摘要:

Eutrophication has several direct and indirect effects on reservoir water quality and uses. The paper describes assessment procedures recently developed for application to Corps of Engineer reservoirs. Study phases include problem identification, data gathering, data reduction, and model implementation. Three interactive computer programs (FLUX, PROFILE, BATHTUB) assist in the last two phases. Eutrophication-related water quality conditions (expressed in total phosphorus, total nitrogen, particulate phosphorus, and hypolimnetic oxygen depletion rate) are predicted using empirical relationships calibrated and tested for reservoir applications. Based upon research using several independent data sets, previous “northern-lake-based” empirical modeling approaches have been modified to account for effects of (1) nonlinear nutrient sedimentation kinetics; (2) algal growth limitation by phosphorus, nitrogen, light, and flushing rate; (3) inflow nutrient partitioning (bioavailability of dissolved versus particulate loadings); (4) seasonal variations in loadings and morphometry; and (5) spatial variations in nutrients and related trophic-state indicators. To reflect input data limitations and inherent model errors, inputs and outputs can abe expressed in probabilistic terms. The segmented model can be applied to single reservoirs (mixed or spatially segmented), networks of reservoirs (hydrologically linked), or collections of reservoirs (hydrologically independent). The last type of application permits regional comparisons of reservoir conditions, controlling factors, and model performance.

ISSN:1040-2381    

DOI:10.1080/07438148609354617

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A stochastic modification of the basic Vollenweider model was used to represent variability in daily phosphorus concentrations in a small southern hypereutrophic lake. Uncertainty measurements, arising from defining initial conditions such as loading estimates, and a lumped white-noise parameter were used to project probability distributions of mean daily in-lake phosphorus concentrations. Additional consideration of spatial variability permitted comparison of model projections with monitoring data. Model calibration was performed with over 500 temporally and spatially distributed total phosphorus observations, ranging from 0.171 to 1.575 mg/L, taken from a 70-day intensive monitoring program in 1983. Results indicate the model's potential usefulness, particularly in unstable systems, although short-term oxygen depression, stratification, and catastrophic events, such as a 12.7 cm rainstorm, limited its predictive capabilities.

ISSN:1040-2381    

DOI:10.1080/07438148609354618

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

State and regional agencies frequently must use a model or models to assess limnological relationships, like that between phosphorus and chlorophyll, in a large number of lakes. If lake behavior in all lakes is essentially identical, then it is reasonable to pool information across lakes concerning the relationships and to make inferences on the basis of a universal model. Alternatively, if all lakes are unique, then inferences must be drawn from lake-specific models. The truth probably lies somewhere in between these two extremes. On that basis, empirical Bayes estimation is used to fit a simple model relating phosphorus to chlorophyll in lakes. The model is then applied to each lake in such a way that the chlorophyll prediction is based on both lake-specific and regional lake information. For lakes as a whole, the empirical Bayes estimator should result in improved predictions over standard approaches.

ISSN:1040-2381    

DOI:10.1080/07438148609354619

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Recent studies of Flathead Lake, the largest freshwater lake in the western United States, suggest that it may be experiencing the effects of nutrient enrichment. Two measures to control the amount of phosphorus entering the lake from wastewater sources have been suggested to help alleviate this change. One measure instituted in the fall of 1983 was to limit the effluent concentrations from the treatment plants in the basin to 1 mg/L total phosphorus. Plants are to be on line by November 1986. In the interim, a phosphorus detergent ban is under consideration as a second control measure. This study was undertaken to assess alternative interim wastewater control measures. It was estimated that effluent limitations on the municipal plants could reduce the wastewater phosphorus load by 66 percent while a phosphorus detergent ban would reduce the load by about 28 percent. These reductions correspond to approximately 15 percent and 6 percent, respectively, of the estimated bioavailable phosphorus loading to the lake. Because of the greater impact of effluent limitations, the four treatment plants in the basin were investigated for the feasibility of immediately implementing simultaneous chemical precipitation of phosphorus. The investigations indicated that it was feasible at the three largest plants and would require relatively small capital expenditures. Annual per capita costs for phosphorus removal at the three plants were estimated to be $5, $9, and $14/person/year and would result in a phosphorus load reduction of 15 metric tons per year to Flathead Lake. Annual costs to the consumer of a phosphate detergent ban were conservatively estimated to be $11 per household. Thus, the estimated annual costs of the two strategies are $10.23/kg P reduction for phosphorus removal at the treatment plants and $32.37/kg P reduction for a phosphate detergent ban. The study concluded that immediate implementation of chemical treatment at the municipal treatment plants rather than a phosphorus detergent ban should be pursued vigorously as a more effective means of controlling wastewater phosphorus sources.

ISSN:1040-2381    

DOI:10.1080/07438148609354620

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Controlling nonpoint pollution from developed urban areas has generally been considered impractical. In basinwide studies of toxicants upstream of two new nutrient-sensitive drinking water reservoirs, 516 small urban subdrainage basins in eight North Carolina cities were analyzed in detail. Each subbasin's area and land use were determined and pollutant loading factors lbs/acres/yr) applied. Except for nutrients, urban nonpoint sources contributed more pollutants than urban point sources. Pollutants were not evenly distributed across these cities; one-third of the area contributed about two-thirds of each city's copper, lead, zinc, total phosphorus, and total suspended solids (TSS), and about one-half of the total nitrogen, total Kiedahl nitrogen (TKN), and chemical oxygen demand (COD). If small detention basins were installed to control runoff from this one-third of each city, about one-half of the lead and total suspended solids and one-third of the zinc and total phosphorus would be removed from runoff from the entire city.

ISSN:1040-2381    

DOI:10.1080/07438148609354621

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Nutrient sources influencing eutrophication of Moses Lake, Wash., have been evaluated in a multistage investigation of urban and agricultural land uses in the watershed. Nutrient loadings from surface and groundwater contributions were quantified in a year-long monitoring program. Subsequent studies have assessed effectiveness of various control techniques to reduce nutrient input to the lake. These recent (1984) investigations include full-scale field demonstrations of agricultural irrigation practices involving cablegation, wheel line, and center pivot systems monitoring nutrient and water movement through coarse native soils. Over 75 percent of local farmers are trying control measures under a unique agricultural cost-sharing program. Other nutrient sources and controls evaluated and ranked for nutrient removal effectiveness include shallow detention ponds to enhance nutrient trapping, local septic tank management policies, animal waste and fish hatchery controls, and miscellaneous in-lake improvements affecting circulation, water depth, and macrophyte harvesting. This paper describes the proposed control strategies and the prioritizing system used to implement and fund them.

ISSN:1040-2381    

DOI:10.1080/07438148609354622

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The concentrations and amounts of soluble and total phosphorus in rainfall, runoff, impoundments, and stream flow from several unfertilized watersheds in the Southern Plains have been monitored for the past decade to assess the effects of varying land uses on water quality as indicated by phosphorus concentration. Mean annual soluble and total phosphorus concentrations of 12 and 25 μg L−1were observed in rainfall, 199 and 710 μg L−1in runoff from unfertilized grassland, and 165 and 1,875 μg L−1from unfertilized cropland. Soluble phosphorus from rainfall averaged 41 g ha−1, while that exported in runoff averaged 119 and 82 g ha−1yr−1for grassland and cropland watersheds, respectively. The load enrichment of phosphorus in runoff compared to rainfall was related to the water soluble phosphorus content of surface soil for each watershed (r2= 0.96 to 0.99). Soluble and total phosphorus concentrations in rainfall, runoff, and stream flow were sufficient to stimulate accelerated eutrophication according to critical phosphorus concentration guidelines. These guidelines — 10 and 20 μg L−1for soluble and total phosphorus, respectively—have been slightly modified by states for stream flow criteria. Data on phosphorus concentrations in rainfall and runoff from unfertilized watersheds at other U.S. and overseas locations are similarly above critical values; therefore, best management practices may not lower phosphorus concentrations on cultivated or grazed land to the critical values in runoff or stream flow. Management practices aimed at reducing nonpoint source phosphorus loading should be focused for areas where soil phosphorus levels have been raised above natural levels by applying fertilizers, manure, or crop residues.

ISSN:1040-2381    

DOI:10.1080/07438148609354623

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The Electric Power Research Institute (EPRI) is completing a review of methods used or useful for recommending instream flows below reservoirs. The three principal conclusions: no consensus exists on the number or identity of input variables needed to model the biological effects of flow alteration; although mechanistic models predicting the biological effects of flow alterations would be highly desirable, none yet exists; and, the only models that seem geographically transportable are ones that select site-specific input variables, use site-specific data transformation schemes, or adjust parameters to correspond to regional characteristics. The existing methods are equally represented by those recommending a particular flow regime from only basin or hydraulic variables without clear justification; those producing a relationship between flow and an unmeasurable habitat index (such as the U.S. Fish and Wildlife Service Habitat Suitability Indexes or Weighted Usable Area); and those producing an empirically descriptive (but not usually predictive) equation relating flow to standing crop of fish, invertebrates, or riparian vegetation. This paper discusses the results of the EPRI study and suggests future approaches to making instream flow recommendations.

ISSN:1040-2381    

DOI:10.1080/07438148609354624

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The progress made in the past two years on improving dissolved oxygen (DO) and flow conditions below Tennessee Valley Authority (TVA) hydropower projects is discussed. New methods of turbine aspiration have resulted in dissolved oxygen increases of up to 3.5 mg/L with efficiency losses of about 0.5 percent. A regulation weir made from gabions has provided a continuous minimum streamflow of 5.7 m3/sec below a hydropower project where previously no flow had existed for extended periods. Comparisons between sluicing, adding a small hydroturbine to the powerhouse, providing a regulating weir, and pulsing existing turbines resulted in the selection of a small hydro addition to provide a continuous minimum flow below a second project.

ISSN:1040-2381    

DOI:10.1080/07438148609354625

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Lake Taneycomo, a 700-ha hydropower impoundment in southwestern Missouri, supports an excellent put-grow-and-take trout fishery with a benefit:cost ratio of 22:1. However, seasonal dissolved oxygen fluctuations resulting from the hypolimnetic discharge from upstream Table Rock Lake have been a concern since 1970. The biological and socioeconomic effects of low levels of dissolved oxygen on the fishery were recently documented. When dissolved oxygen drops below 6 mg/L, fishing success declines. This change in fishing quality affects visitation to the area and the economic benefits generated by the fishery. The net economic benefit of the fishery to the local economy is $9.9 million, and the current estimated loss of benefits is $358,000 per year because of low dissolved oxygen. The U.S. Army Corps of Engineers has proposed a structural modification of Table Rock Dam to solve the problem.

ISSN:1040-2381    

DOI:10.1080/07438148609354626

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor