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At least 1,117 records · Page 62Linked to original sources
USGS2014

The relative impacts of climate and land-use change on conterminous United States bird species from 2001 to 2075

Species distribution models often use climate data to assess contemporary and/or future ranges for animal or plant species. Land use and land cover (LULC) data are important predictor variables for determining species range, yet are rarely used when modeling future distributions. In this study, maximum entropy modeling was used to construct species distribution maps for 50 North American bird species to determine relative contributions of climate and LULC for contemporary (2001) and future (2075) time periods. Species presence data were used as a dependent variable, while climate, LULC, and topographic data were used as predictor variables. Results varied by species, but in general, measures of model fit for 2001 indicated significantly poorer fit when either climate or LULC data were excluded from model simulations. Climate covariates provided a higher contribution to 2001 model results than did LULC variables, although both categories of variables strongly contributed. The area deemed to be "suitable" for 2001 species presence was strongly affected by the choice of model covariates, with significantly larger ranges predicted when LULC was excluded as a covariate. Changes in species ranges for 2075 indicate much larger overall range changes due to projected climate change than due to projected LULC change. However, the choice of study area impacted results for both current and projected model applications, with truncation of actual species ranges resulting in lower model fit scores and increased difficulty in interpreting covariate impacts on species range. Results indicate species-specific response to climate and LULC variables; however, both climate and LULC variables clearly are important for modeling both contemporary and potential future species ranges.

PLoS ONE↗
USGS2006

Annual ground-water discharge by evapotranspiration from areas of spring-fed riparian vegetation along the eastern margin of Death Valley, 2000-02

Flow from major springs and seeps along the eastern margin of Death Valley serves as the primary local water supply and sustains much of the unique habitat in Death Valley National Park. Together, these major spring complexes constitute the terminus of the Death Valley Regional Ground-Water Flow System--one of the larger flow systems in the Southwestern United States. The Grapevine Springs complex is the least exploited for water supply and consequently contains the largest area of undisturbed riparian habitat in the park. Because few estimates exist that quantify ground-water discharge from these spring complexes, a study was initiated to better estimate the amount of ground water being discharged annually from these sensitive, spring-fed riparian areas. Results of this study can be used to establish a basis for estimating water rights and as a baseline from which to assess any future changes in ground-water discharge in the park. Evapotranspiration (ET) is estimated volumetrically as the product of ET-unit (general vegetation type) acreage and a representative ET rate. ET-unit acreage is determined from high-resolution multi-spectral imagery; and a representative ET rate is computed from data collected in the Grapevine Springs area using the Bowen-ratio solution to the energy budget, or from rates given in other ET studies in the Death Valley area. The ground-water component of ET is computed by removing the local precipitation component from the ET rate. Two different procedures, a modified soil-adjusted vegetation index using the percent reflectance of the red and near-infrared wavelengths and land-cover classification using multi-spectral imagery were used to delineate the ET units within each major spring-discharge area. On the basis of the more accurate procedure that uses the vegetation index, ET-unit acreage for the Grapevine Springs discharge area totaled about 192 acres--of which 80 acres were moderate-density vegetation and 112 acres were high-density vegetation. ET-unit acreage for two other discharge areas delineated in the Grapevine Springs area (Surprise Springs and Staininger Spring) totaled about 6 and 43 acres, respectively; and for the discharge areas delineated in the Furnace Creek area (Nevares Springs, Cow Creek-Salt Springs, Texas Spring, and Travertine Springs) totaled about 29, 13, 11, and 21 acres, respectively. In discharge areas other than Grapevine Springs, watering and spring diversions have altered the natural distribution of the vegetation. More...

Scientific Investigations Report↗
USGS2017

Parcels versus pixels: modeling agricultural land use across broad geographic regions using parcel-based field boundaries

Land use and land cover (LULC) change occurs at a local level within contiguous ownership and management units (parcels), yet LULC models primarily use pixel-based spatial frameworks. The few parcel-based models being used overwhelmingly focus on small geographic areas, limiting the ability to assess LULC change impacts at regional to national scales. We developed a modified version of the Forecasting Scenarios of land use change model to project parcel-based agricultural change across a large region in the United States Great Plains. A scenario representing an agricultural biofuel scenario was modeled from 2012 to 2030, using real parcel boundaries based on contiguous ownership and land management units. The resulting LULC projection provides a vastly improved representation of landscape pattern over existing pixel-based models, while simultaneously providing an unprecedented combination of thematic detail and broad geographic extent. The conceptual approach is practical and scalable, with potential use for national-scale projections.

Journal of Land Use Science↗
USGS2013

Land use and carbon dynamics in the southeastern United States from 1992 to 2050

Land use and land cover change (LUCC) plays an important role in determining the spatial distribution, magnitude, and temporal change of terrestrial carbon sources and sinks. However, the impacts of LUCC are not well understood and quantified over large areas. The goal of this study was to quantify the spatial and temporal patterns of carbon dynamics in various terrestrial ecosystems in the southeastern United States from 1992 to 2050 using a process-based modeling system and then to investigate the impacts of LUCC. Spatial LUCC information was reconstructed and projected using the FOREcasting SCEnarios of future land cover (FORE-SCE) model according to information derived from Landsat observations and other sources. Results indicated that urban expansion (from 3.7% in 1992 to 9.2% in 2050) was expected to be the primary driver for other land cover changes in the region, leading to various declines in forest, cropland, and hay/pasture. The region was projected to be a carbon sink of 60.4 gC m −2 yr −1 on average during the study period, primarily due to the legacy impacts of large-scale conversion of cropland to forest that happened since the 1950s. Nevertheless, the regional carbon sequestration rate was expected to decline because of the slowing down of carbon accumulation in aging forests and the decline of forest area.

Environmental Research Letters↗
USGS1978

An "optimal" filter for maps showing nominal data

An "optimal" filtering technique for use with nominal data, such as land use and land cover categories, has been developed. This method is based on the conditional probability joins of neighboring data elements. In addition to its use in performing filtering, the method can be used to calculate the likelihood of each data element being properly classified. The technique was tested on a land use data set for an area in Walnut Valley, Calif. The computer program performing the filtering process proved to be computationally efficient and produced satisfactory results. Useful statistics of the error estimation process were also generated. Future applications of the method to spectrally classified Landsat data are being explored.

Journal of Research of the U.S. Geological Survey↗
USGS2004

Edwards plateau: Analysis of land cover trends

The Land Cover Trends project studies the rates, causes, and consequences of contemporary (1973-2000) change in land use and land cover in the United States on an ecoregional basis. The Edwards Plateau ecoregion is the focus of this report. Landsat imagery from five dates during a nearly 30-year period are interpreted for randomly selected sample blocks. The resulting data provide the foundation for estimating change. Along with the image analysis, site visits to 90% of the sampled areas, geographical profiles, and socioeconomic data for the ecoregion are synthesized to assess regional driving forces and consequences of change. Complete project methodology can be found in Loveland et al [1].

Conference Paper↗
USGS2003

Comparison of two methods for delineating land use near monitoring wells used for assessing quality of shallow ground water

Two methods were compared for delineating land use near shallow monitoring wells. These wells were used to assess the effects of agricultural cropland on the quality of recently recharged ground water in two sand and gravel aquifers located near land surface. The two methods for delineating land use near wells were (1) the sector method, which used potentiometric-surface maps to estimate average flow direction and a ground-water-flow model to estimate maximum length of contributing area to the monitoring well within an upgradient sector; and (2) the circle method, which used a 500- meter radius circle around the well based on a national empirical analysis. Land uses were compiled for 29 wells in each of two surficial aquifers in the Red River of the North Basin within the area defined by each method. Land use near each well was interpreted from orthorectified photographs and site inspection for both delineation methods. Land use near individual wells characterized by each method varied greatly, which can affect the results of statistical correlations between land use and water quality. Land use determined by the circle method related more closely to the land use for each entire study area. Land use determined by the sector method (within 200 meters from the wells) compared more favorably to ground-water quality based on nitrate concentrations. The maximum length of contributing areas to wells estimated in this study may be of value for other studies of unconsolidated sand and gravel aquifers with similar hydrogeological characteristics of permeability, water-table slopes, recharge, and depth to water. The additional effort required for estimating the model delineation of land use and land cover for the sector method must be weighed against the improved confidence in statistical correlation between land use and the quality of shallow ground water. Improved scientific confidence and understanding of relations between land use and quality of ground water may encourage more effective implementation of land and water management for protecting water quality

Minnesota, North Dakota↗
USGS2020

Temporospatial shifts in Sandhill Crane staging in the Central Platte River Valley in response to climatic variation and habitat change

Over 80% of the Mid-Continent Sandhill Crane ( Antigone canadensis ) Population (MCP), estimated at over 660,000 individuals, stops in the Central Platte River Valley (CPRV) during spring migration from mid-February through mid-April. Research suggests that the MCP may be shifting its distribution spatially and temporally within the CPRV. From 2002 to 2017, we conducted weekly aerial surveys of Sandhill Cranes staging in the CPRV to examine temporal and spatial trends in their abundance and distribution. Then, we used winter temperature and drought severity measures from key wintering and early migratory stopover locations to assess the impacts of weather patterns on annual migration chronology in the CPRV. We also evaluated channel width and land cover characteristics using aerial imagery from 1938, 1998, and 2016 to assess the relationship between habitat change and the spatial distribution of the MCP in the CPRV. We used generalized linear models, cumulative link models, and Akaike’s information criterion corrected for small sample sizes (AICc) to compare temporal and spatial models. Temperatures and drought conditions at wintering and migration locations that are heavily used by Greater Sandhill Cranes ( A. c. tabida ) best predicted migration chronology of the MCP to the CPRV. The spatial distribution of roosting Sandhill Cranes from 2015 to 2017 was best predicted by the proportion of width reduction in the main channel since 1938 (rather than its width in 2016) and the proportion of land cover as prairie-meadow habitat within 800 m of the Platte River. Our data suggest that Sandhill Cranes advanced their migration by an average of just over 1 day per year from 2002 to 2017, and that they continued to shift eastward, concentrating at eastern reaches of the CPRV. Climate change, land use change, and habitat loss have all likely contributed to Sandhill Cranes coming earlier and staying longer in fewer reaches of the CPRV, increasing their site use intensity. These historically unprecedented densities may present a disease risk to Sandhill Cranes and other waterbirds, including Whooping Cranes ( Grus americana ). Our models suggest that conservation actions may be maintaining Sandhill Crane densities in areas that would otherwise be declining in use. We suggest that management actions intended to mitigate trends in the distribution of Sandhill Cranes, including wet meadow restoration, may similarly benefit prairie- and braided river–endemic species of concern.

Nebraska↗
USGS2014

Using high-resolution digital aerial imagery to map land cover

The Upper Midwest Environmental Sciences Center (UMESC) has used aerial photography to map land cover/land use on federally owned and managed lands for over 20 years. Until recently, that process used 23- by 23-centimeter (9- by 9-inch) analog aerial photos to classify vegetation along the Upper Mississippi River System, on National Wildlife Refuges, and in National Parks. With digital aerial cameras becoming more common and offering distinct advantages over analog film, UMESC transitioned to an entirely digital mapping process in 2009. Though not without challenges, this method has proven to be much more accurate and efficient when compared to the analog process.

Fact Sheet↗
USGS2021

Moose habitat selection and fitness consequences during two critical winter tick life stages in Vermont, United States

The moose ( Alces alces ) is a charismatic species in decline across much of their southern distribution in North America. In the northeastern United States, much of the reduction has been attributed to winter tick ( Dermacentor albipictus ) infestations. Winter ticks are fairly immobile throughout all life stages, and therefore their distribution patterns at any given time are shaped largely by the occurrence of moose across the landscape during the peak of two critical time periods: fall questing (when ticks latch onto moose) and spring drop-off (when engorged female ticks detach from moose). We used recent land cover and lidar data within a dynamic occupancy modeling framework to estimate first-order habitat selection (use vs. non-use) of female moose ( n = 74) during the tick questing and drop-off periods. Patch extinction and colonization rates between the fall questing and spring drop-off periods were strongly influenced by habitat and elevation, but these effects were diminished during the fall questing period when moose were more active across the landscape. From the fall questing period to the spring drop-off period, patches where colonization was high and extinction was low had higher proportions of young (shrub/forage) mixed forest at higher elevations. Further, we evaluated the fitness consequences of habitat selection by adult females during the fall questing period, when females and their calves acquire ticks. We compared Resource Selection Functions (RSF) for five females that successfully reared a calf to age 1 with five females whose calves perished due to ticks. Adult female moose whose offspring perished selected habitats in the fall that spatially coincided with areas of high occupancy probability during the spring tick drop-off period. In contrast, adult female moose whose offspring survived selected areas where the probability of occupancy during the spring drop-off was low; at present, natural selection may favor female adults who do not select the same habitats in fall as in spring. Our model coefficients and mapped results define “hotspots” that are likely encouraging the deleterious effects of the tick-moose cycle. These findings fill knowledge gaps about moose habitat selection that may improve the effectiveness of management aimed at reversing declining population trends.

Vermont↗
USGS2008

Summary and Evaluation of the Quality of Stormwater in Denver, Colorado, October 2001 to October 2005

Stormwater in the Denver area was sampled by the U.S. Geological Survey, in cooperation with the Urban Drainage and Flood Control District, in a network of five monitoring stations - three on the South Platte River and two on tributary streams, beginning in October 2001 and continuing through October 11, 2005. Composite samples of stormwater were analyzed at the U.S. Geological Survey National Water Quality Laboratory during water years 2003-2005 and the Metro Wastewater Reclamation District Laboratory during water year 2002 for water-quality properties such as pH, specific conductance, hardness, and residue on evaporation at 105 degrees Celsius; and for constituents such as major ions (calcium, chloride, fluoride, magnesium, potassium, sodium, and sulfate) in 2005, organic carbon and nutrients, including ammonia, nitrite plus nitrate, ammonia plus organic nitrogen, phosphorus, and orthophosphate; and for metals, including total and dissolved phases of copper, lead, manganese, and zinc. Samples analyzed for bacteriological indicators such as Escherichia coli and fecal coliform collected during selected storms also were analyzed at the Metro Wastewater Reclamation Laboratory. Discrete samples collected during selected storms were analyzed at the U.S. Geological Survey National Water Quality Laboratory for a suite of water-quality properties and constituents similar to those analyzed in the composite samples but that did not include determinations for total phases of metals. Streamflow characteristics associated with 176 composite stormwater samples indicate that most samples were collected from hydrographs classified as falling or event hydrographs and that only a few samples were collected from rising hydrographs. Results from laboratory analyses of the composite samples indicate spatial patterns in which concentrations for some constituents increase with contributing drainage area in the South Platte River and Sand Creek, but no well-defined relation with the amount of urban land cover was identified using data available from the U.S. Geological Survey National Land Cover data. Results from 22 discrete samples collected during two storms and used to obtain composited results with various weighting methods indicate that correlation coefficients between time-weighted and volume-weighted concentrations were generally at least 0.65, indicating a strong direct correlation between the two weighting methods for the stations involved in this study. In addition, the central tendency for relative percent differences between the time- and volume-weighting methods typically has an absolute value of about 10 or less, indicating good agreement for these weighting methods for data collected as part of this study. Comparison of stormwater results to numeric standards for streams developed by the Colorado Department of Public Health and Environment on the basis of use classifications indicates that, for water-quality properties and constituents other than bacteriological indicators, there were very few exceptions to numeric standards. Bacteriological indicators, however, such as Escherichia coli and fecal coliform consistently exceeded numeric standards in all bacteriological samples. An evaluation of laboratory results from composite samples on the basis of annual means indicates the presence of some simple upward and downward temporal trends in concentrations. In general, for annual means of results for all stations, hardness, ammonia plus organic nitrogen, total phosphorus, most dissolved metals (lead, manganese, and zinc), and all total metals (copper, lead, manganese, and zinc) all indicate annual means that decrease each year, or downward trends. Some trends were indicated only at individual stations in the network rather than at all stations. Ammonia as nitrogen at Union, Denver, and Henderson, orthophosphate at Sand Creek, and nitrite plus nitrate at Denver and Henderson all indicate decreasing annual means, or downward tr

Scientific Investigations Report↗
USGS2014

U.S. Geological Survey Science for the Wyoming Landscape Conservation Initiative - 2013 Annual Report

This is the sixth report produced by the U.S. Geological Survey (USGS) for the Wyoming Landscape Conservation Initiative (WLCI) to detail annual activities conducted by USGS for addressing specific management needs identified by WLCI partners. In FY2013, there were 25 ongoing and new projects conducted by the USGS. These projects fall into 8 major categories: (1) synthesizing and analyzing existing data to describe (model and map) current conditions on the landscape; (2) developing models for projecting past and future landscape conditions; (3) monitoring indicators of ecosystem conditions and the effectiveness of on-the-ground habitat projects; (4) conducting research to elucidate the mechanisms underlying wildlife and habitat responses to changing land uses; (5) managing and making accessible the large number of databases, maps, and other products being developed; (6) helping to integrate WLCI outcomes with future habitat enhancement and research projects; (7) coordinating efforts among WLCI partners; and (8) providing support to WLCI decision-makers and assisting with overall evaluation of the WLCI program. The two new projects initiated in FY2013 address (1) important agricultural lands in southwestern Wyoming, and (2) the influence of energy development on native fish communities. The remaining activities entailed our ongoing efforts to compile data, model landscape conditions, monitor trends in habitat conditions, conduct studies of wildlife responses to energy development, and upgrade Web-based products in support of both individual and overall WLCI efforts. Milestone FY2013 accomplishments included completing the development of a WLCI inventory and monitoring framework and the associated monitoring strategies, protocols, and analytics; and initial development of an Interagency Inventory and Monitoring Database, which will be accessible through the Monitoring page of the WLCI Web site at http://www.wlci.gov/monitoring. We also completed the initial phase of the mountain shrub-mapping project in the Big Piney-La Barge mule deer winter range. Finally, a 3-year survey of pygmy rabbits in four major gas-field areas was completed and used to validate the pygmy rabbit habitat model/map developed earlier in the project. Important products that became available for use by WLCI partners included publication of USGS Data Series report (http://pubs.usgs.gov/ds/800/pdf/ds800.pdf) that compiles our WLCI land cover and land use data, which depict current and historical patterns of sage-grouse habitat in relation to energy development and will be used to pose “what-if” scenarios to evaluate possible outcomes of alternative land-use strategies and practices on habitat and wildlife. Another important FY2013 product was a journal article (http://aapgbull.geoscienceworld.org/content/97/6/899.full) that describes the Mowry Shale and Frontier formation, which harbors coalbed methane and shale gas resources in Wyoming, Colorado, and Utah, for use in future scenario-building work. We also produced maps and databases that depict the structure and condition of aspen stands in the Little Mountain Ecosystem, and then presented this information to the Bureau of Land Management, Wyoming Game and Fish Department, and other interested entities for supporting aspen-management objectives.

Open-File Report↗
USGS2016

Prioritizing landscapes for longleaf pine conservation

We developed a spatially explicit model and map, as a decision support tool (DST), to aid conservation agencies creating or maintaining open pine ecosystems. The tool identified areas that are likely to provide the greatest benefit to focal bird populations based on a comprehensive landscape analysis. We used NLCD 2011, SSURGO, and SEGAP data to map the density of desired resources for open pine ecosystems and six focal species of birds and 2 reptiles within the historic range of longleaf pine east of the Mississippi River. Binary rasters were created of sites with desired characteristics such as land form, hydrology, land use and land cover, soils, potential habitat for focal species, and putative source populations of focal species. Each raster was smoothed using a kernel density estimator. Rasters were combined and scaled to map priority locations for the management of each focal species. Species’ rasters were combined and scaled to provide maps of overall priority for birds and for birds and reptiles. The spatial data can be used to identify high priority areas for conservation or to compare areas under consideration for maintenance or creation of open pine ecosystems.

Cooperator Science Series↗
USGS2012

History of land cover mapping

The historical roots of land-cover mapping reside in the early history of aerial photography and applications spanning forestry, agriculture, urban planning, and water-resources management. Considering this long span of mapping, any attempt to provide an exhaustive treatment of the full history of land-cover mapping will necessarily be incomplete. For that reason, this chapter on the history of land-cover mapping emphasizes the “modern” era of land-cover mapping, which has been arbitrarily defined to begin in the early 1970s. This was when civil space-based remote sensing came of age, and intellectual efforts focused on strategies for using new observations in understanding the characteristics of, and the changes in, land use and land cover.

Book chapter↗
USGS2017

Future scenarios of land change based on empirical data and demographic trends

Changes in land use and land cover (LULC) have important and fundamental interactions with the global climate system. Top-down global scale projections of land use change have been an important component of climate change research; however, their utility at local to regional scales is often limited. The goal of this study was to develop an approach for projecting changes in LULC based on land use histories and demographic trends. We developed a set of stochastic, empirical-based projections of LULC change for the state of California, for the period 2001–2100. Land use histories and demographic trends were used to project a “business-as-usual” (BAU) scenario and three population growth scenarios. For the BAU scenario, we projected developed lands would more than double by 2100. When combined with cultivated areas, we projected a 28% increase in anthropogenic land use by 2100. As a result, natural lands were projected to decline at a rate of 139 km 2 yr −1 ; grasslands experienced the largest net decline, followed by shrublands and forests. The amount of cultivated land was projected to decline by approximately 10%; however, the relatively modest change masked large shifts between annual and perennial crop types. Under the three population scenarios, developed lands were projected to increase 40–90% by 2100. Our results suggest that when compared to the BAU projection, scenarios based on demographic trends may underestimate future changes in LULC. Furthermore, regardless of scenario, the spatial pattern of LULC change was likely to have the greatest negative impacts on rangeland ecosystems.

California↗
USGS2009

Development of a local-scale urban stream assessment method using benthic macroinvertebrates: An example from the Santa Clara Basin, California

Research that explores the biological response to urbanization on a site-specific scale is necessary for management of urban basins. Recent studies have proposed a method to characterize the biological response of benthic macroinvertebrates along an urban gradient for several climatic regions in the USA. Our study demonstrates how this general framework can be refined and applied on a smaller scale to an urbanized basin, the Santa Clara Basin (surrounding San Jose, California, USA). Eighty-four sampling sites on 14 streams in the Santa Clara Basin were used for assessing local stream conditions. First, an urban index composed of human population density, road density, and urban land cover was used to determine the extent of urbanization upstream from each sampling site. Second, a multimetric biological index was developed to characterize the response of macroinvertebrate assemblages along the urban gradient. The resulting biological index included metrics from 3 ecological categories: taxonomic composition ( Ephemeroptera, Plecoptera, and Trichoptera), functional feeding group (shredder richness), and habit ( clingers). The 90 th -quantile regression line was used to define the best available biological conditions along the urban gradient, which we define as the predicted biological potential. This descriptor was then used to determine the relative condition of sites throughout the basin. Hierarchical partitioning of variance revealed that several site-specific variables (dissolved O 2 and temperature) were significantly related to a site's deviation from its predicted biological potential. Spatial analysis of each site's deviation from its biological potential indicated geographic heterogeneity in the distribution of impaired sites. The presence and operation of local dams optimize water use, but modify natural flow regimes, which in turn influence stream habitat, dissolved O 2 , and temperature. Current dissolved O 2 and temperature regimes deviate from natural conditions and appear to affect benthic macroinvertebrate assemblages. The assessment methods presented in our study provide finer-scale assessment tools for managers in urban basins. ?? North American Benthological Society.

Journal of the North American Benthological Societ↗
USGS1993

Using multisource data in global land-cover characterization: concepts, requirements, and methods

Global land-cover data are needed as baseline information for global change research. Multisource data, both coarse resolution satellite data and ancillary data, were used to produce a land-cover characteristics database for the conterqinous United States. Ancillary data, including elevation and ecological region data sets, were critical to the development, refinement, and information content of each class in the database. They contributed essential evidence for labeling and refining land-cover classes where differing types were represented by single spectral-temporal signatures. The characterization process can be expanded to a global effort depending on (1) the availability of global satellite coverage, (2) the quality and availability of ancillary data, and (3) the evolution of more sophisticated data visualization and analysis techniques.

Photogrammetric Engineering and Remote Sensing↗
USGS2009

Water-Quality Characterization of Surface Water in the Onondaga Lake Basin, Onondaga County, New York, 2005-08

Water-resources managers in Onondaga County, N.Y., have been faced with the challenge of improving the water-quality of Onondaga Lake. To assist in this endeavor, the U.S. Geological Survey undertook a 3-year basinwide study to assess the water quality of surface water in the Onondaga Lake Basin. The study quantified the relative contributions of nonpoint sources associated with the major land uses in the basin and also focused on known sources (streams with large sediment loads) and presumed sinks (Onondaga Reservoir and Otisco Lake) of sediment and nutrient loads, which previously had not been evaluated. Water samples were collected and analyzed for nutrients and suspended sediment at 26 surface-water sites and 4 springs in the 285-square-mile Onondaga Lake Basin from October 2005 through December 2008. More than 1,060 base-flow, stormflow, snowmelt, spring-water, and quality-assurance samples collected during the study were analyzed for ammonia, nitrite, nitrate-plus-nitrite, ammonia-plus-organic nitrogen, orthophosphate, phosphorus, and suspended sediment. The concentration of total suspended solids was measured in selected samples. Ninety-one additional samples were collected, including 80 samples from 4 county-operated sites, which were analyzed for suspended sediment or total suspended solids, and 8 precipitation and 3 snowpack samples, which were analyzed for nutrients. Specific conductance, salinity, dissolved oxygen, and water temperature were periodically measured in the field. The mean concentrations of selected constituents in base-flow, stormflow, and snowmelt samples were related to the land use or land cover that either dominated the basin or had a substantial effect on the water quality of the basin. Almost 40 percent of the Onondaga Lake Basin is forested, 30 percent is in agricultural uses, and almost 21 percent, including the city of Syracuse, is in developed uses. The data indicated expected relative differences among the land types for concentrations of nitrate, ammonia-plus-organic nitrogen, and orthophosphate. The data departed from the expected relations for concentrations of phosphorus and suspended sediment, and plausible explanations for these departures were posited. Snowmelt concentrations of dissolved constituents generally were greater and those of particulate constituents were less than concentrations of these constituents in storm runoff. Presumably, the snowpack acted as a short-term sink for dissolved constituents that had accumulated from atmospheric deposition, and streambed erosion and resuspension of previously deposited material, rather than land-surface erosion, were the primary sources of particulate constituents in snowmelt flows. Longitudinal assessments documented the changes in the median concentrations of constituents in base flows and event flows (combined stormflow and snowmelt) from upstream to downstream monitoring sites along the two major tributaries to Onondaga Lake - Onondaga Creek and Ninemile Creek. Median base-flow concentrations of ammonia and phosphorus and event concentrations of ammonia increased in the downstream direction in both streams. Whereas median event concentrations of other constituents in Onondaga Creek displayed no consistent trends, concentrations of ammonia-plus-organic nitrogen, orthophosphate, phosphorus, and suspended sediment in Ninemile Creek decreased from upstream to downstream sites. Springs discharging from the Onondaga and Bertie Limestone had measureable effects on water temperatures in the receiving streams and increased salinity and values of specific conductance in base flows. Loads of selected nutrients and suspended sediment transported in three tributaries of Otisco Lake were compared with loads from 1981-83. Loads of ammonia-plus-organic nitrogen and orthophosphate decreased from 1981-83 to 2005-08, but those of nitrate-plus-nitrite, phosphorus, and suspended sediment increased. The largest load increase was for suspende

Scientific Investigations Report↗