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At least 1,657 records · Page 92Linked to original sources
USGS2019

Offshore shallow structure and sediment distribution, Punta Gorda to Point Arena, Northern California

This publication consists of two map sheets that display shallow geologic structure, along with sediment distribution and thickness, for an approximately 150-km-long offshore section of the northern California coast between Punta Gorda and Point Arena. Each map sheet includes three maps at scales of either 1:100,000 or 1:200,000, and together the sheets include 30 figures that contain representative high-resolution seismic-reflection profiles. The maps and seismic-reflection surveys cover most of the continental shelf in this region. In addition, the maps show the locations of the shelf break and the 3-nautical-mile limit of California’s State Waters. The seismic-reflection data, which are the primary dataset used to develop the maps, were collected to support the California Seafloor Mapping Program, U.S. Geological Survey Offshore Geologic Hazards projects, and National Oceanic and Atmospheric Administration’s (NOAA’s) Ocean Explorer program. In addition to the two map sheets, this publication includes geographic information system data files of faults, sediment thicknesses, and depths-to-base of sediment The map area includes the northernmost section of the right-lateral San Andreas Fault, which extends offshore from Point Arena in the south to Point Delgada in the north. The San Andreas Fault is the primary structure in the widely distributed plate boundary between the Pacific Plate and the Sierra Nevada–Great Valley Microplate, with estimates of cumulative right slip of as much as up to 450 km. South of Point Delgada, fault-related transtension has resulted in development of the Noyo Basin. North of Point Delgada, the San Andreas Fault transitions into a complex contractional zone in and (or) south of the King Range, including a possible nearshore fault that may connect with the Mattole Canyon Fault. Quaternary sediments and bedrock underlie the shelf. On the seismic-reflection profiles, we digitally traced the thickness and depth of the uppermost seismic-stratigraphic unit, which is a focus of this publication. The upper contact of this unit is the seafloor; the lower contact is a transgressive surface of erosion, a commonly angular, wave-cut unconformity characterized by an upward change to lower amplitude, more diffuse reflections. On the basis of this lower contact, this stratigraphic unit is inferred to have been deposited on the shelf in the last about 21,000 years during the sea-level rise that followed the last major lowstand and the Last Glacial Maximum (LGM). Maps in this publication show both the thickness of this upper sediment unit and the depth to the base of the sediment unit. Within the map region, five different “domains” of post-LGM shelf sediment are delineated on the basis of sediment thickness and coastal geomorphology. Maximum sediment thickness (as much as 67 m) is found in the northern part of the region, along the steep south flank of the King Range. Minimum sediment thickness (areas of exposed bedrock) is found on fault-bounded uplifts, which include Tolo bank and Punta Gorda bank. Mean sediment thickness for the entire shelf in the map area between Punta Gorda and Point Arena is 8.9 m, and total sediment volume is 12,824×10 6 m 3 .

California↗
USGS2003

A bibliography of Klamath Mountains geology, California and Oregon, listing authors from Aalto to Zucca for the years 1849 to Mid-2003

This bibliography of Klamath Mountains geology was begun, although not in a systematic or comprehensive way, when, in 1953, I was assigned the task of preparing a report on the geology and mineral resources of the drainage basins of the Trinity, Klamath, and Eel Rivers in northwestern California. During the following 40 or more years, I maintained an active interest in the Klamath Mountains region and continued to collect bibliographic references to the various reports and maps of Klamath geology that came to my attention. When I retired in 1989 and became a Geologist Emeritus with the Geological Survey, I had a large amount of bibliographic material in my files. Believing that a comprehensive bibliography of a region is a valuable research tool, I have expended substantial effort to make this bibliography of the Klamath Mountains as complete as is reasonably feasible. My aim was to include all published reports and maps that pertain primarily to the Klamath Mountains, as well as all pertinent doctoral and master's theses. In addition, I included reports in which the Klamath Mountains are of significance but not the primary focus; these latter kinds are mostly reports that correlate the Klamath terranes with those of other provinces, that compare the genesis of Klamath rocks with those elsewhere, or that include the Klamath Mountains in a continental framework. Reports describing the geology of the overlap sequences such as the Great Valley sequence, Hornbrook Formation, and Tertiary sediments and volcanics are included where those rocks lie within the limits of the Klamath Mountains province, but are only selectively included where the overlap sequences are mainly peripheral to the province. The alphabetical part of the bibliography consists of approximately 1700 entries. The list of primary references probably is virtually complete through 1994 and includes some 1995 references. The earliest reference is to James Dwight Dana in 1849. In order to restrict the size of the topical part of the bibliography to reasonable limits, each reference is listed under only one subject although many references may be applicable to two or more subjects. Titles in the topical section are abbreviated to conserve space and still retain identity. The bibliography was compiled from a variety of sources. Some of the references have not been checked against the original publications for accuracy. Caveat emptor! I would appreciate being informed of any errors or ommissions in order that a corrected and updated version of the bibliography may be prepared. I thank Nancy Blair for assistance in verifying some of the references, and thank Mary Donato and Robert Brown for helpful suggestions regarding the topical part of the bibliography. Since the first version of this bibliography was released in 1995, the total number of entries has increased from approximately 1700 to 1937, which indicates a continued high interest in the geology of the Klamath Mountains province. The total number of entries includes 73 Ph.D. theses and 123 Masters theses representing 26 universities.

Open-File Report↗
USGS1977

Atlantic Margin Coring Project 1976: Preliminary Report on Shipboard and Some Laboratory Geotechnical data

This report presents reduced shipboard geotechnical data collected during the 1976 Atlantic Margin Coring Project; results of laboratory tests of specific gravity, water content, bulk density, and Atterberg limits; and sedimentation-compression e log p curves showing consolidation. A description of the procedures used at sea and in the laboratory and a short preliminary summary of the shipboard results also is included. The involvement of Marine Geotechnical Laboratory (MGL), Lehigh University, personnel in the 1976 Atlantic Margin Coring Project can be divided into two phases. In Phase One, the Lehigh nuclear-transmission densitometer was rebuilt to process cores at sea more rapidly than previously had been done in the laboratory, the equipment was assembled and tested aboard the Glomar Conception, and at-sea geotechnical measurements were made during the duration of the cruise. Data sheets were prepared for both unopened core sections (Appendix III) and split-core samples (Appendix IV). Completed data forms are on file at the MGL and at the Geological Survey in Woods Hole. Phase Two included reduction of the shipboard data, testing of all geotechnical samples taken from cores split aboard the ship, and certain other analytical work ashore utilizing the geotechnical measurements. Water content and weight/volume bulk density tests were performed at the MGL. Specific gravity and Atterberg limit tests and certain calculations were performed by Geological Survey personnel at the Corpus Christi, Texas, laboratory. During Phase One, 37 unopened, 1.5-m-long core sections were selected by Lehigh personnel for subsequent static and dynamic triaxial and consol­idation testing ashore. The disposition of these cores is controlled by Geological Survey Project personnel; they are not further discussed in this report. A depth convention has been adopted in this report for the convenience of labeling core sections and analyzing the data. Each 9.2-m-long (30 ft) core liner had a maximum penetration depth referenced to the water-sediment interface; these data are given in Hathaway, et al. (1976). Each 9.2-m-long core liner was cut into six or fewer sections, each 1.5 m (5 ft) in length, aboard the ship. To the maximum penetration depth, 0.2 m was subtracted to obtain the depth at the bottom of the first 1.5 m section above the core catcher. To obtain values at the bottom of the remaining 1.5 m sections, an additional 1.5 m was added for each section. The depth of the bottom of each core section was used for all values obtained using the nuclear densitometer. Tests within core sections and samples collected from core sections were assigned depths based on the location of the test or sample within the core section. It should be clearly recognized that all depths within a 9.2-m-long core are estimates of the true depth, which cannot be uniquely calculated because of the uncertainty of the relationship of sediment contained within the core liner to true in situ depths. This report is considered to be preliminary because the author has not had access to the final lithologic logs or paleontological results, upon which a more accurate description of geotechnical results could be based. It would be inappropriate to comment on geological hazards until this information is made available.

Atlantic Ocean↗
USGS1994

Selected data on characteristics of glacial-deposit and carbonate-rock aquifers, Midwestern Basin and Arches region

In 1988, the Geological Survey (USGS) began study to examine the hydrogeologic framework, ground-water-flow systems, water chemistry, and withdrawal response of aquifers in glacial deposits and carbonate rock in the Midwestern Basins and Arches Region in western Ohio and eastern Indiana. As part of this study, data from pumped-well tests and instantaneous-rechange tests (slug tests) of wells completed in the glacial-deposit and carbonate-rock aquifers were compiled from reports and information on file with State agencies, environmental consulting firms, drilling firms, municipalities, universities, and the USGS. The data, from 73 counties in Ohio and Indiana, were entered into a computerized data base in a spreadsheet format and subsequently into a geographic information system (GIS). Aquifer-characteristics data from this compilation include the results of 105 pumped-well tests and 39 slug tests in wells completed in glacial deposits, 174 pumped-well tests in wells completed in the carbonate-rock aquifer, and 4 slug tests in wells completed in limestones and shales of Ordovician age. Transmissivities from the pumped-well tests in wells completed in glacial till and glacial-deposit aquifers (sands and gravels) range from 1.54 to 69,700 feet squared per day. Storage coefficients or specific yields range from 0.00002 to 0.38 at these wells. Horizontal-hydraulic conductivities from the slug tests in wells completed in glacial-deposit aquifers range from 0.33 to 1,000 feet per day. Transmissivities from the pumped-well tests in wells completed in the carbonate-rock aquifer range from 70 to 52,000 feet squared per day. Storage coefficient or specific yields at these wells range from 0.00001 to 0.05. Horizontal hydraulic conductivities from the slug tests in wells completed in limestones and shales of Ordovician age range from 0.0016 to 12 feet per day. These data are summarized in tables and figures within this report. The collection and compilation of selected aquifer-characteristic data for the glacial-deposit and carbonate-rock aquifers within the Midwestern Basin and Arches Region of Shaver (1985) are an essential part of the Midwestern Basins and Arches Regional Aquifer-Systems Analysis (Midwestern Basins and Arches RASA) project of the U.S. Geological Survey (USGS). Specifically, the data are needed to help describe ground-water flow in the regional aquifer system, which isone of the objectives of the Midwestern Basins and Arches RASA project (Bugliosi, 1990). To meet this objective, the Midwestern Basins and Arches RASA began subprojects in the Ohio and Indiana offices of the USGS to collect and compile available aquifer-characteristics data from aquifer tests of the glacial-deposit and carbonate-rock aquifers. The data were not reanalyzed to verify accuracy because of time constraints and insufficient data in many cases.

Illinois, Indiana, Kentucky, Ohio, West Virginia↗
USGS1981

Arctic summary report: Outer Continental Shelf and onshore oil and gas activities and impacts in the Arctic : a summmary report, October 1981

Due to the amount of Federal and State oil and gas activity in the Arctic subregion and the need for comprehensive planning, State and local officials requested coverage of all oil and gas activity in the area. The first lease sale of offshore lands in the Beaufort Sea was held by the State of Alaska in 1969. The leasing process for oil and gas exploration on the Beaufort Sea Outer Continental Shelf (OCS) began in April 1976 with the first Federal lease sale in the subregion (Joint Federal/State Beaufort Sea Lease Sale) held in 1979. This sale was held jointly by the Department of the Interior and the State of Alaska because of conflicting jurisdictional claims to certain tracts in the sale area. The jurisdictional dispute will be resolved by the U.S. Supreme Court, but a decision is not expected for several years. The joint sale was held on December 11, 1979. However, bids on the Federal tracts were not accepted until July 1980 because of litigation. Of the 117 tracts offered, 86 were leased as a result of the sale. Of these 86 tracts, 24 are federally managed and 62 are State-managed. Two exploration plans have been submitted for the federally managed joint lease sale (Sale BF) area. Both plans call for building a gravel island and exploratory drilling of several tracts, but no drilling permits have yet been filed. Three exploratory wells have been drilled on or into State-managed tracts. These include one well drilled directionally into Tract 75, one into Tract 76, and one well drilled from Challenge Island, a natural barrier island. Additional exploratory wells are planned for the 1981-82 drilling season on State-managed tracts. The next OCS sale in the Beaufort Sea, Lease Sale 71, is proposed for September 1982. The first two sales in the National Petroleum Reserve in Alaska are being planned for December 1981 and the late spring or early summer of 1982 and will involve a total of 2 million acres (809,200 hectares). In anticipation of future leasing, plans for geophysical surveys in the Arctic National Wildlife Refuge are also being formulated. Four State lease sales have been held in the Arctic, in addition to the Joint Federal/State Lease Sale. These onshore sales have resulted in the leasing of lands on which a number of commercial discoveries have been made, including the discovery of the largest hydrocarbon accumulation in North America at Prudhoe Bay. Exploration, development, and production are continuing on these State lands. The State of Alaska has plans for three future lease sales in the Arctic to be held in the spring of 1982 and 1983 and the fall of 1984. Leasing and exploration are also under way on Arctic Slope Regional Corporation lands. Transportation systems in the Arctic have been developed to accommodate production on State lands. Some of the production from OCS tracts, as well as other Arctic lands, may be handled by the existing Trans-Alaska Pipeline System. However, a number of additional transportation strategies are being considered, including the Alaska Natural Gas Transportation System, additional oil pipelines, and tanker transport. The pace of oil and gas production in the Arctic will depend in part on the number and type of transportation modes available. The support bases at Prudhoe Bay are expected to be used to some extent for future activities on the OCS. However, expanded and new facilities will also be required, depending on the location of discoveries on the OCS and on other Arctic lands. The impacts resulting from OCS activities in the Arctic will be particularly important because of their contribution to the regionwide and cumulative impacts arising from Federal onshore, State, and regional corporation oil and gas exploration, development, and production in the Arctic.

Alaska↗
USGS1939

Geological report on water conditions at Platt National Park, Oklahoma

Platt National Park, located in southern Oklahoma, containing 842 acres, was established by Acts of Congress in 1902, 1904, and 1906. The reason for the setting aside of this area was the presence in the area of some 30 'mineral' springs, the water from which contains sulphur, bromide, salt, and other minerals, which are believed to possess medicinal qualities. For many generations the sulphur springs of the Chickasaw Nation had been known for their reputed healing qualities. It had long been the custom for families to come from considerable distances on horseback and in wagons and camp near the springs, in order to drink the water. In course of time a primitive town, known as Sulphur Springs, grew up near a group of springs known since as Pavilion Springs at the mouth of Sulphur Creek, now known as Travertine Creek. This town was still in existence at the time of my first visit to the locality in July, 1901. At this time, in company with Joseph A. Taff, of the United States Geological Survey, I spent a week riding over the country making a preliminary survey looking toward the setting aside of the area for a National Park. After the establishment of the National Park, the old town of Sulphur Springs was abandoned, and when the present boundaries of the park had been established the present town of Sulphur, now county seat of Murray County, grew up. In July 1906, on request of Superintendent Joseph F. Swords, I visited the park and made an examination of the various springs and submitted a report, dated August 15, 1906, to Secretary of the Interior E.A. Hitchcock. Copies of this report are on file in the Regional Office and at Platt National Park. In this report I set forth the approximate amount of flow of the various springs, the character of the water in each, and the conditions of the springs as of that date. I also made certain recommendations regarding proposed improvements of each spring. In this report I say: 'In the town of Sulphur, four wells have been drilled to a depth of between 450 and 500 feet in which artesian water has been secured. These wells are said to flow 200,000 gallons each per day.' I also say: 'From a study of the log of one of these wells, it appears that the artesian water is derived from the upper part of the Simpson sandstone. It is very probable that the water of the springs is derived from the same source.' This early was recognized the relation between the water from the mineral springs and that from the artesian wells. As the years have passed, other wells have been drilled in the town of Sulphur, chiefly to supply water for mineral baths and for swimming pools, so that to date more than 30 wells have been drilled. The exact number is not known. The custom has usually been to turn the wells loose and permit them to flow at full capacity, although some of the wells have been 'valved in' and the flow reduced. An estimate furnished me by the Secretary of the Chamber of Commerce in 1937, referred to later in this report, indicated that at that time 16 wells were flowing approximately 28,800,000 gallons of water per day, practically all of which ran to waste. For many years geologists in Oklahoma and elsewhere have watched this unrestricted waste of water from the artesian wells at Sulphur with growing concern. Remembering the history of other artesian basins throughout the world, these geologists believed that in all probability it was only a question of time until the water in the Sulphur artesian basin would begin to fail. On two different occasions the State Geologist of Oklahoma, bearing these conditions in mind, has prepared and had introduced into the State Legislature a bill which, if enacted into law, would have regulated the flow of water in artesian wells throughout the State. Both bills died in committee. Partly on account of the drought of the past three years, the matter has been brought to a head. In September 1938, Buffalo and Antelope Springs at the hea

Open-File Report↗
USGS1996

Level II scour analysis for Bridge 42 (RANDVT00120042) on State Highway 12, crossing Third Branch White River, Randolph, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure RANDVT00120042 on State Highway 12 crossing the Third Branch White River, Randolph, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). A Level I study is included in Appendix E of this report. A Level I study provides a qualitative geomorphic characterization of the study site. Information on the bridge available from VTAOT files was compiled prior to conducting Level I and Level II analyses and can be found in Appendix D. The site is in the Green Mountain physiographic division of central Vermont in the town of Randolph. The 61.9-mi 2 drainage area is in a predominantly rural drainage basin. In the vicinity of the study site, the left and right banks have moderate tree cover with residential and commercial buildings on the overbank areas. In the study area, the Third Branch White River has a sinuous channel with a slope of approximately 0.013 ft/ft, an average channel top width of 133 ft and an average channel depth of 5 ft. The predominant channel bed material is gravel with a median grain size ( D 50 ) of 49.6 mm (0.163 ft). Bank material is sand and gravel (D 50 is 3.08 mm or 0.010 ft). The geomorphic assessment at the time of the Level I site visits on July 8, 1994 and December 13, 1994, indicated that the reach has experienced vertical degradation. A drop structure has been constructed downstream of the bridge to prevent further degradation. In addition to the degradation of the stream bed, there is local pier scour at the bridge site as well. At the nose of the pier in the main channel, the bed is approximately three feet below the mean thalweg and two feet below the bottom of the pier footing. The State Highway 12 crossing of the Third Branch White Riveris a 220-ft-long, two-lane bridge consisting of four concrete spans. The maximum span length is 57 ft. (Vermont Agency of Transportation, written commun., July 29, 1994). The bridge is supported by vertical, concrete abutments and three concrete piers. The toe of the left abutment is at the channel edge. The toe of the right abutment is set back on the right over-bank. The roadway centerline on the structure has a slight horizontal curve; however, the main channel is skewed approximately 5 degrees to the bridge. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1993). Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. The scour analysis results are presented in tables 1 and 2 and a graph of the scour depths is presented in figure 8.

Vermont↗
USGS2011

Tectonic and metallogenic model for northeast Asia

This document describes the digital files in this report that contains a tectonic and metallogenic model for Northeast Asia. The report also contains background materials. This tectonic and metallogenic model and other materials on this report are derived from (1) an extensive USGS Professional Paper, 1765, on the metallogenesis and tectonics of Northeast Asia that is available on the Internet at http://pubs.usgs.gov/pp/1765/; and (2) the Russian Far East parts of an extensive USGS Professional Paper, 1697, on the metallogenesis and tectonics of the Russian Far East, Alaska, and the Canadian Cordillera that is available on the Internet at http://pubs.usgs.gov/pp/pp1697/. The major purpose of the tectonic and metallogenic model is to provide, in movie format, a colorful summary of the complex geology, tectonics, and metallogenesis of the region. To accomplish this goal four steps were taken: (1) 13 time-stage diagrams, from the late Neoproterozoic (850 Ma) through the present (0 Ma), were adapted, generalized, and transformed into color static time-stage diagrams; (2) the 13 time-stage diagrams were placed in a computer morphing program to produce the model; (3) the model was examined and each diagram was successively adapted to preceding and subsequent diagrams to match the size and surface expression of major geologic units; and (4) the final version of the model was produced in successive iterations of steps 2 and 3. The tectonic and metallogenic model and associated materials in this report are derived from a project on the major mineral deposits, metallogenesis, and tectonics of the Northeast Asia and from a preceding project on the metallogenesis and tectonics of the Russian Far East, Alaska, and the Canadian Cordillera. Both projects provide critical information on bedrock geology and geophysics, tectonics, major metalliferous mineral resources, metallogenic patterns, and crustal origin and evolution of mineralizing systems for this region. The major scientific goals and benefits of the projects are to: (1) provide a comprehensive international data base on the mineral resources of the region that is the first extensive knowledge available in English; (2) provide major new interpretations of the origin and crustal evolution of mineralizing systems and their host rocks, thereby enabling enhanced, broad-scale tectonic reconstructions and interpretations; and (3) promote trade and scientific and technical exchanges between North America and eastern Asia.

Summit, Colorado↗
USGS2013

Evaluation of the groundwater flow model for southern Utah and Goshen Valleys, Utah, updated to conditions through 2011, with new projections and groundwater management simulations

The U.S. Geological Survey (USGS), in cooperation with the Southern Utah Valley Municipal Water Association, updated an existing USGS model of southern Utah and Goshen Valleys for hydrologic and climatic conditions from 1991 to 2011 and used the model for projection and groundwater management simulations. All model files used in the transient model were updated to be compatible with MODFLOW-2005 and with the additional stress periods. The well and recharge files had the most extensive changes. Discharge to pumping wells in southern Utah and Goshen Valleys was estimated and simulated on an annual basis from 1991 to 2011. Recharge estimates for 1991 to 2011 were included in the updated model by using precipitation, streamflow, canal diversions, and irrigation groundwater withdrawals for each year. The model was evaluated to determine how well it simulates groundwater conditions during recent increased withdrawals and drought, and to determine if the model is adequate for use in future planning. In southern Utah Valley, the magnitude and direction of annual water-level fluctuation simulated by the updated model reasonably match measured water-level changes, but they do not simulate as much decline as was measured in some locations from 2000 to 2002. Both the rapid increase in groundwater withdrawals and the total groundwater withdrawals in southern Utah Valley during this period exceed the variations and magnitudes simulated during the 1949 to 1990 calibration period. It is possible that hydraulic properties may be locally incorrect or that changes, such as land use or irrigation diversions, occurred that are not simulated. In the northern part of Goshen Valley, simulated water-level changes reasonably match measured changes. Farther south, however, simulated declines are much less than measured declines. Land-use changes indicate that groundwater withdrawals in Goshen Valley are possibly greater than estimated and simulated. It is also possible that irrigation methods, amount of diversions, or other factors have changed that are not simulated or that aquifer properties are incorrectly simulated. The model can be used for projections about the effects of future groundwater withdrawals and managed aquifer recharge in southern Utah Valley, but rapid changes in withdrawals and increasing withdrawals dramatically may reduce the accuracy of the predicted water-level and groundwater-budget changes. The model should not be used for projections in Goshen Valley until additional withdrawal and discharge data are collected and the model is recalibrated if necessary. Model projections indicate large drawdowns of up to 400 feet and complete cessation of natural discharge in some areas with potential future increases in water use. Simulated managed aquifer recharge counteracts those effects. Groundwater management examples indicate that drawdown could be less, and discharge at selected springs could be greater, with optimized groundwater withdrawals and managed aquifer recharge than without optimization. Recalibration to more recent stresses and seasonal stress periods, and collection of new withdrawal, stream, land-use, and discharge data could improve the model fit to water-level changes and the accuracy of predictions.

Utah↗
USGS2019

Offshore shallow structure and sediment distribution, Point Sur to Point Arguello, central California

This publication consists of three map sheets that display shallow geologic structure, along with sediment distribution and thickness, for an about 225-km-long offshore section of the central California coast between Point Sur and Point Arguello. Each map sheet includes three maps, at scales of either 1:150,000 or 1:200,000, as well as a set of figures that contain representative high-resolution seismic-reflection profiles. The maps and seismic-reflection surveys cover most of the continental shelf in this region. In addition, the maps show the locations of the shelf break and the 3-nautical-mile limit of California’s State Waters. The seismic-reflection data, which are the primary dataset used to develop the maps, were collected to support the California Seafloor Mapping Program and U.S. Geological Survey Offshore Geologic Hazards projects. In addition to the three map sheets, this publication includes geographic information system data files of interpreted faults, folds, sediment thicknesses, and depths-to-base of sediment. The faults and folds shown on the maps have been locally simplified as appropriate for the map scales. The right-lateral San Gregorio–Hosgri Fault (SGHF) is the most significant structure in the map area. On a regional scale, the SGHF is part of a 400-km-long, right-lateral fault system that extends northwestward from Point Arguello to the area offshore of San Francisco, where it merges with the San Andreas Fault. From north to south in this part of central California, the SGHF lies offshore between the south flank of Point Sur and the north flank of Point Piedras Blancas, then comes onshore at Point Piedras Blancas, before heading offshore again between the south flank of Point Piedras Blancas and Point Arguello. Cumulative fault offset along the SGHF is as much as 150 to 160 km, decreasing to the south by transferring slip on to northwest-striking faults that converge with the SGHF both onland and offshore from the east. In the map area, the offshore-converging faults include the Los Osos Fault, the Shoreline–Point Buchon Fault, the Casmalia Fault, and the Lions Head Fault. Quaternary sediments and bedrock underlie the shelf. On the seismic-reflection profiles, we divide Quaternary shelf sediments into two units. Characterizing the younger, upper unit is a focus of this publication. This unit is inferred to have been deposited on the shelf in the last about 21,000 years during the sea-level rise that followed the last major lowstand and the Last Glacial Maximum (LGM). This upper unit overlies a transgressive surface of erosion, a commonly angular, wave-cut unconformity, and is generally characterized by low-amplitude, continuous to moderately continuous, diffuse, subparallel, generally flat reflections. Maps in this publication show both the thickness of this upper sediment unit and the depth to the base of the sediment unit. Within the map region, 11 different “domains” of post-LGM shelf sediment are delineated on the basis of sediment thickness and coastal geomorphology. Maximum sediment thickness is in the southern part of the region, offshore of the mouths of the Santa Ynez and Santa Maria Rivers. Minimum sediment thickness is found offshore of prominent rocky points, including Point Buchon and Piedras Blancas. Mean sediment thickness for the entire shelf in the map area between Point Sur and Point Arguello is 12.2 m, and total sediment volume is 24.7 million cubic meters.

California↗
USGS2017

Potential effects of existing and proposed groundwater withdrawals on water levels and natural groundwater discharge in Snake Valley and surrounding areas, Utah and Nevada

Several U.S. Department of Interior (DOI) agencies are concerned about the cumulative effects of groundwater development on groundwater resources managed by, and other groundwater resources of interest to, these agencies in Snake Valley and surrounding areas. The new water uses that potentially concern the DOI agencies include 12 water-right applications filed in 2005, totaling approximately 8,864 acre-feet per year. To date, only one of these applications has been approved and partially developed. In addition, the DOI agencies are interested in the potential effects of three new water-right applications (UT 18-756, UT 18-758, and UT 18-759) and one water-right change application (UT a40687), which were the subject of a water-right hearing on April 19, 2016. This report presents a hydrogeologic analysis of areas in and around Snake Valley to assess potential effects of existing and future groundwater development on groundwater resources, specifically groundwater discharge sites, of interest to the DOI agencies. A previously developed steady-state numerical groundwater-flow model was modified to transient conditions with respect to well withdrawals and used to quantify drawdown and capture (withdrawals that result in depletion) of natural discharge from existing and proposed groundwater withdrawals. The original steady-state model simulates and was calibrated to 2009 conditions. To investigate the potential effects of existing and proposed groundwater withdrawals on the groundwater resources of interest to the DOI agencies, 10 withdrawal scenarios were simulated. All scenarios were simulated for periods of 5, 10, 15, 30, 55, and 105 years from the start of 2010; additionally, all scenarios were simulated to a new steady state to determine the ultimate long-term effects of the withdrawals. Capture maps were also constructed as part of this analysis. The simulations used to develop the capture maps test the response of the system, specifically the reduction of natural discharge, to future stresses at a point in the area represented by the model. In this way, these maps can be used as a tool to determine the source of water to, and potential effects at specific areas from, future well withdrawals. Downward trends in water levels measured in wells indicate that existing groundwater withdrawals in Snake Valley are affecting water levels. The numerical model simulates similar downward trends in water levels; simulated drawdowns in the model, however, are generally less than observed water-level declines. At the groundwater discharge sites of interest to the DOI agencies, simulated drawdowns from existing well withdrawals (projected into the future) range from 0 to about 50 feet. Following the addition of the proposed withdrawals, simulated drawdowns at some sites increase by 25 feet. Simulated drawdown resulting from the proposed withdrawals began in as few as 5 years after 2014 at several of the sites. At the groundwater discharge sites of interest to the DOI agencies, simulated capture of natural discharge resulting from the existing withdrawals ranged from 0 to 87 percent. Following the addition of the proposed withdrawals, simulated capture at several of the sites reached 100 percent, indicating that groundwater discharge at that site would cease. Simulated capture following the addition of the proposed withdrawals increased in as few as 5 years after 2014 at several of the sites.

Nevada, Utah↗
USGS2014

Potential effects of existing and proposed groundwater withdrawals on water levels and natural groundwater discharge in Snake Valley, Juab and Millard Counties, Utah, White Pine County, Nevada, and surrounding areas in Utah and Nevada

Applications have been filed for several water-right changes and new water rights, with total withdrawals of about 1,800 acre-feet per year, in Snake Valley near Eskdale and Partoun, Utah. The Bureau of Land Management has identified 11 sites where the Bureau of Land Management holds water rights and 7 other springs of interest that could be affected by these proposed groundwater withdrawals. This report presents a hydrogeologic analysis of areas within Snake Valley to assess the potential effects on Bureau of Land Management water rights and other springs of interest resulting from existing and proposed groundwater withdrawals. A previously developed numerical groundwater-flow model was used to quantify potential groundwater drawdown and the capture, or groundwater withdrawals that results in depletion, of natural discharge resulting from existing and proposed groundwater withdrawals within Snake Valley. Existing groundwater withdrawals were simulated for a 50-year period prior to adding the newly proposed withdrawals to bring the model from pre-development conditions to the start of 2014. After this initial 50-year period, existing withdrawals, additional proposed withdrawals, and consequent effects were simulated for periods of 5, 10, 25, 50, and 100 years. Downward trends in water levels measured in wells indicate that the existing groundwater withdrawals in Snake Valley are affecting water levels. The numerical model simulated similar downward trends in water levels. The largest simulated drawdowns caused by existing groundwater withdrawals ranged between 10 and 26 feet and were near the centers of the agricultural areas by Callao, Eskdale, Baker, Garrison, and along the Utah-Nevada state line in southern Snake Valley. The largest simulated water-level declines were at the Bureau of Land Management water-rights sites near Eskdale, Utah, where simulated drawdowns ranged between 2 and 8 feet at the start of 2014. These results were consistent with, but lower than, observations from several wells monitored by the U.S. Geological Survey that indicated water-level declines of 6 to 18 feet near the Eskdale area since the mid-1970s and 1980s. The model cells where the simulated capture of natural groundwater discharge resulting from the existing withdrawals was greatest were those containing Kane Spring, Caine Spring, and Unnamed Spring 5, where existing groundwater withdrawals capture 13 to 29 percent of the total simulated natural discharge in these cells. Simulated drawdown and simulated capture of natural groundwater discharge resulting from the proposed withdrawals started in as few as 5 years at seven of the sites. After 100 years, four sites showed simulated drawdowns ranging between 1 and 2 feet; eight sites showed simulated drawdowns ranging between 0.1 and 0.9 feet; and five sites showed no simulated drawdown resulting from the proposed withdrawals. The largest amounts of simulated capture of natural groundwater discharge resulting from the proposed withdrawals after 100 years were in the model cells containing Coyote Spring, Kane Spring, and Caine Spring, which had capture amounts ranging between 5.5 and 9.1 percent of the total simulated natural discharge in these cells.

Nevada, Utah↗
USGS2022

Compilation and evaluation of data used to identify groundwater sources under the direct influence of surface water in Pennsylvania

A study was conducted to compile and evaluate data used to identify groundwater sources that are under the direct influence of surface water (GUDI) in Pennsylvania. In the early 1990s, the Pennsylvania Department of Environmental Protection (PADEP) implemented the Surface Water Identification Protocol (SWIP) for the identification of GUDI sources. Since the establishment of the SWIP, PADEP has classified more than 500 individual sources across Pennsylvania as GUDI, but Pennsylvania’s complex geology and physiography provide a challenge for a uniform method of GUDI determination. Components used in this study to compile and evaluate data associated with GUDI determination include: (1) a preliminary review of file information for 43 public water-supply wells, (2) quality control and addition of data to PADEP’s database for public water-supply systems to prepare data for analysis, and (3) exploratory evaluation of existing GUDI sources in the database with respect to hydrogeologic and source-construction characteristics that are currently utilized in the assessment methodology. Case files for 43 wells from PADEP’s Northcentral and Southcentral regions were reviewed to: (1) provide a better understanding of how the SWIP was applied in practice, (2) verify and compile missing data, and (3) find additional attributes not previously available that might explain a well’s categorization as GUDI. Review of file information showed that the SWIP outlined in PADEP technical guidance was usually followed, but for some sources, the GUDI determination was more complex and could not be easily summarized. Data compiled for study analyses provided by PADEP include source data derived from public water-supply system case files, a source-information database for public water-supply systems, and Microscopic Particulate Analysis (MPA) results and associated water-quality data for public water-supply system groundwater sources. Data from the Pennsylvania Drinking Water Information System (PADWIS) , which is PADEP’s database for public water-supply systems, were also used for this study. The PADWIS database originally included data for 12,147 groundwater sources (11,812 groundwater sources not under the direct influence of surface water (non-GUDI) wells and 335 GUDI wells). A subset (4,018 wells consisting of 3,842 non-GUDI wells and 175 GUDI wells) of the PADWIS database was created for an analysis and includes only community wells evaluated in accordance with the SWIP. MPA results for 631 community and noncommunity wells were compiled, along with associated water-quality data (alkalinity, chloride, Escherichia coli , fecal coliform, nitrate, pH, sodium, specific conductance, sulfate, total coliform, total dissolved solids, total residue, and turbidity) populated from the PADEP Bureau of Laboratories Sample Information System. Data compiled from sources other than PADEP include spatial data, both naturogenic (for example, average precipitation or distance to closest hydrologic feature) and anthropogenic (for example, percentage of developed or agricultural land cover within a specific vicinity of a public water-supply system well) data representing spatially derived variables. Comparison among wells in the PADWIS dataset subset using the nonparametric Kruskal-Wallis test showed that GUDI wells had significantly older median construction years, shallower depths, and static water levels closer to the land surface than non-GUDI wells and that carbonate aquifers had the highest percentages of wells designated as GUDI (12 percent; 57 wells). Further comparison of wells in the PADWIS database subset using the Spearman’s rho monotonic correlation test illustrated that public water-supply wells designated as GUDI largely occur in unconfined aquifers and have high average yield and shallow static water levels. Assessment of the MPA database subset using the Kruskal-Wallis test showed wells with MPA total risk-factor scores that exceeded zero had older median construction years and shallower casing depths than wells with MPA total risk-factor scores of zero and that carbonate aquifers had the highest percentages of wells with MPA total risk-factor scores exceeding zero (30 percent; 63 wells). Spearman’s rho correlations showed that wells completed in aquifers with depths to major water-bearing zones closer to the land-surface had higher total risk-factor scores resulting from MPA samples. Based on the results of the analyses described in this report, broad conclusions can be drawn regarding site-specific well characteristics as well as anthropogenic and naturogenic factors that could be responsible for a well being designated as GUDI, but the accuracy of these results is dependent on the quality of the data being analyzed. Ultimately, study results serve as an added resource for initial desktop screening of wells to determine if additional site-specific investigation is warranted and underscore the need for field evaluation.

Pennsylvania↗
USGS2015

California State Waters Map Series — Offshore of Point Reyes, California

This publication about the Offshore of Point Reyes map area includes ten map sheets that contain explanatory text, in addition to this descriptive pamphlet and a data catalog of geographic information system (GIS) files. Sheets 1, 2, and 3 combine data from four different sonar surveys to generate comprehensive high-resolution bathymetry and acoustic-backscatter coverage of the map area. These data reveal a range of physiographic features (highlighted in the perspective views on sheet 4) such as the flat, sediment-covered seafloor in Drakes Bay, as well as abundant “scour depressions” on the Bodega Head–Tomales Point shelf (see sheet 9) and local, tectonically controlled bedrock uplifts. To validate geological and biological interpretations of the sonar data shown in sheets 1, 2, and 3, the U.S. Geological Survey towed a camera sled over specific offshore locations, collecting both video and photographic imagery; these “ground-truth” surveying data are summarized on sheet 6. Sheet 5 is a “seafloor character” map, which classifies the seafloor on the basis of depth, slope, rugosity (ruggedness), and backscatter intensity and which is further informed by the ground-truth-survey imagery. Sheet 7 is a map of “potential habitats,” which are delineated on the basis of substrate type, geomorphology, seafloor process, or other attributes that may provide a habitat for a specific species or assemblage of organisms. Sheet 8 compiles representative seismic-reflection profiles from the map area, providing information on the subsurface stratigraphy and structure of the map area. Sheet 9 shows the distribution and thickness of young sediment (deposited over the last about 21,000 years, during the most recent sea-level rise) in both the map area and the larger Salt Point to Drakes Bay region, interpreted on the basis of the seismic-reflection data, and it identifies the Offshore of Point Reyes map area as lying within the Bodega Head–Tomales Point shelf, Point Reyes bar, and Bolinas shelf domains. Sheet 10 is a geologic map that merges onshore geologic mapping (compiled from existing maps by the California Geological Survey) and new offshore geologic mapping that is based on integration of high-resolution bathymetry and backscatter imagery (sheets 1, 2, 3), seafloor-sediment and rock samples (Reid and others, 2006), digital camera and video imagery (sheet 6), and high-resolution seismic-reflection profiles (sheet 8), as well as aerial-photographic interpretation of nearshore areas. The information provided by the map sheets, pamphlet, and data catalog have a broad range of applications. High-resolution bathymetry, acoustic backscatter, ground-truth-surveying imagery, and habitat mapping all contribute to habitat characterization and ecosystem-based management by providing essential data for delineation of marine protected areas and ecosystem restoration. Many of the maps provide high-resolution baselines that will be critical for monitoring environmental change associated with climate change, coastal development, or other forcings. High-resolution bathymetry is a critical component for modeling coastal flooding caused by storms and tsunamis, as well as inundation associated with longer term sea-level rise. Seismic-reflection and bathymetric data help characterize earthquake and tsunami sources, critical for natural-hazard assessments of coastal zones. Information on sediment distribution and thickness is essential to the understanding of local and regional sediment transport, as well as the development of regional sediment-management plans. In addition, siting of any new offshore infrastructure (for example, pipelines, cables, or renewable-energy facilities) will depend on high-resolution mapping. Finally, this mapping will both stimulate and enable new scientific research and also raise public awareness of, and education about, coastal environments and issues.

California↗
USGS2012

Coordinated bird monitoring: Technical recommendations for military lands

The Department of Defense (DoD) is subject to several rules and regulations establishing responsibilities for monitoring migratory birds. The Sikes Act requires all military installations with significant natural resources to prepare and implement Integrated Natural Resources Management Plans (INRMPs). These plans guide the conservation and long-term management of natural resources on military lands in a manner that is compatible with and sustains the military mission. An INRMP also supports compliance with all legal requirements and guides the military in fulfilling its obligation to be a good steward of public land.The management and conservation of migratory birds is addressed in installation INRMPs. The National Environmental Policy Act (NEPA) requires federal agencies to evaluate and disclose the potential environmental impacts of their proposed actions. More recently, DoD signed an MOU (http://www.dodpif.org/downloads/EO13186_MOU-DoD.pdf) for migratory birds, under Executive Order 13186, with the US Fish and Wildlife Service (USFWS) in July 2006 and a Migratory Bird Rule (http://www.dodpif.org/downloads/MigBirdFINALRule_FRFeb2007.pdf) was passed by Congress in February 2007. The Migratory Bird Rule addresses the potential impacts of military readiness activities on populations of migratory birds and establishes a process to implement conservation measures if and when a military readiness activity is expected to have a significant adverse impact on a population of migratory bird species (as determined through the NEPA process). The MOU states that for nonmilitary readiness activities, prior to initiating any activity likely to affect populations of migratory birds DoD shall (1) identify the migratory bird species likely to occur in the area of the proposed action and determine if any species of concern could be affected by the activity, and (2) assess and document, using NEPA when applicable, the effect of the proposed action on species of concern. By following these procedures, DoD will minimize the possibility for a proposed action to unintentionally take migratory birds at a level that would violate any of the migratory bird treaties and potentially impact mission activities. In addition, implementing conservation and monitoring programs for migratory birds supports the ecosystem integrity necessary to sustain DoD's natural resources for the military mission.Non-compliance with the procedural requirements of the MBTA could result in a private party lawsuit under the Administrative Procedures Act (APA). A lawsuit filed under APA involving a Navy bombing range is the basis for a court ruling that unintentional take of migratory birds applies to federal actions. Ensuring the necessary data is available to adequately assess impacts of a proposed action will help avoid lawsuits or help ensure such lawsuits have no grounds. The data gathered in a bird monitoring program will provide the best scientific data available to assess the expected impacts of a proposed action on migratory bird species through the NEPA process. This report presents recommendations developed by the U.S. Geological Survey (USGS) for the Department of Defense (DoD) on establishing a "Coordinated Bird Monitoring (CBM) Plan." The CBM Plan is intended to ensure that DoD meets its conservation and regulatory responsibilities for monitoring birds (Chapter 1). The report relies heavily on recommendations in the report, "Opportunities for improving avian monitoring" (http://www.nabci-us.org/aboutnabci/monitoringreportfinal0307.pdf), by the U.S. North American Bird Conservation Initiative (U.S. NABCI Monitoring Subcommittee, 2007) and on a review of 358 current DoD bird monitoring programs carried out as part of this project (Chapter 2). This report contains 12 recommendations which, if followed, would result in a comprehensive, efficient, and useful approach to bird monitoring. The recommendations are based on the entire report but are presented together at the end of Chapter 1. DoD has agreed to consider implementing these recommendations; however, final decisions will be based upon such factors as the availability of resources and military mission considerations. These recommendations from USGS can be summarized into 6 major themes: A major report on monitoring was released in 2007 by the U.S. North American Bird Conservation Initiative (http://www.nabci-us.org/main2.html). DoD can be consistent with this report by establishing policy that monitoring will be explicitly acknowledged as an integral element of bird management and conservation (Recommendation 1). The design of monitoring and assessment programs for birds should include the following steps: Preparation of a document describing the program's goals, objectives, and methods similar to a format we provide (Recommendation 2, Chapter 4). Selection of field methods using an "expert system" developed in this project (Recommendation 3, Chapter 5) or another well-documented system. Preparation and storage of metadata describing the monitoring program in the Natural Resources Monitoring Partnership (NRMP), and other appropriate databases Recommendation 4, Chapter 6). Entry of the survey data using eBird (http://ebird.org/content/dod) or the Coordinated Bird Monitoring Database (CBMD) and long-term storage of the data in the CBMD and the Avian Knowledge Network (AKN; Recommendation 5, Chapter 6; http://www.avianknowledge.net/). Submission of major results from the monitoring program for publication in a peer reviewed journal (Recommendation 6). The DoD Legacy Resource Management Program (Legacy; https://www.dodlegacy.org), Environmental Security Technology Certification Program (ESTCP; http://www.serdp.org/), and Strategic Environmental Research and Development Program (SERDP; http://www.serdp.org/) should be encouraged to continue their significant contributions to the foundations of bird monitoring (Recommendation 7, Chapters 1 and 3). Appropriate monitoring should be conducted to identify species of concern on installations. A year-round, one-time survey of birds on installations with habitat for migratory birds would provide the most information to assist compliance with the MOU, the Final Rule, and the NEPA analyses of proposed actions. However, less intensive survey efforts can still be conducted to yield useful information. We describe how various levels of survey effort might be organized and conducted. In addition, continuing surveys, as feasible, would further assist in documenting effects of military readiness and non-readiness activities on species of concern (SOC) (Recommendation 8, Chapter 7). Participation in well-designed, large-scale surveys [(e.g., North American Breeding Bird Survey (BBS; http://www.pwrc.usgs.gov/bbs/), Monitoring Avian Productivity and Survivorship (MAPS; http://www.birdpop.org/maps.htm)] on land that DoD manages or on lands where the results will be of high interest to DoD, will provide DoD and other NABCI members with information important to bird conservation (Recommendation 9, Chapter 8). Review and implementation of the CBM Plan should involve both higher level management and installation-level natural resources managers (Recommendation 11), be implemented through cooperative partnerships (Recommendation 12), and be followed on U.S territory lands and Army Corps of Engineers projects (Recommendation 10).Additional recommendations that pertain to implementing the DoD CBM Plan are discussed in Chapter 9.

Open-File Report↗
USGS2019

Numerical model simulations of potential changes in water levels and capture of natural discharge from groundwater withdrawals in Snake Valley and adjacent areas, Utah and Nevada

The National Park Service (NPS) and the Bureau of Land Management (BLM) are concerned about cumulative effects of groundwater development on groundwater-dependent resources managed by, and other groundwater resources of interest to, these agencies in Snake Valley and adjacent areas, Utah and Nevada. Of particular concern to the NPS and BLM are withdrawals from all existing approved, perfected, certified, permitted, and vested groundwater rights in Snake Valley totaling about 55,272 acre-feet per year (acre-ft/yr), and from several senior water-right applications filed by the Southern Nevada Water Authority (SNWA) totaling 50,680 acre-ft/yr. An existing groundwater-flow model of the eastern Great Basin was used to investigate where potential drawdown and capture of natural discharge is likely to result from potential groundwater withdrawals from existing groundwater rights in Snake Valley, and from groundwater withdrawals proposed in several applications filed by the SNWA. To evaluate the potential effects of the existing and proposed SNWA groundwater withdrawals, 11 withdrawal scenarios were simulated. All scenarios were run as steady state to estimate the ultimate long-term effects of the simulated withdrawals. This assessment provides a general understanding of the relative susceptibility of the groundwater resources of interest to the NPS and BLM, and the groundwater system in general, to existing and future groundwater development in the study area. At the NPS and BLM groundwater resource sites of interest, simulated drawdown resulting from withdrawals based on existing approved, perfected, certified, permitted, and vested groundwater rights within Snake Valley ranged between 0 and 159 feet (ft) without accounting for irrigation return flow, and between 0 and 123 ft with accounting for irrigation return flow. With the addition of proposed SNWA withdrawals of 35,000 acre-ft/yr (equal to the Unallocated Groundwater portion allotted to Nevada in a draft interstate agreement), simulated drawdowns at the NPS and BLM sites of interest increased to range between 0 and 2,074 ft without irrigation return flow, and between 0 and 2,002 ft with irrigation return flow. With the addition of the proposed SNWA withdrawals of an amount equal to the full application amounts (50,680 acre-ft/yr), simulated drawdowns at the NPS and BLM sites of interest increased to range between 1 and 3,119 ft without irrigation return flow, and between 1 and 3,044 ft with irrigation return flow. At the NPS and BLM groundwater resource sites of interest, simulated capture of natural discharge resulting from withdrawals based on existing groundwater rights in Snake Valley, both with and without irrigation return flow, ranged between 0 and 100 percent; simulated capture of 100 percent occurred at four sites. With the addition of proposed SNWA withdrawals of an amount equal to the Unallocated Groundwater portion allotted to Nevada in the draft interstate agreement, simulated capture of 100 percent occurred at nine additional sites without irrigation return flow, and at eight additional sites with irrigation return flow. With the addition of the proposed SNWA withdrawals of an amount equal to the full application amounts, simulated capture of 100 percent occurred at 11 additional sites without irrigation return flow, and at 9 additional sites with irrigation return flow. The large simulated drawdowns produced in the scenarios that include large portions or all of the proposed SNWA withdrawals indicate that the groundwater system may not be able to support the amount of withdrawals from the proposed points of diversion (PODs) in the current SNWA water-right applications. Therefore, four additional scenarios were simulated where the withdrawal rates at the SNWA PODs were constrained by not allowing drawdowns to be deeper than the assumed depth of the PODs (about 2,000 ft). In the constrained scenarios, total withdrawals at the SNWA PODs were reduced to about 48 percent of the Unallocated Groundwater portion allotted to Nevada (35,000 acre-ft/yr reduced to 16,817 acre-ft/yr or 16,914 acre-ft/yr, without or with irrigation return flow, respectively), and about 44 percent of the full application amounts (50,680 acre-ft/yr reduced to 22,048 acre-ft/yr or 22,165 acre-ft/yr, without or with irrigation return flow, respectively). This indicates that the SNWA may need to add more PODs, or PODs in different locations, in order to withdraw large portions or all of the groundwater that has been applied for. At the NPS and BLM groundwater resource sites of interest, simulated drawdown resulting from the addition of the constrained SNWA withdrawals applied to the Unallocated Groundwater amount ranged between 0 and 290 ft without irrigation return flow, and between 0 and 252 ft with irrigation return flow. With the addition of the constrained SNWA withdrawals applied to the full application amounts, simulated drawdowns at the NPS and BLM sites of interest ranged between 0 and 358 ft without irrigation return flow, and between 0 and 313 ft with irrigation return flow. At the NPS and BLM groundwater resource sites of interest, with the addition of the constrained SNWA withdrawals applied to the Unallocated Groundwater amount, simulated capture of 100 percent of the natural discharge occurred at five additional sites without irrigation return flow, and at two additional sites with irrigation return flow (in addition to the four captured from existing water rights both with and without irrigation return flow). With the addition of the constrained SNWA withdrawals applied to the full application amounts, simulated capture of 100 percent occurred at six additional sites both with and without irrigation return flow.

Nevada, Utah↗
USGS1963

Dispersion in natural streams

Eleven tests were conducted to study the dispersion patterns of a radiotracer in five natural stream channels and in one canal. The radiotracer was injected as a line source. The patterns of dispersion that were observed in these channels were compared with patterns predicted by the theoretical models for one-dimensional flow developed by Taylor and other investigators. Analysis of the relation between time and concentration of the tracer at several sections in each of the six reaches shows that the available theoretical models are not adequate to describe the dispersion patterns actually observed. Dispersion coefficients determined from the test data are from 2 to 30 times greater than those predicted by the theoretical models. It is apparent that a better understanding of the dispersal phenomenon is needed in order to predict dispersion patterns in natural streams.

Open-File Report↗