摘要:

Even as attention to our nation's lake resources has sharpened in the past decade, water quality surveys repeatedly indicate deteriorating lake water quality. Several recent surveys indicate that the percentage of lake and reservoir waters impaired or threatened by pollution is higher than that of streams, rivers, estuaries, or groundwaters. This paper was prepared to stimulate debate on the need for specific numerical standards for managing water quality in lakes and reservoirs, and argues for them. A panel of reviewers representing different interest groups debated the issues presented in this paper at a plenary session at the 1986 Conference of the North American Lake Management Society; comments from the debate and additional opinions follow the paper. The principal authors also worked with contributors from a wide variety of institutions in writing this paper. This brought viewpoints ranging from engineering and agricultural perspectives in the university community to local, state, and federal government organizations. After reviewing the status of water quality in U.S. lakes and reservoirs and discussing innovative, comprehensive approaches for achieving point and nonpoint source pollution reduction, the authors conclude that degradation of our lake resources is a very serious national problem, one that does not appear to be adequately addressed by existing institutions. The paper addresses alternative lake protections approaches – from technology-based point and nonpoint control standards, to lake inflow or in-lake water quality standards and innovative watershed-based practices – the advantages and limitations of using simulation modeling to establish standards, and the importance of biological monitoring in establishing ecologically-based standards. Case studies illustrate the utility and limits of the various approaches. The paper particularly emphasizes a case study of watershed-based, point/nonpoint pollution reduction tradeoffs in Colorado, and a watershed-based, special classification system and non-point source control cost-sharing program for eutrophic reservoirs in North Carolina. The authors suggest possible federal and state approaches for using specific, numerical or ecologically-based standards to restore and protect lake and reservoir water quality.

ISSN:1040-2381    

DOI:10.1080/07438148709354755

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:1040-2381    

DOI:10.1080/07438148709354756

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Erie and Campbell Lakes are two shallow, nonstratified lakes located in Skagit County, Washington. Both lakes suffered from dense blooms of blue-green algae during late summer. Erie Lake also suffers from occasional fish kills. A Phase I diagnostic study conducted in 1981–82 identified phosphorus as the nutrient controlling algal growth, and internal phosphorus loading via sediment release and aquatic plants was viewed as the most significant controllable sources. The restoration plan recommended aluminum sulfate (alum) to control sediment P release and mechanical harvesting to remove plant phosphorus. Harvesting would also provide recreational benefits and control any increased plant colonization made possible by improved water clarity. Both lakes were treated with liquid alum during Fall 1985, and the harvesting program was implemented in Summer 1986. The 1986 post restoration values indicate a dramatic improvement in the quality of Erie Lake. Mean summer total phosphorus concentrations were reduced from 115 to 26 μgP/L, chlorophyll a concentrations were reduced from 58 to 5 μg/L, while water clarity increased from 1.7 to 2.5 + meters. Improvements in Campbell Lake were significant but not as dramatic as Erie Lake; mean summer total phosphorus concentrations were reduced from 49 to 28 (μgP/L, chlorophyll a concentrations were reduced from 18 to 10 μg/L, but water clarity remained similar to pre-restoration values (1.8 meters).

ISSN:1040-2381    

DOI:10.1080/07438148709354757

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Phosphorus external and internal loading to Pine Lake was estimated and potential restoration measures were recommended. External sources contributed approximately 57 percent of the total phosphorus load, and internal sources the remaining 43 percent. External and internal loading together exceeded the critical level expected for a mesotrophic state. About one-third of the external load, or about 20 percent of the total, entered through a channel draining a wetland. Total phosphorus concentration in this source was more than six times that in the lake; nearly 90 percent was soluble reactive phosphorus. This inflow will be diverted to the outflow in 1986. Another one third of the external load represented a “residual” occurring during the wet season. This was attributed to cultural activities, namely leachate from near-shore septic systems, although direct evidence was limited. About 35 percent of the total load entered from-internal sources, largely from littoral sediments and photosynthetically elevated pH during the spring algal bloom. This source of input is particularly important because it enriches the epilimnetic waters when the potential for increased algal growth is great. Wetland diversion and correction of failing near-shore septic systems should result in a lower mesotrophic state and greater than a 60 percent reduction in total phosphorus during the spring bloom period if productivity is reduced sufficiently to prevent elevated pH. The success of restoring Pine Lake depends on whether or not internal loading during the spring bloom is substantially reduced. A “worst-case” improvement is only a 12 percent reduction in total phosphorus during the spring bloom maximum, which assumes no change in the pre-diversion littoral sediment phosphorus release rate. However, diversion alone should result in less productivity, lower pH, and less sediment phosphorus release.

ISSN:1040-2381    

DOI:10.1080/07438148709354758

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

In 1968, a 2 km long water diversion was built to flush Chain Lake, British Columbia with nutrient-poor subai-pine water. Unfortunately in some years, blue-green algal blooms (chla> 100 μg/L) and fish kills still occur. The incomplete success of the diversion is related to the asynchrony of water flow and phosphorus release from the sediments. Internal loading represents about 78 percent of the phosphorus supply to the lake in summer, and water flow is minimal during phosphorus release. Phosphorus in surface sediments is five times more concentrated than in sediments deeper than 80 cm. Diatoms in sediment cores indicate that the lake has been eutrophic for at least 300 years. The accumulation of a diatomaceous ooze in the lake was measured by three methods to be between 0.5 and 1 cm a year. A larger diversion would suppress plankton blooms, but in this shallow lake it would enhance the growth of macro-phytes; sediment dredging may be a more effective in situ treatment.

ISSN:1040-2381    

DOI:10.1080/07438148709354759

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Moses Lake has received dilution water in 9 of 10 years since treatment began in 1977. The average input for those years was 143 ± 79 × 106m3/yr over 93 days, which represents flushing rates of about 13 percent/day for Parker Horn where the dilution water enters, and 1 percent/day for the whole lake. As a result, lake quality has improved at least 50 percent in terms of chlorophyllaand total phosphorus and by nearly 100 percent in transparency. Pumping diluted lake water from Parker Horn beginning in 1982 and diverting sewage effluent in 1984 markedly improved water quality in a section that received treated effluent and little or no dilution water. Total phosphorus has declined by 90 percent and chlorophyllaby 60 percent, although transparency increased only about 0.2 m because of that section's shallowness. Diluted nitrate concentration in the inflow has been considered the cause for control of algae, but a switch from largely flood to spray irrigation, as well as sewage diversion, has resulted in lower inflow phosphorus concentrations and a gradual change from N to P limitation. Despite favorable improvements in average conditions, however, blooms of blue-green algae still develop in late summer. The largest bloom in the 10 + year study occurred from late August through September 1985, when the lake was well diluted and received no sewage. This is attributed to increased mixing following lower than normal temperature and to a 50 percent increase in internal phosphorus loading. Buoyant blue-green algae rising from the sediment surface are hypothesized to be the transport mechanism.

ISSN:1040-2381    

DOI:10.1080/07438148709354760

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Artificial circulation is a lake management technique which can sometimes improve the quality of eutrophic impoundments. While improvements associated with extension of oxygenated habitats are common, other benefits such as reduction of algal biomass and changes in phytoplankton and zooplankton species composition are less certain. Circulation was implemented from June through October 1982 in eutrophic Silver Lake, Summit County, Ohio. Dissolved oxygen was maintained at the bottom of most stations, with a concomitant increase in zooplankton and benthic macroinvertebrate ranges. Negative results included increases of surface phosphorus, chlorophyll, and algal biomass, a slight decline in transparency, and the continued predominance of blue-green algae at the surface. One station was partially isolated by basin morphometry and functioned as an in-lake control which remained physically, chemically, and biologically stratified. The overall trophic state of the lake as measured by phosphorus, transparency and chlorophyll declined. Reasons for these undesirable results include failure of the system to maintain isothermal conditions, failure to achieve a pH and phytoplankton shift, and mixing of sediments into the water column from placement of the diffuser directly on the lake bottom.

ISSN:1040-2381    

DOI:10.1080/07438148709354761

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

To maintain an oxygen concentration of at least 6 mg/L in the discharge, an oxygen injection system was designed for the Corps of Engineers peaking hydropower project on the 10,785 ha Richard B. Russell Lake (Georgia-South Carolina). To aid in the operation of the oxygenation system, a mathematical model was developed to compute the amount of oxygen required to meet the desired discharge standard. Factors considered by the model included the outflow rate, oxygen depletion rates, hypolimnetic volume, oxygen deficit, selective withdrawal patterns and oxygenation efficiency. Oxygen depletion rates and hypolimnetic oxygen deficit were computed from in situ profiles; selective withdrawal patterns were computed based on temperature profiles and hourly project operation records. Results for the 1985 season indicated that the model could be used to provide a rapid and more accurate estimate of oxygen requirements than previously available. When compared with operation of the system based only on maintaining downstream discharge requirements, use of the model could result in a substantial cost savings.

ISSN:1040-2381    

DOI:10.1080/07438148709354762

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Aluminum sulfate was applied to eutrophic Eau Galle Lake to control internal phosphorus recycling from anoxic sediments for a period of five years, and to provide increased user benefits at a reasonable cost. Treatment dose (11.3 g Al/m2) was based on mass balance estimates of summer Internal phosphorus loading rates; no attempt was made to curtail external loading rates. Phosphorus concentrations in bottom waters, internal phosphorus loading rate, and the abundance of blue-green algae were reduced relative to previous years; however, algal biomass remained relatively high. The proliferation of the dinoflagellateCeratiumhirundinella, a vertical migrator, suggested that these algae may have obtained phosphorus from interflowing river waters having a high nutrient content.

ISSN:1040-2381    

DOI:10.1080/07438148709354763

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Assessment of costs and benefits of lake restoration techniques aids lake management by identifying the most cost effective approach, determining who benefits from the approach, and identifying who should pay for the approach. Traditional lake restoration techniques rely upon fairly straightforward methods for determining costs of the project and identifying the benefits. However incorporating nonpoint source controls into lake water quality management strategies requires understanding the costs of nonpoint source pollution as well as the potential benefits of different management strategies. Yet cost-benefit analyses of nonpoint source pollution impacts and corrective practices have traditionally focused on a narrow range of onsite costs and benefits to the owner-operator. To become an effective water quality management tool, these analyses must encompass a broader view and become sensitive to how political and social processes will influence the negotiation of economic costs and benefits. This paper reviews existing cost-benefit models and discusses criteria for their use as lake management tools and discusses the implications that a broader negotiation approach can have on lake management decisionmaking.

ISSN:1040-2381    

DOI:10.1080/07438148709354764

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor