Showing papers on "Secchi disk published in 2004"

Mapping lake water clarity with Landsat images in Wisconsin, U.S.A.

Abstract: Landsat thematic mapper (TM) and enhanced thematic mapper plus (ETM+) images are being used to map lake water clarity region-wide in the Upper Midwest states of Minnesota, Wisconsin, and Michigan using a standardized image processing protocol In Wisconsin, lake clarity estimates have been produced for 8645 lakes in the 1999-2001 time period In addition to satellite imagery, the protocol relies on Secchi disk data collected by a network of citizen volunteers for development and validation of models The most significant term in the regression model relating the satellite imagery to the field data is the ratio of spectral radiance values in the blue and red bands (ratio of Landsat band 1 to Landsat band 3) The resulting database of satellite-derived lake water clarity estimates represents an important new resource for lake managers in the region, and for those studying the linkages between lakes and their surrounding landscapes

Effect of mechanical removal of water hyacinth (Eichhornia crassipes) on the water quality and biological communities in a Mexican reservoir

Abstract: The Valsequillo reservoir, located near the city of Puebla, Mexico, is a hard-water eutrophic subtropical system, with minimum temperatures in winter (November–December), and marked dry-rain seasons with fluctuating depth. The reservoir has been infested with water hyacinth for over three decades. A management program involving the use of triturating machines was applied from December 1996 to February 1997. After trituration, remains were allowed to settle to the bottom. The purpose of this study was to monitor the changes in the water quality and the biological communities before and after physical control of weeds. A monthly sampling of surface water was performed at four stations one year before the treatment. After trituration, one year sampling was also carried out. Variables measured included temperature, Secchi disk transparency, depth, pH, dissolved oxygen, oxygen saturation, hardness, nitrate content, nitrite content, ammonia, orthophosphates, and numerical abundance of phytoplankton, zooplankton...

Patterns and dynamics of coastal waters in multi-temporal satellite images: support to water quality monitoring in the Archipelago Sea, Finland

Abstract: The Archipelago Sea in the northern Baltic is a coastal region with a highly dynamic water flow regime, where the need for a methodology to monitor water quality accurately is encountered. In order to contribute to the development of an appropriate strategy to meet this need, the dynamics of the surface waters in the region were analysed using data from six Landsat TM/ETM+ images from the late 1990s. Single images were enhanced by principal component transformation and multi-temporal image combination was based on unsupervised classification. The visual patterns discernible in the single images as well as the classification result of the multi-temporal data were compared with the reference data from long-term water quality analyses (Secchi disk depth and chlorophyll- a ). The satellite images confirmed dynamic surface flow patterns in the region, indicating gradual and abrupt gradients in water quality, flow directions and forms. These patterns suggest short-term variability in the surface water quality within the region, presenting a challenge for water monitoring. The average Secchi depths increased gradually from the mainland coast until ca. 3–5 m near the open sea. The spatial distribution of chlorophyll- a was found to be more homogeneous, ca. 2–4 μg l −1 . The importance of evaluating the location of an in situ sampling site in relation to the surrounding hydrographic realm is pronounced in regions where field sampling and other monitoring methods remain insufficient in their ability to reflect water quality patterns credibly. In such areas, accurate and cost-effective water quality monitoring and forecasting require an integrated monitoring system, consisting of space and airborne surveillance, field surveys and hydrodynamic modelling.

Transparency tube provides reliable water-quality measurements

Abstract: We examined the efficacy of using transparency-tube measurements to estimate turbidity, total suspended solids (TSS) and particulate nitrogen and phosphorus concentrations in several California waterways. Just as lowering a black-and-white disk (Secchi disk) into a lake provides a convenient way to measure its water clarity, a transparency tube offers a practical alternative for measuring water clarity and suspended solids concentrations in California streams and waterways. While transparency relationships with turbidity and TSS are strongest within a given sampling location, these relationships are relatively robust across a wide range of water bodies displaying contrasting conditions. However, transparency-tube measurements appear to have limited value in predicting particulate nutrient concentrations, even at a given sampling site. The low cost, ease of use and excellent repeatability of measurement make the transparency tube a potentially valuable tool for anyone interested in monitoring water quality, including farmers, ranchers, citizen volunteer groups, schools and local governments seeking to get involved in watershed monitoring programs.

Eutrophication Modeling in Shihmen Reservoir, Taiwan

Abstract: Based on the measured data, including total phosphorus, chlorophyll a, and Secchi disk depth, the Shihmen Reservoir in the state of mesotrophic to eutrophic. A two-dimensional, laterally averaged, finite-difference hydrodynamic, and water quality model was applied to simulate water quality conditions in the reservoir to determine appropriate strategies for the management of water quality. Data collected in the field for a two-year period were utilized to calibrate and verify the model. The model calibration and verification were achieved with water surface elevation, temperature, and water quality constituents such as nutrients, dissolved oxygen, and chlorophyll a. Then the model was used to simulate chlorophyll a concentrations under several scenarios corresponding to various waste load reduction ratios. A 90% reduction of nutrient loadings will upgrade the existing eutrophic/mesotrophic conditions to oligotrophic condition in both 2001 and 2002, exception January in 2001. The modeling effort had yielded valuable information that can be used by decision maker for the evaluation of different management strategies of reduction of nutrients coming from the catchment area.

Abundance of Ohio Shrimp (Macrobrachium ohione) and Glass Shrimp (Palaemonetes kadiakensis) in the Unimpounded Upper Mississippi River

Abstract: Large rivers of the United States have been altered by construction and maintenance of navigation channels, which has resulted in habitat loss and degradation. Using 7 y of Long Term Resource Monitoring Program data collected from the unimpounded upper Mississippi River, we investigated Ohio and Glass Shrimp abundance collected from four physical habitats of the unimpounded upper Mississippi River: main channel border, main channel border with wing dike, open side channel and closed side channel. Our objective was to assess associations between Ohio and Glass Shrimp abundance, environmental measurements and the four habitats to better understand the ecology of these species in a channelized river system. Ohio Shrimp were most abundant in the open side channels, while Glass Shrimp were most abundant in the main channel border wing dike habitat. Thirty-two percent of the variance in Glass Shrimp abundance was explained by year 1995, year 1998, water temperature, depth of gear deployment, Secchi disk transparency and river elevation. Approximately 8% of variation in Ohio Shrimp abundance was explained by Secchi disk transparency. Catch-per-unit-effort (CPUE) was greatest in 1998 for Glass Shrimp but lowest in 1997. Conversely, CPUE was greatest in 1996 for Ohio Shrimp and lowest in 2000. Both species exhibited inter-annual variability in CPUE. Long-term impacts of river modifications on aquatic invertebrates have not been well documented in many large river systems and warrants further study. The findings from this study provide ecological information on Glass and Ohio Shrimp in a channelized river system.

Long-term temporal-spatial dynamics of marine coastal water quality in the Tolo Harbor, Hong Kong, China

Abstract: The long-term temporal and spatial dynamics of marine coastal water quality in Tolo Harbor, Hong Kong were explored. The Harbor is divided into three zones represented as Harbor, Buffer, and Channel Subzones. The time range for the study covers the period from the 1970s to the 1990s. The selected indicators for the comprehensive assessment of water quality consist of physical, chemical and biological aspects, including suspended solids(SS), Secchi disk depth(SD), 5-day biochemical oxygen demand(BOD5), total nitrogen (TN), total phosphorus(TP), faecal coliform, chlorophyll-a(Chl-a), and the number of red tide occurrences. The results indicated the presence of obvious temporal and spatial trends with regard to changes in water quality. Spatially, water quality in the Channel Subzone is the best, while that in the Harbor Subzone is the worst. On a temporal basis, the average trend from bad to good was 1980s > 1990s > 1970s as indicated by most of the selected water quality indicators. Water quality during the late 1980s reached its worst level with the lowest SD, the highest BOD5, TN, TP, Chl-a concentrations, and the number of red tide occurrences. These long-term temporal-spatial water quality trends were also found in other studies of the Tolo Harbor. The large quantity of pollutants produced as a result of increasing population, industrial and commercial actives, and urbanization and industrialization trends in both Shatin and Tai Po seem to be primarily responsible for the changes in marine coastal water quality.

Assessing the utility of spectral band operators to reduce the influence of total suspended solids on the relationship between chlorophyll concentration and the bidirectional reflectance factor in Amazon waters

Abstract: Measurements of reflectance spectra, total suspended solids (TSS), chlorophyll a+phaeophytin (CLH) and dissolved organic carbon (DOC) plus pH, Secchi disk transparency and water depth were made in lakes associated with the Amazons and Negro rivers upstream from Manaus. Reflectance spectra were acquired between 400 and 900 nm using a spectroradiometer with a nominal resolution of 3 nm. Two spectral band operators designed to detect the CHL signal in waters with high TSS concentrations were examined with the aid of linear and nonlinear regression methods. Results showed that none of the proposed operators were successful in Amazon white water systems.

The ability of aquatic macrophytes to maintain water clarity in two tropical ponds

Abstract: The ability of aquatic macrophytes to maintain water clarity was investigated in two tropical ponds [1999–2001]. Low chlorophyll‐a concentration (0.2–3.5 mg/m3) was observed throughout the study period, which reflected the absence of any algal bloom. At a high coverage (≥ 90%), the ability of Vallisneria spiralis to maintain Secchi disk transparency (> 2 m) extended to the deepest point (3.5–4.4 m) even at high Kjeldahl nitrogen (1.2–29.8 mg/l) and total phosphorus levels (0.2–1.2 mg/l).

Some physical and chemical characteristics of Lake Atnsjøen

Abstract: The physical and chemical characteristics of the dimictic, ultraoligotrophic, and subalpine Lake Atnsjoen are described based on data from the period 1985-2001. The temperature stratification of the lake is weakly developed, with the thermocline at about 10 m depth. The surface temperature during summer is usually lower than 14-15 °C. The Secchi disk transparency is normally higher than 8-10 m in summer and autumn, but can be as low as 4.3 m during spring. The pH is about 6.0, and the specific conductivity about 1.0 mS m-1. The dominating cation and anion are Ca (≈0.8 mg 1-1 or 42 µeq 1-1), and SO4 (≈1.5 mg 1-1 or 33 µeq 1-1), respectively. The concentration of bicarbonate (HCO3, µeq 1-1) is sometimes lower, sometimes higher than that of SO4.

[Physical-chemical features and determination of pesticides in the lagoon water in Gandoca, Limón, Costa Rica. ].

Abstract: Nutrients and chlorophylls concentrations, as well as salinity, temperature and Secchi disk depth were determined from November 1999 to April 2000, at three stations and two depths, at Gandoca lagoon, Gandoca-Manzanillo National Wildlife Refuge, Limon, Costa Rica. Salinity profiles indicated that the lagoon was a salt wedge estuary with a partially mixed region near the mouth. No processes of eutrophication were found. The distribution and abundance of nutrients and chlorophylls showed a slight influence of continental water and water circulation patterns in the lagoon. A preliminary study was done in order to analyze the presence of 20 organochlorated and organophosphorated pesticides along the Gandoca lagoon in February 2000. None of the pesticides were detected by the analysis of residues from liquid-liquid extractions. The absence of the pesticides may be due to the fact that they did not reach the lagoon or, if they did, they were washed away by the strong rains during the sampling period.

Transparency tube provides reliable water-quality measurements - eScholarship

Abstract: We examined the efficacy of using transparency-tube measurements to estimate turbidity, total suspended solids (TSS) and particulate nitrogen and phosphorus concentrations in several California waterways. Just as lowering a black-and-white disk (Secchi disk) into a lake provides a convenient way to measure its water clarity, a transparency tube offers a practical alternative for measuring water clarity and suspended solids concentrations in California streams and waterways. While transparency relationships with turbidity and TSS are strongest within a given sampling location, these relationships are relatively robust across a wide range of water bodies displaying contrasting conditions. However, transparency-tube measurements appear to have limited value in predicting particulate nutrient concentrations, even at a given sampling site. The low cost, ease of use and excellent repeatability of measurement make the transparency tube a potentially valuable tool for anyone interested in monitoring water quality, including farmers, ranchers, citizen volunteer groups, schools and local governments seeking to get involved in watershed monitoring programs.

An ecological assessment of the trophic structure of York Pond in Coos County Milan, NH

Abstract: We examined the physical, chemical and biological properties of York Pond in Coos County Milan, NH as a part of a 6-lake study. Chemical and physical characteristics measured included: total phosphorus and nitrogen, turbidity, light profiles with Secchi disk depth, specific conductivity, oxidation-reduction potential, dissolved oxygen, and temperature. Biological analysis included: phytoplankton percentage, chlorophyll a fluorescence, zooplankton abundance and zooplankton biomass. York Pond had eutrophic levels of several parameters in the epilimnion, including: chlorophyll a (39.4 + 1.04 µgL -1 ), total phosphorus (46.3 + 0.67 µgL -1 ), total nitrogen (843.3 + 18.48 µgL -1 ), turbidity (22.0 + 0.09 NTU), and percentage of cyanobacteria at (42.0 + 9.60 %). Cyanobacteria were even more dominant deeper in the water column, making up more than 70% of the net phytoplankton. The primary source of nutrient loading appears to be effluent from the fish raceways at the Berlin fish hatchery. Eutrophication has shifted the phytoplankton of York Pond toward cyanobacteria, with Anabaena as the dominant genus in the fall. The could have impacts across multiple trophic levels. Comparisons of York Pond to other study lakes suggest that Secchi disk, chlorophyll a and total phosphorus may be useful predictors of cyanobacteria dominance in New England lakes.