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At least 199 records · Page 11Linked to original sources
USGS2023

Learning from arid and urban aquatic ecosystems to inform more sustainable and resilient futures

The hydrology and aquatic ecology of arid environments has long been understudied relative to temperate regions. Yet spatially and temporally intermittent and ephemeral waters characterized by flashy hydrographs typify arid regions that comprise a substantial proportion of the Earth. Additionally, drought, intense storms, and human modification of landscapes increasingly affect many temperate regions, resulting in hydrologic regimes more similar to aridlands. Here we review the contributions of Dr. Nancy Grimm to aridland hydrology and ecology, and applications of these insights to urban ecosystems and resilience of social-ecological-technological systems. Grimm catalyzed study of nitrogen cycling in streams and characterized feedbacks between surface water-groundwater exchange, nitrogen transformations, and aquatic biota. In aridlands, outcomes of these interactions depend on short- and long-term variation in the hydrologic regime. Grimm and colleagues applied hydrological and biogeochemical insights gained from study of aridland streams to urban ecosystems, integrating engineering, social and behavioral sciences, and geography. These studies evolved from characterizing the spatial heterogeneity of urban systems (i.e., watersheds, novel aquatic systems) and its influence on nutrient dynamics to an approach that evaluated human decision-making as a driver of disturbance regimes and changes in ecosystem function. Finally, Grimm and colleagues have applied principles of urban ecology to look toward the future of cities, considering scenarios of sustainable and resilient futures. We identify cross-cutting themes and approaches that have motivated discoveries across Grimm’s multi-decadal career, including spatial and temporal heterogeneity, hydrologic connectivity and regime, disturbance, systems thinking, and resilience. Finally, we emphasize Grimm’s broad contributions to science via support of long-term research, dedication to mentoring, and extensive collaborations that facilitated transdisciplinary research.

Journal of Hydrology↗
USGS2012

Hydrogeology, water chemistry, and transport processes in the zone of contribution of a public-supply well in Albuquerque, New Mexico, 2007-9

The National Water-Quality Assessment Program (NAWQA) of the U.S. Geological Survey began a series of groundwater studies in 2001 in representative aquifers across the Nation in order to increase understanding of the factors that affect transport of anthropogenic and natural contaminants (TANC) to public-supply wells. One of 10 regional-scale TANC studies was conducted in the Middle Rio Grande Basin (MRGB) in New Mexico, where a more detailed local-scale study subsequently investigated the hydrogeology, water chemistry, and factors affecting the transport of contaminants in the zone of contribution of one 363-meter (m) deep public-supply well in Albuquerque. During 2007 through 2009, samples were collected for the local-scale study from 22 monitoring wells and 3 public-supply (supply) wells for analysis of major and trace elements, arsenic speciation, nutrients, dissolved organic carbon, volatile organic compounds (VOCs), dissolved gases, stable isotopes, and tracers of young and old water. To study groundwater chemistry and ages at various depths within the aquifer, the monitoring wells were divided into three categories: (1) each shallow well was screened across the water table or had a screen midpoint within 18.3 m of the water level in the well; (2) each intermediate well had a screen midpoint between about 27.1 and 79.6 m below the water level in the well; and (3) each deep well had a screen midpoint about 185 m or more below the water level in the well. The 24-square-kilometer study area surrounding the "studied supply well" (SSW), one of the three supply wells, consists of primarily urban land within the MRGB, a deep alluvial basin with an aquifer composed of unconsolidated to moderately consolidated deposits of sand, gravel, silt, and clay. Conditions generally are unconfined, but are semiconfined at depth. Groundwater withdrawals for public supply have substantially changed the primary direction of flow from northeast to southwest under predevelopment conditions, to west to east under modern conditions. Analysis of age tracers indicates that groundwater from most sampled wells is dominated by old (pre-1950) water, ranging in mean age from about 4,000 years to more than 22,000 years, but includes a fraction of young (post-1950) recharge. Patterns in chemical and isotopic data are consistent with the conclusions that shallow groundwater in the area typically includes a fraction that evaporated prior to recharge and (or) flushed accumulated solutes out of the unsaturated zone during recharge, and that shallow groundwater has mixed to deeper parts of the aquifer, which receives recharge mainly by seepage from the Rio Grande. Among shallow and intermediate wells that produced water with a fraction of young recharge, that fraction ranged between 1.5 and 46 percent. Samples from the two deep wells had groundwater ages exceeding 18,000 years, with no fraction of young recharge. Two supply wells (including the SSW) had a fraction of young recharge, which ranged between about 3 and 11 percent, despite mean groundwater ages exceeding 10,000 years. The fraction of young recharge to the SSW varied seasonally, probably because seasonal pumping patterns affected local hydraulic gradients and (or) because of flow through the well bore when the SSW is not pumping. Well-bore flow data collected during winter (low-pumping season) indicated that about 61 percent of the water pumped from the SSW entered the well from the intermediate part of the aquifer, and that the remaining 39 percent entered from the deep part of the aquifer. Volatile organic compounds (VOCs) were detected in samples from most shallow and intermediate monitoring wells and from two of three supply wells, including the SSW. Detected VOCs were primarily chlorinated solvents or their degradation products. Many of the wells in which most of these VOCs were detected are located near known sites of solvent contamination that were targeted for sampling because trichloroethylene (TCE) and cis-1,2-dichloroethylene had been detected in the SSW, and several of these wells may have become contaminated at least partly because of enhanced vertical migration associated with the pumping of and (or) direct migration down deep well bores. Except for TCE in the sample from a shallow monitoring well, all detections of VOCs were at concentrations below Maximum Contaminant Levels (MCLs) set by the U.S. Environmental Protection Agency. Concentrations of all VOCs detected in the supply wells were less than one-tenth of the corresponding MCLs. However, the presence of VOCs in all but deep groundwater, including the detection of chloroform (a chlorination byproduct) in several shallow wells, indicates that groundwater in the study area commonly is affected by human activities, even to substantial depths. The only natural contaminant detected at concentrations near or above its MCL was arsenic, which has been detected at elevated concentrations across broad areas of the MRGB. Concentrations of arsenic, present primarily as arsenate, exceeded the MCL of 10 micrograms per liter (μg/L) in water from the two deep wells (one of which had the highest concentration, 35 μg/L), from one intermediate well, and from two supply wells, including the SSW. Water-quality and solid-phase data from this study are consistent with elevated arsenic concentrations in groundwater being related to pH-dependent desorption of arsenic from ferric oxyhydroxides in sediments in deep parts of the aquifer. Concentrations of nitrate ranged between 1.3 and 5.4 milligrams per liter (mg/L) in water from shallow wells screened across the water table, but were less than 0.9 mg/L in water from all but one deeper well. Nitrogen isotopes and chloride/bromide ratios for shallow wells were consistent with natural soil nitrogen. Nitrate concentrations and nitrogen isotopes indicated that denitrification is occurring at intermediate aquifer depths, and that the progress of the denitrification reaction typically is greatest for wells that include a fraction of groundwater associated with particular recharge sources or with known sites of contamination contributing organic compounds that can provide a carbon source for microbial respiration. Overall, hydrologic and chemical data from the study area indicate that young recharge is reaching the aquifer across broad areas and is migrating from shallow to intermediate depths of the aquifer as a result of mixing that is associated with human development of groundwater. Consequently, groundwater that human activities in the urban study area have affected is present at depths that are within the screened intervals of public-supply wells, resulting in detections of VOCs and implying greater vulnerability to anthropogenic contamination than might be assumed based on the dominantly old age of the regional groundwater. However, the fractions of old groundwater that public-supply wells produce substantially dilute the anthropogenic contaminants, while contributing natural contaminants (primarily arsenic) to the wells. Based on data from the SSW, vulnerability of public-supply wells to natural and anthropogenic contaminants in the area changes through time, including with seasonal changes in pumping stresses that alter the fractions of young and old water being contributed to wells.

New Mexico↗
USGS2021

Using landscape metrics to characterize towns along an urban-rural gradient

Context Urban-rural gradients are useful tools when examining the influence of human disturbances on ecological, social and coupled systems, yet the most commonly used gradient definitions are based on single broad measures such as housing density or percent forest cover that fail to capture landscape patterns important for conservation. Objectives We present an approach to defining urban–rural gradients that integrates multiple landscape pattern metrics related to ecosystem processes important for natural resources and wildlife sustainability. Methods We develop a set of land cover composition and configuration metrics and then use them as inputs to a cluster analysis process that, in addition to grouping towns with similar attributes, identifies exemplar towns for each group. We compare the outcome of the cluster-based urban-rural gradient typology to outcomes for four commonly-used rule-based typologies and discuss implications for resource management and conservation. Results The resulting cluster-based typology defines five town types (urban, suburban, exurban, rural, and agricultural) and notably identifies a bifurcation along the gradient distinguishing among rural forested and agricultural towns. Landscape patterns (e.g., core and islet forests) influence where individual towns fall along the gradient. Designations of town type differ substantially among the five different typologies, particularly along the middle of the gradient. Conclusions Understanding where a town occurs along the urban-rural gradient could aid local decision-makers in prioritizing and balancing between development and conservation scenarios. Variations in outcomes among the different urban-rural gradient typologies raise concerns that broad-measure classifications do not adequately account for important landscape patterns. We suggest future urban-rural gradient studies utilize more robust classification approaches.

Connecticut. Maine, Massachusetts, New Hampshire, ↗
USGS2022

Loss of phylogenetic diversity under landscape change

Habitat alteration and destruction are primary drivers of biodiversity loss. However, the evolutionary dimensions of biodiversity loss remain largely unexplored in many systems. For example, little is known about how habitat alteration/loss can lead to phylogenetic deconstruction of ecological assemblages at the local level. That is, while species loss is evident, are some lineages favored over others? Using a long-term dataset of a globally, ecologically important guild of invertebrate consumers, stream leaf “shredders,” we created a phylogenetic tree of the taxa in the regional species pool, calculated mean phylogenetic distinctiveness for >1000 communities spanning >10 year period, and related species richness, phylogenetic diversity, and distinctiveness to watershed-scale impervious cover. Using a combination of changepoint and compositional analyses, we learned that increasing impervious cover produced marked reductions in all three measures of diversity. These results aid in understanding both phylogenetic diversity and mean assemblage phylogenetic distinctiveness. Our findings indicate that, not only are species lost when there is an increase in watershed urbanization, as other studies have demonstrated, but that those lost are members of more distinct lineages relative to the community as a whole.

Science of the Total Environment↗
USGS2003

Effects of daily precipitation and evapotranspiration patterns on flow and VOC transport to groundwater along a watershed flow path

MTBE and other volatile organic compounds (VOCs) are widely observed in shallow groundwater in the United States, especially in urban areas. Previous studies suggest that the atmosphere and/or nonpoint surficial sources could be responsible for some of those VOCs, especially in areas where there is net recharge to groundwater. However, in semi-arid locations where annual potential evapotranspiration can exceed annual precipitation, VOC detections in groundwater can be frequent. VOC transport to groundwater under net discharge conditions has not previously been examined. A numerical model is used here to demonstrate that daily precipitation and evapotranspiration (ET) patterns can have a significant effect on recharge to groundwater, water table elevations, and VOC transport. Ten-year precipitation/ET scenarios from six sites in the United States are examined using both actual daily observed values and “average” pulsed precipitation. MTBE and tetrachloroethylene transport, including gas-phase diffusion, are considered. The effects of the precipitation/ET scenarios on net recharge and groundwater flow are significant and complicated, especially under low-precipitation conditions when pulsed precipitation can significantly underestimate transport to groundwater. In addition to precipitation and evapotranspiration effects, location of VOC entry into the subsurface within the watershed is important for transport in groundwater. This is caused by groundwater hydraulics at the watershed scale as well as variations in ET within the watershed. The model results indicate that it is important to consider both daily precipitation/ET patterns and location within the watershed in order to interpret VOC occurrence in groundwater, especially in low-precipitation settings.

Environmental Science & Technology↗
USGS2024

Urbanization and water management control stream water quality along a mountain to plains transition

Urbanization can have substantial effects on water quality due to altered hydrology and introduction of constituents to water bodies. In arid and semi-arid environments, streams are further stressed by dewatering as a result of diversions. We conducted a high-resolution synoptic survey of two streams in Colorado, USA that transition abruptly from granitic/metamorphic forested mountains to sedimentary urbanized plains and are both highly managed for water supply, yet differ in degree of urbanization. A synoptic mass balance approach developed for mine drainage applications was adapted to elucidate effects of urbanization, geology, and diversions on stream chemistry during baseflow conditions. Urbanization was a more important driver of stream concentrations than geology. The urban area was a strong source of bromide, calcium, chloride, and manganese, while lanthanum and dissolved organic carbon were primarily sourced from the mountains. A majority of streamflow was removed by diversions near the mountains/plains interface. Groundwater accounted for 31% of the subsequent flow increase to the urbanized stream, and delivered at least 33% of chloride loading. Constituents that were primarily urban-derived (bromide, calcium, chloride, and manganese) were 2–3 times higher in the urban region due to diversions; without diversions, stream water quality would have largely retained characteristics of forested streams through the urban reach. This study provides insights into processes that affect water quality in highly managed streams of the semi-arid western USA.

Colorado↗
USGS2016

Life history of the vulnerable endemic crayfish Cambarus (Erebicambarus) maculatus Hobbs and Pflieger, 1988 (Decapoda: Astacoidea: Cambaridae) in Missouri, USA

The vulnerable freckled crayfish, Cambarus maculatus Hobbs and Pflieger, 1988, is endemic to only one drainage in eastern Missouri, USA, which is impacted by heavy metals mining and adjacent to a rapidly-expanding urban area. We studied populations of C. maculatus in two small streams for 25 months to describe annual reproductive cycles, and gather information about fecundity, sex ratio, size at maturity, size-class structure, and growth, capturing a monthly average of more than 50 individuals from each of the two study populations. Information about the density of the species at supplemental sampling streams was also obtained. The species exhibited traits consistent with a K-strategist life history; long-lived, slow-growing, with fewer but larger eggs than sympatric crayfish species. Breeding season occurred in mid- to late autumn, potentially extending into early winter. Egg brooding occurred primarily in May. Young of year were first observed in June. We estimated that these populations contained four to six size-classes, observed smaller individuals grew faster than larger individuals, and most became sexually mature in their second year of life. Densities of C. maculatus were low relative to several sympatric species of Orconectes Cope, 1872. Life history information presented herein will be important for anticipated future conservation efforts.

Missouri↗
USGS1987

Surface- and ground-water quality data at selected landfill sites in Mecklenburg County, North Carolina, 1980-86

The U.S. Geological Survey initiated an urban water quality study in 1979 in cooperation with the City of Charlotte and Mecklenburg County, North Carolina, to study, among other things, the effects of solid waste disposal on the water quality in Mecklenburg County. Water quality samples (747 inorganic and 168 organic) were collected at 20 surface water sites and 53 monitoring wells at four selected landfills from 1980 to 1986. Samples were analyzed for 142 selected physical and biological parameters, major ions, nutrients, trace metals, and (or) organic compounds. Results from all analyses are presented in tabular form in the appendices. Each appendix is divided into a surface water and a groundwater section. Within each water quality table the data is presented in the following order: field measurements, physical properties, biological constituents (if analyzed), major cations, major anions, dissolved and total solids, nutrients, trace inorganic constituents, and organic constituents.

North Carolina↗
USGS2015

Trace-metal and organic constituent concentrations in bed sediment at Big Base and Little Base Lakes, Little Rock Air Force Base, Arkansas—Comparisons to sediment-quality guidelines and indications for timing of exposure

This report compares concentrations for a wide range of inorganic and organic constituents in bed sediment from Big Base Lake and Little Base Lake, which are located on Little Rock Air Force Base, Arkansas, to sediment-quality guidelines. This report also compares trace-metal concentrations in a bed-sediment core sample to sediment age to determine when the highest concentrations of trace metals were deposited in Big Base Lake. Trace-metal results often were higher than background concentrations in the surrounding Pulaski County area, and concentrations of arsenic, cadmium, cobalt, copper, lead, manganese, mercury, nickel, and zinc at one or more of three study sites were higher than median concentrations for a study involving 98 urban streams in seven metropolitan areas of the United States. Concentrations for most polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine pesticides in all three bed-sediment samples were less than the laboratory reporting limit or were detected at low concentrations. Some contaminants were detected at concentrations that are potentially toxic to sediment-dwelling biota; however, in general, the analyses suggest that the risk of sediment toxicity may be relatively low. Threshold effect concentrations were exceeded for 14 constituents—arsenic, copper, lead, nickel, and zinc, five polycyclic aromatic hydrocarbons compounds, chlordane, and all three dichlorodiphenyltrichloroethane (DDT) congeners—which suggests potential toxicity to some sediment-dwelling biota. Only two constituents had concentrations that exceeded published probable effect concentrations—arsenic (at the deepest site in Big Base Lake, NS6) and p,p’-dichlorodiphenyldichloroethylene (p,p’-DDE; at both sites in Big Base Lake, NS5 and NS6). Regarding highest concentrations and associated timing of exposure, trace metals analyzed in the sediment core seem to indicate three fairly distinct exposure patterns. For 11 trace metals that had the highest concentration measured in the shallowest and most recently deposited sediment, the most likely explanation is recent exposure by anthropogenic activities. Most of the 11 trace metals with highest concentrations in shallow sediment are relatively innocuous; however, arsenic, copper, selenium, and zinc are among the U.S. Environmental Protection Agency’s 126 priority pollutants. For three trace metals (cadmium, lead, and mercury), for which concentrations were highest in sediments that were 16–20 centimeters down the core, it is likely that a source associated with those contaminants during the period when those sediments were deposited, was reduced or eliminated. The eight remaining trace metals, for which concentrations were highest in sediments that were just below the prereservoir surface, likely had sources that were eliminated soon after lake construction or occurred at relatively high background concentrations in soils in the area around Little Rock Air Force Base.

Arkansas↗
USGS2019

Life history of the endemic saddleback crayfish, Faxonius medius (Faxon, 1884), (Decapoda: Cambaridae) in Missouri, USA

The saddleback crayfish, Faxonius medius (Faxon, 1884), is endemic to a single drainage in eastern Missouri, USA, that is affected by heavy metals mining, and adjacent to a rapidly-expanding urban area. We studied populations of F. medius in two small streams for 18 months to describe the annual reproductive cycle and gather information about fecundity, sex ratio, size at maturity, and size-class structure. We also obtained information about the species’ density at supplemental sites. The species, though rare in a geographic context, is locally abundant; we captured a monthly average of more than 75 F. medius from each of the two study populations. Densities of F. medius were high relative to several sympatric species of Faxonius Cope, 1872 and Cambarus Erichson, 1846. The species exhibited traits of an r-strategist life history; it was relatively short-lived and early to maturity. Its fecundity and egg size were comparable to Ozark congeners. Breeding season occurred in autumn, perhaps extending into early winter. Egg brooding occurred primarily in April. Young of year first appeared in samples in June. We estimated that these populations contained 2 to 3 size-classes, and most individuals became sexually mature in their first year of life. Life history information presented herein will be important for future conservation efforts.

Missouri↗
USGS2012

Contaminants in stream sediments from seven United States metropolitan areas: part I: distribution in relation to urbanization

Organic contaminants and trace elements were measured in bed sediments collected from streams in seven metropolitan study areas across the United States to assess concentrations in relation to urbanization. Polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine pesticides, the pyrethroid insecticide bifenthrin, and several trace elements were significantly related to urbanization across study areas. Most contaminants (except bifenthrin, chromium, nickel) were significantly related to the total organic carbon (TOC) content of the sediments. Regression models explained 45–80 % of the variability in individual contaminant concentrations using degree of urbanization, sediment-TOC, and study-area indicator variables (which represent the combined influence of unknown factors, such as chemical use or release, that are not captured by available explanatory variables). The significance of one or more study-area indicator variables in all models indicates marked differences in contaminant levels among some study areas, even after accounting for the nationally modeled effects of urbanization and sediment-TOC. Mean probable effect concentration quotients (PECQs) were significantly related to urbanization. Trace elements were the major contributors to mean PECQs at undeveloped sites, whereas organic contaminants, especially bifenthrin, were the major contributors at highly urban sites. Pyrethroids, where detected, accounted for the largest share of the mean PECQ. Part 2 of this series (Kemble et al. 2012) evaluates sediment toxicity to amphipods and midge in relation to sediment chemistry.

Archives of Environmental Contamination and Toxico↗
USGS2021

Drivers of extreme water levels in a large, urban, high-energy coastal estuary – A case study of the San Francisco Bay

Reliable and long-term hindcast data of water levels are essential in quantifying return period and values of extreme water levels. In order to inform design decisions on a local flood control district level, process-based numerical modeling has proven an essential tool to provide the needed temporal and spatial coverage for different extreme value analysis methods. To determine the importance of different physical processes to the extreme water levels we developed a process-based numerical model (Delft3D Flexible Mesh) and applied it to simulate a large, urban, high-energy coastal estuary (the San Francisco Bay). The unstructured grid with 1D/2DH model elements, allows for efficient model simulations and therefore it was possible to simulate over 70 years between 1950 and 2019. Results show significant skill in reproducing observations for the entire modeled time period with an average root-mean-square error of 8.0 cm. A process-based modeling approach allows for the explicit in- and exclusion of different physical processes to quantify their importance to the extremes. For the 100-year still water level (SWL), tide (70%) and non-tidal residual (NTR) (25%) explain the majority of the simulated high water levels in the Bay relative to Mean Higher High Water (MHHW). However, closer to the Delta, local fluvial inflow increases in importance. For longer return periods, the importance of tide decreases and the importance of remote NTRs and fluvial inflow increases.

California↗
USGS2013

Assessment of macroinvertebrate communities in adjacent urban stream basins, Kansas City, Missouri, metropolitan area, 2007 through 2011

Macroinvertebrates were collected as part of two separate urban water-quality studies from adjacent basins, the Blue River Basin (Kansas City, Missouri), the Little Blue River and Rock Creek Basins (Independence, Missouri), and their tributaries. Consistent collection and processing procedures between the studies allowed for statistical comparisons. Seven Blue River Basin sites, nine Little Blue River Basin sites, including Rock Creek, and two rural sites representative of Missouri ecological drainage units and the area’s ecoregions were used in the analysis. Different factors or levels of urban intensity may affect the basins and macroinvertebrate community metrics differently, even though both basins are substantially developed above their downstream streamgages (Blue River, 65 percent; Little Blue River, 52 percent). The Blue River has no flood control reservoirs and receives wastewater effluent and stormflow from a combined sewer system. The Little Blue River has flood control reservoirs, receives no wastewater effluent, and has a separate stormwater sewer system. Analysis of macroinvertebrate community structure with pollution-tolerance metrics and water-quality parameters indicated differences between the Blue River Basin and the Little Blue River Basin. A four-metric score (total taxa richness, Ephemeroptera plus Plecoptera plus Trichoptera taxa richness, Macroinvertebrate Biotic Index, and Shannon Diversity Index) for richest-targeted habitat was used to calculate a Stream Condition Index (SCI) in order to evaluate the aquatic-life status of the streams. About 80 percent of all samples combined were determined to be less than fully biologically supporting, and about 11 percent of spring samples were fully biologically supporting. No sites within the Blue River Basin had a fully supporting score. The aquatic-life status scores for the Little Blue River and its tributaries were higher (indicating more optimal conditions) than for the Blue River and its tributaries. Fall samples scored higher than spring samples. However, fall samples were collected at the Little Blue River Basin and rural sites only. The Little Blue River sites scored higher for fall samples than spring samples; about 39 percent fully biologically supporting and 61 percent partially biologically supporting; more similar to the rural comparison sites, 40 percent fully biologically supporting and 60 percent partially biologically supporting. The SCI was compared to other multimetric indices with more or other component metrics to determine if the SCI effectively described differences among sites. Environmental variables (streamflow, water quality, land use, impervious cover, and population density) were used in statistical analyses to evaluate relations to macroinvertebrate metrics. Multimetric indices (MMIs) were modeled using step regression with a simple urban intensity index (SUII) based on percentage of impervious cover, population density, and forest cover in a 30-meter stream-buffer zone, and two were selected for further analysis. Three other multimetric indices composed of metrics common to local and national studies show results similar to the two modeled MMIs. A common Benthic Index of Biotic Integrity (R 2 equals 0.71) developed for a national study had the highest correlation with urban intensity as measured with the SUII, followed by a modeled 6-metric index (R 2 equals 0.61). The other MMIs and the SCI explained less than a half of the variability in macroinvertebrate communities in relation to the SUII. Wastewater-treatment plant discharges during base flow, which elevated specific conductance and nutrient concentrations, combined sewer overflows, and nonpoint sources likely contributed to water-quality impairment and lower aquatic-life status at the Blue River Basin sites. Releases from upstream reservoirs to the Little Blue River likely decreased specific conductance, suspended-sediment, and dissolved constituent concentrations and may have benefitted water quality and aquatic life of main-stem sites. Chloride concentrations in base-flow samples, attributable to winter road salt application, had the highest correlation with the SUII (Spearman’s ρ equals 0.87), were negatively correlated with the SCI (Spearman’s ρ equals -0.53) and several pollution sensitive Ephemeroptera plus Plecoptera plus Trichoptera abundance and percent richness metrics, and were positively correlated with pollution tolerant Oligochaeta abundance and percent richness metrics. Study results show that the easily calculated SUII and the selected modeled multimetric indices are effective for comparing urban basins and for evaluation of water quality in the Kansas City metropolitan area.

Missouri↗
USGS2006

Factors affecting occurrence and distribution of selected contaminants in ground water from selected areas in the Piedmont Aquifer System, Eastern United States, 1993-2003

Results of ground-water sampling from 255 wells and 19 springs in 11 studies done by the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program within the Piedmont Aquifer System (PAS) were analyzed to determine the factors affecting occurrence and distribution of selected contaminants. The contaminants, which were selected on the basis of potential human-health effects, included nitrate, pesticides, volatile organic compounds (VOCs), and radon. The PAS was subdivided on the basis of the general rock type of the aquifers into three areas for the study—crystalline, carbonate, and siliciclastic. The 11 studies were designed to areally represent an individual aquifer rock type and overall are representative of the PAS in their distribution; 7 studies are in the crystalline-rock aquifers, 3 studies are in the siliciclasticrock aquifers, and 1 study is in the carbonate-rock aquifers. Four of the studies were focused on land use, 1 in an agricultural area and 3 in urban areas. The remaining studies had wells representing a range of land-use types. Analysis of results of nitrate sampling indicated that in 8 of the 10 areas where nitrate concentrations were measured, median concentrations of nitrate were below 3 mg/L (milligrams per liter); 2 of the 10 areas had statistically significant higher median concentrations when compared to the other 8 areas. The agricultural land-use study in the carbonate-rock aquifer in the Lower Susquehanna River Basin had the highest median nitrate concentration (11 mg/L), and 60 percent of the wells sampled exceeded the U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Level (MCL) of 10 mg/L. The major aquifer study in the crystalline-rock aquifer of the Lower Susquehanna River Basin Study Unit had the second-highest median nitrate concentration. Nitrate concentrations were positively correlated to the percentage of agricultural land use around the well, the total input of nitrogen from all sources, dissolved oxygen concentration, lithology, depth to water, and soil-matrix characteristics. A linear regression model was used to determine that increases in the percentage of agricultural land use, the input of nitrogen from all sources, and dissolved oxygen were the most significant variables affecting increased concentration of nitrate. A logistic regression model was used to determine that those same factors were the most significant variables affecting whether or not the nitrate concentration would exceed 4 mg/L. Of the analysis of samples from 253 wells and 19 springs for 47 pesticides, no sample had a pesticide concentration that exceeded any USEPA MCL. The most frequently detected pesticide was desethyl atrazine, a degradation product of atrazine; the detection frequency was 47 percent. Other frequently detected pesticides included atrazine, metolachlor, simazine, alachlor, prometon, and dieldrin. Detection frequency was affected by the analytical reporting limits; the frequency of detection was somewhat lower when all pesticides were censored to the highest common detection limit. Source factors such as agricultural land use (for agricultural herbicides), urban land use (for insecticides), and the application rate were found to have positive statistical correlations with pesticide concentration. Transport factors such as depth to water and percentage of well-drained soils, sand, or silt typically were positively correlated with higher pesticide concentrations. Sampling for VOCs was conducted in 187 wells and 19 springs that were sampled for 59 VOCs. There were 137 detections of VOCs above the common censoring limit of 0.2 µg/L. The most frequently detected VOCs were chloroform, a trihalomethane, and methyl-tert butyl ether (MTBE), a fuel oxygenate. Seventy-nine wells had at least one VOC detected. The detections were related to land use and well depth. Kendall’s tau correlations indicated a significant positive correlation between chloroform concentration and urban land use, leaking underground storage tanks, population density, and well depth. MTBE concentrations also were positively correlated to urban land use, leaking underground storage tanks, population density, and well depth. Radon was sampled at 205 sites. The subdivisions used for analysis of other contaminants were not adequate for analysis of radon because radon varies on the basis of variations in mineralogy that are not reflected by the general lithologic categories used for the rest of the studies. Concentrations of radon were highest in areas where the crystalline-rock aquifers had felsic mineralogy, and the lowest concentrations of radon were in areas where the crystalline-rocks aquifer had mafic mineralogy. Water from wells in siliciclastic-rock aquifers had concentrations of radon lower than that in the felsic crystalline-rock aquifers. More than 90 percent of the wells sampled for radon exceeded the proposed MCL of 300 pCi/L (picoCuries per liter); however, only 13 percent of those wells had concentrations in water that exceeded the alternative maximum contaminant level (AMCL), a higher level that can be used by municipalities addressing other sources of radon exposure. Overall, concentrations of constituents were related to land-use factors for nitrate, pesticides, VOCs, and to aquifer lithology for radon. None of the 47 pesticides or 59 VOCs analyzed exceeded the MCLs where those constituents were sampled. Concentrations exceeded the MCL for nitrate in 11 percent of the wells sampled. Nearly 91 percent of the wells sampled exceeded the proposed MCL for radon. Additional sampling in selected areas would improve overall understanding of the PAS and increase the possibility of creating predictive models of ground-water quality in this area.

Alabama, Delaware, Georgia, Maryland, New Jersey, ↗
USGS2008

Effects of urbanization on stream ecosystems in the Willamette River basin and surrounding area, Oregon and Washington

This report describes the effects of urbanization on physical, chemical, and biological characteristics of stream ecosystems in 28 watersheds along a gradient of urbanization in the Willamette River basin and surrounding area, Oregon and Washington, from 2003 through 2005. The study that generated the report is one of several urban-effects studies completed nationally by the U.S. Geological Survey National Water-Quality Assessment Program. Watersheds were selected to minimize natural variability caused by factors such as geology, elevation, and climate, and to maximize coverage of different stages of urban development among watersheds. Because land use or population density alone often are not a complete measure of urbanization, a combination of land use, land cover, infrastructure, and socioeconomic variables were integrated into a multimetric urban intensity index (UII) to represent the degree of urban development in each watershed. Physical characteristics studied include stream hydrology, stream temperature, and habitat; chemical characteristics studied include sulfate, chloride, nutrients, pesticides, dissolved and particulate organic and inorganic carbon, and suspended sediment; and biological characteristics studied include algal, macroinvertebrate, and fish assemblages. Semipermeable membrane devices, passive samplers that concentrate trace levels of hydrophobic organic contaminants such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls, also were used. The objectives of the study were to (1) examine physical, chemical, and biological responses along the gradient of urbanization and (2) determine the major physical, chemical, and landscape variables affecting the structure of aquatic communities. Common effects documented in the literature of urbanization on instream physical, chemical, and biological characteristics, such as increased contaminants, increased streamflow flashiness, increased concentrations of chemicals, and changes in aquatic community structure toward a more tolerant community associated with organically enriched conditions, generally were observed in this study. The strongest correlations to the UII and to many of the algal, macroinvertebrate, and fish assemblage metrics and community ordination involved water-chemistry metrics including the total pesticide concentration, toxic equivalents (extract assay from semipermeable membrane devices), and dissolved oxygen. Hydrologic variability metrics, such as flashiness, that normally are considered to be one of the main processes of urban disturbance had a strong association to the algal and fish assemblages in this study; however, the hydrologic variables for macroinvertebrates were secondary to the water-chemistry metrics mentioned above. Generally, the high urban intensity sites had high abundances of eutrophic and lower dissolved oxygen-indicating diatoms, high abundances of noninsects and tolerant insects, and high abundances of nonnative fish species. On the other hand, the low urban intensity sites had higher abundances of pollution sensitive diatoms, larger numbers of the sensitive macroinvertebrate EPT taxa (Ephemeroptera, Plecoptera and Trichoptera Orders), and fish assemblages with higher abundances of sensitive salmonids. The percent salmonid and macroinvertebrate EPT richness metrics plotted against the UII indicated a possible threshold response at about 25 on the UII, which is equivalent to an impervious surface value of about 5 percent. However, due to the added agricultural land use at sites within the 25 to 60 UII range, this possible threshold probably is not solely due to urbanization, but a combination of urban and agricultural land use. The effects of agricultural and urban land use could not be distinguished from each other, yet combined they provide a good assessment of overall watershed disturbance.

Oregon, Washington↗
USGS1996

Pesticides in streams draining agricultural and urban areas in Colorado

A study was conducted from April 1993 through April 1994 to describe and compare the occurrence and distribution of pesticides in streams in a small agricultural and a small urban area in Colorado. Twenty-five water samples collected at least monthly at the mouths of two tributary streams of the South Plate River were analyzed for 47 pesticides. The results indicate that both agricultural and urban areas are probable sources for pesticides in streams. In the agricultural area, 30 pesticides were detected, and in the urban area, 22 pesticides were detected in one or more samples. Most often, the more frequently detected pesticides in both areas also were some of the more commonly used pesticides. In both areas, pesticide concentrations were higher during the summer (application period) with maximum concentrations generally occurring in storm runoff. The year-round detection of some pesticides in both areas at consistently low concentrations, regardless of season or streamflow volume, could indicate that these compounds persist in the shallow alluvial aquifer year-round.

Environmental Science & Technology↗
USGS2010

Judging a brook by its cover: The relation between ecological condition of a stream and urban land cover in new England

The US Geological Survey conducted an urban land-use study in the New England Coastal Basins (NECB) area during 2001 to determine how urbanization relates to changes in the ecological condition of streams. Thirty sites were selected that differed in their level of watershed development (low to high). An urban intensity value was calculated for each site from 24 landscape variables. Together, these 30 values reppresented a gradient of urban intensity. Among various biological, chemical, and physical factors surveyed at each site, benthic invertebrate assemblages were sampled from stream riffles and also from multiple habitats along the length of the sampling reach. We use some of the NECB data to derive a four-variable urbanintensity index (NECB-UII), where each variable represents a distinct component of urbanization: increasing human presence, expanding infrastructure, landscape development, and riparian vegetation loss. Using the NECB-UII as a characterization of urbanization, we describe how landscape fragmentation occurs with urbanization and how changes in the invertebrate assemblages, represented by metrics of ecological condition, are related to urbanization. Metrics with a strong linear response included EPT taxa richness, percentage richness of non-insect taxa, and pollution-tolerance values. Additionally, we describe how these relations can help in estimating the expected condition of a stream for its level of urbanization, thereby establishing a baseline for evaluating possible affects from specific point-source stressors.

Northeastern Naturalist↗
USGS1995

Flood-frequency relations for urban streams in Georgia; 1994 update

A statewide study of flood magnitude and frequency in urban areas of Georgia was made to develop methods of estimating flood characteristics at ungaged urban sites. A knowledge of the magnitude and frequency of floods is needed for the design of highway drainage structures, establishing flood- insurance rates, and other uses by urban planners and engineers. A U.S. Geological Survey rainfall-runoff model was calibrated for 65 urban drainage basins ranging in size from 0.04 to 19.1 square miles in 10 urban areas of Georgia. Rainfall-runoff data were collected for a period of 5 to 7 years at each station beginning in 1973 in Metropolitan Atlanta and ending in 1993 in Thomasville, Ga. Calibrated models were used to synthesize long-term annual flood peak discharges for these basins from existing Long-term rainfall records. The 2- to 500-year flood-frequency estimates were developed for each basin by fitting a Pearson Type III frequency distribution curve to the logarithms of these annual peak discharges. Multiple-regression analyses were used to define relations between the station flood-frequency data and several physical basin characteristics, of which drainage area and total impervious area were the most statistically significant. Using theseregression equations and basin characteristics, the magnitude and frequency of floods at ungaged urban basins can be estimated throughout Georgia.

Georgia↗