摘要:

Alternative devices for reservoir aeration are briefly reviewed. It is noted that each device is best suited for particular applications and objectives. It is recommended that care be taken by the designer to select the appropriate device for the particular application. Advantages and disadvantages of the various devices are given along with representative destratification and oxygenation efficiencies. Design considerations are discussed including techniques for sizing units, the effects of inflows and releases, the effects of reservoir stratification, evaluation of aeration impact on the reservoir temperature regime, and the possible development of nitrogen supersaturation.

ISSN:1040-2381    

DOI:10.1080/07438148409354573

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Lake Cachuma, Calif., has historically experienced severe hypolimnetic oxygen depletion during summer stratification. To alleviate this problem and improve the water quality of the reservoir, a diffused-air aeration system was installed in May 1981. A limnological study was conducted from April 1980 through November 1982. Results showed a weakening of the stratification, increased oxygen and temperature in the hypolimnion, increased green algae, and increases in the populations ofBosminaand Chironomids. Lake turnover in 1981 and 1982 occurred approximately one month earlier than in 1980. Water quality problems of manganese and hydrogen sulfide were effectively controlled.

ISSN:1040-2381    

DOI:10.1080/07438148409354574

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Two general methods exist for artificially destratifying an impoundment: (a) pneumatic destratification using compressed air jets, and (b) hydraulic destratification using water jets. Results from laboratory parametric investigations of hydraulic destratification are presented for a variety of test conditions. A practicable limit of destratification, the 80 percent mixed state, was identified and regression analysis used to define the time required for development of this 80 percent mixed state in terms of reservoir geometry, stability, and pumping rates. Results of the regression analysis showed the dimensionless mixing time to the 80 percent mixed state to be a function of a “destratification” densimetric Froude number. The use of these results in a design procedure is discussed.

ISSN:1040-2381    

DOI:10.1080/07438148409354575

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Density stratification limits or negates vertical mixing in lakes and reservoirs with the result that vertical strata of decreasing water quality are formed. Releases from the lowest of these strata, the hypolimnion, may be of generally poor quality due to oxygen deficiency resulting from the coupling of limited vertical mixing and hypolimnetic oxygen demand. A simple, cost-effective method to enhance these releases, localized mixing, utilizes the effects of jet mixing to transport high-quality epilimnetic water down to the hypolimnetic withdrawal zone and dilute the release. To effectively enhance downstream release quality, the localized mixing system must produce a jet of sufficient quantity and initial momentum so that it will both penetrate into the hypolimnion and adequately dilute the release. Laboratory investigations showed jet penetration into the hypolimnion to be a linear function of the densimetric Froude number at the thermocline. Dilution was observed to be a function of effective pumping ratios. An example design based on these laboratory results is given.

ISSN:1040-2381    

DOI:10.1080/07438148409354576

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Illinois Soil and Water Conservation Districts (SWCD's) working through the Association of Illinois Soil and Water Conservation Districts (AISWCD) have developed a strategy for nonpoint source pollution abatement which recognizes SWCD priorities and assigns available information, technical assistance, and incentive resources to solving soil erosion and sediment problems in lake watersheds. Elements of that strategy include: (1) SWCD and AISWCD staff field reviews of lake watersheds designated by the Illinois Environmental Protection Agency; (2) classification of watersheds based on watershed resource information and SWCD priorities; (3) encouragement and assistance for SWCD's to work with appropriate local, as well as, state and Federal agencies to solve nonpoint source pollution problems through a local work plan; (4) development of cost efficient land-operator incentives such as the conservation tillage risk share program being used in one lake watershed; (5) encouragement for lake managers and monitors to work through their SWCD to put soil and water conservation practices in the watershed; and (6) reinforcement of SWCD informational and promotional materials to improve lake watershed management. AISWCD has developed an innovative program based on grass roots support for SWCD watershed programs. Benefits of this approach will be projected for other areas, and this will prove useful, particularly for persons in areas experiencing funding reductions.

ISSN:1040-2381    

DOI:10.1080/07438148409354577

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A number of pollutants acting either singly or in combination affect lakes and reservoirs. Attention is turning towards nonpoint sources and watershed management as offering a potential for more cost-effective control. Nutrient reductions below 1.0 mg/l from municipal treatment plants come with an extremely high reduction cost factor as a result of increased hardware, operations, and maintenance costs. Several nonpoint source control demonstration projects have been implemented since the passage of PL 92–500. Some were directed at the unknowns surrounding the control of runoff from both urban and agricultural sources. For agriculture there were questions about the agricultural institutional arrangement and the effectiveness of practices. One restriction was the voluntary nature of participation, deemed the only feasible implementation method. Several projects have now been completed and conclusions and recommendations made. The project approach is emerging as an effective method of focusing resources to control identified natural resource problems. Some projects did not meet all objectives because the problem was not clearly defined and early implementation was demanded. A strong relationship exists, suggesting that nutrient reductions may be obtained from watershed treatment, but quantification is still lacking. Other factors influenced the implementation and kept the focus from zeroing in on critical sources and areas, making project evaluation difficult. Modifications in project development and implementation steps will be discussed based on these findings and suggestions made for more efficient management of watershed projects.

ISSN:1040-2381    

DOI:10.1080/07438148409354578

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Watershed management activities in Albemarle County and the city of Charlottesville in the Piedmont Region of Virginia have been examined. In recent years these two localities have exhibited an unusual spirit of cooperation and compromise in protecting the area's water supplies. Creation of a unique position of Watershed Management Official, funded equally by both localities, was one of the first steps taken locally in recognizing that watershed management was a continuing process that required the coordination and integration of many diverse activities and recognizing that proper watershed management requires more than best management practices manuals and ordinances; it requires constant site investigations and surveillance of all watershed activities. Protection of existing water supplies is the major goal of watershed management; however, planning for additional and future needs has not been forgotten. Charlottesville and Albemarle County have again taken that necessary first step in planning for the future by providing the mechanism whereby land for a supplemental water supply impoundment and associated buffer area protection zone will be acquired in the near future even though the actual impoundment will not be needed for 20 or 30 years. The aspects and the degree of the cooperation and compromise needed for a successful watershed management program are examined.

ISSN:1040-2381    

DOI:10.1080/07438148409354579

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In the summer of 1983, 106 lakes in the city of Orlando, Fla. were considered in a selection process to determine which most needed restoration in the City's Lake Enhancement Program. The existing lake systems were thoroughly investigated with regard to historical water quality data; existing water quality data; current public uses; visual, physical, and chemical condition; the drainage basins; the stormwater structures and management controls; as well as surface color aerial and false color infarared aerial photometric reconnaissance. These were analyzed to provide an objective screening process to determine a discrete set of lakes, approximately four to six, which may be top candidates for a pilot lake project. This paper describes the screening process.

ISSN:1040-2381    

DOI:10.1080/07438148409354580

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Initial water quality planning efforts documented that agriculture activities are a major source of pollution in Illinois. The most severe agricultural related problem is soil erosion resulting in sedimentation. In Illinois, estimated gross erosion exceeds 180 million tons annually, with 88 percent from cropland. Illinois Environmental Protection Agency in cooperation with various U.S. Department of Agriculture agencies evaluated the water quality impacts of resource managment system implementation under the ACP Special Water Quality Project in the Blue Creek Watershed. The physical, biological, and chemical characteristics of the Blue Creek Watershed Lake have been studied since 1979. A comprehensive monitoring network for the entire Blue Creek Watershed was established to document the basic hydroiogical, meteroiogical, and water quality factors of the project area during 1980. The duration, timing and quantity of nonpoint source pollutants were evaluated within the watershed. The monitoring program was designed to link water quality to what is happening on the land. To understand the processes of soil erosion and nutrient/sediment transport and to draw meaningful conclusions about land use effects, focus was given to sources and movement from sources to the lake outlet. This evaluation integrated reservoir sedimentation surveys, lake water quality monitoring, biological monitoring, water quality monitoring at stream gauging stations and small field sites, a channel dynamics study, and a computerized gross erosion estimate. The stream gauging station and field site monitoring were event-oriented sampling to supplement the baseline monitoring on the stream network and in the lake. There were obvious seasonal and spatial trends exhibited by several physical and chemical parameters within the lake and watershed. In Illinois, erosion control is being used as a surrogate for sediment control because sediment control is less amenable to quantitative analysis. This reflects the current lack of knowledge concerning sediment origin, transport, deposition, and control technology. Integration of source and sediment budget studies with realistic concepts of storm runoff production results from this project will clarify some aspects of the interrelationships between gross erosion and water quality impacts.

ISSN:1040-2381    

DOI:10.1080/07438148409354581

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A synthesis of a 5-year study on the efficient regulation of Lake Como in Northern Italy is presented. Its main result was the proposal of a new operating rule for the lake, which has been implemented on a microcomputer. This has been operated daily for 1 year and a first evaluation of the impact of this innovation on the lake manager's attitude is briefly outlined.

ISSN:1040-2381    

DOI:10.1080/07438148409354582

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor