Showing papers on "Secchi disk published in 1992"

Landsat Thematic Mapper monitoring of turbid inland water quality

Abstract: This study reports on an investigation of water quality calibration algorithms under turbid inland water conditions using Landsat Thematic Mapper (TM) multispectral digital data. TM data and water quality observations (total suspended solids and Secchi disk depth) were obtained near-simultaneously and related using linear regression techniques. The relationships between reflectance and water quality for Green Bay and Lake Michigan were compared with results for Yellowstone and Jackson Lakes, Wyoming. Results show similarities in the water quality-reflectance relationships, however, the algorithms derived for Green Bay - Lake Michigan cannot be extrapolated to Yellowstone and Jackson Lake conditions.

Sources, concentrations and characteristics of organic matter in softwater lakes and streams of the Swedish forest region

Abstract: 18 Swedish forest lakes covering a wide range of dystrophy were studied in order to quantify and characterize the organic matter in the water with respect to origin (allochthonous or autochthonous), physical state (particulate or dissolved) and phosphorus content. Samples were collected repeatedly during a two-year period with unusually variable hydrological conditions. Water from three different depths and from tributaries was analysed with standard monitoring methods, including water colour, Secchi disk transparency, total organic carbon (TOC), CODCr, CODMn, total phosphorus and molybdate reactive phosphorus. Interrelationships were used to compare different methods and to assess the concentration and composition of organic matter. It is estimated that in remote softwater lakes of the Swedish forest region, autochthonous carbon is typically 200 g Pt m−3) the proportion can exceed 90%. Secchi depth readings were related similarly to organic matter from both sources and provided good estimates of TOC with a single optical measurement. Water colour was used to distinguish allochthonous and autochthonous matter. High concentrations of phosphorus were found in humic waters, most of it being molybdate reactive, and probably associated with humic matter rather than as dissolved free inorganic forms. CODMn yielded only 25–60% of TOC and appears to include mainly truly dissolved substances of low molecular weight.

The sanabria lake. the largest natural freshwater lake i n spain

Abstract: The Lake of Sanabria, at an altitude of 1000 m. above sea level, and a surface area of 3,187,500 m 2 is of glacial origin. According to its physical and chemical factors this lake is oligotrophic, monomictic temperate, with a winter circulation at 8T and thermal stratification in the summer. Its transparency is high (5-9 m., Secchi disk). The main nutrients are present at low concentrations, with a vertical distribution that is nearly homogeneous during winter circulation and with an orthograde trend during thermal stratification. Its nutrient levels are not very closely related to greater abundances of phytoplanktonic algae. Chlorophyll levels are generally low ( mean 2,2 pgr.1-'). Chroococcal Cyanophyceae and Chlorococcal Chlorophyceae are the best represented groups in the phytoplankton, specially during chlorophyll peaks. Other groups, such as Diatoms, Chrisophyceae and Criptophyceae are scarce. Macrophytes are represented along the poorest ground shores by Isoetes i.,elata, M)iriophyllum alter-niflor-um and other species, and in the richest ones by Equisetum fluviatile and Eleochur-is palinstris. Zooplankton are represented by 12 main Rotifer and Crustacean species that follow a stable pattern of succession. Their composition is characteristic of an oligotrophic lake.

Use of Messr-Mos Data to Assess Water Quality in Small Lakes

Abstract: green 50 The main objective of this study was to assess the technical feasibility of using MESSR-hlOS data to evaluate, both qualitatively and quantitatively, the general water quality of small lakes, using as experimental test sites, lakes in Piedmont region (North-West of Italy). Water bodies at very different sea level have been considered (respectively at 1983 m, 351 m and 230m above sea-level). Both in raw- and corrected-images, even though the three lakes are of small dimension and limnologically homogeneous, two different categories of spectral response can be easily recognised: a wide core with lower reflectance values and a narrow rim with higher values. The used ground reference data were Secchi disk depth measurements: good relationships were found between MESSR data and such ground data allowing self consistent results. The use of corrected and raw data to evaluate the suspended sediment concentrations and their comparisons with the curves available in the literature, has proved the good capability of the MESSR in the field of continuous monitoring of internal water,