Assessing Influences of Hydrology,Physicochemistry, and Habitat on Stream Fish Assemblages Across a Changing Landscape1

Abstract: We evaluated the impact of land cover on fish assemblages by examining relationships between stream hydrology, physicochemistry, and instream habitat and their association with fish responses in streams draining 18 watersheds of the Lower Piedmont of western Georgia. Several important relationships between land use and physicochemical, hydrological, and habitat parameters were observed, particularly higher frequency of spate flows, water temperatures, and lower dissolved oxygen (DO) with percentage impervious surface (IS) cover, higher habitat quality with percentage forest cover, and elevated suspended solid concentrations with percentage pasture cover. Fish assemblages were largely explained by physicochemical and hydrological rather than habitat variables. Specifically, fish species diversity, richness, and biotic integrity were lower in streams that received high frequency of spate flows. Also, overall fish assemblage structure as determined by nonmetric multidimensional scaling was best described by total dissolved solids (TDS) and DO, with high TDS and low DO streams containing sunfish‐based assemblages and low TDS and high DO streams containing minnow‐based assemblages. Our results suggest that altered hydrological and physicochemical conditions, induced largely by IS, may be a strong determinant of fish assemblage structure in these lowland streams and allow for a more mechanistic understanding of how land use ultimately affects these systems.     

Spatial Variations in the Relationships between Land Use and Water Quality across an Urbanization Gradient in the Watersheds of Northern Georgia, USA

A spatial statistical technique, Geographically Weighted Regression (GWR) is applied to study the spatial variations in the relationships between four land use indicators, including percentages of urban land, forest, agricultural land, and wetland, and eight water quality indicators including specific conductance (SC), dissolved oxygen, dissolved nutrients, and dissolved organic carbon, in the watersheds of northern Georgia, USA. The results show that GWR has better model performance than ordinary least squares regression (OLS) to analyze the relationships between land use and water quality. There are great spatial variations in the relationships affected by the urbanization level of watersheds. The relationships between urban land and SC are stronger in less-urbanized watersheds, while those between urban land and dissolved nutrients are stronger in highly-urbanized watersheds. Percentage of forest is an indicator of good water quality. Agricultural land is usually associated with good water quality in highly-urbanized watersheds, but might be related to water pollution in less-urbanized watersheds. This study confirms the results obtained from a similar study in eastern Massachusetts, and so suggest that GWR technique is a very useful tool in water environmental research and also has the potential to be applied to other fields of environmental studies and management in other regions.     

RELATION OF MACROINVERTEBRATE COMMUNITY IMPAIRMENT TO CATCHMENT CHARACTERISTICS IN NEW JERSEY STREAMS1

ABSTRACT: The level of macroinvertebrate community impairment was statistically related to selected basin and water-quality characteristics in New Jersey streams. More than 700 ambient biomonitoring stations were chosen to evaluate potential and known anthropogenic effects. Macroinvertebrate communities were assessed with a modified rapid-bioassessment approach using three impairment ratings (nonimpaired, moderately impaired, and severely impaired). Maximum-likelihood multiple logistic-regression analysis was used to develop equations defining the probability of community impairment above predetermined impairment levels. Seven of the original 140 explanatory variables were highly related to the level of community impairment. Explanatory variables found to be most useful for predicting severe macroinvertebrate community impairment were the amount of urban land and total flow of municipal effluent. Area underlain by the Reading Prong physiographic region and amount of forested land were inversely related to severe impairment. Nonparametric analysis of variance on rank-transformed bioassessment scores was used to evaluate differences in level of impairment among physiographic regions and major drainage areas simultaneously. Rejection of the null hypothesis indicated that the levels of impairment among all six physiographic regions and five major drainage areas were not equal. Physiographic regions located in the less urbanized northwest portion of New Jersey were not significantly different from each other and had the lowest occurrence of severely impaired macroinvertebrate communities. Physiographic regions containing urban centers had a higher probability of exhibiting a severely impaired macroinvertebrate community. Analysis of major drainage areas indicates that levels of impairment in the Atlantic Coastal Rivers drainage area differed significantly from those in the Lower Delaware River drainage area.     

Specific Conductance and pH as Indicators of Watershed Disturbance in Streams of the New Jersey Pinelands, USA

/ We used linear regression to independently and jointly relate specific conductance and pH measured at New Jersey Pinelands stream sites to the percentage of altered land in a watershed. Percentage altered land included developed and agricultural land uses and represented watershed disturbance for a given site. Median values calculated for a 2-year period (September 1992 through August 1994) characterized pH and specific conductance at the study sites. We found the relationships between the median values for both water-quality measures and percentage altered land for a site to be consistent across subregion and dominant altered-land use. Our results also demonstrated that the water-quality/altered-land relationships developed using median values were similar to relationships developed using data from any single-sample period within the entire study period. Individually, pH and specific conductance explained 48% and 56%, respectively, of the variability in watershed disturbance among study sites. The joint use of pH and specific conductance explained 79% of the watershed disturbance variability among sites. The joint use of these easily obtained water-quality measures can provide a quick assessment of instream water-quality impacts from upstream watershed disturbance at any Pinelands stream site. Additionally, a range in pH and specific conductance, and hence a range in ambient water quality, can be predicted for a given altered-land percentage or a change in existing altered-land conditions.     

WATER QUALITY IN AGRICULTURAL,URBAN, AND MIXED LAND USE WATERSHEDS1

ABSTRACT: Water quality and nonpoint source (NPS) pollution are important issues in many areas of the world, including the Inner Bluegrass Region of Kentucky where urban development is changing formerly rural watersheds into urban and mixed use watersheds. In watersheds where land use is mixed, the relative contributions of NPS pollution from rural and urban land uses can be difficult to separate. To better understand NPS pollution sources in mixed use watersheds, surface water samples were taken at three sites that varied in land use to examine the effect of land use on water quality. Within the group of three watersheds, one was predominately agriculture (Agricultural), one was predominately urban (Urban), and a third had relatively equal representation of both types of land uses (Mixed). Nitrogen (N), phosphorus (P), total suspended solids (TSS), turbidity, pH, temperature, and streamflow were measured for one year. Comparisons are made among watersheds for concentration and fluxes of water quality parameters. Nitrate and orthophosphate concentrations were found to be significantly higher in the Agricultural watershed. Total suspended solids, turbidity, temperature, and pH, were found to be generally higher in the Urban and Mixed watersheds. No differences were found for streamflow (per unit area), total phosphorus, and ammonium concentrations among watersheds. Fluxes of orthophosphate were greater in the Agricultural watershed that in the Urban watershed while fluxes of TSS were greater in the Mixed watershed when compared to the Agricultural watershed. Fluxes of nitrate, ammonium, and total phosphorus did not vary among watersheds. It is apparent from the data that Agricultural land uses are generally a greater source of nutrients than the Urban land uses while Urban land uses are generally a greater source of suspended sediment.     

Relationship of Land‐Use/Land‐Cover Patterns and Surface‐Water Quality in The Mullica River Basin1

Abstract: We describe relationships between pH, specific conductance, calcium, magnesium, chloride, sulfate, nitrogen, and phosphorus and land‐use patterns in the Mullica River basin, a major New Jersey Pinelands watershed, and determine the thresholds at which significant changes in water quality occur. Nonpoint sources are the main contributors of pollutants to surface waters in the basin. Using multiple regression and water‐quality data for 25 stream sites, we determine the percentage of variation in the water‐quality data explained by urban land and upland agriculture and evaluate whether the proximity of these land uses influences water‐quality/land‐use relationships. We use a second, independently collected water‐quality dataset to validate the statistical models. The multiple‐regression results indicate that water‐quality degradation in the study area is associated with basin‐wide upland land uses, which are generally good predictors of water‐quality conditions, and that both urban land and upland agriculture must be included in models to more fully describe the relationship between watershed disturbance and water quality. Including the proximity of land uses did not improve the relationship between land use and water quality. Ten‐percent altered‐land cover in a basin represents the threshold at which a significant deviation from reference‐site water‐quality conditions occurs in the Mullica River basin.     

PRESENCE AND DISTRIBUTION OF TRACE ELEMENTS IN NEW JERSEY STREAMBED SEDIMENTS1

ABSTRACT: The distribution of trace elements in New Jersey streambed sediments is described with respect to physiographic provinces and major drainage areas. Samples were collected during 1976–1993 at 295 sites distributed throughout New Jersey. Copper, chromium, lead, and zinc were detected with the greatest frequency and at the highest concentrations of the elements. Concentrations of most trace elements were significantly higher in streambed sediments from the New England (glaciated) and Piedmont physiographic provinces - the provinces with the lowest and highest percentages of urban land use, respectively - than in sediments from the other provinces. High trace-element concentrations in the New England (glaciated) province reflect previous mining of extensive magnetite deposits, whereas those in the Piedmont province most likely reflect urban land use. Significantly lower trace-element concentrations in streambed sediments from the Coastal Plain are attributable to the low pH of the streamwater, the lack of iron and manganese available to form coatings that scavenge trace elements, and the relatively low percentage of urban land use in the province. Trace-element concentrations were related to land use, population, or point sources in the drainage basin specific to the sampling location by using logistic regression. Results of this analysis indicate a relation between arsenic and agricultural land use; chromium and physiographic province; and copper, lead, and zinc and population density.     

Delineation and evaluation of hydrologic-landscape regions in the United States using geographic information system tools and multivariate statistical analyses

Hydrologic-landscape regions in the United States were delineated by using geographic information system (GIS) tools combined with principal components and cluster analyses. The GIS and statistical analyses were applied to land-surface form, geologic texture (permeability of the soil and bedrock), and climate variables that describe the physical and climatic setting of 43,931 small (approximately 200 km2) watersheds in the United States. (The term "watersheds" is defined in this paper as the drainage areas of tributary streams, headwater streams, and stream segments lying between two confluences.) The analyses grouped the watersheds into 20 noncontiguous regions based on similarities in land-surface form, geologic texture, and climate characteristics. The percentage of explained variance (R-squared value) in an analysis of variance was used to compare the hydrologic-landscape regions to 19 square geometric regions and the 21 U.S. Environmental Protection Agency level-II ecoregions. Hydrologic-landscape regions generally were better than ecoregions at delineating regions of distinct land-surface form and geologic texture. Hydrologic-landscape regions and ecoregions were equally effective at defining regions in terms of climate, land cover, and water-quality characteristics. For about half of the landscape, climate, and water-quality characteristics, the R-squared values of square geometric regions were as high as hydrologic-landscape regions or ecoregions.     

Effects of flooding and drought on water quality in Gulf Coastal Plain streams in Georgia

Since 1994, water-quality constituents have been measured monthly in three adjacent Coastal Plain watersheds in southwestern Georgia. During 1994, rainfall was 650 mm above annual average and the highest flows on record were observed. From November 1998 through November 2000, 19 months had below average rainfall. Lowest flows on record were observed during the summer of 2000. The watersheds are human-dominated with row-crop agriculture and managed forestlands being the major land uses. However, one watershed (Chickasawhatchee Creek) had 10 to 13% less agriculture and greater wetland area, especially along the stream. Suspended particles, dissolved organic carbon, NH4-N, and soluble reactive phosphorus concentrations were greater during wet and flood periods compared with dry and drought periods for each stream. Regional hydrologic conditions had little effect on NO3-N or dissolved inorganic carbon. Chickasawhatchee Creek had significantly lower suspended sediment and NO3-N concentrations and greater organic and inorganic carbon concentrations, reflecting greater wetland area and stronger connection to a regional aquifer system. Even though substantial human land use occurred within all watersheds, water quality was generally good and can be attributed to low stream drainage density and relatively intact floodplain forests. Low drainage density minimizes surface run-off into streams. Floodplain forests reduce nonpoint-source pollutants through biological and physical absorption. In addition to preserving water quality, floodplain forests provide important ecological functions through the export of nutrients and organic carbon to streams. Extreme low flows may be disruptive to aquatic life due to both the lack of water and to the scarcity of biologically important materials originating from floodplain forests.     

Assessing Water Quality at Large Geographic Scales: Relations Among Land Use,Water Physicochemistry,Riparian Condition,and Fish Community Structure

Data collected from 172 sites in 20 major river basins between 1993 and 1995 as part of the US Geological Survey's National Water-Quality Assessment Program were analyzed to assess relations among basinwide land use (agriculture, forest, urban, range), water physicochemistry, riparian condition, and fish community structure. A multimetric approach was used to develop regionally referenced indices of fish community and riparian condition. Across large geographic areas, decreased riparian condition was associated with water-quality constituents indicative of nonpoint source inputs—total nitrogen and suspended sediment and basinwide urban land use. Decreased fish community condition was associated with increases in total dissolved solids and rangeland use and decreases in riparian condition and agricultural land use. Fish community condition was relatively high even in areas where agricultural land use was relatively high (>50% of the basin). Although agricultural land use can have deleterious effects on fish communities, the results of this study suggest that other factors also may be important, including practices that regulate the delivery of nutrients, suspended sediments, and total dissolved solids into streams. Across large geographic scales, measures of water physicochemistry may be better indicators of fish community condition than basinwide land use. Whereas numerous studies have indicated that riparian restorations are successful in specific cases, this analysis suggests the universal importance of riparian zones to the maintenance and restoration of diverse fish communities in streams.     

EMPIRICAL MODELING OF HYDROLOGIC AND NFS POLLUTANT FLUX IN AN URBANIZING BASIN1

ABSTRACT: Long term effects of precipitation and land use/land cover on basin outflow and nonpoint source (NFS) pollutant flux are presented for up to 24 years for a rapidly developing headwater basin and three adjacent headwater basins on the urban fringe of Washington, D.C. Regression models are developed to describe the annual and seasonal responses of basin outflow and IMPS pollutant flux to precipitation, mean impervious surface (IS), and land use. To quantify annual change in mean IS, a variable called delta IS is created as a temporal indicator of urban soil disturbance. Hydrologic models indicate that total annual surface outflow is significantly associated with precipitation and mean IS (r²= 0.65). Seasonal hydrologic models reveal that basin outflow is positively associated with IS during the summer and fall growing season (June to November). NPS pollutant flux models indicate that total and storm total suspended solids (TSS) flux are significantly associated with precipitation and urban soil disturbance in all seasons. Annual NPS total nitrogen flux is significantly associated with both urban and agricultural soil disturbance (r²= 0.51). Seasonal models of phosphorus flux indicate a significant association of total phosphorus flux with urban soil disturbance during the growing season. Total soluble phosphorus (TSP) flux is significantly associated with IS (r²= 0.34) and urban and agricultural soil disturbance (r²= 0.58). In urbanizing Cub Run basin, annual TSP concentrations are significantly associated with IS and cultivated agriculture (r²= 0.51).     

NUTRIENT LOADS TO WISCONSIN LAKES: PART I. NITROGEN AND PHOSPHORUS EXPORT COEFFICIENTS1

ABSTRACT: Export coefficients (kg/km²/yr) for dissolved ortho-phosphate (OP), total phosphorus (TP), total inorganic nitrogen (TIN), and total nitrogen (TN) were derived for watersheds in Wisconsin using data bases available for 17 basins from the U.S. Environmental Protection Agency — National Eutrophication Survey, U.S. Geological Survey, and the Wisconsin Department of Natural Resources. Three general land use categories, representative of most regions in Wisconsin, were established: forest, mixed, and agricultural. Data for the 17 basins indicated greater exports of OP. TP, TIN, and TN as the percentage of forest decreased and agriculture increased. These region-specific coefficients are compared to the values reported in the literature representing much broader areas of the U.S.     

Cumulative impact of marinas on estuarine water quality

The purpose of this work is to present a modeling approach for assessing and managing the cumulative impact of marinas on estuarine systems. In doing so, both a water-quality model and a planning and management model are developed. The water-quality model predicts biochemical oxygen demand (BOD) and fecal coliform (FC) loadings from marina sources in a hypothetical North Carolina estuary. By running the water-quality model repeatedly with varied loading input, impact coefficients are determined. These impact coefficients are used in the planning and management model, the output of which gives the sizes and locations of marinas in the estuarine system such that dissolved oxygen (DO) and FC water-quality standards are maintained.Five different estuarine development scenarios are considered. Each scenario is evaluated with respect to both maximum and uniform land development constraints. In addition, two alternative fecal coliform standards are used with each of the development options.     

URBAN IMPACTS ON PHYSICAL STREAM CONDITION: EFFECTS OF SPATIAL SCALE,CONNECTIVITY, AND LONGITUDINAL TRENDS1

ABSTRACT: An assessment of physical conditions in urban streams of the Puget Sound region, coupled with spatially explicit watershed characterizations, demonstrates the importance of spatial scale, drainage network connectivity, and longitudinal downstream trends when considering the effects of urbanization on streams. A rapid stream assessment technique and a multimetric index were used to describe the physical conditions of multiple reaches in four watersheds. Watersheds were characterized using geographic information system (GIS) derived landscape metrics that represent the magnitude of urbanization at three spatial scales and the connectivity of urban land. Physical conditions, as measured by the physical stream conditions index (PSCI), were best explained for the watersheds by two landscape metrics: quantity of intense and grassy urban land in the subwatershed and quantity of intense and grassy urban land within 500 m of the site (R²= 0.52, p > 0.0005). A multiple regression of PSCI with these metrics and an additional connectivity metric (proximity of a road crossing) provided the best model for the three urban watersheds (R²= 0.41, p > 0.0005). Analyses of longitudinal trends in PSCI within the three urban watersheds showed that conditions improved when a stream flowed through an intact riparian buffer with forest or wetland vegetation and without road crossings. Results demonstrate that information on spatial scale and patterns of urbanization is essential to understanding and successfully managing urban streams.     

Factors Affecting Sediment Oxygen Demand Dynamics in Blackwater Streams of Georgia’s Coastal Plain1

Abstract: Sediment oxygen demand (SOD) is believed to be an important process affecting dissolved oxygen (DO) concentrations in blackwater streams of the southeastern coastal plain. Because very few data on SOD are available, it is common for modelers to take SOD values from the literature for use with DO models. In this study, SOD was measured in seven blackwater streams of the Suwannee River Basin within the Georgia coastal plain for between August 2004 and April 2005. SOD was measured using four in situ chambers and was found to vary on average between 0.1 and 2.3 g O₂/m/day across the seven study sites throughout the study period. SOD was found to vary significantly between the watersheds within the Suwannee River Basin. However, land use was not found to be the driving force behind SOD values. Statistical analyses did find significant interaction between land use and watersheds suggesting that an intrinsically different factor in each of the watersheds may be affecting SOD and the low DO concentrations. Further research is needed to identify the factors driving SOD dynamics in the blackwater streams of Georgia’s coastal plain. Results from this study will be used by the Georgia Department of Natural Resources – Environmental Protection Division as model input data for the development and evaluation of DO total maximum daily loads in the Georgia coastal plain.     

EFFECTS OF LAND COVER AND GEOLOGY ON STREAM CHEMISTRY IN WATERSHEDS OF CHESAPEAKE BAY1

ABSTRACT: We measured the base‐flow stream chemistry in all the major physiographic provinces of the Chesapeake Bay drainage basin. The spatial variation of stream chemistry was closely related to differences in geology and land cover among the sampled watersheds. Some stream chemistry variables were strongly affected by geological settings in the watersheds while others were more influenced by land cover. The effects of land cover differed among chemical constituents and regions. Concentrations of Ca²⁺, Mg²⁺, pH, total alkalinity, and conductivity were mainly functions of carbonate bedrock, especially in the Great Valley. Nitrate‐N and total dissolved N were closely related to cropland and increased as the percentage of cropland increased. The rate of increase varied from region to region with the highest in the Piedmont. Na⁺ and Cl^? were mainly affected by the percentage of developed area in a watershed, especially in the Coastal Plain and Piedmont. We observed no significant effects of region or land cover on species of phosphorus because samples were collected under base flow conditions and only dissolved forms were measured. Dissolved silicate (DSi) was not related to any other water chemistry variables. DSi increased as developed area decreased and cropland increased in the Coastal Plain, but these patterns were reversed in the Piedmont. There was no consistent pattern in the spatial variation of land cover effects on the reduced forms of N, dissolved organic P, dissolved organic matter, and K⁺.     

WATERSHED URBANIZATION AND CHANGES IN FISH COMMUNITIES IN SOUTHEASTERN WISCONSIN STREAMS1

ABSTRACT: We compared watershed land‐use and fish community data between the 1970s and 1990s in 47 small streams in southeastern Wisconsin. Our goal was to quantify effects of increasing urbanization on stream fishes in what had been a predominantly agricultural region. In the 43 test watersheds, mean surface coverage by agricultural lands decreased from 54 percent to 43 percent and urban lands increased from 24 percent to 31 percent between 1970 and 1990. Agriculture dominated the four reference watersheds, but neither agriculture (65–59 percent) nor urban (4.4–4.8 percent) land‐uses changed significantly in those watersheds during the study period. From the 1970s to the 1990s the mean number of fish species for the test stream sites decreased 15 percent, fish density decreased 41 percent, and the index of biotic integrity (IBI) score dropped 32 percent. Fish community attributes at the four reference sites did not change significantly during the same period, although density was substantially lower in the 1990s. For both the 1970s and 1990s test sites, numbers of fish species and IBI scores were positively correlated with watershed percent agricultural land coverage and negatively correlated with watershed urban land uses, as indexed by percent effective connected imperviousness. Numbers of fish species per site and IBI scores were highly variable below 10 percent imperviousness, but consistently low above 10 percent. Sites that had less than 10 percent imperviousness and fewer than 10 fish species in the 1970s suffered the greatest relative increase in imperviousness and decline in species number over the study period. Our findings are consistent with previous studies that have found strong negative effects of urban land uses on stream ecosystems and a threshold of environmental damage at about 10 percent imperviousness. We conclude that although agricultural land uses often degrade stream fish communities, agricultural land impacts are generally less severe than those from urbanization on a per‐unit‐area basis.     

INPUTS OF COPPER‐BASED CROP PROTECTANTS TO COASTAL CREEKS FROM PASTICULTURE RUNOFF1

ABSTRACT: Inputs of copper‐based crop protectants from tomato fields grown under plastic mulch agriculture (plasticulture) to an estuarine creek were investigated. Copper was measured in runoff from diverse land‐uses including conventional agriculture, plasticulture, residences, and natural areas. Water column and sediment copper concentrations were measured in plasticulture and control (nonagriculture) watersheds. Copper concentrations in plasticulture‐impacted creeks exceeded background levels episodically. High concentrations occurred during or immediately after runoff‐producing rains. Concentrations of 263 μg/L total copper and 126 μg/L dissolved copper were measured in a tidal creek affected by plasticulture; concentrations exceeded the shellfish LC₅₀ values and the water quality criteria of 2.9 μg/L dissolved copper. Control watersheds indicated background water column levels of ≤ 4 μg/L dissolved copper with similar copper levels during periods with and without rain. The copper concentrations in tomato plasticulture field runoff itself contained up to 238 μg/L dissolved copper. Copper concentrations in runoff from other land‐uses were less than 5 μg/L dissolved copper. Creek sediment samples adjacent to a plasticulture field contained significantly higher copper concentrations than sediments taken from nonplasticulture watersheds.     

STATISTICAL ANALYSIS OF DAILY WATER QUALITY DATA1

ABSTRACT. The stochastic nature of some water quality time series were examined. These time series include nine years of daily observations in: (1) the stream flow (Q), (2) the water temperature (T), (3) the dissolved oxygen (DO), and (4) the biochemical oxygen demand (BOD) of the Passaic River at Little Falls, New Jersey. It was found that the random component contributes more than 60 per cent of the variance in the BOD series, but only 30 per cent or less in the DO series. Autocorrelation analysis suggest that DO and BOD residual series have a persistence of about 30 days. Significant crosscorrelation between DO and temperature T was found when DO lags T for up to 30 days, which indicates that the critical DO probably lags the critical temperature. Also, spectral anlaysis shows multiple peaks in the BOD series, reflecting effects of storm runoff and other non-point source pollution on river water quality.     

CHARACTERIZATION OF SURFACE WATER QUALITY ALONG A WATERSHED DISTURBANCE GRADIENT1

ABSTRACT. Characterizing ecological indicators such as water quality is necessary to effectively manage human-dominated systems such as the New Jersey Pinelands. Pinelands surface waters are naturally acidic and low in nutrients and other dissolved substances. Water quality for 14 Pinelands stream sites monitored by the U.S. Geological Survey was characterized in relation to land use. A gradient of increasing pH, specific conductance, and concentration of dissolved calcium, dissolved magnesium, total nitrite + nitrate-nitrogen, total ammonia-nitrogen, and total phosphorus was associated with a watershed disturbance gradient of increasing land use intensity and waste water flow. These two parallel gradients emphasized the significant effect that watershed disturbance can have on natural water chemistry in the Pinelands. The results of this study can be applied to planning and regulatory programs in the Pinelands.