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At least 235 records · Page 13Linked to original sources
USGS2015

Biodiversity influences plant productivity through niche–efficiency

The loss of biodiversity is threatening ecosystem productivity and services worldwide, spurring efforts to quantify its effects on the functioning of natural ecosystems. Previous research has focused on the positive role of biodiversity on resource acquisition (i.e., niche complementarity), but a lack of study on resource utilization efficiency, a link between resource and productivity, has rendered it difficult to quantify the biodiversity–ecosystem functioning relationship. Here we demonstrate that biodiversity loss reduces plant productivity, other things held constant, through theory, empirical evidence, and simulations under gradually relaxed assumptions. We developed a theoretical model named niche–efficiency to integrate niche complementarity and a heretofore-ignored mechanism of diminishing marginal productivity in quantifying the effects of biodiversity loss on plant productivity. Based on niche–efficiency, we created a relative productivity metric and a productivity impact index (PII) to assist in biological conservation and resource management. Relative productivity provides a standardized measure of the influence of biodiversity on individual productivity, and PII is a functionally based taxonomic index to assess individual species’ inherent value in maintaining current ecosystem productivity. Empirical evidence from the Alaska boreal forest suggests that every 1% reduction in overall plant diversity could render an average of 0.23% decline in individual tree productivity. Out of the 283 plant species of the region, we found that large woody plants generally have greater PII values than other species. This theoretical model would facilitate the integration of biological conservation in the international campaign against several pressing global issues involving energy use, climate change, and poverty.

Proceedings of the National Academy of Sciences of↗
USGS2024

Climate change amplifies ongoing declines in sagebrush ecological integrity

Understanding how climate change will contribute to ongoing declines in sagebrush ecological integrity is critical for informing natural resource management, yet complicated by interactions with wildfire and biological invasions. Here, we assessed potential future changes in sagebrush ecological integrity under a range of scenarios using an individual plant-based simulation model, integrated with remotely sensed estimates of current sagebrush ecological integrity. The simulation model allowed us to estimate how climate change, wildfire, and invasive annuals interact to alter the potential abundance of key plant functional types that influence sagebrush ecological integrity: sagebrush, perennial grasses, and annual grasses. Our results suggest that climate driven reductions in sagebrush ecological integrity may occur over broader areas than increases in sagebrush ecological integrity. Declines in sagebrush ecological integrity were most likely in hot and dry regions while increases were more likely in cool and wet regions. Increases in wildfire probability, largely driven by increasing invasive annual grass abundance, resulted in projected declines in sagebrush abundance and sagebrush ecological integrity in some regions, particularly the Great Basin. The most common projected transitions in sagebrush habitat classification were declines from Core Sagebrush Area to Growth Opportunity Area and from Growth Opportunity Area to Other Rangeland Area. Responses varied considerably across projections from different global climate models, highlighting the importance of climate uncertainty. However, our projections tended to be robust in areas that currently have the highest sagebrush ecological integrity. Our results provide a long-term perspective on the vulnerability of sagebrush ecosystems to climate change and may inform geographic prioritization of conservation and restoration investments. These results suggest that ongoing threats, such as the continued invasion by annual grasses and increased wildfire frequency, are likely to be amplified by climate change, and imply that the current imbalance between capacity for conservation to address threats to sagebrush will grow as the climate warms.

Rangeland Ecology and Management↗
USGS2021

Sedex hydrothermal systems triggered upheavals to marine chemistry and mass extinctions: Applications for ore genesis research and mineral exploration

New USGS research reveals that the discharge of metal-rich brine that formed sedex deposits on ancient seafloors had profound effects on global ocean chemistry and biologic evolution. For example, brine expulsion caused short-duration positive excursions (“spikes”) in the global marine Sr isotope record. While these spikes are unexplained by conventional oceanic models, our chronostratigraphic correlations of major sedex events, combined with mass balance evidence and oceanographic modeling, confirm that the flux of radiogenic Sr from sedex brines during ore formation was sufficient to cause these once enigmatic 87Sr/86Sr spikes. Recognition that the timing of peak 87 Sr/ 86 Sr spikes correlates exactly with global δ 13 C (and δ 18 O) spikes, climate change, deposition of metal-rich black shales and ironstones, metal-induced malformation (teratology) of marine organisms, and mass extinctions, establishes a causal relationship between sedex deposits and these dramatic events in earth history. The relationships among these features are not fully understood. However, our new model demonstrates that the flux of key biolimiting nutrients and metals contained in sedex brines exceeds that of the total modern riverine flux to the ocean. Undoubtably, these immense nutrient fluxes spurred ocean eutrophication, which, ultimately, through a series of positive feedback mechanisms, may be a previously unrecognized trigger of global ocean anoxic events (OAEs) that produced these chemical and biological perturbations. A derivative result from this integrative research is the recognition that OAEs resulted in the formation of “bathtub rim” deposits at redox boundaries along continental margins that concentrated various redox sensitive critical minerals. For example, we have identified midcontinent phosphorite deposits that contains heavy REE grades and tonnages that rival any REE deposit in the world. The recognition that sedex-forming fluid expulsion events are recorded in the global marine isotopic, geologic, and biological records, defines a new approach to the study of and exploration for sedex deposits. Traditional ore genesis research, coupled with chronostratigraphic correlation and high-resolution 87 Sr/ 86 Sr isotope chemostratigraphy can be used to answer long-standing questions about geologic processes responsible for formation of these extraordinary deposits. This approach allows us to constrain, for the first time, the age, duration, and fluxes of fluids and metals vented into the ocean by these giant hydrothermal systems. Accordingly, the fact that large mineralizing events are recorded in the marine sedimentary record opens the tantalizing prospect that we have the ability to conduct effective resource assessments and define prospective basins anywhere in the world. This innovative approach allows for identification of favorable stratigraphic ages and basins and remote evaluation of the size (and, thus, the mineral potential) of undiscovered mineral deposits. This methodology could be applied on regional basin-wide assessments, to evaluate sedimentary basin prospectivity, resource favorability of specific horizons therein, and to the evaluation of the potential of early-stage prospects.

Geological Society of Nevada Newsletter↗
USGS2002

Use of sediment quality guidelines and related tools for the asssessment of contaminated sediments: Executive summary sooklet of a SETAC Pellston Workshop

This publication summarizes the results of a Pellston Workshop sponsored by the Society of Environmental Toxicology and Chemistry (SETAC), held 17-22 August 2002 in Fairmont, Montana, USA. The full technical proceedings of the workshop will be published separately by SET AC in 2003. Previous SETAC workshops have focused on sediment ecological risk assessment (ERA) (Dickson et al. 1987; Ingersoll et al. 1997) and porewater toxicity testing (Carr and Nipper 2003). Another recent workshop addressed the application of weight-of-evidence (WOE) methods in ERA (Burton et al. 2002). These previous workshops focused on how, when, and why ERAs are needed in sediment assessments. However, more focused discussion among scientists, environmental regulators, and environmental managers is now needed to build on this previous work. Specifically, additional guidance is needed on procedures that can be used to integrate the information derived from multiple chemical and biological lines of evidence (LOE). These LOE, which are developed through the application of different assessment tools, often include the use of chemically based sediment quality guidelines (SQGs) to evaluate sediment contamination and to help practitioners in sediment assessment and management formulate risk management decisions. This workshop focused on evaluation of the scientific foundations supporting different chemically based numeric SQGs and methods to improve the integration of SQGs into different sediment quality assessment frameworks that include information derived from multiple chemical and biological LOE.

SETAC Pellston Workshop↗
USGS2018

Predicting biological conditions for small headwater streams in the Chesapeake Bay watershed

A primary goal for Chesapeake Bay watershed restoration is to improve stream health and function in 10% of stream miles by 2025. Predictive spatial modeling of stream conditions, when accurate, is one method to fill gaps in monitoring coverage and estimate baseline conditions for restoration goals. Predictive modeling can also monitor progress as additional data become available. We developed a random forests model to predict biological condition of small streams (<200 km 2 in drainage) in the Chesapeake Bay watershed. Biological condition was measured with the Chesapeake Bay Basin-wide Index of Biotic Integrity (Chessie BIBI), a stream macroinvertebrate index. Our goal was to predict biological condition in all unsurveyed small streams present in a 1:24,000 scale catchment layer as a 2004–2008 baseline. We reclassified the 5-category Chessie BIBI ratings into two categories, poor and fair/good, to align with management goals of the Chesapeake Bay Program. The model included 12 geospatial predictor variables including measures on spatial location, bioregion, land cover, soil, precipitation, and number of dams in local catchments. We trained the model with a random 75% subset of Chessie BIBI data ( n = 1449), and used the remaining 25% of Chessie BIBI data ( n = 484) as test data. The model performed well, correctly predicting 72% of samples in training data and 73% of samples in test data, but model accuracy varied among bioregions. We performed uncertainty analyses by adding bands of either ±0.05 or ±0.10 BIBI units to the cutoff between poor and fair/good. These uncertainty analyses resulted in 14.5% (±0.05 band) and 24.8% (±0.10 band) of samples in test data being classified as in uncertain condition. For 95,877 small stream reaches in the Chesapeake Bay watershed, the model predicted 64% in fair/good condition, the ±0.05 uncertainty analyses predicted 57% in fair/good condition, and the ±0.10 uncertainty analysis predicted 50% in fair/good condition. These reported values have different implications for the number of improved stream miles required to meet the goal of improving 10%. Incorporating uncertainty provides an assessment of model strength as well as confidence in predictions. We, therefore, suggest increased reporting of uncertainty in studies that spatially predict stream conditions.

Chesapeake Bay watershed↗
USGS2026

Integrating fecal DNA and telemetry to estimate wildlife densities in anthropogenic landscapes

Density estimation is central to wildlife management efforts but can be challenging in anthropogenically-dominated landscapes due to small parcel sizes, access restrictions, and limited green space. Reliable density estimates are especially important for managing white-tailed deer ( Odocoileus virginianus ), whose high abundance in urbanized areas increases the need for accurate population assessments to guide management and reduce negative human–wildlife interactions. Herein, we evaluated (a) the use of a plot-based spatial capture-recapture sampling design to estimate deer density in developed landscapes and (b) if integrating telemetry data improved the precision or biological inferences of density estimates. We conducted fecal sampling at 2 study areas reflecting different characteristics of the urbanization gradient in Durham and eastern Orange counties, North Carolina: (1) rural (i.e., forested, large parcels) and (2) suburban (i.e., small parcels, limited continuous access, diversity of landscape features). We collected 223 fecal samples during a 3-week sampling period in July and September 2022, resulting in 157 individual deer detected (112 F:45 M). Rural densities were estimated at 54 deer/km 2 (95% CI = 35–84) and suburban densities at 75 deer/km 2 (95% CI = 48–117). Integrating telemetry data allowed estimation of sex-specific space use and densities, which were not possible from fecal data alone; however, precision of total density estimates was similar across integrated and fecal-only analyses. Overall, our results highlighted key trade-offs inherent to plot-based spatial capture-recapture in suburban landscapes, most notably low recapture rates, accessibility challenges to maintain optimal trap spacing, and the importance of considering auxiliary data streams as part of the study design.

North Carolina↗
USGS2026

Statistical facilitation in environmental science: Integrating results from complementary statistical analyses can improve ecological interpretations

Professionals working in biological conservation seek to understand, manage, and restore populations of native organisms using many techniques. A common approach for this discipline is using long-term data collections to inform decision making. However, several quantitative issues complicate statistical analysis of monitoring datasets and can reduce the utility of results for conservation decision making. Integrating results from multiple analyses applied to the same dataset (i.e., approaching the same biological problem using different techniques) is one way to address concerns related to field data that violate statistical assumptions. This process allows data analysts, researchers, and managers to assemble insights based on the weight of evidence. Here we tested whether three different statistical techniques [(1) multiple logistic regression on original data, (2) multiple logistic regression on standardized data (i.e., mean of 0 and standard deviation of 1), and (3) random forest analysis] identified a similar hierarchy for selecting natural and anthropogenic habitat regressors. Our examination of how environmental variables affected Plains Minnow ( Hybognathus placitus ), a state-threatened fish, is relevant to other taxa and locations. We gained useful information from redundancies (i.e., agreements across analyses). New directions also emerged by addressing ambiguities (i.e., disagreements among results across analyses). When multiple analyses were integrated into one ecological story, a clearer interpretation emerged. Viewing different statistical tests as facilitators that provide mutual advantages can advance the understanding and application of statistical analyses applied to non-experimental field datasets.

Kansas↗
USGS2012

Development and application of methods used to source prehistoric Southwestern maize: a review

Archaeological cobs free of mineral contaminants should be used to source the soils in which they were grown. Mineral contaminants often contain much higher concentrations of metals than vegetal materials and can alter a cob’s apparent metal and heavy-isotope content. Cleaning a cob via immersion in an acid solution for more than a few minutes will result in the incongruent and sometimes complete leaching of metals, including strontium (Sr), from the cob. When using 87 Sr/ Sr to determine the location of potential agriculture fields, it is best to either integrate several depth-integrated soil samples or to integrate several vegetation samples from individual fields. Biologically labile Sr in semi-arid Southwestern soils largely originates from eolian source or sources and usually is not derived from underlying bedrock. Existing Sr-isotope data indicate that archaeological cobs from Aztec Ruins came from either the Mesa Verde-McElmo Dome or Totah areas, that Pueblo Bonito and Chetro Ketl cobs, from Chaco Canyon that predate A.D. 1130, probably came from the Rio Chaco corridor, and that cobs from Chaco Canyon, that postdate A.D. 1130, probably came from either the Totah or Zuni areas.

Journal of Archaeological Science↗
USGS2024

National-scale remotely sensed lake trophic state from 1984 through 2020

Lake trophic state is a key ecosystem property that integrates a lake’s physical, chemical, and biological processes. Despite the importance of trophic state as a gauge of lake water quality, standardized and machine-readable observations are uncommon. Remote sensing presents an opportunity to detect and analyze lake trophic state with reproducible, robust methods across time and space. We used Landsat surface reflectance data to create the first compendium of annual lake trophic state for 55,662 lakes of at least 10 ha in area throughout the contiguous United States from 1984 through 2020. The dataset was constructed with FAIR data principles (Findable, Accessible, Interoperable, and Reproducible) in mind, where data are publicly available, relational keys from parent datasets are retained, and all data wrangling and modeling routines are scripted for future reuse. Together, this resource offers critical data to address basic and applied research questions about lake water quality at a suite of spatial and temporal scales.

Scientific Data↗
USGS2020

Resolving species boundaries in the critically imperiled freshwater mussel species, Fusconaia mitchelli (Bivalvia: Unionidae)

Species are a fundamental unit of biology, and defining accurate species boundaries is integral to effective conservation and management of imperiled taxa. Freshwater mussels (Bivalvia: Unionidae) are among the most imperiled groups of organisms in North America, yet species boundaries remain uncertain for many taxa. The False Spike, Fusconaia mitchelli (Simpson in Dall, 1895), is a freshwater mussel considered to be endemic to central Texas (Brazos, Colorado, and Guadalupe drainages). Recent research revealed significant intraspecific genetic variation between geographically separated populations of F . mitchelli , which could be indicative of speciation; however, small sample sizes for several of the populations precluded formal taxonomic revision. Here, we increase taxon sampling and use multilocus DNA sequence data and traditional morphometrics to re‐evaluate species boundaries in F . mitchelli . We sequenced three loci: the protein‐coding mitochondrial DNA genes cytochrome c oxidase subunit 1 and NADH dehydrogenase 1 , and the nuclear internal transcribed spacer 1 . Phylogenetic analyses depicted deep genetic divergence between F . mitchelli in the Guadalupe and those in the Brazos and Colorado drainages, which was further supported by available biogeographic information. Morphometric analyses and coalescent‐based species delimitation models integrating both DNA sequence and morphological data provided strong support for the divergence observed between the two geographically isolated clades of F . mitchelli . Based on these results, we revise taxonomy accordingly by elevating the junior synonym Fusconaia iheringi (Wright, 1898) to represent the Brazos and Colorado populations and restrict the distribution of F . mitchelli to the Guadalupe River drainage. Our findings may impact pending management decisions to protect F . mitchelli under the U.S. Endangered Species Act.

Journal of Zoological Systematics and Evolutionary↗
USGS2012

Downscaling future climate scenarios to fine scales for hydrologic and ecological modeling and analysis

Introduction Evaluating the environmental impacts of climate change on water resources and biological components of the landscape is an integral part of hydrologic and ecological investigations, and the resultant land and resource management in the twenty-first century. Impacts of both climate and simulated hydrologic parameters on ecological processes are relevant at scales that reflect the heterogeneity and complexity of landscapes. At present, simulations of climate change available from global climate models [GCMs] require downscaling for hydrologic or ecological applications. Methods Using statistically downscaled future climate projections developed using constructed analogues, a methodology was developed to further downscale the projections spatially using a gradient-inverse-distance-squared approach for application to hydrologic modeling at 270-m spatial resolution. Results This paper illustrates a methodology to downscale and bias-correct national GCMs to subkilometer scales that are applicable to fine-scale environmental processes. Four scenarios were chosen to bracket the range of future emissions put forth by the Intergovernmental Panel on Climate Change. Fine-scale applications of downscaled datasets of ecological and hydrologic correlations to variation in climate are illustrated. Conclusions The methodology, which includes a sequence of rigorous analyses and calculations, is intended to reduce the addition of uncertainty to the climate data as a result of the downscaling while providing the fine-scale climate information necessary for ecological analyses. It results in new but consistent data sets for the US at 4 km, the southwest US at 270 m, and California at 90 m and illustrates the utility of fine-scale downscaling to analyses of ecological processes influenced by topographic complexity.

Ecological Processes↗
USGS2009

U.S. Geological Survey (USGS) Western Region; Santa Barbara Channel Coastal and Ocean Science

USGS coastal and ocean science in the Western United States and the Pacific integrates scientific expertise in geology, water resources, biology, and geography. Operating from 10 major science centers in the Western Region, the USGS is addressing a broad geographic and thematic range of important coastal and marine issues. In California, the Santa Barbara Channel represents one area of focus.

Fact Sheet↗
USGS2022

Eastern Ecological Science Center — Fish and aquatic animal health

Science provided by the U.S. Geological Survey (USGS) Eastern Ecological Science Center (EESC) helps to protect fish and aquatic animal health and support disease management of our Nation’s fisheries and aquatic animal populations. Our capabilities and expertise span diverse, yet highly integrated disciplines related to all aspects of biology, ecology, and animal health. Our scientists work to identify novel and emerging pathogens and diseases to assess fish and aquatic animal responses to parasites, pathogens, adverse environmental conditions, and chemical exposures. Eastern Ecological Science Center research is conducted both in laboratories and in the field in various aquatic environments ranging from headwater streams to the ocean. The EESC team provides science leadership and support for fisheries and aquatic species specialists nationwide.

Fact Sheet↗
USGS2012

Protocols for collection of streamflow, water-quality, streambed-sediment, periphyton, macroinvertebrate, fish, and habitat data to describe stream quality for the Hydrobiological Monitoring Program, Equus Beds Aquifer Storage and Recovery Program, city of Wichita, Kansas

The city of Wichita, Kansas uses the Equus Beds aquifer, one of two sources, for municipal water supply. To meet future water needs, plans for artificial recharge of the aquifer have been implemented in several phases. Phase I of the Equus Beds Aquifer Storage and Recovery (ASR) Program began with injection of water from the Little Arkansas River into the aquifer for storage and subsequent recovery in 2006. Construction of a river intake structure and surface-water treatment plant began as implementation of Phase II of the Equus Beds ASR Program in 2010. An important aspect of the ASR Program is the monitoring of water quality and the effects of recharge activities on stream conditions. Physical, chemical, and biological data provide the basis for an integrated assessment of stream quality. This report describes protocols for collecting streamflow, water-quality, streambed-sediment, periphyton, macroinvertebrate, fish, and habitat data as part of the city of Wichita's hydrobiological monitoring program (HBMP). Following consistent and reliable methods for data collection and processing is imperative for the long-term success of the monitoring program.

Kansas↗
USGS1982

Liming of acidified waters: issues and research - a report of the International Liming Workshop

Acidic deposition is a problem of significant national and international concern. It is strongly suspected that acidic deposition has adversely affected aquatic resources in Scandinavia and North America. While substantial resources are being devoted to understanding the causative factors associated with surface water acidification, much less research is being conducted on mitigative strategies. Mitigative techniques involving liming may be useful for short-term protection of specific component of aquatic communities or for renovation of seriously impacted aquatic ecosystems. The selection of effective liming strategies is based on an integrated understanding of the following key factors: biological systems, water chemistry, sediment chemistry, hydrology, and watershed characteristics, effectiveness of neutralizing materials, and application techniques. Research in Scandinavia, Canada, and the U.S. has led to a partial understanding of some of the key factors for successful neutralization of surface waters (Bengtsson, 1982; Fraser and Britt, 1982). However, conflicting results of liming operations and experiments have been reported. (Fraser et al., 1982; Fraser and Britt, 1982; Sverdrup and Bjerle, 1982). Additional research is required to improve the ability of scientists and resource managers to select effective liming strategies. An International Liming workshop was convened during 19-25 September 1982 at the University of Washington's Friday Harbor Laboratories. The major objective of this workshop were: - To identify the most critical deficiencies in the scientific understanding of liming techniques and their long-term consequences. - To develop and document a research strategy to address information deficiencies that are pertinent to the protection or renovation of acidic surface waters in the United States. The participants who contributed to this workshop are listed in Table 1.

FWS/OBS↗
USGS2000

Persistence of spilled oil on shores and its effects on biota

Over two million tonnes of oil are estimated to enter the world's oceans every year. A small percentage, but still a large volume, of this oil strands onshore, where its persistence is governed primarily by the action of physical forces. In some cases, biota influence the persistence of stranded oil or the rate of its weathering. Oil's deleterious effects on biota are frequently related to the persistence and degree of weathering of the oil, with long-lasting effects in low-energy environments such as salt marshes and coastal mangroves, or in higher-energy environments where oil is sequestered. However, an oil spill can have disproportionately large biological effects when it affects key species or processes (e.g., structurally important species, predators, prey, recruitment, or succession). In these cases, the continuing presence of oil is not always a prerequisite for continuing biological effects. There are relatively few long-term studies of the effects of oil spills; data from these suggest that oil can persist for decades in some environments or situations, and that biological effects can be equally persistent. Broad-based, integrated studies have been the most revealing in terms of the importance of direct and indirect effects, spillover effects between different parts of the environment, and continuing linkages between residual oil and biologic effects. Clean-up and treatment techniques applied to spilled or stranded oil can also have significant, long-lasting effects and need to be carefully evaluated prior to use.

Seas at the millennium - an environmental evaluati↗
USGS1995

Environmental Setting and Implications on Water Quality, Upper Colorado River Basin, Colorado and Utah

The Upper Colorado River Basin in Colorado and Utah is 1 of 60 study units selected for water-quality assessment as part of the U.S. Geological Survey's National Water-Quality Assessment program, which began full implementation in 1991. Understanding the environmental setting of the Upper Colorado River Basin study unit is important in evaluating water-quality issues in the basin. Natural and human factors that affect water quality in the basin are presented, including an overview of the physiography, climatic conditions, general geology and soils, ecoregions, population, land use, water management and use, hydrologic characteristics, and to the extent possible aquatic biology. These factors have substantial implications on water-quality conditions in the basin. For example, high concentrations of dissolved solids and selenium are present in the natural background water conditions of surface and ground water in parts ofthe basin. In addition, mining, urban, and agricultural land and water uses result in the presence of certain constituents in the surface and ground water of the basin that can detrimentally affect water quality. The environmental setting of the study unit provides a framework of the basin characteristics, which is important in the design of integrated studies of surface water, ground water, and biology.

Water-Resources Investigations Report↗
USGS2017

Evaluation of long-term trends in hydrologic and water-quality conditions, and estimation of water budgets through 2013, Chester County, Pennsylvania

An evaluation of trends in hydrologic and water quality conditions and estimation of water budgets through 2013 was done by the U.S. Geological Survey in cooperation with the Chester County Water Resources Authority. Long-term hydrologic, meteorologic, and biologic data collected in Chester County, Pennsylvania, which included streamflow, groundwater levels, surface-water quality, biotic integrity, precipitation, and air temperature were analyzed to determine possible trends or changes in hydrologic conditions. Statistically significant trends were determined by applying the Kendall rank correlation test; the magnitudes of the trends were determined using the Sen slope estimator. Water budgets for eight selected watersheds were updated and a new water budget was developed for the Marsh Creek watershed. An average water budget for Chester County was developed using the eight selected watersheds and the new Marsh Creek water budget. Annual and monthly mean streamflow, base flow, and runoff were analyzed for trends at 10 streamgages. The periods of record at the 10 streamgages ranged from 1961‒2013 to 1988‒2013. The only statistically significant trend for annual mean streamflow was for West Branch Brandywine Creek near Honey Brook, Pa. (01480300) where annual mean streamflow increased 1.6 cubic feet per second (ft 3 /s) per decade. The greatest increase in monthly mean streamflow was for Brandywine Creek at Chadds Ford, Pa. (01481000) for December; the increase was 47 ft 3 /s per decade. No statistically significant trends in annual mean base flow or runoff were determined for the 10 streamgages. The greatest increase in monthly mean base flow was for Brandywine Creek at Chadds Ford, Pa. (01481000) for December; the increase was 26 ft 3 /s per decade. The magnitude of peaks greater than a base streamflow was analyzed for trends for 12 streamgages. The period of record at the 12 stream gages ranged from 1912‒2012 to 2004–11. Fifty percent of the streamgages showed a small statistically significant increase in peaks greater than the base streamflow. The greatest increase was for Brandywine Creek at Chadds Ford, Pa. (01481000) during 1962‒2012; the increase was 1.8 ft 3 /s per decade. There were no statistically significant trends in the number of floods equal to or greater than the 2-year recurrence interval flood flow. Twenty‒one monitoring wells were evaluated for statistically significant trends in annual mean water level, minimum annual water level, maximum annual water level, and annual range in water-level fluctuations. For four wells, a small statistically significant increase in annual mean water level was determined that ranged from 0.16 to 0.7 feet per decade. There was poor or no correlation between annual mean groundwater levels and annual mean streamflow and base flow. No correlation was determined between annual mean groundwater level and annual precipitation. Despite rapid population growth and land-use change since 1950, there appears to have been little or no detrimental effects on groundwater levels in 21 monitoring wells. Long-term precipitation and temperature data were available from the West Chester (1893‒2013) and Phoenixville, Pa. (1915‒2013) National Oceanic and Atmospheric Administration (NOAA) weather stations. No statistically significant trends in annual mean precipitation or annual mean temperature were determined for either station. Both weather stations had a significant decrease in the number of days per year with precipitation greater than or equal to 0.1 inch. Annual mean minimum and maximum temperatures from the NOAA Southeastern Piedmont Climate Division increased 0.2 degrees Fahrenheit (F) per decade between 1896 and 2014. The number of days with a maximum temperature equal to or greater than 90 degrees F increased at West Chester and decreased at Phoenixville. No statistically significant trend was determined for annual snowfall amounts. Data from 1974 to 2013 for three stream water-quality monitors in the Brandywine Creek watershed were evaluated. The monitors are on the West Branch Brandywine Creek at Modena, Pa. (01480617), East Branch Brandywine Creek below Downingtown, Pa. (01480870), and Brandywine Creek at Chadds Ford, Pa. (01481000). Statistically significant upward trends were determined for annual mean specific conductance at all three stations, indicating the total dissolved solids load has been increasing. If the current trend continues, the annual mean specific conductance could almost double from 1974 to 2050. The increase in specific conductance likely is due to increases in chloride concentrations, which have been increasing steadily over time at all three stations. No correlation was found between monthly mean specific conductance and monthly mean streamflow or base flow. Statistically significant upward trends in pH were determined for all three stations. Statistically significant upward trends in stream temperature were determined for East Branch Brandywine Creek below Downingtown, Pa. (01480870) and Brandywine Creek at Chadds Ford, Pa. (01481000). The stream water-quality data indicate substantial increases in the minimum daily dissolved oxygen concentrations in the Brandywine Creek over time. The Chester County Index of Biotic Integrity (CC-IBI) determined for 1998‒2013 was evaluated for the five biological sampling sites collocated with streamgages. CC-IBI scores are based on a 0‒100 scale with higher scores indicating better stream quality. Statistically significant upward trends in the CC-IBI were determined for West Branch Brandywine Creek at Modena, Pa. (01480617) and East Branch Brandywine Creek below Downingtown, Pa. (01480870). No correlation was found between the CC-IBI and streamflow, precipitation, or stream specific conductance, pH, temperature, or dissolved oxygen concentration. A Chester County average water budget was developed using the nine estimated watershed water budgets. Average precipitation was 48.4 inches, and average streamflow was 21.4 inches. Average runoff and base flow were 8.3 and 13.1 inches, respectively, and average evapotranspiration and estimation of errors was 27.2 inches."

Pennsylvania↗