摘要:

This study investigates the potential of satellite-based remote sensing to assess water quality in the 11 reservoirs of the Catawba River basin. Near-simultaneous acquisition of both Landsat TM (Thematic Mapper) data andin situwater quality observations (turbidity, secchi disk depth, chlorophyll and surface temperature), in May of 1995, provided a statistical foundation for the development of algorithms that convert TM reflectance to each water quality parameter. The conversion models defined for turbidity, secchi disk depth, chlorophyll (power law function) and temperature (linear function) were used to produce digital cartographic products that depict the distribution of each parameter in the 11 reservoirs. A analysis of error demonstrates that accurate quantitative data products can be produced from Landsat TM imagery for the surface waters of the major reservoirs in this system with a spatial resolution of 30 m for turbidity and secchi disk depth, and a 120-m resolution for surface temperature. Landsat TM appeared to have an inadequate spectral resolution for the quantitative assessment of chlorophyll. In this study, an additional experiment was performed in October 1995 to evaluate the applicability of the reflectance-based conversion algorithms to TM data acquired at other times and from other reservoirs. Though not quantitatively conclusive, the predicted values derived by the conversion algorithms were as consistent with ground observations for all water quality parameters except chlorophyll as that seen in the initial experiment.

ISSN:1040-2381    

DOI:10.1080/07438149809354347

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Agricultural nonpoint sources of nutrients and sediment threaten the quality of the Cane Creek Reservoir, a Piedmont North Carolina water supply lake, in the absence of detailed monitoring, the Agricultural NonPoint Source Pollution Model (AGNPS) was used to predict water runoff and the delivery of dissolved and sediment-attached nitrogen and phosphorus to stream tributaries to the lake. The findings of the distributed parameter modeling study included four dairy watersheds (53 to 195 ha) and were part of a management plan developed to protect the impoundment from further degradation. Annual total nitrogen and total phosphorus export predictions for entire farms ranged from 1.0 to 3.7 and 0.7 to 1.8 kg · ha−1for current conditions. Simulated exports of total nitrogen and total phosphorus were between 0.9 to 3.1 and between 0.4 to 1.6 kg · ha−1due to best management practices (BMPs) installed. In addition, simulation studies of smaller areas such as individual pastures, cropland fields, and feedlots showed substantial nutrient export reductions due to refinements in dairy manure management, depending upon the site. For one feedlot needing structural improvements, simulated BMPs reduced annual total nitrogen and total phosphorus loads from 74 and 21 kg · ha−1to 0.85 and 0.4 kg · ha−1. Also included are recommendations for additional BMPs and the cost for implementation.

ISSN:1040-2381    

DOI:10.1080/07438149809354348

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Spanish Harbour (Lake Huron, Ontario) and the lower Spanish River are designated as an Area of Concern (AoC) by the International joint Commission. This paleolimnological study was initiated to provide the missing historical data for the past conditions of the AoC for the Spanish Harbour Remedial Action Plan (RAP), which has been developed to restore and protect the water quality of Spanish Harbour. The study has shown that anthropogenic activities in the watershed have changed the water quality considerably. The changes started about 1930 when metal concentrations started to increase in die basin, and reached maximum levels by ca. 1970. Since about 1970, metal concentrations have declined significantly. The recovery is closely associated with the reductions in emissions from the Sudbury smelters since die early 1970s. The timing of the increase in metal contamination and the post-1970 recovery in Spanish Harbour are similar to the geochemical trends seen in many Sudbury lakes. Although metal concentrations have decreased, the area has continued to receive high nutrient inputs from the drainage basin. Based on the fossil diatom and chrysophyte assemblages, nutrient enrichment appears to have increased in the harbour since the mid-1970s.

ISSN:1040-2381    

DOI:10.1080/07438149809354349

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We examined the relationship between chlorophylla(chla) and phosphorus (P) concentration among 52 clear, 21 organically stained (yellow colored), and 14 glacially turbid (silty) lakes in Alaska. A weak correlation (r2= 0.14) exists between seasonal mean chlaand total phosphorus (TP) with most of die error related to the glacial lakes. However, nonbiologically available P represents 52% of TP in glacial lakes compared to only 12% in clear lakes and 15% in stained lakes. TP corrected for nonbiologically available phosphorus (CTP) explains 55% of the variation in chlaacross lake typologies. However, chlaresponse to CTP is greater in clear lakes compared to stained lakes. Despite having higher CTP concentrations, the CTP-chlarelationship is not significant for the glacial lakes, suggesting the influence of other factors on chla. Considering clear, stained, and glacial lakes together, adding turbidity and color along with CTP accounts for 60% of the variation in chla. The additional variability explained (32%) by the multivariate model represents a composite measure of the influence of lake typology on the TP-chlarelationship. Despite the comparatively narrow range in chla(0.1 to 9.9 μg · L−1) and CTP concentrations (1.7 to 36.2 μg · L−1) and the wide range in turbidity (0.2 to 48.6 NTU) and color (2 to 55 platinum-cobalt units), our multivariate model provides a foundation for defining specific lake typology criteria (other than P) that can better predict chla. Application of our model will benefit assessment of regional changes in water quality, trophic status, and fish habitat across a variety of lake types.

ISSN:1040-2381    

DOI:10.1080/07438149809354350

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

While the relationship between productivity and adult fish yield has been extensively studied, it has been viewed as a static relationship, whereas interactions among organisms and trophic levels change dramatically with the life stage of the interacting organisms. As such, little attention has been given to mechanisms that might control this relationship. Toward this end, we examined the influence of trophic status on larval fish abundance in four reservoirs in Alabama and Georgia, USA. Larval fish communities in eutrophic reservoirs were dominated by gizzard shad (Dorosoma cepedianum) and threadfin shad (D. petenense), while crappie (Pomoxisspp.) and sunfish (Lepomisspp.) contributed a relatively larger percentage of the fish community in the oligotrophic reservoir, similar to findings for older fishes from previously published work. However, while larval shad and lepomid sunfish were more abundant in eutrophic than in oligotrophic reservoirs, larval crappie showed the opposite trend. Why larval shad and lepomid sunfish appeared to be controlled by lower trophic levels while larval crappie appeared to be controlled by upper trophic levels was not clear. However, when our larval fish abundance results were compared with previous results for older fishes, they suggest that while the mechanism controlling abundance and eventual year-class strength may differ across species, actual abundance and year-class strength within species is likely set during early life.

ISSN:1040-2381    

DOI:10.1080/07438149809354351

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Paleolimnological analyses using diatoms preserved in a 34-cm sediment core from the presently eutrophic Collins Lake, southeastern Ontario, were used to determine the lake's natural trophic state, as well as the impacts of past watershed activities on water quality. The presence of eutrophic diatoms (especiallyFragilaria crotonensisandAulacoseira ambigua) and low chrysophyte cyst to diatom frustule ratios in the pre-setdement section of the sediment core suggested that the lake was naturally somewhat productive. Further eutrophication occurred, as demonstrated by relative increases in eutrophic diatom taxa such asAulacoseira granulata, F. crotonensis, andAsterionella formosa, with the onset of European settlement, deforestation of the catchment vegetation, and agricultural practices. Finally, in the early to mid-1970s, land-use changes from primarily rural to more residential and recreational resulted in further nutrient enrichment of Collins Lake, likely from increased point-source nutrient inputs from private septic systems and household phosphate-based fertilizers. Total phosphorus concentrations inferred using a quantitative diatom-based transfer function confirmed the above qualitative assessments of the recent trophic state changes of Collins Lake. However, the naturally-productive nature of Collins Lake, as inferred from this paleolimnological study, contradicts the results obtained from applying the Ontario Ministry of the Environment's Ontario Trophic Status Model (TSM), which hindcast oligotrophic conditions for the lake, prior to European settlement. These paleolimnological data have important implications for lake management issues.

ISSN:1040-2381    

DOI:10.1080/07438149809354352

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A phosphorus budget was constructed for Delavan Lake Inlet, a perennial riverine wetland with submersed and floating aquatic vegetation in southeastern Wisconsin, to better understand the phosphorus dynamics in natural wetlands and the role of wetlands in lake-rehabilitation efforts. During the growing season, the inlet served as a net source of phosphorus, primarily due to the release of phosphorus from the sediments. More phosphorus was released from the sediments of the inlet (600 kg) than was input from the upstream watershed (460 kg). This release was caused by high pH associated with high photosynthetic activity. During the remainder of the year, the inlet served as a net sink for phosphorus, retaining 6% of die phosphorus input from the watershed. Over the entire year, this wetland was a net source of over 500 kg of phosphorus to downstream Delavan Lake. A constructed riverine wetland upstream of Delavan Lake Inlet demonstrated a similar periodic release of phosphorus. However, in this case, the summer release of phosphorus was less than that trapped during the remainder of the year. The constructed wetland served as a net sink for approximately 20% of the input phosphorus on an annual time scale. The role of existing and constructed wetlands as phosphorus traps is complex. Wetlands can act as a source or a sink for phosphorus depending on the ambient conditions in die wetland. Howa wetland fits into a rehabilitation plan depends upon its net retention efficiency and the importance of the periodic releases of phosphorus to downstream waters.

ISSN:1040-2381    

DOI:10.1080/07438149809354353

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor