Showing papers in "Lake and Reservoir Management in 1999"
TL;DR: In this article, the effectiveness and longevity of alum treatments were evaluated in 21 lakes (or lake basins) across the United States; 9 were polymictic and 12 were dimictic.
Abstract: Effectiveness and longevity of alum treatments were evaluated in 21 lakes (or lake basins) across the United States; 9 were polymictic and 12 were dimictic. Effectiveness was judged from reductions in lake TP (total phosphorus) and internal loading rate, as well as chlorophyll a (chl a), both initially and over periods ranging from 4 to 20 years following treatment. Internal loading rate was reduced in six of nine polymictic lakes/basins by an average of two-thirds, and lake TP was reduced by about one-half, which persisted for 5–11 years. Internal loading rate in dimictic lakes (7 of 7 with adequate data) remained reduced by an average of 80% for 4 to 21 years (average 13 yrs). For the six polymictic lakes, in which treatment was effective, chl a decreased by an average of two-thirds initially, but was about 40% less than die pre-treatment level after 5 to 11 years. Chl a decreased in seven dimictic lakes by an average of 57% initially and 42% after 5–18 years. In some cases, response was indepe...
194 citations
TL;DR: A number of short-term experimental hypolimnetic oxygenation systems were operated in the 1970s, but large scale systems were not implemented until the 1980s as discussed by the authors, and these systems have been operating in Lakes Sempach, Baldegg, and Hallwil, Switzerland, since the early 1980s to ameliorate cultural eutrophication.
Abstract: Hypolimnetic aeration is an increasingly common management technique that aerates the hypolimnion while preserving thermal stratification. While most hypolimnetic aeration systems use air as an oxygen source, use of pure oxygen is growing. Potential benefits of hypolimnetic oxygenation include maintenance of an oxygenated source of cool water to meet consumer and environmental needs, decreases in internal nutrient loading, inhibition of sediment release of problematic reduced compounds, and maintenance of summertime habitat for cold-water fish, zooplankton and zoobenthos. A number of short-term experimental oxygenation systems were operated in the 1970s, but large scale systems were not implemented until the 1980s. Deep oxygen injection systems have been operating in Lakes Sempach, Baldegg, and Hallwil, Switzerland, since the early 1980s to ameliorate cultural eutrophication. Deep oxygen injection has also been used to increase DO in hydroelectric releases from a number of large reservoirs in the...
177 citations
TL;DR: In this paper, five variables gave strong indications of change in the trophic state of New Zealand lakes, namely, concentrations of chlorophyll a, total phosphorus and total nitrogen, as well as Secchi depth and Secchi depths.
Abstract: Five variables gave strong indications of change in the trophic state of New Zealand lakes, namely; concentrations of chlorophyll a, total phosphorus and total nitrogen, as well as Secchi depth and
109 citations
TL;DR: In this paper, the amount of aluminum needed to deplete mobile inorganic sediment phosphorus and transform it to Al-P was estimated in vitro in Lake Delavan, Wind Lake, and Bass Bay sediments.
Abstract: The dose of aluminum (Al) needed to deplete mobile inorganic sediment phosphorus (P) [loosely-sorbed P and Iron (Fe)-bound P] and transform it to Al-P was estimated in vitro in Lake Delavan, Wind Lake, and Bass Bay sediments. The formation of Al-P was logarithmically related to increased Al added as buffered alum. Results of the in vitro treatments were compared with the observed effect on sediment-P composition from the 1991 alum treatment (12 g Al·m−2) in Lake Delavan. That 1991 dose resulted in the formation of 2.2 g P·m−2, measured as Al-P, which was apparently the maximum amount of P that could be adsorbed with that alum dose. Based on in vitro alum additions, 150 g Al·m−2, twelve times that added, would have been required to nearly deplete mobile P in surface (0–4 cm) sediment of Lake Delavan (16 m). Wind Lake contained less mobile P, so a dose of 80 g Al·m−2 was required to remove mobile P in sediments from its deep hole (14m), while an addition of only 20 g Al·m−2 was needed for sediments...
90 citations
TL;DR: A floristic quality metric for Wisconsin lake plant communities is developed and calibrated it for ecoregional and lake type differences to evaluate the closeness of the flora of an area to undisturbed conditions.
Abstract: Floristic quality is a rapid assessment metric designed to evaluate the closeness of the flora of an area to undisturbed conditions. To be useful for a variety of monitoring applications it has to be calibrated for local conditions. Based on data from 554 lakes, this paper develops a floristic quality metric for Wisconsin lake plant communities and calibrates it for ecoregional and lake type differences. The Northern Lakes and Forests ecoregion had the highest floristic quality with flowages having the highest number of species and lakes having the highest average coefficient of conservatism ([Cbar]). Floristic quality in lakes and flowages in the North Central Hardwoods region and the Southeastern Till Plain region were not significantly different and were combined into a single group. Their floristic quality was intermediate between the Northern Lakes and Forest groups and the final group that was a combined Driftless Area and Mississippi River Backwater lake group. When applied to a limited nu...
50 citations
TL;DR: A computer model of the operation of the Shasta Lake temperature control device (TCD) confirms the device's ability to maximize power production and simultaneously reduce summer discharge water temperatures.
Abstract: A computer model of the operation of the Shasta Lake temperature control device (TCD) confirms the device's ability to maximize power production and simultaneously reduce summer discharge water temperatures The TCD's in-reservoir thermal effects were consistent for a wide range of hydrologic conditions Changes in the thermal structure were most pronounced in the hypolimnion, where summer water temperatures were about 1°C cooler, but up to 5°C warmer in the late fall compared to without-TCD conditions Epilimnetic effects of the TCD were negligible, with mean temperature differences between with- and without-TCD conditions in the top 20 meters of the reservoir of less than 05°C throughout die year The zone of impact of the TCD was unexpectedly large; in-reservoir temperature changes were seen up to 20 km upstream of the dam in all three major branches However, in-reservoir temperature changes did not carry over into subsequent years with continued TCD use Discharge temperature targets were n
49 citations
TL;DR: In Lake Morey, a pre-treatment (1977-1985) and posttreatment (1986-1998) data indicated that significant improvements occurred in all water quality variables measured as discussed by the authors.
Abstract: Lake Morey received one hypolimnetic treatment with alum and sodium aluminate in 1986 to reduce the occurrence of algae blooms caused by internal P loading. Thirteen years of post-treatment monitoring have documented a sustained improvement in water quality in the lake. Comparison of pre-treatment (1977–1985) and post-treatment (1986–1998) data indicated that significant improvements occurred in all water quality variables measured, including spring TP (reduced 66%), summer photic zone TP (reduced 68%), summer photic zone Chi a (reduced 61%), summer Secchi disk transparency (increased 79%), late summer hypolimnetic TP (reduced 83%), and late summer hypolimnetic DO (increased 193%). The one-time alum/aluminate treatment of Lake Morey has thus far succeeded in breaking a cycle of sediment P release and re-precipitation that was initiated during an earlier period in the lake's history. Relative weight loss was observed in samples of large yellow perch during the 3 years immediately following the tre...
40 citations
TL;DR: History, general lake and basin characteristics, and the quantitative analysis indicate that Lake Apopka was mesotrophic; with clear-water and native, submersed macrophyte beds; in both the pristine and antecedent conditions.
Abstract: Lake Apopka is a large (12,500 ha), hypertrophic lake in central Florida which is the subject of a state-sponsored restoration program. We used three quantitative methods in concert with an analysis of the history and general character of the lake and drainage basin to infer the past conditions. We specifically examined two past conditions: 1) pristine (before any major anthropogenic disturbance) and 2) antecedent (before a specific, major anthropogenic disturbance). For Lake Apopka the pristine condition ended in the 1890s when a canal was dug which lowered the elevation for surface water outflow. The antecedent condition ended in the late 1940s when most of the lake's 8,900 ha of floodplain marsh was drained for farming. History, general lake and basin characteristics, and the quantitative analysis indicate that Lake Apopka was mesotrophic; with clear-water and native, submersed macrophyte beds; in both the pristine and antecedent conditions. The three quantitative methods (reference lakes, emp...
31 citations
TL;DR: The effects of a reduction in total phosphorus concentration on the water quality and plankton community structure in a 86-ha hypereutrophic sandpit lake with high internal phosphorus loading were assessed by dosing an isolated 4.6-ha section of the lake with alum.
Abstract: The effects of a reduction in total phosphorus concentration on the water quality and plankton community structure in a 86-ha hypereutrophic sandpit lake with high internal phosphorus loading were assessed by dosing an isolated 4.6-ha section of the lake with 34,065 L (dose = 10 mg Al·L−1) of liquid aluminum sulfate (alum). During the three summers following treatment, hypolimnetic total dissolved phosphorus, epilimnetic total phosphorus, and eplimnetic total nitrogen were decreased by 97%, 74%, and 36%, respectively, in the treated section. Secchi depth was 134% greater in the treated area. Alum treatment also increased the volume of usable fish habitat by 22%, as the depth of the 3.0-mg/l dissolved oxygen isocline was 52% deeper in the treated portion than in the untreated portion. Total phytoplankton biovolume decreased by 40% and chl a concentration by 65% in the treated area. Although cyanophytes continued to dominate in die treated area, there was a shift in relative abundance from cyanophy...
27 citations
TL;DR: In this article, the authors compared the seasonal changes in trophic state index (TSI) values and log-log regression models relating total phosphorus (TP), total nitrogen (TN), chlorophyll a (CHLA), and Secchi transparency (SD) were considered.
Abstract: Ten years of monthly water quality data were compared from two large shallow lakes in Florida, USA – Lakes Okeechobee and Apopka. Seasonal changes in trophic state index (TSI) values and log-log regression models relating total phosphorus (TP), total nitrogen (TN), chlorophyll a (CHLA), and Secchi transparency (SD) were considered. The objective was to quantify the extent to which empirical models might vary due to the heterogeneous nature of benthic-pelagic coupling that can occur in shallow lakes. In the offshore region of Lake Okeechobee, TP and SD-based TSI values increase dramatically during winter, while CHLA-based TSI declines. These changes coincide with the windy season in south Florida, when average wind velocities can exceed 20 km h−1. Resuspension of bottom sediments occurs and this reduces light penetration to the extent that the growth of phytoplankton is inhibited. During summer, winds are calm, and these conditions occur less often. Log-log regression models of CHLA vs. TP have a ...
22 citations
TL;DR: In this article, the authors used a stagewise regression technique to screen a variety of models and select export coefficients that were reasonable, based on the literature, and which offered a good fit to the data.
Abstract: In an effort to develop Total Maximum Daily Loads of total phosphorus for hundreds of Massachusetts lakes we reanalyzed the land use export coefficients of previously published diagnostic/feasibility studies. Typically, literature values for phosphorus loading per unit area of land use overestimate total phosphorus loading to Massachusetts lakes. We used a stagewise regression technique to screen a variety of models and to select export coefficients that were reasonable, based on the literature, and which offered a good fit to the data. The final model was verified by predicting phosphorus loadings to an independent set of Massachusetts lakes with an average error of 36 percent. The process has been automated with the use of the Arcview Geographic Information System computer system and digital maps of land use. With additional data, the model can also be used to predict lake total phosphorus concentrations under a variety of proposed land use management plans.
TL;DR: During the last decade, water quality monitoring data have indicated declines in Secchi transparency in the southwestern pelagic region of Lake Okeechobee, but in recent years there has been no relationship between Secchi depth and chlorophyll a.
Abstract: During the last decade, water quality monitoring data have indicated declines in Secchi transparency in the southwestern pelagic region of Lake Okeechobee. Sampling stations that previously displayed intra-annual variation in Secchi depths from 0.2 to 2.7 m now display Secchi depths that never exceed 1.0 m. The historical changes in transparency occurred abruptly, and the recent low transparencies have been very stable. Ratios of Secchi/total depth indicate that light often may have reached the lake bottom (ratios > 0.5, and as high as 1.0) prior to the new stable state, but never reached the bottom afterwards (ratios <0.3). Secchi depth vs. chorophyll a relationships also have changed in the southwestern pelagic region. Stations previously displayed significant inverse log relationships between the two variables, similar to what is observed today at near-shore, sand-bottomed sites in Lake Okeechobee. In recent years, there has been no relationship between Secchi depth and chlorophyll a. This is ...
TL;DR: Changes in the benthic community, and in the feeding, growth and polychlorinated biphenyl concentrations in three littoral zone fishes (pumpkinseed, Lepomis gibbosus, blu...
Abstract: We assessed changes in the benthic community, and in the feeding, growth and polychlorinated biphenyl (PCB) concentrations in three littoral zone fishes (pumpkinseed, Lepomis gibbosus, bluegill, Le...
TL;DR: In this article, the Vollenweider (1969) mixed-reactor lake model was rearranged and used to calculate apparent settling velocity (Vs) for total phosphorus (TP) for three lakes treated with alum to reduce the internal flux of P to the water column (Delavan Lake, Wisconsin; Lake Morey, Vermont; and West Twin Lake, Ohio).
Abstract: The apparent settling velocity (Vs) is a term used in empirical, steady-state, mass-balance lake models to represent the net phosphorus flux from the water column. The Vollenweider (1969) mixed-reactor lake model was rearranged and used to calculate Vs values for total phosphorus (TP) for three lakes treated with alum to reduce the internal flux of P to the water column (Delavan Lake, Wisconsin; Lake Morey, Vermont; and West Twin Lake, Ohio). An analysis of Vs values was conducted using data from these three lakes for both the pre- and post-alum treated conditions. Analysis of Vs values for both the pre- and post-alum conditions in Lake Morey and West Twin Lake resulted in a post-treatment mean Vs value of 7 ± 2.0 m·yr−1. The effect of the alum treatment, although short-lived in Delavan Lake, resulted in a mean post-treatment Vs value of 3.4 ± 0.3 m·yr−1. The consistency in the post-treatment Vs values in Lake Morey and West Twin Lake is used to demonstrate a predictive analysis method for water ...
TL;DR: The reservoir was eutrophic according to all the criteria assessed and practices aimed at reducing phosphorus and sediment loadings are suggested to improve water quality.
Abstract: The trophic state of Clinton Lake was assessed. Typical longitudinal gradients were observed with nutrient concentrations (TN, TP, NO3-N, NH4-N, PO4-P) decreasing from the riverine areas of the reservoir to the main basin. The TN:TP ratio went from 6.7 in the riverine zones to 14.2 in the main basin. The reservoir was eutrophic according to all the criteria assessed. Using growing season means for the main basin: chlorophyll a = 16 μg·L−1 > 10 μg·L−1, TP = 39 μg·L−1 >20 μg·L−1, TN = 0.52 mg·L−1 > 0.50 mg·L−1, Secchi disk depth = 1.13m < 2 m. Practices aimed at reducing phosphorus and sediment loadings are suggested to improve water quality.
TL;DR: The effect of sampling frequency and wind velocity on estimates of total phosphorus (TP) concentrations were evaluated in Lake Okeechobee, Florida, a shallow, polymictic lake.
Abstract: The effect of sampling frequency and wind velocity on estimates of total phosphorus (TP) concentrations were evaluated in Lake Okeechobee, Florida, a shallow, polymictic lake. It was hypothesized that estimates of TP would be affected by sampling frequency because the lake's P-rich bottom sediments are frequently resuspended during wind events. However, differences in estimates of annual mean TP were small (< 5 %) when daily, weekly, bi-monthly, and monthly sampling frequencies were compared. In contrast, estimates of monthly mean TP often varied by 20 to 30 percent among sampling frequencies and differences in monthly maximum and minimum TP values commonly varied by 50 to 250 μg·L−1. Bottom sediments were most likely to be resuspended during the windy season (November-April) when calculated threshold wind velocities were exceeded more than 40 percent of the time. On a monthly basis, wind velocity explained as much as 70 percent of the daily variability in TP during the windy season. In compariso...
TL;DR: Aquashade™, a colorant and dye registered by the US Environmental Protection Agency (USEPA) for use in aquatic environments to manage plant growth, does not reduce the visibility of water that otherwise would meet safe swimmming standards.
Abstract: Aquashade™, a colorant and dye registered by the US Environmental Protection Agency (USEPA) for use in aquatic environments to manage plant growth, does not reduce the visibility of water that otherwise would meet safe swimmming standards. This product was examined for its potential impact on underwater visibility in surface waters used for recreational swimming. Aquashade™ treatments of 0, 1, and 5 mg L−1 were evaluated in 3-m deep outdoor tanks containing reservoir water. Transparency and light attenuation were examined using a Secchi disk and an underwater photo synthetically active radiation (PAR) meter. In the first experiment, filtered lake water was used, while in the second, bentonite clay was added to provide a light transparency of approximately 1 m. In filtered lake water, Aquashade™ treatments (1 mg L−1 and 5 mg L−1) reduced light transparency by approximately 10% and 30%, respectively, but the transparency (272 and 194 cm, respectively) was well above typical international (100 cm) a...
TL;DR: In this paper, changes in phyto-and zooplankton assemblage and abundance were observed in a regulated, shallow, hypertrophic lake following temporary drawdown and refilling.
Abstract: Marked changes in phyto- and zooplankton assemblage and abundance were observed in a regulated, shallow, hypertrophic lake following temporary drawdown and refilling. Despite significant increases in the ambient concentrations of nitrogen and phosphorus, levels of chlorophyll-a fell from a mean of 260 νg·L−1 before drawdown and refilling to 70 μg·L−1 thereafter. The concentration of chlorophyll-a fell to 3 μg·L−1 during aspring clearwater phase previously unobserved in Zeekoevlei, but observed in other, adjacent shallow lakes. This clearwater phase was characterized by an increase in mean water transparency from 0.3 to 0.75 m. A marked swing towards an algal assemblage comprised of chlorophyte species occurred during aseasonal period historically-dominated by cyanophytes. Levels of pH and dissolved oxygen declined with the reduced phytoplankton activity in the lake. The zooplankton assemblage was dominated by large-bodied cladocerans, this in contrast to dominance by cyclopoid copepods. It is hyp...
TL;DR: In this article, the reaeration rate estimates in water bodies are used to estimate water quality modeling and water quality analysis, which is a primary concern for limnologists, oceanographers and other researchers because of its importance in water quality modelling.
Abstract: Obtaining accurate reaeration rate estimates in water bodies remains a primary concern for limnologists, oceanographers and other researchers because of its importance in water quality modeling and...
TL;DR: A study of 11 north-central Florida lakes was conducted to determine if surface sampling provided the same estimates of chlorophyll, total phosphorus, and total nitrogen concentrations as samples collected with a Kemmerer bottle, and a 2-m pvc tube sampler (integrated column).
Abstract: A study of 11 north-central Florida lakes was conducted to determine if surface sampling (0.5 m) provided the same estimates of chlorophyll, total phosphorus, and total nitrogen concentrations as samples collected with a Kemmerer bottle at 1 m and 2 m, and a 2-m pvc tube sampler (integrated column). The absolute values of differences between surface estimates of chlorophyll, total phosphorus, and total nitrogen concentrations and estimates obtained by use of other sampling methods were small and from a practical standpoint would not preclude the use of the surface estimates. Only a few statistically significant differences were detected for some individual lakes. For this group of Florida lakes, the greatest amount of variability in estimates was attributed to differences among lakes (≥95%). Surface estimates were also highly correlated (r ranged from 0.95 to 0.98) to estimates obtained by other methods. Because surface sampling is simple, cost-effective, and provides comparable estimates of chlo...
TL;DR: Sensitivity analysis shows the lake is hydro biochemically similar to other mainstem reservoirs, but also that phytoplankton production may be nitrogen limited, and the embayment segment tests suggest a different ecological subsystem that requires further study to effectively characterize.
Abstract: Lake Wateree (5,548-ha, 382.4 × 106m3), a eutrophic reservoir on the South Carolina Piedmont, is downstream from a large urban area that is rapidly expanding. A 7-segment WASP5 eutrophication model was developed to enhance our understanding of the water quality dynamics of the lake. We used monitoring data from 3 time intervals for model calibration (1993), verification (1995), and scenario analysis (1991–1996). Parameters calibrated (Kolmogorov-Smirnov 2-sample goodness-of-fit test; p<.05) were chlorophyll a, ammonia-N, nitrate-N, dissolved oxygen, and total phosphorus. Mainstem segments tested well (19 of 20). The embayment segment tests (3 of 5) suggest a different ecological subsystem that requires further study to effectively characterize. Sensitivity analysis shows the lake is hydro biochemically similar to other mainstem reservoirs, but also that phytoplankton production may be nitrogen limited. Nutrient loading analysis to predict the possible effect of increased urbanization upstream (15...
TL;DR: Assessment of the aquatic plant communities and management techniques for nine Southeast Wisconsin lakes for a period of 6 to 9 years prior to 1996 to assess the long-term population changes of Eurasian watermilfoil subjected to different management regimes suggests the native aquatic plant community increased in average number of plant species per sample location or remained constant.
Abstract: Declines and increases in Eurasian watermilfoil populations (Myriophyllum spicatum L.) throughout North American Lakes have highlighted the need for long-term studies. Similarly, understanding the long-term implications of different aquatic plant management techniques (e.g., mechanical harvesting, chemical treatment, no management) is a crucial component of aquatic plant management. We examined the aquatic plant communities and management techniques for nine Southeast Wisconsin lakes for a period of 6 to 9 years prior to 1996 to assess the long-term population changes of Eurasian watermilfoil subjected to different management regimes. In eight of the nine lakes, the Eurasian watermilfoil populations either declined in frequency or remained constant; while in seven of the nine lakes the native aquatic plant community either increased in average number of plant species per sample location or remained constant The long-term aquatic plant community information for these nine case study lakes suggest ...
TL;DR: A synoptic inventory of physical and chemical properties and plankton assemblages of 27 mountain lakes was conducted at Mount Rainier National Park in 1988 to determine inter-annual change within die set of characteristics surveyed in 1988, and to provide guidance to park management about the value of a long-term lake monitoring program.
Abstract: A synoptic inventory of physical and chemical properties and plankton assemblages of 27 mountain lakes was conducted at Mount Rainier National Park in 1988 From 1990–1993, die opportunity was presented to resurvey six of these lakes to determine inter-annual change within die set of characteristics surveyed in 1988 If changes were evident, a second objective was to provide guidance to park management about the value of a long-term lake monitoring program Secchi-disk clarity, water temperature, and pH of the lakes in 1988 were within the range of values obtained between 1990 and 1993 Conductivities and concentration of nutrients in some lakes were not consistent in 1990–1993 with the values recorded in 1988 Although the dominant phytoplankton taxa in die lakes varied among years, die taxa in individual lakes were in consistent among years, with die exception of two lakes Rotifer assemblages were consistent among years, but most of die lakes exhibited dramatic changes in some years, as did cr
TL;DR: In this paper, Colloidal material extracted from lower Fox River sediments was analyzed for chemical (total organic carbon), elemental and mineralogical analyses, isoelectric point (HIEP), particle size distribution (PSD), solids and moisture content, surface area, and subjected to batch aggregation studies under cont cont
Abstract: Resuspension of aquatic sediments with HOCs (hydrophobic organic contaminants) can disrupt existing sorption equilibria and cause HOC desorption, and increase the exposure of water column biota to HOCs Resuspension can also increase levels of aqueous colloidal material in the overlying water column Furthermore, because colloidal material partly determines the transport and ultimate fate of sediment-derived HOCs, physical and chemical characterizations of sediment colloids that are subject to resuspension are necessary to assess the full impact of activities that disturb contaminated sediments (eg, dredging, navigation, chemical treatment, high flow events) Colloidal material extracted from lower Fox River sediments was analyzed for chemical (total organic carbon (TOC), elemental and mineralogical analyses, isoelectric point (pHIEP)) and physical (particle size distribution (PSD), solids and moisture content, surface area) characteristics, and subjected to batch aggregation studies under cont
TL;DR: The TMDL management process is based on a technical analysis that quantifies pollutant sources and is used to test alternative pollution control strategies that address a mix of both wastewater discharges and non-point sources as mentioned in this paper.
Abstract: The Total Maximum Daily Load (TMDL) management process established in the Clean Water Act of the United States is applied to a reservoir in the Eastern Slovak Republic. The TMDL is a water quality management approach sometimes used in the United States. With the recent change in environmental perspective in Post-Soviet Eastern Bloc Europe, the TMDL model was tested for relevancy in reservoir water quality management in this region. The TMDL management process is based on a technical analysis that quantifies pollutant sources. The analysis is used to test alternative pollution control strategies that address a mix of both wastewater discharges and non-point sources. The analysis shows that in order to meet standards, domestic wastewater must be removed and the most efficient nonpoint source control measures implemented. The information is being used by a non-governmental organization in a series of community forums to decide which pollution control options should be implemented. These meetings foc...
TL;DR: A neural network approach is presented that can efficiently, effectively, and consistently mimic human expertise in identification of days that contain abnormal water temperature in Lake Okeechobee.
Abstract: Lake Okeechobee data are routinely collected by sensors and transcribed from field forms to an electronic format. Occasionally, the effects of extraneous objects, device failure, and human errors may distort these field data. At present, the data are inspected manually by qualified engineers/scientists/technicians to identify abnormalities. This manual process is slow, costly, and sometimes inconsistent among inspectors. This paper presents a neural network approach that can efficiently, effectively, and consistently mimic human expertise in identification of days that contain abnormal water temperature. The approach begins with training 12 backpropagation neural networks (one per month) using the normal and abnormal daily patterns selected by the domain expert. The trained networks can then be used for identification in lieu of human experts. A total of 623 days of data from Lake Okeechobee were used: 241 days for training and 382 days for testing the networks. The results for the test data indi...