RESPONSE OF PHYSICAL AND CHEMICAL PARAMETERS TO ELIMINATING THERMAL STRATIFICATION IN A RESERVOIR1

ABSTRACT The effects of maintaining a 19 ha Colorado montane reservoir in a thermally destratified condition for one year were evaluated. Water temperatures were kept nearly vertically agd horizontally isothermal throughout the year. The weighted mean temperature of the lake was 1-4°C colder in winter and 1-2°C warmer in summer than normal. Deep water in summer was up to 6°C warmer than typical hypolimnion temperatures, but summer surface temperature was unaltered. Without destratification dissolved oxygen depletion develops in summer and winter, but by eliminating stratification, oxygen was kept near saturation throughout the year. Alkalinity, pH, conductivity, and total residue were not significantly affected. Seston decreased which was probably due to declines in planktonic diatom populations. Increases in iron and manganese did not occur in deep water during destratification. Calcium concentrations increased slightly. Magnesium and most anions (chloride, nitrate-N, and silica) were not greatly altered, but sulfate concentration was reduced. Artificial destratification, as a reservoir management tool, will be very useful in altering chemical problems; particularly increasing oxygen and decreasing iron and manganese concentrations.     

STRATIFICATION VARIABILITY IN THREE MORPHOMETRICALLY DIFFERENT LAKES UNDER IDENTICAL METEOROLOGICAL FORCING1

ABSTRACT: Synoptic water temperature measurements were taken in three temperate lakes located within 25 km of one another to study the effects of morphometry (and changes in weather) on seasonal and short-term thermal stratification characteristics. Two of the lakes had nearly the same surface areas and two had nearly identical mean depths; all were exposed to identical weather conditions. The dominance of weather over morphometry on the water surface temperature response was illustrated by the synoptic measurements in two different years. Stratification structure was also found to be dominated by weather for sufficiently deep lakes. Surface area effects were most subtle but explainable as sheltering effects. The onset of stratification was not, as traditionally described, a simple, gradual response of a lake to the annual solar radiation cycle. Rather it depends on a series of alternating heating, cooling, and mixing cycles similar to annual and diel cycles but with a period of approximately five days. These were in direct response to the passage of major weather systems and displayed no apparent time lag. No comparable synoptic water temperature data set could be found in the literature.     

DEEP RESERVOIR THERMAL STRATIFICATION MODEL1

ABSTRACT. A method of predicting reservoir temperature profiles is presented. The model requires monthly averaged meteorological and hydrological data along with reservoir physical characteristics. The one-dimensional profiles are predicted by solving the time-dependent energy equation with an assumed epilimnetic depth and a diffusion coefficient applicable below the epilimnion. The model is verified using an existing reservoir.     

NUMERICAL MODELING OF THERMAL STRATIFICATION IN A RESERVOIR WITH LARGE DISCHARGE-TO-VOLUME RATIO1

ABSTRACT: A numerical model study of thermal stratification in a high discharge-to-volume reservoir is described. Predicted temperature profiles are compared with field data for two different years. The model accurately predicts the date of fall turnover, and predicts degree of stratification and depth of the thermocline within about 20% for both years simulated. A parametric study of stratification mechanics for a high flow reservoir indicated that diffusion was the predominant heat transport mechanism in the hypolimnion, while surface effects dominated the epilimnion. Flow effects for the particular case studied, in which all inflows and outflows occur in the epilimnion, did not significantly affect stratification behavior.     

A CARLSON-TYPE TROPHIC STATE INDEX FOR NITROGEN IN FLORIDA LAKES1

: A data base consisting of predominantly nitrogen limited Florida lakes from the National Eutrophication Survey (NES) was used to develop a trophic state index based on total nitrogen concentration. This index was compared with Carlson's (1977) index based on total phosphorus concentration, and the lesser of the two values for each lake was averaged with indices based on Secchi disk transparency and chlorophyll a concentration to assess the trophic state of the 40 Florida NES lakes.     

IN-LAKE WATER QUALITY MANAGEMENT PLAN FOR A RECREATIONAL LAKE IN CENTRAL ILLINOIS1

Johnson Sauk Trail Lake remains highly eutrophic, even though the watershed has long been returned to an undisturbed condition with permanent vegetative cover and with little or no land disturbance in the watershed. Internal regeneration of nutrients has been identified as the major source of nutrients to the lake. Lake destratification, selective harvesting and removal of weeds, and control of algal blooms using chelated copper sulfate application followed by potassium permanganate application have all been chosen as management techniques for improving water quality conditions in the lake. These in-lake techniques are considered not as palliative measures, but as necessary tools in enhancing the lake's water quality characteristics.     

A TEST OF SEVERAL EVAPORATION EQUATIONS FOR WATER TEMPERATURE SIMULATIONS IN LAKES1

ABSTRACT: Evaporative heat loss is an essential component of any heat budget used for the modeling of lake water temperatures. Seven evaporative heat loss equations were tested in a year-round, physically-based temperature and dissolved oxygen model for lakes. Deciding which equation to choose for use in the year-round model was based on the goodness of fit of the simulated vs. measured surface temperatures, which were taken at a depth of 1 m below the water surface. An equation which includes free and forced convection components and which was previously used for cooling ponds gave the best fit between temperature simulations and measurements.     

PREDICTIVE MODELS FOR THE BIOMASS OF BLUE-GREEN ALGAE IN LAKES1

In lakes which experience water quality problems due to the nuisance growth of blue-green algae, summer concentrations of chlorophyll a may not always be a meaningful measure of water quality for making management decisions. Models for the prediction of summer mean blue-green algal biomass were thus developed from data collected from five systems located in North America and Sweden. It is suggested that the model of choice is log BG =?0.142 + 0.596 log TP – 0.963 log Z, where BG is the biomass of blue-green algae (g m^?3), TP is the concentration of total phosphorus (mg m^?3), and Z is the mean depth of the lake (m). When coupled to current loading models, this model can potentially be used to assess the impacts of phosphorus loading reductions on threshold odor in water supplies.     

THE EFFECTS OF DIURNAL MIXING ON THERMAL STRATIFICATION OF STATIC IMPOUNDMENTS1

ABSTRACT: The time variation in the temperature distribution of a static water impoundment is predicted. The body of water is modeled as a discrete number of horizontally isothermal layers and the energy equation is solved using an implicit numerical scheme. Vertical energy transport mechanisms included are solar absorption, molecular diffusion, and convective mixing due to nocturnal turnover. The latter mechanism, called diurnal mixing, is found to have a profound effect on the stratification, particularly in the eplimnion patterns for a typical deep static impoundment.     

PREDICTIVE MODELS FOR GREAT LAKES HYDROLOGY1

ABSTRACT: The individual hydrologic components are assumed to be normally distributed for each month and linear regression equations are estimated for predicting the value of the individual monthly hydrologic components. It is shown that some of the hydrologic components for downwind (in this case downstream) lakes are dependent upon hydrologic events for the upwind lakes. This is particularly so for precipitation in the downwind lake basins which appears to be dependent upon evaporation values for upwind lakes.     

A TECHNIQUE FOR MEASURING RAINFALL POTENTIAL1

ABSTRACT The roles played by thermodynamic stability and precipitable water in the production of rainfall are of prime importance. These two variables have been combined into a “Rainfall Potential” function by the use of multivariate statistical techniques. Data from weather stations in southern New Mexico and southwest Texas were used in the study. The results appear promising for further investigation, possibly in relation to the occurrence of rare but extremely heavy rains     

SEMI-INFINITE SOLID MODEL FOR PREDICTION OF TEMPERATURE IN DEEP RESERVOIRS AND LAKES1

ABSTRACT: A lake or reservoir, heated mainly through the air-water interface, is visualized as a solid which is bounded by the interface plane (x = 0) and extends to infinity in the positive x-direction. Analytical expressions give the surface temperature, the temperature profile (with depth) and the position of the thermocline as a function of time (Julian Day). Preliminary model results indicate that the general shape of the temperature profile and the position of the thermocline are influenced primarily by the air-water heat exchange and the time lapse since an isothermal condition existed in the water body.     

AN EFFICIENT METHOD OF APPLYING ALUMINUM SALTS FOR SEDIMENT PHOSPHORUS INACTIVATION IN LAKES1

ABSTRACT: Alum and sodium aluminate were injected into the hypolimnion of eutrophic Kezar Lake, New Hampshire, with a specially designed applicator mechanism. This new method of applying aluminum salts to achieve phosphorus inactivation included two separate chemical distribution systems mounted on a hydraulic weed harvester. The design of the applicator system is described, and its cost-effectiveness is compared with other aluminum salt injections.     

A FIELD TECHNIQUE FOR WEIGHING BEDLOAD SAMPLES1

ABSTRACT: A technique for weighing bedload samples that was developed for laboratory use has been modified for field application. The technique involves determining the submerged weight of bedload samples as they are collected. The submerged weights are converted to dry weights from a knowledge of the specific gravity of the bedload material. The technique makes bedload transport data available immediately and eliminates costly and time-consuming steps involved with saving samples for laboratory analysis. Only samples designated for particle-size or other lab analyses need to be saved.     

REGIONAL CHEMISTRY OF LAKES IN MASSACHUSETTS 1

ABSTRACT: We surveyed over 2000 lakes in the State of Massachusetts (1983–1984) to examine the spatial variations in their acid-base chemistry. Our survey differed from previous surveys by including small lakes and nonpristine urban lakes. For samples collected in October 1983 and 1984, the median acid neutralizing capacity (ANC) was 184 μeq L^?1 and 5.9 percent were acidic (ANC≤O). Small lakes (<4 ha) were more likely to be acidic than large lakes. Generally, sulfate was the dominant acidifying agent, although organic anions were dominant in some of the lakes in the Cape Cod Region. The ionic composition of the lakes showed strong regional patterns which appear to be related to geology and human population density. An analysis of variance of ANC shows the six regional categories in the state explain 51 percent of the variance, while a combined general linear model of lake drainage type, color, elevation, size, silica, and hydrogen ion deposition could explain only 4.9 percent of the variation in ANC. Calcium rich, high ionic strength lakes were present in the marble bedrock in the west, and relatively dilute lakes dominated by sodium and chloride were found near the coast. Chloride concentrations were also related to population density, suggesting road salt as a likely contributing source.     

LAKEMAP: A 2-D AND 3-D MAPPING SYSTEM FOR VISUALIZING WATER QUALITY DATA IN LAKES1

ABSTRACT: The visualization of water quality data in lakes was achieved by integrating the U.S. Environmental Protection Agency's (EPA) STORET water quality database, lake shoreline polygons from EPA's Reach File (version 3), and the UNIMAP 2-D and 3-D interactive mapping and modeling software. Based on lake name (and state abbreviation), a lake shoreline polygon can be accessed from the Reach File. The coordinates of the polygon are portrayed by the U.S. Geological Survey (USGS) 1:100,000 scale Digital Line Graph (DLG) hydrography layer. This polygon is passed, in turn, to the STORET water quality file. Monitoring stations located within the polygon boundary are extracted along with the complete sampling survey. Specific parameters, such as total phosphorus, pH, ammonia, and optional time and depth restrictions can be selected to build a file of x, y, z₁, z₁…, zn data which is imported to UNIMAP. Up to four parameters, including depth, can be selected at a time. Within UNIMAP, the data is gridded and then displayed as a 2-D color contour map, 3-D perspective contour map, or 2-D projected time or depth slices. This system operates on the EPA ES9000 mainframe computer located in Research Triangle Park (RIP), North Carolina. LAKEMAP is the culmination of an effort to bridge the gap between the vast array of environmental data collected by the EPA and the complex analytical and display software resident on the mainframe.     

WATER QUALITY STRATIFICATION IN SHALLOW WASTEWATER STABILIZATION PONDS1

ABSTRACT: The physical limnology of three modern wastewater stabilization ponds serving a small community in Minnesota was investigated over a 1-year period (July 1989 - October 1990). Water temperatures and associated meteorological parameters were recorded continuously; underwater light, dissolved oxygen, pH, and Secchi depth were measured intermittently (about weekly). Measurements of nutrients and planktonic species were made by other investigators. Water quality stratification dynamics were studied by analyzing variations of water temperature, dissolved oxygen, and pH distributions with time and over depth. Intermittent stratification and mixing of the shallow waste stabilization ponds (1–2 m deep) were documented and related to weather. The strong response of the ponds to seasonal and daily weather variations was observed. Three types of pond stratification conditions have been identified: (1) completely mixed during consecutive day and night, (2) stratified during the day and well-mixed during the night, and (3) continuously stratified during day and night. A diurnal cycle of stratification dynamics was first noticed in late April and persisted through summer and into fall. Differences in light attenuation and hence temperature stratification and DO distribution between pond 1 (primary), pond 2 (second primary) and pond 3 (secondary) in the wastewater treatment system were documented and related to different waste loading conditions. Temperature stratification affects chemical, microbial, and planktonic processes in the ponds. Results presented in this paper can be used to provide guidance for water quality sampling in monitoring of pond performance. Information on true mixing conditions is also needed to gain better understanding of important factors affecting pond operation, and for process simulations and reactor modeling of waste stabilization ponds.     

EMPIRICAL MODELS FOR TROPHIC STATE IN SOUTHEASTERN U.S. LAKES AND RESERVOIRS1

ABSTRACT: A cross-sectional data set of 80 lakes and reservoirs in nine southeastern states was examined to specify and parameterize trophic state relationships. The relationships fitted are based on measurements of several limnological variables taken over the course of a growing season or year in each of the lakes. The trophic state models relate phosphorus and nitrogen loading to inlake phosphorus and nitrogen concentrations, which in turn are related to maximum chlorophyll level, Secchi disk depth, dominant algal species, and hypolimnetic dissolved oxygen status. Due to the empirical nature of the study, causal conclusions are limited; rather, the models are most useful for prediction of average growing season conditions related to trophic state.