn in 1982 at a rate of 1.4 m3s−1during July through August. Algal biomass was reduced largely because of cell washout, because undiluted water was pumped after July, but chl a actually increased as a result of increased N availability to previously N-deficient cells. Transparency remained at the same low levels (0.4 m) that existed prior to dilution due to large amounts of nonalgal turbidity, which may not improve even if low NO3water is added and sewage effluent is diverted.

ISSN:1040-2381    

DOI:10.1080/07438148409354564

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Multiple phase drawdowns have been suggested as a possible restoration technique for controlling the aquatic weed Hydrilla and for consolidating sediments. Brevard County, in cooperation with the Florida Game and Freshwater Fish Commission, implemented such a program in 1979–80. Fox Lake is a small 44.5 ha (110 acre) freshwater lake in Brevard County on Florida's east coast. This lake, the location of a major regional park, had become unusable to boaters and fishermen due to an excessive growth of Hydrilla. In addition to the Hydrilla, the lake had minimal fish and wildlife benefits due to a thick layer of unconsolidated muck. While the use of proper technique is important, the restoration of Fox Lake required methods which insure full community support, and the cooperation of other agencies and local elected officials' and public involvement are necessary. Techniques must be flexible enough to meet unforeseen or changing conditions. For example, during the Fox Lake drawdowns, lake conditions required innovations such as air boat pull plows and amphibious craft. The Fox Lake project demonstrated that lake restoration projects with maximum and innovative use of local resources can be completed with minimal impacts on local government budgets.

ISSN:1040-2381    

DOI:10.1080/07438148409354565

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

During the past century, increased fertilization and the resultant algal and macrophyte growths have severely impaired the quality and use of many lakes throughout the world. A notable case has been the deterioration of Sebasticook Lake. The lake began showing signs of cultural eutrophication in the early 1950's. By the late 1960's it had become hypereutrophic and has remained in that condition despite remedial efforts. Currently a major effort to restore the lake has been undertaken by the State of Maine, U.S. Environmental Protection Agency, U.S. Department of Agriculture and local communities. Estimates of annual external phosphorus loading range from 3,900 to 11,800 kg with an estimate of 9,000 kg considered as the most accurate estimate of the current load. Sources include 2,300 kg and 2,200 kg from the towns of Dexter and Corinna respectively, and 4,500 kg from nonpoint sources of which 85 percent is culturally generated from farmland. Using a mass balance model it is estimated that an annual external load of 4,500 kg of total phosphorus would maintain the lake at a desired concentration of 15 μg/l and suppress the chronic algal blooms. Strategy to control external sources includes advanced wastewater treatment to reduce the loading from Dexter and Corinna to 300 kg and 700 kg, and improved farm practices to reduce nonpoint sources to 3,500 kg. Since the recycle of phosphorus from the lake sediments is estimated to contribute 6,900–9,900 kg into the water column annually, control of internal recycling was also imperative. Because of the large size of Sebasticook Lake (1,798 ha) the most promising means to reduce internal phosphorus was to alter the flushing regime of the lake. Epilimnetic phosphorus reaches peak concentration during late summer stratification. At that time, the lake volume is reduced by one half, decanting the phosphorus rich epilimnetic water. Refill of the lake does not commence until the following spring when phosphorus-poor melt water is available. Drawdown of the lake is accomplished through constructing a 4-meter deep canal and gate structure at the outlet. Initial trials of the structure were estimated to export about 4,200 kg of phosphorus annually.

ISSN:1040-2381    

DOI:10.1080/07438148409354566

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The Minneapolis Chain of Lakes, a series of five lakes covering some 445 ha (1,100 acres) within an urban residential setting, is an important recreational and aesthetic resource. The lakes support swimming, fishing, sailing, and canoeing and are almost entirely surrounded by public parkland. However, the lakes exhibit increasing cultural eutrophication. The city of Minneapolis obtained an EPA Clean Lakes grant for demonstrating vacuum street sweeping and first-flush runoff diversion as means for improving the lakes. The project was completed in 1981 following 2 years of monitoring and pilot implementation. In 1979 and 1980, the city regularly vacuum swept streets throughout the Lake Harriet watershed (46 curb-km in 340 ha). During these years, consultants monitored lake quality, weather, runoff flow, and quality in major storm drains to Lake Harriet, and quantity and quality of vacuum swept materials. Runoff data were used to analyze first-flush diversion. Data analysis resulted in estimated runoff coefficients ranging from 0.05 to 0.5 for individual drainage areas throughout the chain. Seasonal patterns of runoff quality were found. Total phosphorus export from the entire watershed of the chain was estimated to average 5.2 kg per hectare (1 pound per acre) in a climatologically normal year (with no allowance for sweeping or diversion). Detailed water and nutrient budgets, including ground water and inter-lake flows, were developed. Runoff and direct precipitation contributed nearly equally to the water budget, but runoff accounted for over 95 percent of phosphorus inputs. Water outflow was predominantly via seepage. Phosphorus retention in the lakes was high, totaling over 90 percent for the whole chain. Vacuum sweeping was found to remove 3 kg phosphorus/curb-km and 69.5 kg organic matter/curb-km (0.26 lb phosphorus/curb-mile and 74 lb organic matter/curb-mile) per sweeping. These are average values: seasonal variations were significant. Weekly sweeping was projected to remove 38 percent of Lake Harriet's phosphorus load. First-flush diversion was analyzed by taking into account the frequency distribution of storms with respect to total precipitation. Diversion was found to be cost effective in some areas and capable of reducing the phosphorus load to Lake of the Isles by 42 percent. A combination of sweeping and diversion throughout the Chain of Lakes watershed was found most cost-effective. This scheme could reduce the whole chain's phosphorus load by 27 percent, at an estimated 10-year cost of $4 million. Predicted transparency increases averaged .77 m (2 ft.) and ranged from .2 m to 1.9 m (one-half to five feet) for individual lakes.

ISSN:1040-2381    

DOI:10.1080/07438148409354567

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Alum treatment of lakes has been found to be a generally effective method for reducing P concentrations in lakes over a period of 2 to 3 years after treatment. However, the long-term benefits of lake alum treatment in most cases have not been determined. In this study, three Wisconsin lakes treated 9 to 12 years previously were re-examined in 1982 to evaluate the long-term effects of the treatment projects. Results indicated that many years after treatment P levels in all three lakes remained lower than before the lakes were treated. Horseshoe Lake, the first U.S. lake treated with alum in 1970, was more eutrophic in 1982 than immediately after treatment but is still much improved over pretreatment conditions. The reduced levels of phosphorus in 1982 compared with before the alum treatment, indicate the alum layer is preventing the migration of phosphorus from the deep sediments. The 1982 phosphorus concentrations in the hypolimnion of Snake Lake are similar to levels experienced following the 1972 treatment despite continued input of stormwater runoff to the lake. While the previous two lakes are dimictic, Pickerel Lake is a polymictic lake. The increased mixing action has redistributed much of the alum toward the center of the lake. The alum treatment appeared to have little effect on the internal phosphorus dynamics of the lake.

ISSN:1040-2381    

DOI:10.1080/07438148409354568

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Water level fluctuations, a naturally occurring phenomena in the Great Lakes, cause a continuing rejuvenation of lake-influenced wetlands. Two Lake Ontario wetlands (Campbell and Sage Creek Marshes) were mapped for 1 ft. contour intervals and habitat-vegetation type. Historical habitat/vegetation conditions were evaluated through interpretation of aerial photography. The photography was selected to represent water levels different from the current. Habitat types defined at Campbell Marsh and their most important herbaceous species include: (1) narrow-leaved persistent emergents,Typha glauca; (2) aquatic bed,Ceratophyllum demersum; (3) grass sedge,Calamagrostis canadensis; (4) scrub/shrub,Cornusspp; and (5) flooded deciduous forest,Fraxinusspp. Habitat types defined at Sage Creek Marsh and their most important herbaceous species include: (1) narrow-leaved nonpersistent emergent,Sparganium eurycarpum; (2) broad-leaved nonpersistent emergent,Pontederia cordata; (3) aquatic bed,Elodea canadensisand (4) grass sedge,Calamagrostis canadensis. Computerized data analysis showed that vegetation types occured within rather distinctive elevational ranges. As water levels changed, the area of the various habitat types changed, adjusting to both the new water depth and to the size of the area at that depth. In Sage Creek Marsh a large area of narrow-leaved nonpersistent emergents was lost as water levels increased. The greatest loss in Campbell Marsh occurred to persistent emergents; however, this loss did not have a linear relationship to annual mean water depth.

ISSN:1040-2381    

DOI:10.1080/07438148409354569

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The 48 hectare Lake Josephine was being impacted by urban stormwater runoff flowing directly into the lake from 237 hectares of its 341 hectare watershed. Runoff from 90 hectares — or 37 percent — of this direct drainage area was diverted to a 12 ha wetland treatment system for pretreatment prior to its discharge into Lake Josephine. The first year three monitors revealed the treatment system had removal efficiencies of 62 percent for total phosphorus, 69 percent for orthophosphorus, 48 percent for total Kjeldahl nitrogen, and 79 percent for total suspended solids. Three-year average water quality data from the lake itself was also compared to data obtained for 3 years prior to the diversion. The comparison revealed that after the diversion, total phosphorus concentrations decreased from .092 to .058 mg/l, total Kjeldahl nitrogen concentrations decreased from 1.25 mg/l to .7 mg/l, ortho-phosphorus concentrations decreased from .038 mg/l to .03 mg/l, and Secchi depth transparency increased from 3.83 meters to 5.0 meters.

ISSN:1040-2381    

DOI:10.1080/07438148409354570

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The island of Montreal is part of an archipelago at the confluence of the Ottawa and St. Lawrence Rivers. The mixing of waters from two watersheds, the diversity of channel profiles, substrata, and natural riparian communities, and the great length of shoreline give the area a marked biotic richness and high rate of primary productivity. Longstanding public concern over deteriorating water quality and increasing flood hazard has prompted a comprehensive evaluation of the area's aquatic resources by the provincial government. However, these studies have tended to focus on large scale engineering problems and proposals. Urban expansion and the associate pressures on waterfront land have had a persistent and marked effect on the riparian ecosystem. The loss of upland nesting sites, for example, has rendered much of the area sterile to several duck species. The effects on the aquatic community are less clear. This study was undertaken to determine the effects of shorezone development on the communities of aquatic macrophytes in adjacent areas. It entailed the study of 24 paired sites, one site in each pair being off developed shore, the other site being off nearby natural shore. Twenty-two macrophyte species were recorded in all, withVallisneria americana, Elodea canadensis, andCeratophyllum demersumbeing by far the most abundant. Samples taken off natural sites were significantly higher in average species richness and average biomass values than those taken off developed shore. Differences in profile, substratum, and water quality were assessed as possible causes and it is concluded that changes in depth and perhaps the removal of natural substratum are most likely to have been significant factors. The consequences of the observed changes in terms of habitat utility for aquatic fauna are discussed briefly.

ISSN:1040-2381    

DOI:10.1080/07438148409354571

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The outcome of any lake restoration project depends on numerous variables: e.g., lake morphometry, initial water quality, composition of the biological community, and engineering specifications of the restoration technique. Consequently, a variety of lake responses to restoration attempts can be expected, ranging from complete success to at least partial failure. For example, artificial circulation has improved water quality in many cases, but has often caused adverse ecological impacts, such as increased turibidity or nuisance algal blooms. The benefits of lake restoration can be realized only through accurate prediction of lake responses to alternative management schemes or experimental manipulations. Numerical classification of previous case history data can be used to enhance this predictive capability and to refine lake restoration techniques. By applying Mulitple Discriminant Analysis to case histories of artificial circulation, we defined the critical attributes of a successful restoration project. For each response parameter (e.g., dissolved oxygen, algal density, pH), the initial objective was to maximize separation of lake restoration groups (i.e., successful or unsuccessful) by differentially weighting individual morphometric and mixing-system variables in a discriminant function. When adequate discrimination is obtained, the discriminant function can be used to predict the response of a lake based primarily on physical attributes of the lake (area, volume, depth) and the aeration system (air release depth, air flow rate).

ISSN:1040-2381    

DOI:10.1080/07438148409354572

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor