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At least 973 records · Page 54Linked to original sources
USGS2012

Biotic, water-quality, and hydrologic metrics calculated for the analysis of temporal trends in National Water Quality Assessment Program Data in the Western United States

The U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program was established by Congress in 1991 to collect long-term, nationally consistent information on the quality of the Nation's streams and groundwater. The NAWQA Program utilizes interdisciplinary and dynamic studies that link the chemical and physical conditions of streams (such as flow and habitat) with ecosystem health and the biologic condition of algae, aquatic invertebrates, and fish communities. This report presents metrics derived from NAWQA data and the U.S. Geological Survey streamgaging network for sampling sites in the Western United States, as well as associated chemical, habitat, and streamflow properties. The metrics characterize the conditions of algae, aquatic invertebrates, and fish. In addition, we have compiled climate records and basin characteristics related to the NAWQA sampling sites. The calculated metrics and compiled data can be used to analyze ecohydrologic trends over time.

Open-File Report↗
USGS2012

Temporal and spatial trends of chloride and sodium in groundwater in New Hampshire, 1960–2011

Data on concentrations of chloride and sodium in groundwater in New Hampshire were assembled from various State and Federal agencies and organized into a database. This report provides documentation of many assumptions and limitations of disparate data that were collected to meet wide-ranging objectives and investigates temporal and spatial trends of the data. Data summaries presented in this report and analyses performed for this study needed to take into account the 27 percent of chloride and 5 percent of sodium data that were censored (less than a reporting limit) at multiple reporting limits that systematically decreased over time. Throughout New Hampshire, median concentrations of chloride were significantly greater during 2000-2011 than in every decade since the 1970s, and median concentrations of sodium were significantly greater during 2000-2011 than during the 1990s. Results of summary statistics showed that the 50th, 75th, and 90th percentiles of the median concentrations of chloride and sodium by source (well) from Rockingham and Strafford counties were the highest in the State; and the 75th and 90th percentiles from Carroll, Coos, and Grafton counties were the lowest. Large increases in median concentrations of chloride and sodium for individual wells after 1995 compared with concentrations for years before were found in parts of Belknap and Rockingham counties and in small clusters within Carroll, Hillsborough, and Merrimack counties.

New Hampshire↗
USGS2013

Effects of equipment performance on data quality from the National Atmospheric Deposition Program/National Trends Network and the Mercury Deposition Network

The U.S. Geological Survey Branch of Quality Systems operates the Precipitation Chemistry Quality Assurance project (PCQA) to provide independent, external quality-assurance for the National Atmospheric Deposition Program (NADP). NADP is composed of five monitoring networks that measure the chemical composition of precipitation and ambient air. PCQA and the NADP Program Office completed five short-term studies to investigate the effects of equipment performance with respect to the National Trends Network (NTN) and Mercury Deposition Network (MDN) data quality: sample evaporation from NTN collectors; sample volume and mercury loss from MDN collectors; mercury adsorption to MDN collector glassware, grid-type precipitation sensors for precipitation collectors, and the effects of an NTN collector wind shield on sample catch efficiency. Sample-volume evaporation from an NTN Aerochem Metrics (ACM) collector ranged between 1.1–33 percent with a median of 4.7 percent. The results suggest that weekly NTN sample evaporation is small relative to sample volume. MDN sample evaporation occurs predominantly in western and southern regions of the United States (U.S.) and more frequently with modified ACM collectors than with N-CON Systems Inc. collectors due to differences in airflow through the collectors. Variations in mercury concentrations, measured to be as high as 47.5 percent per week with a median of 5 percent, are associated with MDN sample-volume loss. Small amounts of mercury are also lost from MDN samples by adsorption to collector glassware irrespective of collector type. MDN 11-grid sensors were found to open collectors sooner, keep them open longer, and cause fewer lid cycles than NTN 7-grid sensors. Wind shielding an NTN ACM collector resulted in collection of larger quantities of precipitation while also preserving sample integrity.

Open-File Report↗
USGS2015

Water use in Georgia by county for 2010 and water-use trends, 1985–2010

Water use and water withdrawals and returns in 2010 are estimated for each major river basin, principal aquifer, water-planning region, and county in Georgia using data obtained from various Federal and State agencies and local sources. Offstream water use in 2010 is estimated for the categories of public supply, domestic, commercial, industrial, mining, irrigation, livestock, aquaculture, and thermoelectric power. Water-use trends for 1985 to 2010 are also shown. The period between 2007 and 2010 was a challenging time economically and climatologically in Georgia. During that period, the United States was in the midst of a major recession, resulting in decreases in the manufacturing and construction industries and large increases in unemployment. During 2007, 2008, and the latter half of 2010, precipitation in Georgia was substantially below the 30-year norm. According to the 2010 Census of Population and Housing, nearly 9.7 million people lived in Georgia. The water for about 85 percent of that population was provided by public water suppliers. Estimated total water withdrawals from ground-water and surface-water sources were about 4,670 million gallons per day (Mgal/d) in 2010, about a 15-percent reduction from 2005 (5,471 Mgal/d). In 2010, thermoelectric-power facilities (2,046 Mgal/d) and public-supply uses (1,121 Mgal/d) accounted for 68 percent of all water withdrawn in Georgia. Surface-water withdrawals were greatest for thermoelectric-power generation (2,043 Mgal/d), whereas irrigation used the largest amount of groundwater (599 Mgal/d). Surface water provided 78 percent of the 1,121 Mgal/day withdrawn for public supply in 2010. Typically, counties in northern Georgia withdraw a larger percentage of water from surface water than groundwater sources; whereas, counties in the southern part of the State withdraw more water from groundwater sources. Historically, water withdrawals in Georgia were highest in 1980 (6,725 Mgal/d). By 1990, water use had decreased by 20 percent to 5,353 Mgal/d, but increased to 6,487 Mgal/d in 2000. By 2005, water use had decreased to an estimated 5,471 Mgal/d, and declined further to 4,670 Mgal/d in 2010—a 30-percent decrease since 1980. This decline was evident across all water-use categories, but was greatest for surface-water withdrawals by thermoelectric-power facilities. The estimated total water use per capita in 1985 (total withdrawals for all categories divided by total population) was about 850 gallons per day (gal/d), steadily decreasing to about 798 gal/d in 2000, and decreasing further to 460 gal/d in 2010. Although water use declined among all use categories during that 10-year period, most of the decline in per capita water use was caused by the large decrease in water used for thermoelectric-power generation. Throughout 1985–2010 water withdrawn for thermoelectric-power generation has constituted the largest volume of offstream water use in Georgia. Total withdrawals for thermoelectric-power generation declined about 37 percent between 2000 and 2010, mostly due to the decommissioning of power plants in the State. Also during this period, several power plants were shut down and re-tooled to use natural gas-powered generators; thus, water withdrawals for cooling were substantially reduced. The decline in water withdrawals and use between 2005 and 2010 can probably be attributed to several factors working together during this period: (1) water conservation laws and policies along with advances in water-conservation technology; (2) the onset of a major recession in 2007; and (3) below average rainfall in 2007, 2008, and the latter half of 2010. Because of these factors, water withdrawn by public suppliers decreased by 4.8 percent (despite a nearly 11-percent increase in population served) and per capita use decreased by 19 percent between 2005 and 2010. About 2,225 Mgal/d of water was returned to Georgia streams and lakes in 2010 under the National Pollutant Discharge Elimination System program administered by the Georgia Environmental Protection Division. This amount is about 48 percent of the total water withdrawn from all sources in 2010. Water returns declined 39 percent between 1995 and 2010, mirroring the decline in water withdrawals during that period. In addition, land applications of treated wastewater increased steadily between 1995 and 2010.

Georgia↗
USGS2016

Mountain goat abundance and population trends in the Olympic Mountains, northwestern Washington, 2016

Executive Summary We estimated abundance and trends of non-native mountain goats ( Oreamnos americanus ) in the Olympic Mountains of northwestern Washington, based on aerial surveys conducted during July 13–24, 2016. The surveys produced the seventh population estimate since the first formal aerial surveys were conducted in 1983. This was the second population estimate since we adjusted survey area boundaries and adopted new estimation procedures in 2011. Before 2011, surveys encompassed all areas free of glacial ice at elevations above 1,520 meters (m), but in 2011 we expanded survey unit boundaries to include suitable mountain goat habitats at elevations between 1,425 and 1,520 m. In 2011, we also began applying a sightability correction model allowing us to estimate undercounting bias associated with aerial surveys and to adjust survey results accordingly. The 2016 surveys were carried out by National Park Service (NPS) personnel in Olympic National Park and by Washington Department of Fish and Wildlife (WDFW) biologists in Olympic National Forest and in the southeastern part of Olympic National Park. We surveyed a total of 59 survey units, comprising 55 percent of the 60,218-hectare survey area. We estimated a mountain goat population of 623 ±43 (standard error, SE). Based on this level of estimation uncertainty, the 95-percent confidence interval ranged from 561 to 741 mountain goats at the time of the survey. We examined the rate of increase of the mountain goat population by comparing the current population estimate to previous estimates from 2004 and 2011. Because aerial survey boundaries changed between 2004 and 2016, we recomputed population estimates for 2011 and 2016 surveys based on the revised survey boundaries as well as the previously defined boundaries so that estimates were directly comparable across years. Additionally, because the Mount Washington survey unit was not surveyed in 2011, we used results from an independent survey of the Mount Washington unit conducted by WDFW biologists in 2012 and combined it with the 2011 survey results to produce a complete survey conducted over 2 years. The revised estimates of mountain goat abundance occurring at elevations above 1,520 m were 230 ±19 (SE) in 2004, 350 ±41 (SE) in 2011, and 584 ±39 (SE) in 2016. The difference between the overall 2016 population estimate (623 ±43 [SE]) and the smaller estimate (584 ±39 [SE]) reflected the number of mountain goats counted in the expanded survey areas added in 2011. Based on comparisons within the standardized survey boundary, the mountain goat population in the Olympic Mountains increased at an average finite rate of 6 percent annually from 2004 to 2011, 11 percent annually from 2011 to 2016, and 8 percent annually over the combined period. We caution that the population may have been underestimated in 2011 because of record heavy snows persisting into the survey season. Therefore, the rate of population increase from 2011 and 2016 may be overestimated. The rate of increase measured over the combined period (2004–16) may be more representative of the recent population growth. We conclude that the abundance of mountain goats has increased for more than a decade, and if the recent average rate of population growth were sustained, the population would increase by 45 percent over the next 5 years.

Washington↗
USGS2019

Monitoring annual trends in abundance of eelgrass (Zostera marina) at Izembek National Wildlife Refuge, Alaska, 2018

A lagoon-wide, point-sampling survey of eelgrass ( Zostera marina ) abundance was conducted in Izembek Lagoon, Alaska, August 7–16, 2018, the ninth year of annual surveys (2007–11, 2015–18). Mean predicted aboveground biomass of eelgrass across 116 sampled points was 238 grams per square meter (g m-2) (95 percent confidence interval: 203–278 g m-2) in 2018, an increase of 240 percent from the previous year’s low estimate of 97 g m-2 (95 percent confidence interval: 78–120 g m-2). The increase marked the third year since 2015 where eelgrass biomass was above the long-term mean (158 g m-2). Eelgrass biomass was stable over the 9 years of this survey. A separate (transect) survey for eelgrass abundance at Grant Point-Old Boat Launch showed annual trends in eelgrass biomass similar to the lagoon-wide survey, but over a slightly longer time (2007–18). The estimates of above-average eelgrass biomass in Izembek Lagoon were likely influenced by relatively warm air temperatures and little or no ice in winter (air temperatures 2.7 degrees Celsius greater than the 12-year mean) and average (cool) air temperatures during the growing season (April–August) in 2018.

Alaska↗
USGS2020

Southern (California) sea otter population status and trends at San Nicolas Island, 2017–2020

The southern sea otter ( Enhydra lutris nereis ) population at San Nicolas Island, California, has been monitored annually since the translocation of 140 sea otters to the island was completed in 1990. Monitoring efforts have varied in frequency and type across years. In 2017, the U.S. Navy and the U.S. Fish and Wildlife Service initiated a sea otter monitoring and research plan to determine the effects of military readiness activities on the growth or decline of the southern sea otter population at San Nicolas Island. The monitoring program, at its basic level, includes quarterly seasonal surveys of population abundance, distribution, and foraging activity. From 2017 to 2020, we measured a 22-percent per annum increase in population abundance (95-percent confidence interval =11–34 percent) with 114 total individuals as of February 2020. Coinciding with recent population growth, the sea otter distribution, which previously tended to concentrate on the west side, appears to have shifted toward an expansion of use in the north and especially greater seasonal use in the north and south during winter and spring. Foraging data were collected on a total of 2,675 foraging dives in 167 foraging bouts, and the majority of identified prey on successful dives (n=1,335) were sea urchins (940) followed by snails (240) and crabs (78). Small numbers of lobsters (26), octopus (16), and abalone (5) also were identified. Estimates of energy intake rates averaged 17.3 kilocalories per minute (95-percent confidence interval =15.6–19.0 kilocalories per minute) and suggest possible variations across years and seasons, but confidence intervals based on specific years of data were relatively wide. In addition to abundance, trends, distribution, and forage energy intake across seasons and years, these replicated surveys provide information on the precision of data achieved by quarterly survey effort. We used precision estimates and conducted simulation analyses to assess the power of detecting 10-percent or greater decreases in population growth rates and how this power is likely to change with years of observation, survey effort, and the size of decrease. These results can be useful to the planning of future monitoring and research of sea otters at San Nicolas Island.

California↗
USGS2024

Status of greater sage-grouse in the Bi-State Distinct Population Segment—An evaluation of population trends, habitat selection, and efficacy of conservation actions

Preface This study was completed to provide timely scientific information regarding greater sage-grouse population trends, habitat selection, and the efficacy of previous conservation actions implemented to benefit the Bi-State Distinct Population Segment (DPS). Specifically, we provide these analyses to inform the current (2024) status review and pending listing decision for the DPS being undertaken by the U.S. Fish and Wildlife Service. These findings provide updated, detailed, and comprehensive information regarding the status of a geographically isolated and genetically distinct population of a species of high conservation concern and their habitat. Importantly, this report also provides information on the efficacy of previously implemented conservation actions targeting the Bi-State DPS in a framework that is transferable throughout the species’ range.

California, Nevada↗
USGS1983

Supporting data for Environmental Trends

Information has been compiled as a companion document to ' Environmental Trends ' to provide analysts and researchers with statistical data to understand better how natural and man-made environments were changing. Subjects include land and climate; wetlands; wild areas; historic places; risk zones; settlement patterns; housing units; housing conditions; neighborhood conditions; transportation systems, including use and impacts on the environment such as noise, energy consumption; material use and solid waste; toxic substances, including radiation; cropland , forests and rangeland; wildlife, including extinct, threatened and endangered species; energy; water resources, water quality and air quality; and the biosphere. Statistics in the tables were taken from various published and unpublished sources. Therefore, the number of significant figures for the same information may differ. (Author 's abstract)

Open-File Report↗
USGS1987

National and regional trends in water-well drilling in the United States, 1964-84

Information on national and regional water well drilling activity is important for water resource planning and management and for water related equipment marketing. A study was conducted to analyze drilling trends on the basis of data for selected years from 1964 through 1984. The study focused primarily on the years 1964 and 1980-84, but also included data from 1960. Approximately 397,000 water wells were drilled in the United States in 1984. Seven states--Florida, Texas, New York, Michigan, North Carolina, Virginia, and Ohio--accounted for 39% of all the wells drilled in the United States in 1984. Florida led the nation in drilling activity with 45,600 new wells. The 1984 national drilling total was 2.6% > the total for 1980 (387,000) and 8.5% < the total for 1964 (434,000). However, these moderate differences do not reflect substantial year-to-year fluctuations that may have occurred during that 20-yr period. Qualitative comparisons suggest that drilling activity for a given year is closely related to the number of housing starts for that year. If so, there may have been peaks in drilling activity in 1972 and 1977-78 (corresponding to peaks in housing starts) that are not identified in this study because of a lack of available well drilling data for those years. Well drilling data for 1964 and the 1980-84 period probably represent a low to moderate level of drilling activity, and, if compared to earlier data, suggest that there has been no substantial growth or decline in the water well industry as a whole since the 1940's. (Author's abstract)

Open-File Report↗
USGS1987

Statistical, graphical, and trend summaries of selected water-quality and streamflow data from the Trinity River near Crockett, Texas, 1964-85

Statistical and graphical -.summaries of selected water-quality and'" streamflow data collected between 1964 and 1985 at the Trinity River near" Crockett are presented to document the baseline water quality of the Trinity River at this location. Dissolved oxygen exceeded 7.0 milligrams per liter in more than 50 percent- of the samples analyzed. The mean value of pH'was 7.4 units; the mean values of specific conductance and temperature were 619 microseimens per centimeter at 25 degrees Celsius and 20.5 degrees Celsius, respectively. As part of the statistical summaries, trend tests were conducted. Several small uptrends were detected for total nitrogen, total organic nitrogen, total ammonia nitrogen, total nitrite nitrogen, total nitrate nitrogen, total organic plus ammonia nitrogen, total nitrite plus nitrate nitrogen, and total phosphorus. Small downtrends were detected for biochemical oxygen demand and dissolved magnesium.

Open-File Report↗
USGS1991

Element dispersion in alluvium covering gold deposits east of the Osgood Mountains, Getchell Trend, Humboldt County, Nevada: slides and text of a talk given at the Association of Exploration Geochemists' 15th International Geochemical Exploration Symposium, Reno, Nevada

The current trend in mineral exploration is to search for covered deposits. In the Great Basin, this translates into searching for ore bodies buried by alluvial cover. The exploration techniques used range from random drilling to the use of new and exciting geochemical sampling media and analytical methods. But we have a problem. Many of our geochemical techniques lack a conceptual basis (We tried it and it worked) or the original conceptual basis is now suspect (The method also works when it shouldn't). What we need is a basic understanding of what is going on in the alluvium -- the third dimension. The discovery and development of the alluvium-covered, disseminated gold deposits at Rabbit Creek, Chimney Creek, and Pinson provides us with an opportunity to gain some knowledge of the dispersion of elements in the third dimension. The work presented here is one part of a larger multi-disciplinary study of the Kelly Creek Valley by the U.S. Geological Survey in cooperation with FirstMiss Gold, Inc., Gold Fields Mining Corporation, Pinson Mining Company, and Santa Fe Pacific Mining, Inc.

Nevada↗
USGS1999

Trends in base flows and extreme flows in the Beaver Kill Basin, Catskill Mountains, New York, 1915-94

Long-term records from five streamflow-gaging stations within and near the 300-square mile Beaver Kill Basin were analyzed to determine whether construction and presence of New York State Route 17 (NY 17), which was completed in the late 1960's, could have altered hydrologic processes in the basin and thereby adversely affected the basin's trout populations. The hypothesis investigated is that NY 17 has altered surface-water and shallow ground-water flowpaths where it parallels the stream and has increased runoff rates and thereby (1) increased the range in stream discharge (prolonged the base flows, decreased the low flows, and increased the high flows), and (2) altered stream-channel morphology through increased volume and velocity of stormflows. Analyses of base flows, discharge-duration curves, stage-to-discharge relations, peak and bankfull discharges, and flow extremes at a downstream (Beaver Kill at Cooks Falls) and a small tributary (Little Beaver Kill at Livingston Manor) site provide only limited evidence that NY 17 affected hydrologic processes within the basin. These effects are best indicated by significant increases in the magnitude and (or) the frequency of moderate to large discharges (exceedence probabilities) on an instantaneous basis at the Beaver Kill at Cooks Falls site after 1965. Increases in stormflows can not be attributed solely to NY 17, however, because the trend was evident long before NY 17 was constructed. Changes in land use in parts of the watershed may have contributed to gradual and continuous increases in stormflows throughout the entire 80 (plus) years of record. Changes in most base-flow and low-flow statistics for the downstream (Beaver Kill at Cooks Falls) site after 1965 are not statistically significant, but, changes in flow-duration curves and annual peak flows are evident. Flow-duration curves at this site indicate that there is a 16 percent increase in average daily flows after 1965. Annual peak flow data indicate that peak flows from storms recurring at 2-year (and longer) intervals after 1965 are significantly larger than those that recur at the same frequencies before 1965. The lack of comparable increases in peak flows from several nearby reference sites after 1965 indicate that the observed increases in peak flows may be unique to the Beaver Kill Basin. Flow-duration curves and many base-flow and high-flow statistics for the small tributary paralleled by NY 17 in the in the upper reaches of the basin (Little Beaver Kill at Livingston Manor) appear to be considerably altered since NY 17 was constructed. Flow-duration curves at this site indicate that there is about a 54 percent increase in average daily flows after 1965. Increases in the ratio of average annual base flow to average annual flow until 1965 then subsequent decreases suggest an extreme affect of NY 17 on hydrology of the subbasin. The effect of NY 17 on hydrology of the Little Beaver Kill subbasin cannot be defined with certainty, however, because the flow record after 1965 is too short; discharge monitoring was discontinued in 1981. The increases in peak stormflows in the lower Beaver Kill basin through the period of record may have increased the rates of bed-sediment erosion (degradation) and deposition and accelerated changes in stream-channel morphology, however, these possible effects were not examined. Suggestions for further investigation of the effects of NY 17 and of other factors on hydrology, channel morphology, fish habitat, and fish populations in the Beaver Kill Basin include (1) addition of streamflow gages or a creststage gage network at critical locations, (2) a review of engineering records and other aerial photographs for indications of changes in channel morphology, (3) compilation of temperature data and modeling spatial extent and magnitude of stressful summer temperatures (to selected trout species), and (4) confirming the extent and severity of toxic thermal episodes using in-situ fish toxicity tests.

Open-File Report↗
USGS2012

Central Basin and Range Ecoregion: Chapter 20 in Status and trends of land change in the Western United States--1973 to 2000

This chapter has been modified from original material published in Soulard (2006), entitled “Land-cover trends of the Central Basin and Range Ecoregion” (U.S. Geological Survey Scientific Investigations Report 2006–5288). The Central Basin and Range Ecoregion (Omernik, 1987; U.S. Environmental Protection Agency, 1997) encompasses approximately 343,169 km² (132,498 mi2) of land bordered on the west by the Sierra Nevada Ecoregion, on the east by the Wasatch and Uinta Mountains Ecoregion, on the north by the Northern Basin and Range and the Snake River Basin Ecoregions, and on the south by the Mojave Basin and Range and the Colorado Plateaus Ecoregions (fig. 1). Most of the Central Basin and Range Ecoregion is located in Nevada (65.4 percent) and Utah (25.1 percent), but small segments are also located in Idaho (5.6 percent), California (3.7 percent), and Oregon (0.2 percent). Basin-and-range topography characterizes the Central Basin and Range Ecoregion: wide desert valleys are bordered by parallel mountain ranges generally oriented northsouth. There are more than 33 peaks within the Central Basin and Range Ecoregion that have summits higher than 3,000 m (10,000 ft), but valleys in the ecoregion are also high, most having elevations above 1,200 m (4,000 ft) (Grayson, 1993).

California;Idaho;Nevada;Oregon;Utah↗
USGS2012

Sierra Nevada Ecoregion: Chapter 15 in Status and trends of land change in the Western United States--1973 to 2000

This chapter has been modified from original material published in Raumann and Soulard (2007), entitled “Land-cover trends of the Sierra Nevada Ecoregion, 1973–2000” (U.S. Geological Survey Scientific Investigations Report 2007–5011). The Sierra Nevada Ecoregion covers approximately 53,413 km² (20,623 mi²) with the majority of the area (98 percent) in California and the remainder in Nevada (fig. 1) (Omernik, 1987; U.S. Environmental Protection Agency, 1997). The Sierra Nevada Ecoregion is generally oriented north-south and is essentially defined by the Sierra Nevada physiographic province, which separates California’s Central Valley to the west from the Great Basin to the east. It is bounded by seven other ecoregions: Southern and Central California Chaparral and Oak Woodlands Ecoregion on the west; Klamath Mountains and Eastern Cascades Slopes and Foothills Ecoregions on the north; Southern California Mountains Ecoregion on the south; and Northern Basin and Range, Central Basin and Range, and Mojave Basin and Range Ecoregions on the east (fig. 1). The Sierra Nevada range is a granitic batholith, much of which is exposed at higher elevations, with a gradual western slope and a generally steep eastern escarpment.

California;Nevada↗
USGS2012

Southern California Mountains Ecoregion: Chapter 18 in Status and trends of land change in the Western United States--1973 to 2000

This chapter has been modified from original material published in Soulard and others (2007), entitled “Land-cover trends of the Southern California Mountains ecoregion” (U.S. Geological Survey Scientific Investigations Report 2007–5235). The Southern California Mountains Ecoregion (Omernik, 1987; U.S. Environmental Protection Agency, 1997) encompasses approximately 17,871 km² (6,900 mi²) of land located entirely within California. The ecoregion is bounded on the far north by the Sierra Nevada Ecoregion, on the east by the Mojave Basin and Range Ecoregion, on the southeast by the Sonoran Basin and Range Ecoregion, and on the west and north by Southern and Central California Chaparral and Oak Woodlands Ecoregion. In addition, the northern part of the ecoregion is separated from the Central California Valley Ecoregion by a narrow strip of the Southern and Central California Chaparral and Oak Woodlands Ecoregion (fig. 1).

California↗
USGS2012

Mojave Basin and Range Ecoregion: Chapter 29 in Status and trends of land change in the Western United States--1973 to 2000

This chapter has been modified from original material published in Sleeter and Raumann (2006), entitled “Land-cover trends in the Mojave Basin and Range Ecoregion” (U.S. Geological Survey Scientific Investigations Report 2006–5098). The Mojave Basin and Range Ecoregion (Omernik, 1987; U.S. Environmental Protection Agency, 1997) covers approximately 130,922 km 2 (50,549 mi 2 ) in the southwestern United States. The ecoregion, which encompasses parts of four states, includes the Mojave Desert and much of the other desert areas in southeastern California, as well as a large part of the southern Nevada desert (fig. 1). The ecoregion is bounded on the north by the Central Basin and Range Ecoregion, on the east by the Colorado Plateaus and the Arizona/New Mexico Plateau Ecoregions, on the south by the Sonoran Basin and Range Ecoregion, and on the west by the Southern California Mountains and the Sierra Nevada Ecoregions.

Arizona;California;Nevada;Utah↗