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At least 1,243 records · Page 69Linked to original sources

USGS2002

Tracing sources of sulfur in the Florida Everglades

We examined concentrations and sulfur isotopic ratios ( 34 S/ 32 S, expressed as δ 34 S in parts per thousand [‰] units) of sulfate in surface water, ground water, and rain water from sites throughout the northern Everglades to establish the sources of sulfur to the ecosystem. The geochemistry of sulfur is of particular interest in the Everglades because of its link, through processes mediated by sulfate-reducing bacteria, to the production of toxic methylmercury in this wetland ecosystem. Methylmercury, a neurotoxin that is bioaccumulated, has been found in high concentrations in freshwater fish from the Everglades, and poses a potential threat to fish-eating wildlife and to human health through fish consumption. Results show that surface water in large portions of the Everglades is heavily contaminated with sulfate, with the highest concentrations observed in canals and marsh areas receiving canal discharge. Spatial patterns in the range of concentrations and δ 34 S values of sulfate in surface water indicate that the major source of sulfate in sulfur-contaminated marshes is water from canals draining the Everglades Agricultural Area. Shallow ground water underlying the Everglades and rain water samples had much lower sulfate concentrations and δ 34 S values distinct from those found in surface water. The δ 34 S results implicate agricultural fertilizer as a major contributor to the sulfate contaminating the Everglades, but ground water under the Everglades Agricultural Area (EAA) may also be a contributing source. The contamination of the northern Everglades with sulfate from canal discharge may be a key factor in controlling the distribution and extent of methylmercury production in the Everglades.

Florida↗

USGS2008

Simulated fate and transport of metolachlor in the unsaturated zone, Maryland, USA

An unsaturated-zone transport model was used to examine the transport and fate of metolachlor applied to an agricultural site in Maryland, USA. The study site was instrumented to collect data on soil-water content, soil-water potential, ground water levels, major ions, pesticides, and nutrients from the unsaturated zone during 2002-2004. The data set was enhanced with site-specific information describing weather, soils, and agricultural practices. The Root Zone Water Quality Model was used to simulate physical, chemical, and biological processes occurring in the unsaturated zone. Model calibration to bromide tracer concentrations indicated flow occurred through the soil matix. Simulated recharge rates were within the measured range of values. The pesticide transport model was calibrated to the intensive data collection period (2002-2004), and the calibrated model was then used to simulate the period 1984 through 2004 to examine the impact of sustained agricultural management practices on the concentrations of metolachlor and its degradates at the study site. Simulation results indicated that metolachlor degrades rapidly in the root zone but that the degradates are transported to depth in measurable quantities. Simulations indicated that degradate transport is strongly related to the duration of sustained use of metolachlor and the extent of biodegradation.

Maryland↗

USGS2008

Decadal-scale changes of pesticides in ground water of the United States, 1993-2003

Pesticide data for ground water sampled across the United States between 1993-1995 and 2001-2003 by the U.S. Geological Survey National Water-Quality Assessment Program were evaluated for trends in detection frequency and concentration. The data analysis evaluated samples collected from a total of 362 wells located in 12 local well networks characterizing shallow ground water in agricultural areas and six local well networks characterizing the drinking water resource in areas of variable land use. Each well network was sampled once during 1993-1995 and once during 2001-2003. The networks provide an overview of conditions across a wide range of hydrogeologic settings and in major agricultural areas that vary in dominant crop type and pesticide use. Of about 80 pesticide compounds analyzed, only six compounds were detected in ground water from at least 10 wells during both sampling events. These compounds were the triazine herbicides atrazine, simazine, and prometon; the acetanilide herbicide metolachlor; the urea herbicide tebuthiuron; and an atrazine degradate, deethylatrazine (DEA). Observed concentrations of these compounds generally were <0.12 ??g L-1. At individual wells, changes in concentrations typically were <0.02 ??g L-1. Data analysis incorporated adjustments for changes in laboratory recovery as assessed through laboratory spikes. In wells yielding detectable concentrations of atrazine, DEA, and prometon, concentrations were significantly lower (?? = 0.1) in 2001-2003 than in 1993-1995, whereas detection frequency of these compounds did not change significantly. Trends in atrazine concentrations at shallow wells in agricultural areas were found to be consistent overall with recent atrazine use data. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Conference Paper↗

USGS2008

Near-decadal changes in nitrate and pesticide concentrations in the South Platte River alluvial aquifer, 1993-2004

The lower South Platte River basin of Colorado and Nebraska is an area of intense agriculture supported by surface-water diversions from the river and ground-water pumping from a valley-fill alluvial aquifer. Two well networks consisting of 45 wells installed in the South Platte alluvial aquifer were sampled in the early 1990s and again in the early 2000s to examine near-decadal ground-water quality changes in irrigated agricultural areas. Ground-water age generally increases and dissolved-oxygen content decreases with distance along flow paths and with depdi below the water table, and denitrification is an important natural mitigation mechanism for nitrate in downgradient areas. Ground-water travel time from upland areas to the river ranges from 12 to 31 yr on the basis of apparent ground-water ages. Ground-water nitrate concentrations for agricultural land-use wells increased significantly for oxidized samples over the decade, and nitrogen isotope ratios for oxidized samples indicate synthetic fertilizer as the predominant nitrate source. Ground-water concentrations of atrazine, DEA, and prometon decreased significandy. The decrease in pesticide concentrations and a significant increase in the ratio of DEA to atrazine suggest decreases in pesticide concentrations are likely caused by local decreases in application rates and/or degradation processes and that atrazine degradation is promoted by oxidizing conditions. The difference between results for oxidizing and nitrate-reducing conditions indicates redox state is an important variable to consider when evaluating ground-water quality trends for redox-sensitive constituents such as nitrate and pesticides in the South Platte alluvial aquifer. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Journal of Environmental Quality↗

USGS2010

Trends and transformation of nutrients and pesticides in a Coastal Plain aquifer system, United States

Four local-scale sites in areas with similar corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] agriculture were studied to determine the effects of different hydrogeologic settings of the Northern Atlantic Coastal Plain (NACP) on the transport of nutrients and pesticides in groundwater. Settings ranged from predominantly well-drained soils overlying thick, sandy surficial aquifers to predominantly poorly drained soils with complex aquifer stratigraphy and high organic matter content. Apparent age of groundwater, dissolved gases, N isotopes, major ions, selected pesticides and degradates, and geochemical environments in groundwater were studied. Agricultural chemicals were the source of most dissolved ions in groundwater. Specific conductance was strongly correlated with reconstructed nitrate (the sum of N in nitrate and N gas) (R 2 = 0.81, p < 0.0001), and is indicative of the relative degree of agricultural effects on groundwater. Trends in nitrate were primarily related to changes in manure and fertilizer use at the well-drained sites where aquifer conditions were consistently oxic. Nitrate was present in young groundwater but completely removed over time through denitrification at the poorly drained sites where there were variations in chemical input and in geochemical environment. Median concentrations of atrazine (6-chloro-N-ethyl-N'-(1- methylethyl)-1,3,5-triazine-2,4-diamine), metolachlor (2-chloro-N-(2-ethyl-6- methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide), and some of their common degradates were higher at well-drained sites than at poorly drained sites, with concentrations of degradates generally higher than those of the parent compounds at all sites. An increase in the percentage of deethylatrazine to total atrazine over time at one well-drained site may be related to changes in manure application. Copyright ?? 2010 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Journal of Environmental Quality↗

USGS2015

NLEAP/GIS approach for identifying and mitigating regional nitrate-nitrogen leaching

Improved simulation-based methodology is needed to help identify broad geographical areas where potential NO 3 -N leaching may be occurring from agriculture and suggest management alternatives that minimize the problem. The Nitrate Leaching and Economic Analysis Package (NLEAP) model was applied to estimate regional NO 3 -N leaching in eastern Colorado. Results show that a combined NLEAP/GIS technology can be used to identify potential NO 3 -N hot spots in shallow alluvial aquifers under irrigated agriculture. The NLEAP NO 3 -N Leached (NL) index provided the most promising single index followed by NO 3 -N Available for Leaching (NAL). The same combined technology also shows promise in identifying Best Management Practice (BMP) methods that help minimize NO 3 -N leaching in vulnerable areas. Future plans call for linkage of the NLEAP/GIS procedures with groundwater modeling to establish a mechanistic analysis of agriculture-aquifer interactions at a regional scale.

Book chapter↗

USGS2014

Northern Pintail

This medium-sized dabbling duck of slender, elegant lines and conservative plumage coloration is circumpolar in distribution and abundant in North America, with core nesting habitat in Alaska and the Prairie Pothole Region of southern Canada and the northern Great Plains. Breeders favor shallow wetlands interspersed throughout prairie grasslands or arctic tundra. An early fall migrant, the species arrives on wintering areas beginning in August, after wing molt, often forming large roosting and feeding flocks on open, shallow wetlands and flooded agricultural fields. The birds consume grains, marsh plant seeds, and aquatic invertebrates throughout fall and winter. Northern Pintails are among the earliest nesting ducks in North America, beginning shortly after ice-out in many northern areas. Individuals form new pair bonds each winter but are highly promiscuous during the nesting season, with mated and unmated males often involved in vigorous, acrobatic Pursuit Flights. Annual nest success and productivity vary with water conditions, predation, and weather. Females build nests on the ground, often far from water. Only the female incubates; her mate leaves shortly after incubation begins. Ducklings hatch together in one day, follow the female to water after a day in the nest, and fledge by July or August. Adults and ducklings consume mainly aquatic invertebrates during the breeding season. Predators and farming operations destroy many thousands of Northern Pintail nests annually; farming has also greatly reduced the amount of quality nesting cover available. Winter habitats are threatened by water shortages, agricultural development, contamination, and urbanization. Periods of extended drought in prairie nesting regions have caused dramatic population declines, usually followed by periods of recovery. Over the long term, however, the continental population of Northern Pintails has declined significantly from 6 million birds in the early 1970s to less than 3 million in the late 1980s and early 1990s. Since then, the population appears to have stabilized; in 2013, the estimate was 3.3 million birds, a large number but below conservation goals despite favorable wetland conditions in much of the prairie breeding region. Ongoing conservation measures, however, such as habitat restoration and enhancement of agricultural lands, as well as prudent harvest management, suggest that Northern Pintails should have a secure future in North America.

The Birds of North America↗

USGS2006

The role of the Wetland Reserve Program in conservation efforts in the Mississippi River Alluvial Valley

The Mississippi River Alluvial Valley includes the floodplain of the Mississippi River from Cairo, Illinois, USA, to the Gulf of Mexico. Originally this region supported about 10 million ha of bottomland hardwood forests, but only about 2.8 million ha remain today. Furthermore, most of the remaining bottomland forest is highly fragmented with altered hydrologic processes. During the 1990s landscape-scale conservation planning efforts were initiated for migratory birds and the threatened Louisiana black bear ( Ursus americanus luteolus ). These plans call for large-scale reforestation and restoration efforts in the region, particularly on private lands. In 1990 the Food, Agriculture, Conservation and Trade Act authorized the Wetlands Reserve Program (WRP). The WRP is a voluntary program administered by the United States Department of Agriculture that provides eligible landowners with financial incentives to restore wetlands and retire marginal farmlands from agricultural production. As of 30 September 2005, over 275,700 ha have been enrolled in the program in the Mississippi River Alluvial Valley, with the greatest concentration in Louisiana, Arkansas, and Mississippi, USA. Hydrologic restoration is common on most sites, with open-water wetlands, such as moist-soil units and sloughs, constituting up to 30% of a given tract. Over 33,200 ha of open-water wetlands have been created, potentially providing over 115,000,000 duck-use days. Twenty-three of 87 forest-bird conservation areas have met or exceed core habitat goals for migratory songbirds and another 24 have met minimum area requirements. The WRP played an integral role in the fulfillment of these goals. Although some landscape goals have been attained, the young age of the program and forest stands, and the lack of monitoring, has limited evaluations of the program's impact on wildlife populations.

Mississippi River Alluvial Valley↗

USGS1974

Upland duck nesting related to land use and predator reduction

Duck nesting was studied during 1971 in north-central South Dakota under four conditions: in idle, five or six year old fields of domestic grass-legume mixtures in an area where predators including the red fox ( Vulpes fulva ), raccoon ( Procyon lotor ), striped skunk ( Mephitis mephitis ), and badger ( Taxidea taxus ) were (1) reduced and (2) not reduced. Nesting was also studied in tracts of active agricultural land (primarily croplands and pastures) where predators were (3) reduced, and (4) not reduced. Under condition (1), 260 nests were found on 0.87 km 2 (299 nests/km 2 ), eggs hatched in 92 percent of the nests and production was 22.0 ducklings/hectare. Under condition (2), 187 nests were found on 2.22 km 2 (84 nests/km 2 ), nest success was 68 percent and 4.7 ducklings/hectare were produced. On active agricultural land subject to predator reduction (condition 3), 64 nests were found on 5.14 km 2 (12 nests/km 2 ). Eggs in 85 percent of the nests hatched and production was 0.7 duckling/hectare. On active agricultural land not subject to predator reduction (condition 4), 58 nests were found on 4.01 km 2 (14 nests/km 2 ), nest success was 51 percent and 0.5 duckling/hectare was produced. Idle, 16 to 65-hectare (40 to 160-acre) stands of cool-season, introduced grasses in combination with legumes produced maximum numbers of upland nesting ducks.

South Dakota↗

USGS1995

Spring-staging ecology of midcontinent greater white-fronted geese

A major part of the midcontinent greater white-fronted goose ( Anser albifrons ) population stages for several weeks in spring in the Rainwater Basin Area (RBA) of south-central Nebraska where substantial mortality from disease occurs periodically. Effective management of this population requires better data on use of habitat, vulnerability to disease, and the role of staging areas in migration and reproduction. We studied use of habitat, foods, nutrient dynamics, and effect of changes in agriculture on food availability and habitat needs in spring 1979-80. During daylight, geese were observed primarily in harvested cornfields (76%) and growing winter wheat (23%). Corn grain and winter wheat shoots composed 90 and 9%, respectively, of foods consumed by collected geese ( n = 42). Feeding activity did not vary among post-harvest cornfield treatments except that little feeding occurred ( P < 0.05) in moldboard-plowed fields (<1%). Fat content for all geese increased ( P ≤ 0.01) with Julian date; protein content increased ( P = 0.03) only among adult females, and there was no evidence ( P > 0.05) of temporal variation in calcium content. Adult geese storing 14.2 g of fat per day deposited approximately 582 g of fat between 22 February and 8 April. Energy requirements for thermal regulation were small compared with requirements for fat synthesis and probably had little effect on nutrient deposition. The 34,000 white-fronted geese present on the Harvard Marsh and Prairie Dog Marsh study areas in March 1980 probably used <20% of the corn available within a 5-km radius. We believe that midcontinent white-fronted geese arrive on Arctic breeding grounds with larger and less variable fat reserves than prior to modern agricultural development. We attribute this response to increased food availability on staging areas where the net effect of agricultural changes has been an increase in corn availability. Waterfowl managers can increase dispersion of geese and provide favorable foraging conditions by maintaining well-distributed wetland roosting habitat and by working with private landowners to ensure access to grain in the vicinity of wetlands.

Nebraska↗

USGS1998

Brood sizes of sympatric American black ducks and mallards in Maine

The long-term decline of the American black duck (Anas rubripes) population has been attributed to lower productivity of black ducks that might have been excluded from fertile agricultural wetlands by mallards (Anas platyrhynchos). We monitored broods on 53 wetlands in 1993 and on 58 wetlands in 1994 to determine mean brood sizes of black ducks and mallards in forested and agricultural landscapes. Study wetlands were moderately to highly fertile. We monitored 94 black duck broods each year and 46 (1993) and 52 (1994) mallard broods until they reached Class IIc-III (near fledging). No differences existed (P = 0.71) in mean brood size between black ducks (1993: 3.95 ± 0.23; 1994: 4.59 ± 0.24) and mallards (1993: 3.96 ± 0.35; 1994: 5.00 ± 0.43) either year. Brood size for species, however, was different between years (P = 0.014) and among wetland sites (P = 0.001). Mean sizes of broods were larger (P < 0.05) on 2 large impoundment complexes (Lake Josephine and Lake Christina) compared with brood sizes on other wetlands in forested or agricultural landscapes. No differences (P ≥ 0.41) existed between mean Class IIc-III brood sizes of black ducks and mallards, whether species were alone or together on wetlands. Our data document that mallard productivity is similar to that of black ducks where they breed sympatrically in Maine.

Journal of Wildlife Management↗

USGS1997

Distribution of black-tailed jackrabbit habitat determined by GIS in southwestern Idaho

We developed a multivariate description of black-tailed jackrabbit (Lepus californicus) habitat associations from Geographical Information Systems (GIS) signatures surrounding known jackrabbit locations in the Snake River Birds of Prey National Conservation Area (NCA), in southwestern Idaho. Habitat associations were determined for characteristics within a 1-km radius (approx home range size) of jackrabbits sighted on night spotlight surveys conducted from 1987 through 1995. Predictive habitat variables were number of shrub, agriculture, and hydrography cells, mean and standard deviation of shrub patch size, habitat richness, and a measure of spatial heterogeneity. In winter, jackrabbits used smaller and less variable sizes of shrub patches and areas of higher spatial heterogeneity when compared to summer observations (P < 0.05). During the low population phase, jackrabbits also used agricultural regions more during winter than summer. The association with agricultural regions was emphasized spatially in a GIS map contrasting winter and summer periods. Multivariate habitat means (P < 0.001), but not individual GIS variables (P > 0.05), differed significantly between high and low population phase. We used the Mahalanobis distance statistic to rank all 50-m cells in a 440,000-ha region relative to the multivariate mean habitat vector. On verification surveys to test predicted models, we sighted jackrabbits in areas ranked close to the mean habitat vector. Areas burned by large-scale fires between 1980 and 1992 or in an area repeatedly burned by military training activities had greater Mahalanobis distances from the mean habitat vector than unburned areas and were less likely to contain habitats used by jackrabbits.

Journal of Wildlife Management↗

USGS1983

Environmental contaminant hazards to Attwater's greater prairie-chickens

The Attwater's greater prairie-chicken ( Tympanuchus cupido attwateri ) was declared an endangered species in 1966 and exists only on the upper Gulf Coast prairie of southeast Texas. Since 1975, total numbers have declined from 2,240 to 1,456 in 1981 (Jurries 19679; W. Shifflett, Manager Attwater Prairie Chicken National Wildlife Refuge [APCNWR], personal communication). The total population of this prairie grouse is presently scattered in a norther, largely agricultural, but also urban-rangeland area of 6 counties that contained about 600 individuals in 1971, and a southern, largely rangeland, but also agricultural-urban area of 4 counties that contained about 860 individuals in 1981. During the present study, Attwater's prairie-chickens completely disappeared in Wharton and Waller counties in the northern area ( W. Shifflett, personal communication). Prairie-chickens in the northern area frequent crops of rice, soybeans, peanuts, or corn; those in the southern area frequent sorghum or cotton that are planted on or near ancestral booming grounds. The use of pesticides in the agricultural areas may have contributed to the initial decline of prairie-chicken numbers. In 1927, several hundred prairie-chickens were found dead in and near a cotton field in Wharton County shortly after it had been treated with arsenic (Lehmann and Mauermann 1963). The remains of 5 prairie-chickens were found in sorghum and soybean fields in Refugio and Colorado counties between 1975 and 1977 (R. Haeber and W. Kessler, personal communication) but were too decomposed to be analyzed for evidence of pesticide exposure. Parathion formulations had been applied to the soybeans and near the sorghum. Other pesticide use on the areas was uncertain. The objective of this study was to ascertain pesticide hazards to Attwater's greater prairie-chickens.

Texas↗

USGS2012

An at-grade stabilization structure impact on runoff and suspended sediment

In recent years, agricultural runoff has received more attention as a major contributor to surface water pollution. This is especially true for the unglaciated area of Wisconsin, given this area's steep topography, which makes it highly susceptible to runoff and soil loss. We evaluated the ability of an at-grade stabilization structure (AGSS), designed as a conservation practice to reduce the amount of overland runoff and suspended sediment transported to the surface waters of an agricultural watershed. Eight years of storm and baseflow data collected by the US Geological Survey–Wisconsin Water Science Center on a farm in west central Wisconsin were analyzed for changes in precipitation, storm runoff volume, and suspended sediment concentration before and after installation of an AGSS. The agricultural research site was designed as a paired watershed study in which monitoring stations were installed on the perennial streams draining both control and treatment watersheds. Linear mixed effects model analyses were conducted to determine if any statistically significant changes occurred in the water quality parameters before and after the AGSS was installed. Results indicated no significant changes ( p = 0.51) in average event precipitation and runoff volumes before and after installation of the AGSS in either the treatment (NW) or control (SW) watersheds. However, the AGSS did significantly reduce the average suspended sediment concentration in the event runoff water ( p = 0.02) in the NW from 972 to 263 mg L –1 . In addition, particle size analyses, using light diffraction techniques, were conducted on soil samples taken from within the AGSS and adjacent valley and ridge top to determine if suspended sediments were being retained within the structure. Statistical analysis revealed a significantly ( p < 0.001) larger proportion of clay inside the AGSS (37%) than outside (30%). These results indicate that the AGSS was successful in reducing the amount of suspended sediment transported to nearby surface waters. The cost of an AGSS can range from US$3,500 to US$8,000, depending on size. Thus, these structures provide a cheap and effective means of improving water quality in highly erosive landscapes.

Wisconsin↗

USGS2021

SMaRT: A science-based tiered framework for common ravens

Large-scale increases and expansion of common raven ( Corvus corax ; raven) populations are occurring across much of North America, leading to increased negative consequences for livestock and agriculture, human health and safety, and sensitive species conservation. We describe a science-based adaptive management framework that incorporates recent quantitative analyses and mapping products for addressing areas with elevated raven numbers and minimizing potential adverse impacts to sensitive species, agricultural damage, and human safety. The framework comprises 5 steps: (1) desktop analysis; (2) field assessments; (3) comparison of raven density estimates to an ecological threshold (in terms of either density or density plus distance to nearest active or previous nest); (4) prescribing management options using a 3-tiered process (i.e., habitat improvements, subsidy reductions, and direct actions using StallPOPd.V4 software); and (5) post-management monitoring. The framework is integrated within the Science-based Management of Ravens Tool (SMaRT), a web-based application outfitted with a user-friendly interface that guides managers through each step to develop a fully customized adaptive plan for raven management. In the SMaRT interface, users can: (1) interact with pre-loaded maps of raven occurrence and density and define their own areas of interest within the Great Basin to delineate proposed survey or treatment sites; (2) enter site-level density estimates from distance sampling methods or perform estimation of raven densities using the rapid assessment protocol that we provide; (3) compare site-level density estimates to an identified ecological threshold; and (4) produce a list of potential management options for their consideration. The SMaRT supports decision-making by operationalizing scientific products for raven management and facilitates realization of diverse management goals including sensitive species conservation, protection of livestock and agriculture, safeguarding human health, and addressing raven overabundance and expansion. We illustrate the use of the framework through SMaRT using an example of greater sage-grouse ( Centrocercus urophasianus ) conservation efforts within the Great Basin, USA.

California, Idaho, Nevada, Oregon, Utah↗

USGS2019

Managing effects of drought and other water resource challenges in Alaska and the Pacific Northwest

This is a Cooperator Report. As such, there is no specific abstract. The physical, ecological, and social environments of Alaska and the Pacific Northwest (PNW) region of the United States are extremely diverse. Alaska ranges from the Arctic Ocean and the very cold, dry environments of the North Slope to the cool and very rainy coastal North Pacific region of Southeast Alaska. Most precipitation falls as snow at higher elevations. In Arctic Alaska, average annual temperature is 14.6 F, and average annual precipitation is 11 inches. By contrast, in Southeast Alaska, average annual temperature is 35.8 F, and annual average precipitation is 143 inches. The PNW, defined here as Idaho, Oregon, and Washington, ranges from the Pacific Coast (annual precipitation of 200 inches) to interior semi-arid regions (annual precipitation of 8 inches). Precipitation patterns in the PNW are strongly governed by orographic phenomena, with high, persistent snowpack in the higher mountains (e.g., record annual snowfall of 1,130 in at Mount Baker, Washington in 1999-2000). Ecosystems in the PNW include productive temperate coniferous forests near the Pacific coast and along the (wet) west slope of the Cascade Range, less productive mixed-conifer forest along the (dry) east slope of the Cascades and in interior mountain ranges, and sagebrush-steppe and shrublands at lower elevations in much of the interior and mountain valleys. Large rivers and thousands of smaller tributaries form an extensive network of riparian, wetland, and estuarine systems that provide both critical hydrologic function and biological diversity at broad and fine spatial scales. Although Alaska and the Pacific Northwest differ in important physical, ecological, and social features, the importance of natural resources is evident in both regions. Water is important for wildlife and people. Water provides critical habitat for salmon, which are culturally and economically valuable species. Timber production has declined in recent decades. Recreation has emerged as a major revenue source.

Alaska, Oregon, Washington↗

USGS2026

Decadal trends in the quality of groundwater used for public drinking-water supply in California, 2004–2023, California groundwater ambient monitoring and assessment program, priority basin project

This study provides a comprehensive assessment of decadal changes in the quality of groundwater used for public drinking-water supply at 444 monitoring sites across California during 2004–2023. We assessed decadal step trends in groundwater quality for 145 water-quality constituents and geochemical indicators statewide and across geographic and land-use based network groups. We evaluated the statistical significance of directional changes (predominant increase or decrease of constituent concentrations) and the magnitude of those changes across all network groups. Uranium showed the most widespread directional and high-magnitude increases of all constituents with regulatory benchmarks statewide, particularly in the agriculture-dominated Central Valley as well as urban- and desert-dominated regions of Southern California. Fluoride and perchlorate showed the most widespread directional and high-magnitude decreases of all constituents with regulatory benchmarks statewide, which were also most pronounced in Southern California. Although arsenic and nitrate did not often register significant directional changes across network groups, they showed widespread, high-magnitude changes in both directions (increase and decrease) at levels often exceeding 10 percent of respective regulatory benchmarks statewide. Triazine herbicides (atrazine and simazine) and the gasoline oxygenate methyl tert-butyl ether (MTBE) showed significant directional decreases statewide, but not at levels considered to be of high magnitude compared to respective regulatory benchmarks. We observed significant directional and high-magnitude increases of total dissolved solids (TDS) statewide, which were most pronounced in agricultural areas. Analysis of explanatory geochemical indicators indicated that prevalent statewide increases of alkalinity and calcium were the predominant components of the observed statewide increases in TDS by mass. Widespread increases in groundwater alkalinity and calcium across agricultural and urban areas may be related, in part, to warm-season irrigation and other anthropogenic factors that have shifted soil weathering dynamics over the long term. Increasing alkalinity concentrations were related to increasing uranium concentrations, particularly in areas with aquifer materials derived from granitic rocks. Conversely, increasing calcium concentrations were related to decreasing fluoride concentrations, particularly in areas where fluoride occurred naturally at elevated concentrations. Decrease of perchlorate, triazine herbicides, and MTBE are likely related to decreased anthropogenic source inputs over time and natural attenuation in aquifers.

EarthArXiv↗

USGS2009

Depth to water, saturated thickness, and other geospatial datasets used in the design and installation of a groundwater monitoring-well network in the High Plains Aquifer, Colorado

These datasets were compiled in support of U.S. Geological Survey Data Series 456, Design and Installation of a Groundwater Monitoring-Well Network in the High Plains Aquifer, Colorado. These datasets were developed as part of a cooperative project between the U.S. Geological Survey and the Colorado Department of Agriculture. The purpose of the project was to design a 30-well network and install 20 of the 30 wells to characterize water quality in the High Plains aquifer in areas of irrigated agriculture in Colorado. The five datasets are described as follows and are further described in Data Series 456: (1) ds472_dtw: This dataset represents the depth to groundwater in the High Plains Aquifer in Colorado in 2000. This grid was used to determine areas where the depth to water was less than 200 feet below land surface. (2) Ds472_sat: This dataset represents the saturated thickness of the High Plains aquifer within Colorado in 2000. This grid was used to determine areas where the saturated thickness was greater than 50 feet. (3) Ds472_equalareas: This dataset includes 30 equal-area polygons overlying the High Plains Aquifer in Colorado having a depth to water less than 200 feet, a saturated thickness greater than 50 feet, and underlying irrigated agricultural lands. (4) Ds472_randomsites: This dataset includes 90 randomly-generated potential groundwater sampling sites. This dataset provides a first, second, and third choice placed within the 30 equal area polygons of dataset dsXX_equalareas. (5) Ds472_welldata: This dataset includes point locations and well completion data for the 20 wells installed as part of this project. The datasets that pertain to this report can be found on the U.S. Geological Survey's NSDI (National Spatial Data Infrastructure) Node, the links are provided on the sidebar.

Colorado↗