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Stream Segments (stream + segment)
Selected AbstractsEvaluation of water quality using acceptance sampling by variablesENVIRONMETRICS, Issue 4 2003Eric P. Smith Abstract Under section 303(d) of the Clean Water Act, states must identify water segments where loads of pollutants are violating numeric water quality standards. Consequences of misidentification are quite important. A decision that water quality is impaired initiates the total maximum daily load or TMDL planning requirement. Falsely concluding that a water segment is impaired results in unnecessary TMDL planning and pollution control implementation costs. On the other hand, falsely concluding that a segment is not impaired may pose a risk to human health or to the services of the aquatic environment. Because of the consequences, a method is desired that minimizes or controls the error rates. The most commonly applied approach is to use the Environmental Protection Agency (EPA)'s raw score approach in which a stream segment is listed as impaired when greater than 10 per cent of the measurements of water quality conditions exceed a numeric criteria. An alternative to the EPA approach is the binomial test that the proportion exceeding the standard is 0.10 or less. This approach uses the number of samples exceeding the criteria as a test statistic along with the binomial distribution for evaluation and estimation of error rates. Both approaches treat measurements as binary; the values either exceed or do not exceed the standard. An alternative approach is to use the actual numerical values to evaluate standard. This method is referred to as variables acceptance sampling in quality control literature. The methods are compared on the basis of error rates. If certain assumptions are met then the variables acceptance method is superior in the sense that the variables acceptance method requires smaller sample sizes to achieve the same error rates as the raw score method or the binomial method. Issues associated with potential problems with environmental measurements and adjustments for their effects are discussed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Regional enrichment of local assemblages is robust to variation in local productivity, abiotic gradients, and heterogeneityECOLOGY LETTERS, Issue 2 2006Amy L. Freestone Abstract Theory predicts that the effects of regional richness on the richness of local communities may depend on the productivity, resource availability, and/or heterogeneity of local sites. Using the wetland plant communities of 50 independent streams as ,regions', we tested whether: (1) local richness in 1-m2 quadrats and 50-m stream segments was positively related to regional richness, even after environmental influences were considered; and (2) the effect of regional richness would interact with the effects of biomass, soil moisture, and/or heterogeneity on local richness. In models that explained up to 88% of variation in local richness, we found that richness at both local scales was positively related to regional richness, and that regional richness did not interact with any of the environmental gradients that also shaped local richness. We conclude that species availability from the regional pool may consistently enrich local communities, even while other constraints on local richness operate. [source] Spatial scale and the diversity of macroinvertebrates in a Neotropical catchmentFRESHWATER BIOLOGY, Issue 2 2010RAPHAEL LIGEIRO Summary 1.,Lotic ecosystems can be studied on several spatial scales, and usually show high heterogeneity at all of them in terms of biological and environmental characteristics. Understanding and predicting the taxonomic composition of biological communities is challenging and compounded by the problem of scale. Additive diversity partitioning is a tool that can show the diversity that occurs at different scales. 2.,We evaluated the spatial distribution of benthic macroinvertebrates in a tropical headwater catchment (S.E. Brazil) during the dry season and compared alpha and beta diversities at the scales of stream segments, reaches, riffles and microhabitats (substratum types: gravels, stones and leaf litter). We used family richness as our estimate of diversity. Sampling was hierarchical, and included three stream segments, two stream reaches per segment, three riffles per reach, three microhabitats per riffle and three Surber sample units per microhabitat. 3.,Classification analysis of the 53 families found revealed groups formed in terms of stream segment and microhabitat, but not in terms of stream reaches and riffles. Separate partition analyses for each microhabitat showed that litter supported lower alpha diversity (28%) than did stones (36%) or gravel (42%). In all cases, alpha diversity at the microhabitat scale was lower than expected under a null model that assumed no aggregation of the fauna. 4.,Beta diversity among patches of the microhabitats in riffles depended on substratum type. It was lower than expected in litter, similar in stone and higher in gravel. Beta diversities among riffles and among reaches were as expected under the null model. On the other hand, beta diversity observed was higher than expected at the scale of stream segments for all microhabitat types. 5., We conclude that efficient diversity inventories should concentrate sampling in different microhabitats and stream sites. In the present study, sampling restricted to stream segments and substratum types (i.e. excluding riffles and stream reaches) would produce around 75% of all observed families using 17% of the sampling effort employed. This finding indicates that intensive sampling (many riffles and reaches) in few stream segments does not result in efficient assessment of diversity in a region. [source] Integration of lakes and streams in a landscape perspective: the importance of material processing on spatial patterns and temporal coherenceFRESHWATER BIOLOGY, Issue 3 2000George W. Kling 1. We studied the spatial and temporal patterns of change in a suite of twenty-one chemical and biological variables in a lake district in arctic Alaska, U.S.A. The study included fourteen stream sites and ten lake sites, nine of which were in a direct series of surface drainage. All twenty-four sites were sampled between one and five times a year from 1991 to 1997. 2. Stream sites tended to have higher values of major anions and cations than the lake sites, while the lake sites had higher values of particulate carbon, nitrogen, phosphorous and chlorophyll a. There were consistent and statistically significant differences in concentrations of variables measured at the inlet versus the outlet of lakes, and in variables measured at upstream versus downstream sites in the stream reaches which connect the lakes. In-lake processing tended to consume alkalinity, conductivity, H+, DIC, Ca2+, Mg2+, CO2, CH4, and NO3,, and produce K+ and dissolved organic carbon (DOC). In-stream processing resulted in the opposite trends (e.g. consumption of K+ and DOC), and the magnitudes of change were often similar to those measured in the lakes but with the opposite sign. 3. Observed spatial patterns in the study lakes included mean concentrations of variables which increased, decreased or were constant along the lake chain from high to low altitude in the catchment (stream sites showed no spatial patterns with any variables). The strongest spatial patterns were of increasing conductivity, Ca2+, Mg2+, alkalinity, dissolved inorganic carbon and pH with lake chain number (high to low altitude in the basin). These patterns were partly determined by the effect of increasing catchment area feeding into lakes further downslope, and partly by the systematic processing of materials in lakes and in the stream segments between lakes. 4. Synchrony (the temporal coherence or correlation of response) of variables across all lakes ranged from 0.18 for particulate phosphorus to 0.90 for Mg2+ the average synchrony for all twenty-one variables was 0.50. The synchronous behaviour of lake pairs was primarily related to the spatial location or proximity of the lakes for all variables taken together and for many individual variables, and secondarily, to the catchment to lake area ratio and the water residence time. 5. These results illustrate that, over small geographic areas, and somewhat independent of lake or stream morphometry, the consistent and directional (downslope) processing of materials helps produce spatial patterns which are coherent over time for many limnological variables. We combine concepts from stream, lake and landscape ecology, and develop a conceptual view of landscape mass balance. This view highlights that the integration of material processing in both lakes and rivers is critical for understanding the structure and function of surface waters, especially from a landscape perspective. [source] Predicting Root Density in Streambanks,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2008Candice Piercy Abstract:, Roots of riparian vegetation increase streambank erosion resistance and structural stability; therefore, knowledge of root density and distribution in streambanks is useful for stream management and restoration. The objective of this study was to compare streambank root distributions for herbaceous and woody vegetation and to develop empirical models to predict root density. Root length density, root volume ratio, soil physical and chemical properties, and above-ground vegetation densities were measured at 25 sites on six streams in southwestern Virginia. The Mann-Whitney test was used to determine differences in root density along stream segments dominated by either woody or herbaceous vegetation. Multiple linear regression was used to develop relationships between root density and site characteristics. Study results showed that roots were evenly distributed across the bank face with the majority of roots having diameters less than 2 mm. Soil bulk density and above-ground vegetation were key factors influencing root density. While significant relationships were developed to predict root density, the predictive capabilities of the equations was low. Because of the highly variable nature of soil and vegetation properties, it is recommended at this time that soil erodibility and root density be measured in the field for design and modeling purposes, rather than estimated based on empirical relationships. [source] GROUPWISE MODELING STUDY OF BACTERIALLY IMPAIRED WATERSHEDS IN TEXAS: CLUSTERING ANALYSIS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2006Sabu Paul ABSTRACT: Under the Clean Water Act (CWA) program, the Texas Commission on Environmental Quality (TCEQ) listed 110 stream segments in the year 2000 with pathogenic bacteria impairment. A study was conducted to evaluate the probable sources of pollution and characterize the watersheds associated with these impaired water bodies. The primary aim of the study was to group the water bodies into clusters having similar watershed characteristics and to examine the possibility of studying them as a group by choosing models for total maximum daily load (TMDL) development based on their characteristics. This approach will help to identify possible sources and determine appropriate models and hence reduce the number of required TMDL studies. This in turn will help in reducing the effort required to restore the health of the impaired water bodies in Texas. The main characteristics considered for the classification of water bodies were land use distribution within the watershed, density of stream network, average distance of land of a particular use to the closest stream, household population, density of on-site sewage facilities (OSSFs), bacterial loading from different types of farm animals and wildlife, and average climatic conditions. The climatic data and observed instream fecal coliform bacteria concentrations were analyzed to evaluate seasonal variability of instream water quality. The grouping of water bodies was carried out using the multivariate statistical techniques of factor analysis/principal component analysis, cluster analysis, and discriminant analysis. The multivariate statistical analysis resulted in six clusters of water bodies. The main factors that differentiated the clusters were found to be bacterial contribution from farm animals and wildlife, density of OSSFs, density of households connected to public sewers, and land use distribution. [source] Reproductive ecology of the freshwater red alga Batrachospermum delicatulum (Batrachospermales, Rhodophyta) in three tropical streamsPHYCOLOGICAL RESEARCH, Issue 3 2005Orlando Necchi Junior SUMMARY Batrachospermum delicatulum specimens from three stream segments were analyzed from a tropical region in south- eastern Brazil (20°18,, 20°49,S, 49°13,, 49°46,W). Physical and chemical parameters and the spatial placement of thalli were investigated along with the reproductive characteristics of the gametophytic phase. Sequence data of the cox 2- 3 spacer region was also utilized to evaluate genetic variation in individuals within and among stream segments. Gametophyte occurred under relatively diverse environmental conditions, whereas thalli abundance was weakly or not correlated to environmental variables within the stream segments. All specimens examined were dioecious. The ratio of male/female plants was relatively low (0.5 to 1.3) and male plants tended to occur as clumps (two or three plants together). High reproductive success was observed, as indicated by the occurrence of 100% fertilized (carposporophytic) female plants. This is similar to previous reports for this and other dioecious species, which is remarkable considering the relatively low proportion of male/female plants. Results support the two hypotheses to explain the high reproductive success in dioecious species. The occurrence of male plants in clumps was evidence for a strict spatial relationship (i.e. male plants located in upstream position of female plants in order to release spermatia, which would be carried by eddies through female plants). In contrast, the occurrence of male and female plants adjacent to each other allowed outcrossing among neighboring plants with intermingled male and female branches, which seemed more applicable to some situations (low turbulence habitats). The cox 2- 3 spacer region from the 18 individuals sequenced was 376 bp and the DNA sequence was identical with no base pair substitutions. Likewise, a previous study of another Batrachospermum species showed that the same haplotypes were present in all stream segments from the same drainage basin, even though the stream segments were a considerable distance apart. Short distance dispersal either by small birds or waterway connectivity might explain these findings. [source] Distribution modelling to guide stream fish conservation: an example using the mountain sucker in the Black Hills National Forest, USAAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 7 2008Daniel C. Dauwalter Abstract 1.Conservation biologists need tools that can utilize existing data to identify areas with the appropriate habitat for species of conservation concern. Regression models that predict suitable habitat from geospatial data are such a tool. Multiple logistic regression models developed from existing geospatial data were used to identify large-scale stream characteristics associated with the occurrence of mountain suckers (Catostomus platyrhynchus), a species of conservation concern, in the Black Hills National Forest, South Dakota and Wyoming, USA. 2.Stream permanence, stream slope, stream order, and elevation interacted in complex ways to influence the occurrence of mountain suckers. Mountain suckers were more likely to be present in perennial streams, and in larger, higher gradient streams at higher elevations but in smaller, lower gradient streams at lower elevations. 3.Applying the logistic regression model to all streams provided a way to identify streams in the Black Hills National Forest most likely to have mountain suckers present. These types of models and predictions can be used to prioritize areas that should be surveyed to locate additional populations, identify stream segments within catchments for population monitoring, aid managers in assessing whether proposed forest management will potentially have impacts on fish populations, and identify streams most suitable for stream rehabilitation and conservation or translocation efforts. 4.When the effect of large brown trout (Salmo trutta) was added to the best model of abiotic factors, it had a negative effect on the occurrence of mountain suckers. Negative effects of brown trout on the mountain sucker suggest that management of recreational trout fisheries needs to be balanced with mountain sucker conservation in the Black Hills. However, more spatially explicit information on brown trout abundance would allow managers to understand where the two species interact and where recreational fisheries need to be balanced with fish conservation. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||