OPTICAL CHARACTERISTICS OF NEW ZEALAND RIVERS IN RELATION TO FLOW1

ABSTRACT: Six years (1989–1994) of data from New Zealand's National Rivers Water Quality Network were used to characterize the optical water quality regime of river waters as regards: visual clarity (black disc visibility), turbidity, and light-absorbing aquatic humic material (referred to as ‘yellow substance,’ measured as light absorption at 440 nm). Quantitative relationships between optical water quality variables and flow in rivers are well-described by power law expressions. Visual clarity usually decreases strongly with increasing flow in individual rivers. There is a strong, inverse relationship between turbidity and visibility, but, because of differences between sites, turbidity is not a good general predictor of visual clarity (the attribute of real interest) in rivers. Yellow substance tends to increase with increasing flow, probably because during rainstorms, soil water high in yellow-colored humic material, rather than rain water or ground water, dominates discharge. Therefore, rivers are typically clear and low in humic matter at low flow, and turbid and yellow-colored at high flow.     

IMPACT ASSESSMENT MODEL FOR CLEAR WATER FISHES EXPOSED TO EXCESSIVELY CLOUDY WATER1

ABSTRACT: A new type of empirical model described here enables real time assessment of impacts caused by excessive water cloudiness as a function of (a) reduced visual clarity (excessive cloudiness) and (b) duration of exposure to cloudy conditions, in fisheries or fish life stages adapted to life in clear water ecosystems. This model takes the familiar form used in earlier suspended sediment dose effect models where z is severity of ill effect (SEV), x is duration of exposure (h), y is black disk sighting range (y BD, m)—a measure of water clarity, a is the intercept, and b and c are slope coefficients. As calibrated in this study the model is Severity of ill effect is ranked on a 15‐step scale that ranges from 0 to 14, where zero represents nil effect and 14 represents 100 percent mortality. This model, based on peer consultation and limited meta analysis of peer reviewed reports, accomplishes the following: (a) identifies the threshold of the onset of ill effects among clear water fishes; (b) postulates the rate at which serious ill effects are likely to escalate as a function of reduced visual clarity and persistence; (c) provides a context (the “visual clarity” matrix, with its cell coordinates) to share and compare information about impacts as a function of visual clarity “climate” (d) demonstrates changes in predator prey interactions at exposures greater than and less than the threshold of direct ill effects; (e) calibrates trout reactive distance (cm) as function of water clarity in the form where y represents reactive distance (cm) and x represents visual clarity (black disk sighting range, cm), and where a and b are intercept and slope respectively, such that (f) identifies black disk sighting range, in meters, and its reciprocal, beam attenuation, as preferred monitoring variables; and (g) provides two additional optical quality variables (Secchi disk extinction distance and turbidity) which, suitably calibrated as they have been in this study, expand the range of monitoring options in situations in which the preferred technology—beam attenuation equipment or black disk sighting equipment—is unavailable or impractical to use. This new model demonstrates the efficacy of peer collaboration and defines new research horizons for its refinement.     

TURBIDITY SUSPENI)ED SEDIMENT,AND WATER CLARITY: A REVIEW1

ABSTRACT: Suspended sediment causes a range of environmental damage, including benthic smothering, irritation of fish gills, and transport of sorbed contaminants. Much of the impact, while sediment remains suspended, is related to its light attenuation, which reduces visual range in water and light availability for photosynthesis. Thus measurement of the optical attributes of suspended matter in many instances is more relevant than measurement of its mass concentration. Nephelometric turbidity, an index of light scattering by suspended particles, has been widely used as a simple, cheap, instrumental surrogate for suspended sediment, that also relates more directly than mass concentration to optical effects of suspended matter. However, turbidity is only a relative measure of scattering (versus arbitrary standards) that has no intrinsic environmental relevance until calibrated to a ‘proper’ scientific quantity. Visual clarity (measured as Secchi or black disc visibility) is a preferred optical quantity with immediate environmental relevance to aesthetics, contact recreation, and fish habitat. Contrary to common perception, visual clarity measurement is not particularly subjective and is more precise than turbidity measurement. Black disc visibility is inter‐convertible with beam attenuation, a fundamental optical quantity that can be monitored continuously by beam transmissometry. Visual clarity or beam attenuation should supplant nephelometric turbidity in many water quality applications, including environmental standards.     

Monitored and Modeled Correlations of Sediment and Nutrients with Chesapeake Bay Water Clarity

This article analyzes the correlations of the observed and modeled light attenuation coefficient, Kd, with in situ total suspended solids (TSS) and chlorophyll‐a concentrations in Chesapeake Bay (CB) tidal waters, and with sediment and nutrient loads from the Chesapeake watershed. Light attenuation is closely related to in situ TSS and chlorophyll‐a concentrations, however, the strength of the correlation differs among the CB segments. There are distinct differences between saline and tidal fresh segments in the main Bay, but less distinction among saline and tidal fresh segments in the tidal tributaries. The correlation between Kd with sediment and nutrient loads is complicated by the lag times of TSS and the chlorophyll‐a responses to reductions in nutrient and sediment loads from the watershed, and also due to the diverse load sources. Three sets of model sensitivity scenarios were performed with: (1) differential sediment and nutrient loads; (2) selective sediment source types; and (3) geographically isolated inputs. The model results yield similar findings as those based on observed data and provide information regarding the effect of sediment on specific water bodies. Based on the model results a method was developed to determine sediment and nutrient load reductions needed to achieve the water clarity standards of the CB segments.     

CAUSES OF UGHT AVI'ENUATION IN TAMPA BAY AND CHARLOTTE HARBOR,SOUTHWESTERN FLORIDA1

ABSTRACT: Vertical attenuation of photosynthetically active radiation (PAR) in clear waters of central Florida theoretically can vary almost 50 percent during a sunny summer day as a result of changing solar elevation. We used a simple formula to partially adjust the attenuation coefficient in Tampa Bay and Charlotte Harbor for changing solar elevation of the direct beam and then used multiple regression analysis to estimate the relative contribution of different water properties or constituents to the adjusted attenuation coefficient, k_adj. Color, on an average, was responsible for 18 percent of k_adj, chlorophyll a for 21 percent, nonchiorophyll suspended matter for 55 percent, and seawater for the remaining 6 percent. In both estuaries, k_adj increased with decreasing salinity as a result of freshwater runoff adding color, suspended matter, and nutrients. Nutrients affected attenuation by stimulating phytoplankton growth and increasing concentrations of chlorophyll a. Reduced nutrient loading to upper Tampa Bay (Hilisborough Bay) in the early to mid-1980's appears to have decreased concentrations of chlorophyll a, increased water clarity, and increased seagrass recolonization. Assuming other attenuating substances remained unchanged, the decrease in the average concentration of chlorophyll a from 30 to 15 μg L_?1 would correspond to an increase in the depth of light penetration necessary for seagrass survival (>10 percent incident light) from 1.0 to 1.5 m, which, on a relatively flat sea bed (slope of 2 m/km), would increase the area potentially available for seagram recolonization by 0.25 km²/km of shoreline.     

222RN IN THE WATER DISTRIBUTION SYSTEM OF TUCSON,ARIZONA1

ABSTRACT: A study of ²²²Rn concentrations in the water distribution system of Tucson, Arizona, revealed levels of 60 to 1260 pCi/L in domestic waters. These measurements are comparable to levels of between 80 and 1400 pCi/l for ²²²Rn found in ground water samples in the North-Central Tucson basin (Kahn et al., 1994). Estimated loss of ²²²Rn due to radioactive decay during travel from the well head to the home ranges from 8 to 50 percent.     

CHLOROPHYLL,PHOSPHORUS, SECCHI DISK,AND TROPHIC STATE1

ABSTRACT: The relationship between chlorophyll u, total phosphorus, secchi disk depth, and trophic state were examined using data on U.S. lakes collected by U.S. EPA's National Eutrophication Survey. By comparing predicted secchi disk depths with observed summer secchi disk depths in 757 lakes, it was determined that in many lakes non-chlorophyll related light attenuation is important in controlling the amount of chlorophyll u produced per unit of total phosphorus. Ranking of 44 lakes by 18 different trophic state measurements and single and multivariable indices were compared with rankings provided by mean summer ambient total phosphorus and chlorophyll u. The trophic state measurements and indices were much more successful in ranking the lakes against total phosphorus than chlorophyll u, indicating that there are differences in the relative trophic rankings of many of the lakes depending upon whether primary nutrients or biological manifestations are used as the ranking mechanism. If the manifestations of nutrients rather than their absolute levels are the primary criteria for beneficial use of lakes, the use of many of the commonly employed trophic state measurements, which assume or imply that there is a constant relationship between total phosphorus or secchi disk and chlorophyll, can lead to erroneous conclusions and unnecessary costly management controls. Secchi disk measurements may be more useful as a predictor of ambient lake total phosphorus concentrations than of chlorophyll.     

ESTIMATION OF OPTICAL PROPERTIES OF WATER FROM SECCHI DISK DEPTHS1

ABSTRACT: Optical information on a water body is often required when only Secchi disk depths are available. Many limnologists and water managers have attempted to estimate diffuse light attenuation in water from Secchi depth data assuming a simple inverse relationship. However, we show theoretically that the product of Secchi depth and the diffuse attenuation coefficient is markedly dependent on the reflectance coefficient (“brightness”) of water. Data from 28 New Zealand lakes of diverse optical character demonstrated this dependence over a wide range of reflectance (1.1 to 35.9 percent). Uncritical estimation of attenuation coefficients for diffuse light from Secchi depths, using the currently available simple inverse expressions, is discouraged because of the possibility of bias.     

PHYTOPLANKTON IN THE FOX CHAIN OF LAKES1

ABSTRACT: As part of a comprehensive water quality investigation on the Fox Chain of Lakes during May to October 1975, water samples from the Chain and Cedar Lake (reference) at 25 locations were collected weekly or bi-weekly to determine the species and densities of algae. The results have been evaluated for algal composition, density, and succession for each location. Sixty-four algal species were recovered from 414 samples. The number of species per sampling location varied from 10 at Channel Lake and Lake Marie to 26 on Fox Lake (main) and Grass Lake. Blue green algae were predominant and occurred at 25 of the 25 sampling stations. They consisted mainly of Aphanizomenon flos-aquae. The only flagellate of importance was Ceratium hirundinella, and significant concentrations of this organism were limited to Channel Lake and Lake Catherine. The only green alga bloom was created by Ulothrix variabilis on the waters of Pistakee Lake. Diatoms were quite significant on the shallower water bodies. Algal densities ranged from about 25 to 14,000 cts/ml. The highest count occurred on Mineola Bay. Other high counts (>10,000 cts/ml) observed were waters taken from Channel Lake, Grass Lake, and Fox Lake (main). In Grass Lake, 60 percent of the collections had algal densities in excess of 2,000 cts/ml. Most of these were the diatom Cyclotella meneghiniana.     

SIMPLE TROPHIC STATE CLASSIFICATION OF THE CANADIAN NEARSHORE WATERS OF THE GREAT LAKES1

ABSTRACT: Trophic classification of the Canadian nearshore waters of the Great Lakes is attempted using summer, surface water quality data for the early 1970's. A generalized Composite Trophic Index is developed using paired linear relationships for total phosphorus, chlorophyll a, and Secchi depth data for 66 defined nearshore regions. The chlorophyll a and total phosphorus relationship indicates that the nearshore waters contain a low chlorophyll a concentration for a given total phosphorus concentration than observed for the open waters of the Great Lakes or for smaller Canadian lakes. The most eutrophic nearshore regions occur in areas of relatively restricted circulation and/or high nutrient loadings. These include the Bay of Quinte, Toronto and Hamilton harbours, and portions of Lake We's Western Basin. Lakes Huron and Superior are generally oligotrophic, except for some embayments. Although nearshore water quality is highly variable, this apprach represents a reasonable compromise with respect to analytical complexity. The Composite Trophic Index removes biases introduced through the use of a single trophic state indicator and uniquely describes the nearshore water quality in terms generally comparable to other water bodies.     

CAGED FISH AS MONITORS OF POLLUTION: EFFECTS OF CHLORINATED EFFLUENT FROM A WASTEWATER TREATMENT PLANT1

ABSTRACT: Fish confined to cages were used to determine the effects of effluent from a wastewater treatment plant (WWTP). Control fish were kept in cages in an aquaculture pond. Acute effects of the effluent entering the final oxidation pond of the WWTP were determined by confining channel catfish (Ictalurus punctatus) at the pond inlet; the mean total residual chlorine (TRC) concentration was 0.9 mg/l during this exposure. After 8 h, 42 percent of the fish had died and survivors had severe lesions of the skin and gills. During the first two weeks of exposure, channel catfish at the outlet of the final oxidation pond (mean TRC=0.1 mg/l) were predisposed to bacterial infection but lost the parasitic trematodes that were on the gills when the fish were placed in cages. After several weeks, exposed fish had histologic lesions, enlarged livers, and reduced growth. The presence of unidentified carcinogen(s) in the effluent of this WWTP was indicated by papillomas developing on caged black bullheads (Ictalurus melas) and hepatic-enzyme induction in channel catfish. In situ exposure of caged fish was advantageous because storage and pretreatment of water samples were not required, and exposure levels corresponded to those present in the environment. The use of cages for containment of fish during field exposure allowed confinement to the location of interest and convenient sampling of the fish. Unlike wild fish, the caged fish could be compared to control fish with the same pre-exposure history.     

Impacts of changes in water quality on recreation behavior and benefits in Finland

The implementation of the European Union Water Framework Directive (WFD) requires nationally generalizable estimates of the benefits of protecting inland and coastal waters. As an alternative to benefit transfers and meta-analyses, we utilize national recreation inventory data combined with water quality data to model recreation participation and estimate the benefits of water quality improvements. Using hurdle models, we analyze the association of water clarity in individuals' home municipalities with the three most common water recreation activities – swimming, fishing and boating. The results show no effect on boating, but improved water clarity would increase the frequency of close-to-home swimming and fishing, as well as the number of fishers. Furthermore, to value the potential benefits of the WFD, we estimate the consumer surplus of a water recreation day using a travel cost approach. A water policy scenario with a 1-m improvement in water clarity for both inland and coastal waters indicates that the consumer surplus would increase 6% for swimmers and 15% for fishers. In contrast to previously estimated abatement costs to improve water quality, net benefits could turn out to be positive. Our study is a promising example of applying existing national recreation inventory data to estimate the benefits of water quality improvements for the purposes of the WFD.     

THE EFFECTS OF ARTIFICIAL CIRCULATION ON A SMALL NORTHEASTERN IMPOUNDMENT1

ABSTRACT: Artificial circulation was applied at East Sidney Lake, a small, eutrophic impoundment in New York, to improve the water quality of the reservoir and tailwater. Treatment was successful at both reducing the stability of the reservoir and maintaining higher mean oxygen concentrations in the bottom waters. Discharge waters had lower metals and phosphorus concentrations during treatment years. However, vertical temperature differences, although minimal, were still sufficient to permit chemical stratification and some phosphorus release from the sediments. Frequent mixing events during periods of low stability, and runoff from storm events, also appeared to increase transport of phosphorus into the epilimnion. Overall, treatment did not result in decreases in algal populations or improvements in water clarity.     

OPTICAL HETEROGENEITY IN GREEN BAY1

Differences in light penetration and light attenuating components and processes are documented along 112 km of the major (NE/SW) axis of Green Bay (Lake Michigan) during a three-day cruise (May 25–27, 1982). Measurements included diffuse attenuation of downwelling irradiance (k_d), Secchi disk transparency (SD), phytoplankton pigments (chlorophyll a and phaeophytin), turbidity (T_n), and dissolved color (absorbance). The relative importance of absorption and scattering to attenuation was calculated from paired measurements of k_d and SD. Absorption and scattering coefficients were calculated; value estimates were supported by a strong linear relationship between the scattering coefficient (b) and T_n (b = 0.99 *T_n; r²= 097, n = 12). Light attenuation characteristics, including the extent of light penetration and the magnitudes and relative importance of absorption, scattering and individual attenuating components, were found to be heterogenous in space. This heterogeneity is due to the characteristics and positions of entry of fluvial discharges to the bay as they influence levels of dissolved color (Gelbstoff), phytoplankton standing crop, and inorganic particulates. Identification of key processes regulating light penetration and their potential for response to pollution control measures can aid in the development of a water quality management plan for Green Bay.     

ASPECTS OF THE UNDERWATER LIGHT FIELD OF EIGHT CENTRAL NEW YORK LAKES1

ABSTRACT: The underwater light field of eight central New York lakes, which represent a wide range of trophic state, was characterized through paired measurements of Sechi disc transparency (SD, m) and diffuse light attenuation (K_d, m^?1). A total of 90 paired measurements are included in the data base. Substantial variability in the K_d SD product with time within individual systems, and amongst systems, was observed, which indicates differences in the relative contributions of absorption and scattering to attenuation. More than 50 percent of the temporal variability in K_d was attributable to attendant variations in chlorophyll a (C, mg m^?3) in only two of the lakes. Estimates of the adsorption (a, m^?1) and scattering (b, m^?1) coefficients based on paired K_d and SD measurements compared well with more precise determinations available for one of the lakes. Determinations of a and b for the eight lakes, from SD and K_d measurements, indicated great system-specificity and temporal variability in these characteristics. The temporal variability in relative contributions of a and b to K_d is consistent with covariation of different attenuating components and the lack of correlation between C and K_d in most of the study lakes.     

THE NEED FOR HIGH RESOLUTION TIME SERIES DATA TO CHARACTERIZE HAWAIIAN STREAMS1

ABSTRACT: Streams in the Hawaiian Islands differ from many streams on the U.S. mainland presenting unique challenges to investigators attempting to characterize Hawaiian streams. Hawaiian streams are short; watersheds are small and steep; and rain events are usually short in duration but intense. As a result, most streams in Hawai'i are flashy. Time scales for storm hydrographs in Hawai'i are on the order of hours instead of days and flash flooding is a common hazard. To characterize the streams we were investigating, we found it necessary to obtain streamflow and water quality measurements at relatively short time intervals. While this resolution resulted in large sometimes onerous quantities of data, we would have otherwise missed certain phenomena, such as 60‐fold flow changes in 15 minutes or 30‐fold turbidity changes in five minutes. Even at five‐minute intervals, we found that attempts to predict TSS using a relationship obtained from in situ turbidity were not always satisfactory. Depending on the precision required, either higher resolution measurements or in vitro turbidity measurements of the TSS samples might be necessary. Finally, these high resolution measurements enabled us to observe other cyclical events that might have been missed if the measurement intervals were greater than one hour.     

Before and After Integrated Catchment Management in a Headwater Catchment: Changes in Water Quality

Few studies have comprehensively measured the effect on water quality of catchment rehabilitation measures in comparison with baseline conditions. Here we have analyzed water clarity and nutrient concentrations and loads for a 13-year period in a headwater catchment within the western Waikato region, New Zealand. For the first 6 years, the entire catchment was used for hill-country cattle and sheep grazing. An integrated catchment management plan was implemented whereby cattle were excluded from riparian areas, the most degraded land was planted in Pinus radiata, channel banks were planted with poplar trees and the beef cattle enterprise was modified. The removal of cattle from riparian areas without additional riparian planting had a positive and rapid effect on stream water clarity. In contrast, the water clarity decreased in those sub-catchments where livestock was excluded but riparian areas were planted with trees and shrubs. We attribute the decrease in water clarity to a reduction in groundcover vegetation that armors stream banks against preparatory erosion processes. Increases in concentrations of forms of P and N were recorded. These increases were attributed to: (i) the reduction of instream nutrient uptake by macrophytes and periphyton due to increased riparian shading; (ii) uncontrolled growth of a nitrogen fixing weed (gorse) in some parts of the catchment, and (iii) the reduction in the nutrient attenuation capacity of seepage wetlands due to the decrease in their areal coverage in response to afforestation. Our findings highlight the complex nature of the water quality response to catchment rehabilitation measures.     

EFFECTS OF SELECTED HERBICIDES ON BACTERIAL POPULATIONS IN NONTREATED AND TREATED WATER1

ABSTRACT: Bacterial populations in nontreated and herbicide-treated waters were subjected to three different herbicides. Diuron, dichlobenil, and diquat were added (100 mg/l) to water samples from two fresh water lakes and two herbicide-treated ponds. Total numbers of bacteria were monitored. Bacterial populations in fresh lake water decreased after herbicide additions; however, final populations were significantly greater than the controls. Similar observations were recorded for bacteria in dichlobenil- and diuron-treated waters. Selective enrichment is probably expressed in these experiments.     

MATCHING NATURAL WATER COLORS TO MUNSELL STANDARDS1

ABSTRACT: Color of natural waters strongly influences their aesthetic appeal, suitability for recreational use, and aquatic habitat, but methods for routine specification of color have been lacking. An improved method has been developed for specifying water colors in the field. The water color, seen through an underwater viewer, is matched directly to Munsell standard patches observed simultaneously. The Munsell color-matching method was verified versus measurements of the underwater light field, made with a submersible spectroradiometer in 20 different natural waters in New Zealand (mainly lakes), which varied widely in color and other optical characteristics. Hue, the most important color attribute of natural waters, could be matched accurately; the saturation and brightness less so. Color standard patches are not available covering the full range of typically dark water colors, but fortunately, brightness can be measured with simple submersible light sensors. The Munsell color matching method seems suitable for routine water resources survey and monitoring.     

HERBICIDES AND TRANSFORMATION PRODUCTS IN SURFACE WATERS OF THE MIDWESTERN UNITED STATES1

ABSTRACT: Most herbicides applied to crops are adsorbed by plants or transformed (degraded) in the soil, but small fractions are lost from fields and either move to streams in overland runoff, near surface flow, or subsurface drains, or they infiltrate slowly to ground water. Herbicide transformation products (TPs) can be more or less mobile and more or less toxic in the environment than their source herbicides. To obtain information on the concentrations of selected herbicides and TPs in surface waters of the Midwestern United States, 151 water samples were collected from 71 streams and five reservoir outflows in 1998. These samples were analyzed for 13 herbicides and 10 herbicide TPs. Herbicide TPs were found to occur as frequently or more frequently than source herbicides and at concentrations that were often larger than their source herbicides. Most samples contained a mixture of more than 10 different herbicides or TPs. The ratios of TPs to herbicide concentrations can be used to determine the source of herbicides in streams. Results of a two‐component mixing model suggest that on average 90 percent or more of the herbicide mass in Midwestern streams during early summer runoff events originates from the runoff and 10 percent or less comes from increased ground water discharge.