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At least 1,459 records · Page 81Linked to original sources

USGS2009

Geologic map of the Weaverville 15' quadrangle, Trinity County, California

The Weaverville 15' quadrangle spans parts of five generally north-northwest-trending accreted terranes. From east to west, these are the Eastern Klamath, Central Metamorphic, North Fork, Eastern Hayfork, and Western Hayfork terranes. The Eastern Klamath terrane was thrust westward over the Central Metamorphic terrane during early Paleozoic (Devonian?) time and, in Early Cretaceous time (approx. 136 Ma), was intruded along its length by the massive Shasta Bally batholith. Remnants of overlap assemblages of the Early Cretaceous (Hauterivian) Great Valley sequence and the Tertiary Weaverville Formation cover nearly 10 percent of the quadrangle. The base of the Eastern Klamath terrane in the Weaverville quadrangle is a peridotite-gabbro complex that probably is correlative to the Trinity ophiolite (Ordovician), which is widely exposed farther north beyond the quadrangle. In the northeast part of the Weaverville quadrangle, the peridotite-gabbro complex is overlain by the Devonian Copley Greenstone and the Mississippian Bragdon Formation. Where these formations were intruded by the Shasta Bally batholith, they formed an aureole of gneissic and other metamorphic rocks around the batholith. Westward thrusting of the Eastern Klamath terrane over an adjacent body of mafic volcanic and overlying quartzose sedimentary rocks during Devonian time formed the Salmon Hornblende Schist and the Abrams Mica Schist of the Central Metamorphic terrane. Substantial beds of limestone in the quartzose sedimentary unit, generally found near the underlying volcanic rock, are too metamorphosed for fossils to have survived. Rb-Sr analysis of the Abrams Mica Schist indicates a metamorphic age of approx. 380 Ma. West of Weavervillle, the Oregon Mountain outlier of the Eastern Klamath terrane consists mainly of Bragdon Formation(?) and is largely separated from the underlying Central Metamorphic terrane by serpentinized peridotite that may be a remnant of the Trinity ophiolite. The North Fork terrane is faulted against the west edge of the Central Metamorphic terrane, and its northerly trend is disrupted by major left-lateral offsets along generally west-northwest-trending faults. The serpentinized peridotite-gabbro complex that forms the western base of the terrane is the Permian North Fork ophiolite, which to the east is overlain by broken formation of mafic-volcanic rocks, red chert, siliceous tuff, argillite, minor limestone, and clastic sedimentary rocks. The chert and siliceous tuff contain radiolarians of Permian and Mesozoic ages, and some are as young as Early Jurassic (Pliensbachian). Similar Pliensbachian radiolarians are found in Franciscan rocks of the Coast Ranges. The Eastern Hayfork terrane is broken formation and melange of mainly chert, sandstone, argillite, and various exotic blocks. The cherts yield radiolarians of Permian and Triassic ages but none of clearly Jurassic age. Limestone bodies of the Eastern Hayfork terrane contain Permian microfaunas of Tethyan affinity. The Western Hayfork terrane, exposed only in a small area in the southwestern part of the quadrangle, consists dominantly of mafic tuff and dark slaty argillite. Sparse paleontologic data indicate a Mesozoic age for the strata. The terrane includes small bodies of diorite that are related to the nearby Wildwood pluton of Middle Jurassic age and probably are related genetically to the stratified rocks. The terrane is interpreted to be the accreted remnants of a Middle Jurassic volcanic arc. Shortly after intrusion by Shasta Bally batholith (approx. 136 Ma), much of the southern half of the Weaverville quadrangle was overlapped by Lower Cretaceous, dominantly Hauterivian, marine strata of the Great Valley sequence, and to a lesser extent later during Oligocene and (or) Miocene time by fluvial and lacustrine deposits of the Weaverville Formation. This map of the Weaverville Quadrangle is a digital rendition of U.S. Geological Survey Miscellaneous Field

California↗

USGS2012

Geology of the Prince William Sound and Kenai Peninsula region, Alaska: Including the Kenai, Seldovia, Blying Sound, Cordova, and Middleton Island 1:250,000-scale quadrangles

The Prince William Sound and Kenai Peninsula region includes a significant part of one of the world’s largest accretionary complexes and a small part of the classic magmatic arc geology of the Alaska Peninsula. Physiographically, the map area ranges from the high glaciated mountains of the Alaska and Aleutian Ranges and the Chugach Mountains to the coastal lowlands of Cook Inlet and the Copper River delta. Structurally, the map area is cut by a number of major faults and postulated faults, the most important of which are the Border Ranges, Contact, and Bruin Bay Fault systems. The rocks of the map area belong to the Southern Margin composite terrane, a Tertiary and Cretaceous or older subduction-related accretionary complex, and the Alaska Peninsula terrane. Mesozoic rocks between these two terranes have been variously assigned to the Peninsular or the Hidden terranes. The oldest rocks in the map area are blocks of Paleozoic age within the mélange of the McHugh Complex; however, the protolith age of the greenschist and blueschist within the Border Ranges Fault zone is not known. Extensive glacial deposits mantle the Kenai Peninsula and the lowlands on the west side of Cook Inlet and are locally found elsewhere in the map area. This map was compiled from existing mapping, without generalization, and new or revised data was added where available.

Alaska↗

USGS2011

Geologic map of the Ganiki Planitia quadrangle (V-14), Venus

The Ganiki Planitia (V-14) quadrangle on Venus, which extends from 25° N. to 50° N. and from 180° E. to 210° E., derives its name from the extensive suite of plains that dominates the geology of the northern part of the region. With a surface area of nearly 6.5 x 10 6 km 2 (roughly two-thirds that of the United States), the quadrangle is located northwest of the Beta-Atla-Themis volcanic zone and southeast of the Atalanta Planitia lowlands, areas proposed to be the result of large scale mantle upwelling and downwelling, respectively. The region immediately south of Ganiki Planitia is dominated by Atla Regio, a major volcanic rise beneath which localized upwelling appears to be ongoing, whereas the area just to the north is dominated by the orderly system of north-trending deformation belts that characterize Vinmara Planitia. The Ganiki Planitia quadrangle thus lies at the intersection between several physiographic regions where extensive mantle flow-induced tectonic and volcanic processes are thought to have occurred. The geology of the V-14 quadrangle is characterized by a complex array of volcanic, tectonic, and impact-derived features. There are eleven impact craters with diameters from 4 to 64 km, as well as four diffuse 'splotch' features interpreted to be the product of near-surface bolide explosions. Tectonic activity has produced heavily deformed tesserae, belts of complex deformation and rifts as well as a distributed system of fractures and wrinkle ridges. Volcanic activity has produced extensive regional plains deposits, and in the northwest corner of the quadrangle these plains host the initial (or terminal) 700 km of the Baltis Vallis canali, an enigmatic volcanic feature with a net length of ~7,000 km that is the longest channel on Venus. Major volcanic centers in V-14 include eight large volcanoes and eight coronae; all but one of these sixteen features was noted during a previous global survey. The V-14 quadrangle contains an abundance of minor volcanic features including individual shield volcanoes and localized fissure eruptions as well as many small annular structures and domes, which often serve as the source for local lava flows. The topographic and geophysical characteristics of the Ganiki Planitia quadrangle are less complex than the surface geology, but they yield equally valuable information about the region’s formation and evolution. Referenced to the mean planetary radius of 6051.84 km, the average elevation in the quadrangle is -0.26±0.86 km (2σ) with a full range of -2.58 km to 1.85 km. The highest 2.5 percent of elevations in the quadrangle (above 0.60 km) are associated primarily with the major tessera blocks and the peaks of a few volcanic edifices, whereas the lowest 2.5 percent (below -1.12 km) mostly occur within corona interiors and in the northwest corner of the quadrangle where the plains begin to merge into the Atalanta Planitia lowlands. At the ~4.6 km/pixel scale of the topography data, the mean point-to-point topographic slope is 0.63° and topographic slopes greater than 2° cover less than 5 percent of the region. Overall, the topography of the Ganiki Planitia quadrangle can be characterized as flat, low lying, and nearly devoid of abrupt topographic variation. Complementing this gentle topography, the geoid anomaly has a generally linear gradient that decreases north-northwest from a high of ~20 m at the southern edge of the quadrangle (the northern border of the Atla Regio anomaly) to a low of -30 to -40 m along the northern edge (Konopliv and others, 1999). The vertical component of the gravity anomaly varies from ~50 mGal to -40 mGal, and integrated analysis of the gravity and topography data indicates that dynamically supported regions and areas of thickened crust are both present within the quadrangle. Because the Ganiki Planitia quadrangle is a plains-dominated lowland area that lies between several major physiographic provinces (namely, Atla Regio, Atalanta Planitia, and Vinmara Planitia), a geologic map of the region may yield insight into a wide array of important problems in Venusian geology. The current mapping effort and analysis complements previous efforts to characterize aspects of the region’s geology, for example stratigraphy near parabolic halo crater sites, volcanic plains emplacement, wrinkle ridges, volcanic feature distribution, volcano deformation, coronae characteristics, lithospheric flexure, and various features along a 30±7.58° N. geotraverse. Our current research focuses on addressing four specific questions. Has the dominant style of volcanic expression within the quadrangle varied in a systematic fashion over time? Does the tectonic deformation within the quadrangle record significant regional patterns that vary spatially or temporally, and if so what are the scales, orientations and sources of the stress fields driving this deformation? If mantle upwelling and downwelling have played a significant role in the formation of Atla Regio and Atalanta Planitia as has been proposed, does the geology of Ganiki Planitia record evidence of northwest-directed lateral mantle flow connecting the two sites? Finally, can integration of the tectonic and volcanic histories preserved within the quadrangle help constrain competing resurfacing models for Venus?

Scientific Investigations Map↗

USGS2014

California State Waters Map Series: Offshore of Coal Oil Point, California

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Offshore of Coal Oil Point map area lies within the central Santa Barbara Channel region of the Southern California Bight. This geologically complex region forms a major biogeographic transition zone, separating the cold-temperate Oregonian province north of Point Conception from the warm-temperate California province to the south. The map area is in the southern part of the Western Transverse Ranges geologic province, which is north of the California Continental Borderland. Significant clockwise rotation—at least 90°—since the early Miocene has been proposed for the Western Transverse Ranges province, and geodetic studies indicate that the region is presently undergoing north-south shortening. Uplift rates (as much as 2.0 mm/yr) that are based on studies of onland marine terraces provide further evidence of significant shortening. The cities of Goleta and Isla Vista, the main population centers in the map area, are in the western part of a contiguous urban area that extends eastward through Santa Barbara to Carpinteria. This urban area is on the south flank of the east-west-trending Santa Ynez Mountains, on coalescing alluvial fans and uplifted marine terraces underlain by folded and faulted Miocene bedrock. In the map area, the relatively low-relief, elevated coastal bajada narrows from about 2.5 km wide in the east to less than 500 m wide in the west. Several beaches line the actively utilized coastal zone, including Isla Vista County Park beach, Coal Oil Point Reserve, and Goleta Beach County Park. The beaches are subject to erosion each winter during storm-wave attack, and then they undergo gradual recovery or accretion during the more gentle wave climate of the late spring, summer, and fall months. The Offshore of Coal Oil Point map area lies in the central part of the Santa Barbara littoral cell, which is characterized by littoral drift to the east-southeast. Longshore drift rates have been reported to range from about 160,000 to 800,000 tons/yr, averaging 400,000 tons/yr. Sediment supply to the western and central parts of the littoral cell, including the map area, is largely from relatively small transverse coastal watersheds. Within the map area, these coastal watersheds include (from east to west) Las Llagas Canyon, Gato Canyon, Las Varas Canyon, Dos Pueblos Canyon, Eagle Canyon, Tecolote Canyon, Winchester Canyon, Ellwood Canyon, Glen Annie Canyon, and San Jose Creek. The Santa Ynez and Santa Maria Rivers, the mouths of which are about 100 to 140 km northwest of the map area, are not significant sediment sources because Point Conception and Point Arguello provide obstacles to downcoast sediment transport and also because much of their sediment load is trapped in dams. The Ventura and Santa Clara Rivers, the mouths of which are about 45 to 55 km southeast of the map area, are much larger sediment sources. Still farther east, eastward-moving sediment in the littoral cell is trapped by Hueneme and Mugu Canyons and then transported to the deep-water Santa Monica Basin. The offshore part of the map area consists of a relatively flat and shallow continental shelf, which dips gently seaward (about 0.8° to 1.0°) so that water depths at the shelf break, roughly coincident with the California’s State Waters limit, are about 90 m. This part of the Santa Barbara Channel is relatively well protected from large Pacific swells from the north and northwest by Point Conception and from the south and southwest by offshore islands and banks. The shelf is underlain by variable amounts of upper Quaternary marine and fluvial sediments deposited as sea level fluctuated in the late Pleistocene. The large (130 km2) Goleta landslide complex lies along the shelf break in the southern part of the map area. This compound slump complex may have been initiated more than 200,000 years ago, but it also includes three recent failures that may have been generated between 8,000 to 10,000 years ago. A local, 5- to 10-m-high tsunami may have been generated from these failure events. The map area has had a long history of hydrocarbon development, which began in 1928 with discovery of the Ellwood oil field. Subsequent discoveries in the offshore include South Ellwood offshore oil field, Coal Oil Point oil field, and Naples oil and gas field. Development of South Ellwood offshore field began in 1966 from platform “Holly,” the last platform to be installed in California’s State Waters. The area also is known for “the world’s most spectacular marine hydrocarbon seeps,” and large tar seeps are exposed on beaches east of the mouth of Goleta Slough. Offshore seeps adjacent to South Ellwood oil field release about 40 tons per day of methane and about 19 tons per day of ethane, propane, butane, and higher hydrocarbons. Seafloor habitats in the broad Santa Barbara Channel region consist of significant amounts of soft sediment and isolated areas of rocky habitat that support kelp-forest communities nearshore and rocky-reef communities in deep water. The potential marine benthic habitat types mapped in the Offshore of Coal Oil Point map area are directly related to its Quaternary geologic history, geomorphology, and active sedimentary processes. These potential habitats, which lie primarily within the Shelf (continental shelf) but also partly within the Flank (basin flank or continental slope) megahabitats, range from soft, unconsolidated sediment to hard sedimentary bedrock. This heterogeneous seafloor provides promising habitat for rockfish, groundfish, crabs, shrimp, and other marine benthic organisms.

California↗

USGS2015

California State Waters Map Series: Offshore of Refugio Beach, California

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Offshore of Refugio Beach map lies within the western Santa Barbara Channel region of the Southern California Bight. This geologically complex region forms a major biogeographic transition zone, separating the cold-temperate Oregonian province north of Point Conception from the warm-temperate California province to the south. The map area is in the southern part of the Western Transverse Ranges geologic province, which is north of the California Continental Borderland. Significant clockwise rotation—at least 90°—since the early Miocene has been proposed for the Western Transverse Ranges province, and geodetic studies indicate that the region is presently undergoing north-south shortening. Uplift rates (as much as 0.5 mm/yr) that are based on studies of onland marine terraces provide further evidence of significant shortening. The coastal zone of this map area lies at the steep flank of the Santa Ynez Mountains. The crest of the range, which lies about 8 km from the shoreline (north of the map area), has a maximum elevation of about 780 m. This area is largely open space, partly used for livestock grazing, with no significant towns or population centers. Highway 101 crosses the map area, adjacent to and within a few hundred meters of the shoreline. The most significant developments are the recreational state beaches at El Capitan Beach and Refugio Beach. The beaches are subject to erosion each winter during storm-wave attack, and then they undergo gradual recovery or accretion during the more gentle wave climate of the late spring, summer, and fall months. The Offshore of Refugio Beach map area lies in the west-central part of the Santa Barbara littoral cell, which is characterized by west-to-east transport of sediment from Point Arguello on the northwest to Hueneme and Mugu Canyons on the southeast. Longshore drift rates have been reported to range from about 160,000 to 800,000 tons/yr, averaging 400,000 tons/yr. Sediment supply to the western and central part of the littoral cell, including the map area, is mainly from relatively small coastal watersheds. Within the map area, these coastal watersheds include (from east to west) Cañada del Capitan, Tajiquas Creek, Arroyo Hondo, Cañada del Molino, and several unnamed canyons and creeks. The Santa Ynez and Santa Maria Rivers, the mouths of which are 80 to 120 km northwest of the map area, are not considered significant sediment sources because Point Conception and Point Arguello provide obstacles to downcoast sediment transport and also because much of their sediment load is trapped in dams. The Ventura and Santa Clara Rivers, the mouths of which are about 70 km to the southeast of the map area, are not sediment sources for the map area. The offshore part of the map area consists of relatively flat and shallow continental shelf, which dips gently seaward (about 0.8° to 1.0°) so that water depths at the shelf break, roughly coincident with the California’s State Waters limit, are about 80 to 100 m. This part of the Santa Barbara Channel is relatively well protected from large Pacific swells from the north and northwest by Point Conception and from the south and southwest by offshore islands and banks. The shelf is underlain by variable amounts of upper Quaternary marine and fluvial sediments deposited as sea level fluctuated in the late Pleistocene. In the map area, the shelf break is at depths of about 90 m and lies about 5.6 to 6.4 km offshore. Beyond the shelf break, the slope is steep (as much as about 7°) and unstable. Several submarine landslides, including the large (130 km 2 ) Goleta landslide complex, have been documented offshore of Goleta, a few kilometers east of the map area. This compound slump complex may have been initiated more than 200,000 year ago, but it also includes three recent failures that may have been generated 8,000 to 10,000 years ago. A local, 10-m-high tsunami may have been generated from these failure events. Small folds related to local faulting are superimposed on the homocline that makes up the south flank of the Santa Ynez Mountains. One of these superimposed anticlines hosts the Molino gas field, which was discovered in 1962 and subsequently developed through directional drilling from onshore wells. The Oligocene Sespe and Vaqueros Formations are the reservoirs in the Molino gas field, and the map area includes numerous seafloor hydrocarbon seeps. Seafloor habitats in the broad Santa Barbara Channel region consist of significant amounts of soft, unconsolidated sediment interspersed with isolated areas of rocky habitat that support kelp-forest communities nearshore and rocky-reef communities in deep water. The potential marine benthic habitat types mapped in the Offshore of Refugio Beach map area are directly related to its Quaternary geologic history, geomorphology, and active sedimentary processes. These potential habitats, which lie primarily within the Shelf (continental shelf) but also partly within the Flank (basin flank or continental slope) megahabitats, primarily are composed of soft sediment interrupted by a few carbonate mounds. This homogeneous seafloor of sediment and low-relief bedrock provides promising habitat for groundfish, crabs, shrimp, and other marine benthic organisms.

California↗

USGS2018

Geologic map of the north half of the Lake Walcott 30'×60' quadrangle, Idaho

The geologic map of the northern half of the Lake Walcott 30ʹ×60ʹ quadrangle shows the volcanic geology of the southern part of the Craters of the Moon lava field, the complex geologic features of the Holocene Kings Bowl and Wapi lava fields, and the southern part of the Great Rift volcanic rift zone. The long extent and distribution of skylights in lava-tube systems of the Horse Butte and Wapi Park lava fields are depicted on this map. 40 Ar/ 39 Ar and K/Ar age determinations give detail to the Holocene, late Pleistocene, and late middle Pleistocene volcanic lava fields in this quadrangle. Most of the younger basalt eruptions (less than 150 thousand years [ka]) have occurred along the Great Rift volcanic rift zone, but two of the younger lava fields are located in the western part of the quadrangle. Kimama Butte, a shield volcano, is 87±11 ka, and Shale Butte is dated at 11±6 ka. Paleomagnetic studies have shown that the Horse Butte-Inferno Chasm eruptive fissure system has at least five paleomagnetic-correlative lava fields, the Claasen vent complex consists of at least seven correlative lava fields, and the Streifling-Flat Top vent complex includes at least four correlative lava fields. This map provides geologic, geochronologic, and paleomagnetic data for Holocene lava fields along the southern part of the Great Rift, and for late Pleistocene and late middle Pleistocene lava fields in the central and western parts of the quadrangle. These data can contribute to wise management and preservation of the Craters of the Moon National Monument and for broad-scale understanding of the basaltic-volcanic evolution of the eastern Snake River Plain.

Idaho↗

USGS2022

Geologic map of the South Boston 30' × 60' quadrangle, Virginia and North Carolina

This 1:100,000-scale geologic map of the South Boston 30 ’ × 60 ’ quadrangle, Virginia and North Carolina, provides geologic information for the Piedmont along the I–85 and U.S. Route 58 corridors and in the Roanoke River watershed, which includes the John H. Kerr Reservoir and Lake Gaston. The Raleigh terrane (located on the eastern side of the map) contains Neoproterozoic to early Paleozoic(?) polydeformed, amphibolite-facies gneisses and schists. The Carolina slate belt of the Carolina terrane (located in the central part of the map) contains Neoproterozoic metavolcanic and metasedimentary rocks at greenschist facies. Although locally complicated, the slate-belt structure mapped across the South Boston map area is generally a broad, complex anticlinorium of the Hyco Formation (here called the Chase City anticlinorium) and is flanked to the west and east by synclinoria, which are cored by the overlying Aaron and Virgilina Formations. The western flank of the Carolina terrane (located in the western-central part of the map) contains similar rocks at higher metamorphic grade. This terrane includes epidote-amphibolite-facies to amphibolite-facies gneisses of the Neoproterozoic Country Line complex, which extends north-northeastward across the map. The Milton terrane (located on the western side of the map) contains Ordovician amphibolite-facies metavolcanic and metasedimentary gneisses of the Cunningham complex. Crosscutting relations and fabrics in mafic to felsic plutonic rocks constrain the timing of Neoproterozoic to late Paleozoic deformations across the Piedmont. In the eastern part of the map, a 5- to 9-kilometer-wide band of tectonic elements that contains two late Paleozoic mylonite zones (Nutbush Creek and Lake Gordon) and syntectonic granite (Buggs Island pluton) separates the Raleigh and Carolina terranes. Amphibolite-facies, infrastructural metaigneous and metasedimentary rocks east of the Lake Gordon mylonite zone are generally assigned to the Raleigh terrane. In the western part of the map area, a 5- to 8-kilometer-wide band of late Paleozoic tectonic elements includes the Hyco and Clover shear zones, syntectonic granitic sheets, and amphibolite-facies gneisses along the western margin of the Carolina terrane at its boundary with the Milton terrane. This band of tectonic elements is also the locus for early Mesozoic extensional faults associated with the early Mesozoic Scottsburg, Randolph, and Roanoke Creek rift basins. The map shows fluvial terrace deposits of sand and gravel on hills and slopes near the Roanoke and Dan Rivers. The terrace deposits that are highest in altitude are the oldest. Saprolite regolith is spatially associated with geologic source units and is not shown separately on the map. Mineral resources in the area include gneiss and granite quarried for crushed stone, tungsten-bearing vein deposits of the Hamme district, and copper and gold deposits of the Virgilina district. Surface-water resources are abundant and include rivers, tributaries, the John H. Kerr Reservoir, and Lake Gaston. Groundwater flow is concentrated in saprolite regolith, along fractures in the crystalline bedrock, and along fractures and bedding-plane partings in the Mesozoic rift basins.

North Carolina, Virginia↗

USGS2005

Use of a ground-water flow model to delineate contributing areas to the Puchack Well Field, Pennsauken township and vicinity, Camden county, New Jersey

The New Jersey Department of Environmental Protection (NJDEP) Well Head Protection Program, developed in response to the 1986 Federal Safe Drinking Water Act Amendments, requires delineation of Well Head Protection Areas (WHPA's), commonly called contributing areas, for all public and non-community water-supply wells in New Jersey. Typically, WHPA's for public community water-supply wells in New Jersey are delineated using a two-dimensional ground-water flow model incorporating the regional hydraulic gradient; however, NJDEP guidelines allow for the use of a three-dimensional flow model to delineate contributing areas to wells in complex hydrogeologic settings. The Puchack well field in Pennsauken Township, Camden County, N.J., is an area of strong hydraulic connection between the Lower aquifer of the Potomac-Raritan-Magothy aquifer system and the Delaware River. Interactions among and within the public-supply well fields in the area are complex. To delineate the contributing area to the Puchack well field, the U.S. Geological Survey, in cooperation with the NJDEP, developed an 11-layer ground-water flow model of the Potomac-Raritan-Magothy aquifer system in the Pennsauken Township area to simulate flow in the vicinity of the well field. The model incorporates the interaction between the aquifer system and the Delaware River, and includes boundary flows from an existing regional model of the Camden area. Recharge used in the model ranged from 4.5 to 14 inches per year, and horizontal hydraulic conductivity ranged from 50 to 250 feet per day. Values of vertical hydraulic conductivity ranging from 0.001 to 0.5 feet per day were assigned to zones created on the basis of variations in hydrogeologic conditions observed in geophysical logs from wells. A steady-state simulation was used to calibrate the model to synoptic water-level data collected in March 1998. Near the Puchack well field, simulated heads generally were within 1 foot of the measured heads in both the Middle and Lower aquifers. Simulated water-level differences across the confining units at most of the nested wells were within ? 0.5 feet of the differences calculated from measured water levels. The existing flow model was modified to meet NJDEP guidelines for delineating contributing areas in complex hydrogeologic settings. These modifications included rediscretizing the model grid to a finer grid and preparing the water-use data set for use in the rediscretized model. The contributing area to the Puchack well field was delineated by means of particle tracking. An uncertainty analysis was conducted in which 36 model-input parameters were both increased and decreased until the resulting change in simulated heads exceeded the model-calibration criterion of ? 5 feet at any model cell. Porosity most affected the size and shape of the contributing area. The distribution of withdrawals at the Morris/Delair well field and variations in recharge affected both the size and shape of contributing area to the Puchack well field and the source of water to the Puchack wells. The results of the uncertainty analysis were combined to determine the 'aggregate' contributing area to the Puchack well field--a composite of areas on the land surface that contributed flow to the Puchack well field in less than 12 years in any uncertainty simulation. The shape of the aggregate contributing area was most similar to that associated with a reduction in porosity, which indirectly affected the size and shape of the contributing areas by changing travel time.

Scientific Investigations Report↗

USGS2004

Death Valley regional ground-water flow system, Nevada and California -- hydrogeologic framework and transient ground-water flow model

A numerical three-dimensional (3D) transient ground-water flow model of the Death Valley region was developed by the U.S. Geological Survey for the U.S. Department of Energy programs at the Nevada Test Site and at Yucca Mountain, Nevada. Decades of study of aspects of the ground-water flow system and previous less extensive ground-water flow models were incorporated and reevaluated together with new data to provide greater detail for the complex, digital model. A 3D digital hydrogeologic framework model (HFM) was developed from digital elevation models, geologic maps, borehole information, geologic and hydrogeologic cross sections, and other 3D models to represent the geometry of the hydrogeologic units (HGUs). Structural features, such as faults and fractures, that affect ground-water flow also were added. The HFM represents Precambrian and Paleozoic crystalline and sedimentary rocks, Mesozoic sedimentary rocks, Mesozoic to Cenozoic intrusive rocks, Cenozoic volcanic tuffs and lavas, and late Cenozoic sedimentary deposits of the Death Valley Regional Ground-Water Flow System (DVRFS) region in 27 HGUs. Information from a series of investigations was compiled to conceptualize and quantify hydrologic components of the ground-water flow system within the DVRFS model domain and to provide hydraulic-property and head-observation data used in the calibration of the transient-flow model. These studies reevaluated natural ground-water discharge occurring through evapotranspiration and spring flow; the history of ground-water pumping from 1913 through 1998; ground-water recharge simulated as net infiltration; model boundary inflows and outflows based on regional hydraulic gradients and water budgets of surrounding areas; hydraulic conductivity and its relation to depth; and water levels appropriate for regional simulation of prepumped and pumped conditions within the DVRFS model domain. Simulation results appropriate for the regional extent and scale of the model were provided by acquiring additional data, by reevaluating existing data using current technology and concepts, and by refining earlier interpretations to reflect the current understanding of the regional ground-water flow system. Ground-water flow in the Death Valley region is composed of several interconnected, complex ground-water flow systems. Ground-water flow occurs in three subregions in relatively shallow and localized flow paths that are superimposed on deeper, regional flow paths. Regional ground-water flow is predominantly through a thick Paleozoic carbonate rock sequence affected by complex geologic structures from regional faulting and fracturing that can enhance or impede flow. Spring flow and evapotranspiration (ET) are the dominant natural ground-water discharge processes. Ground water also is withdrawn for agricultural, commercial, and domestic uses. Ground-water flow in the DVRFS was simulated using MODFLOW-2000, a 3D finite-difference modular ground-water flow modeling code that incorporates a nonlinear least-squares regression technique to estimate aquifer parameters. The DVRFS model has 16 layers of defined thickness, a finite-difference grid consisting of 194 rows and 160 columns, and uniform cells 1,500 m on each side. Prepumping conditions (before 1913) were used as the initial conditions for the transient-state calibration. The model uses annual stress periods with discrete recharge and discharge components. Recharge occurs mostly from infiltration of precipitation and runoff on high mountain ranges and from a small amount of underflow from adjacent basins. Discharge occurs primarily through ET and spring discharge (both simulated as drains) and water withdrawal by pumping and, to a lesser amount, by underflow to adjacent basins, also simulated by drains. All parameter values estimated by the regression are reasonable and within the range of expected values. The simulated hydraulic heads of the final calibrated transient model gener

Scientific Investigations Report↗

USGS2006

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

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

Scientific Investigations Report↗

USGS2007

Hydrogeologic Setting and Ground-Water Flow in the Leetown Area, West Virginia

The Leetown Science Center is a research facility operated by the U.S. Geological Survey that occupies approximately 455-acres near Kearneysville, Jefferson County, West Virginia. Aquatic and fish research conducted at the Center requires adequate supplies of high-quality, cold ground water. Three large springs and three production wells currently (in 2006) supply water to the Center. The recent construction of a second research facility (National Center for Cool and Cold Water Aquaculture) operated by the U.S. Department of Agriculture and co-located on Center property has placed additional demands on available water resources in the area. A three-dimensional steady-state finite-difference ground-water flow model was developed to simulate ground-water flow in the Leetown area and was used to assess the availability of ground water to sustain current and anticipated future demands. The model also was developed to test a conceptual model of ground-water flow in the complex karst aquifer system in the Leetown area. Due to the complexity of the karst aquifer system, a multidisciplinary research study was required to define the hydrogeologic setting. Geologic mapping, surface- and borehole-geophysical surveys, stream base-flow surveys, and aquifer tests were conducted to provide the hydrogeologic data necessary to develop and calibrate the model. It would not have been possible to develop a numerical model of the study area without the intensive data collection and methods developments components of the larger, more comprehensive hydrogeologic investigation. Results of geologic mapping and surface-geophysical surveys verified the presence of several prominent thrust faults and identified additional faults and other complex geologic structures (including overturned anticlines and synclines) in the area. These geologic structures are known to control ground-water flow in the region. Results of this study indicate that cross-strike faults and fracture zones are major avenues of ground-water flow. Prior to this investigation, the conceptual model of ground-water flow for the region focused primarily on bedding planes and strike-parallel faults and joints as controls on ground-water flow but did not recognize the importance of cross-strike faults and fracture zones that allow ground water to flow downgradient across or through less permeable geologic formations. Results of the ground-water flow simulation indicate that current operations at the Center do not substantially affect either streamflow (less than a 5-percent reduction in annual streamflow) or ground-water levels in the Leetown area under normal climatic conditions but potentially could have greater effects on streamflow during long-term drought (reduction in streamflow of approximately 14 percent). On the basis of simulation results, ground-water withdrawals based on the anticipated need for an additional 150 to 200 gal/min (gallons per minute) of water at the Center also would not seriously affect streamflow (less than 8 to 9 percent reduction in streamflow) or ground-water levels in the area during normal climatic conditions. During drought conditions, however, the effects of current ground-water withdrawals and anticipated additional withdrawals of 150 to 200 gal/min to augment existing supplies result in moderate to substantial declines in water levels of 0.5-1.2 feet (ft) in the vicinity of the Center's springs and production wells. Streamflow was predicted to be reduced locally by approximately 21 percent. Such withdrawals during a drought or prolonged period of below normal ground-water levels would result in substantial declines in the flow of the Center's springs and likely would not be sustainable for more than a few months. The drought simulated in this model was roughly equivalent to the more than 1-year drought that affected the region from November 1998 through February 2000. The potential reduction in streamflow is a result of capture of ground water tha

Scientific Investigations Report↗

USGS2008

An evaluation of selected extraordinary floods in the United States reported by the U.S. Geological Survey and implications for future advancement of flood science

Thirty flood peak discharges determine the envelope curve of maximum floods documented in the United States by the U.S. Geological Survey. These floods occurred from 1927 to 1978 and are extraordinary not just in their magnitude, but in their hydraulic and geomorphic characteristics. The reliability of the computed discharge of these extraordinary floods was reviewed and evaluated using current (2007) best practices. Of the 30 flood peak discharges investigated, only 7 were measured at daily streamflow-gaging stations that existed when the flood occurred, and 23 were measured at miscellaneous (ungaged) sites. Methods used to measure these 30 extraordinary flood peak discharges consisted of 21 slope-area measurements, 2 direct current-meter measurements, 1 culvert measurement, 1 rating-curve extension, and 1 interpolation and rating-curve extension. The remaining four peak discharges were measured using combinations of culvert, slope-area, flow-over-road, and contracted-opening measurements. The method of peak discharge determination for one flood is unknown. Changes to peak discharge or rating are recommended for 20 of the 30 flood peak discharges that were evaluated. Nine floods retained published peak discharges, but their ratings were downgraded. For two floods, both peak discharge and rating were corrected and revised. Peak discharges for five floods that are subject to significant uncertainty due to complex field and hydraulic conditions, were re-rated as estimates. This study resulted in 5 of the 30 peak discharges having revised values greater than about 10 percent different from the original published values. Peak discharges were smaller for three floods (North Fork Hubbard Creek, Texas; El Rancho Arroyo, New Mexico; South Fork Wailua River, Hawaii), and two peak discharges were revised upward (Lahontan Reservoir tributary, Nevada; Bronco Creek, Arizona). Two peak discharges were indeterminate because they were concluded to have been debris flows with peak discharges that were estimated by an inappropriate method (slope-area) (Big Creek near Waynesville, North Carolina; Day Creek near Etiwanda, California). Original field notes and records could not be found for three of the floods, however, some data (copies of original materials, records of reviews) were available for two of these floods. A rating was assigned to each of seven peak discharges that had no rating. Errors identified in the reviews include misidentified flow processes, incorrect drainage areas for very small basins, incorrect latitude and longitude, improper field methods, arithmetic mistakes in hand calculations, omission of measured high flows when developing rating curves, and typographical errors. Common problems include use of two-section slope-area measurements, poor site selection, uncertainties in Manning’s n -values, inadequate review, lost data files, and insufficient and inadequately described high-water marks. These floods also highlight the extreme difficulty in making indirect discharge measurements following extraordinary floods. Significantly, none of the indirect measurements are rated better than fair, which indicates the need to improve methodology to estimate peak discharge. Highly unsteady flow and resulting transient hydraulic phenomena, two-dimensional flow patterns, debris flows at streamflow-gaging stations, and the possibility of disconnected flow surfaces are examples of unresolved problems not well handled by current indirect discharge methodology. On the basis of a comprehensive review of 50,000 annual peak discharges and miscellaneous floods in California, problems with individual flood peak discharges would be expected to require a revision of discharge or rating curves at a rate no greater than about 0.10 percent of all floods. Many extraordinary floods create complex flow patterns and processes that cannot be adequately documented with quasi-steady, uniform one-dimensional analyses. These floods are most accurately described by multidimensional flow analysis. Within the U.S. Geological Survey, new approaches are needed to collect more accurate data for floods, particularly extraordinary floods. In recent years, significant progress has been made in instrumentation for making direct discharge measurements. During this same period, very little has been accomplished in advancing methods to improve indirect discharge measurements. Greater use of paleoflood hydrology could fill many shortcomings of U.S. Geological Survey flood science today, such as enhanced knowledge of flood frequency. Additional links among flood runoff, storm structure, and storm motion would provide more insight to flood hazards. Significant improvement in understanding flood processes and characteristics could be gained from linking radar rainfall estimation and hydrologic modeling. Additionally, more could be done to provide real-time flood-hazard warnings with linked rainfall/runoff and flow models. Several important recommendations are made to improve the flood-documentation capability of the U.S. Geological Survey. When very large discharges are measured by current meter or hydroacoustics, water-surface slope should be measured as well. This measurement would allow validation of roughness values that can significantly extend the discharge range of verified Manning’s n for 1-dimensional and 2-dimensional flow analyses. At least two of the floods investigated may have had flow so unstable that large waves affected the interpretation of high-water marks. Instability criteria should be considered for hydraulic analysis of large flows in high-gradient, smooth channels. The U.S. Geological Survey needs to modernize its toolbox of field and office practices for making future indirect discharge measurements. These practices could include, first and foremost, a new peak-flow file database that allows greater description and interpretation of flow events, such as stability criteria in high-gradient, smooth channels, debris flow documentation, and details of flood genesis (hurricane, snowmelt, rain-on-snow, dam failure, and the like). Other modernized practices could include (a) establishment of calibrated stream reaches in chronic flash flood basins to expedite indirect computation of flow; (b) development of process-based theoretical rating curves for streamflow-gaging stations; (c) adoption of step-backwater models as the standard surface-water modeling tool for U.S. Geological Survey field offices; (d) development and support for multidimensional flow models capable of describing flood characteristics in complex terrain and high-gradient channels; (e) greater use of the critical-depth method in appropriate locations; (f) deployment of non-contact instruments to directly measure large floods, rather than attempting to reconstruct them; (g) increased use of paleoflood hydrology; and (h) assurance that future collection of hydro-climatic data meets the needs of more robust watershed models.

Scientific Investigations Report↗

USGS2010

Development of an Environmental Flow Framework for the McKenzie River Basin, Oregon

The McKenzie River is a tributary to the Willamette River in northwestern Oregon. The McKenzie River is approximately 90 miles in length and has a drainage area of approximately 1,300 square miles. Two major flood control dams, a hydropower dam complex, and two hydropower canals significantly alter streamflows in the river. The structures reduce the magnitude and frequency of large and small floods while increasing the annual 7-day minimum streamflows. Stream temperatures also have been altered by the dams and other anthropogenic factors, such as the removal of riparian vegetation and channel simplification. Flow releases from one of the flood control dams are cooler in the summer and warmer in the fall in comparison to unregulated flow conditions before the dam was constructed. In 2006, the Oregon Department of Environmental Quality listed a total of 112.4, 6.3, and 55.7 miles of the McKenzie River basin mainstem and tributary stream reaches as thermally impaired for salmonid rearing, salmonid spawning, and bull trout, respectively. The analyses in this report, along with previous studies, indicate that dams have altered downstream channel morphology and ecologic communities. In addition to reducing the magnitude and frequency of floods, dams have diminished sediment transport by trapping bed material. Other anthropogenic factors, such as bank stabilization, highway construction, and reductions of in-channel wood, also have contributed to the loss of riparian habitat. A comparison of aerial photography taken in 1939 and 2005 showed substantial decreases in secondary channels, gravel bars, and channel sinuosity, particularly along the lower alluvial reaches of the McKenzie River. In addition, bed armoring and incision may contribute to habitat degradation, although further study is needed to determine the extent of these processes. Peak streamflow reduction has led to vegetation colonization and stabilization of formerly active bar surfaces. The large flood control dams on Blue River and South Fork McKenzie River likely have had the greatest effect on downstream habitats because these sediment and flood-rich tributaries historically contributed a disproportionate volume of bed material, wood, and peak flows in comparison with the spring-fed tributaries of the upper McKenzie River basin. The ecological effects of the dams were examined by focusing on nine exemplar aquatic and terrestrial species, including spring Chinook salmon, bull trout, Oregon chub, Pacific and western brook lamprey, red-legged frog, western pond turtle, alder, and cottonwood. The changes caused by the dams to streamflow hydrograph affect all these and other species in complex ways, although a few commonalities are apparent. A loss of channel complexity in the McKenzie River basin, which is associated with the reduction in flood events and widespread channel stabilization, is the primary factor related to the observed population declines for all nine exemplar species. The dams also have caused direct ecological effects by blocking access to habitat, changing the amount and timing of available critical habitat, and changing water temperature during important seasons for different life stages.

Scientific Investigations Report↗

USGS2013

Sediment distribution and hydrologic conditions of the Potomac aquifer in Virginia and parts of Maryland and North Carolina

Sediments of the heavily used Potomac aquifer broadly contrast across major structural features of the Atlantic Coastal Plain Physiographic Province in eastern Virginia and adjacent parts of Maryland and North Carolina. Thicknesses and relative dominance of the highly interbedded fluvial sediments vary regionally. Vertical intervals in boreholes of coarse-grained sediment commonly targeted for completion of water-supply wells are thickest and most widespread across the central and southern parts of the Virginia Coastal Plain. Designated as the Norfolk arch depositional subarea, the entire sediment thickness here functions hydraulically as a single interconnected aquifer. By contrast, coarse-grained sediment intervals are thinner and less widespread across the northern part of the Virginia Coastal Plain and into southern Maryland, designated as the Salisbury embayment depositional subarea. Fine-grained intervals that are generally avoided for completion of water-supply wells are increasingly thick and widespread northward. Fine-grained intervals collectively as thick as several hundred feet comprise two continuous confining units that hydraulically separate three vertically spaced subaquifers. The subaquifers are continuous northward but merge southward into the single undivided Potomac aquifer. Lastly, far southeastern Virginia and northeastern North Carolina are designated as the Albemarle embayment depositional subarea, where both coarse- and fine-grained intervals are of only moderate thickness. The entire sediment thickness functions hydraulically as a single interconnected aquifer. A substantial hydrologic separation from overlying aquifers is imposed by the upper Cenomanian confining unit. Potomac aquifer sediments were deposited by a fluvial depositional complex spanning the Virginia Coastal Plain approximately 100 to 145 million years ago. Westward, persistently uplifted granite and gneiss source rocks sustained a supply of coarse-grained sand and gravel. Immature, high-gradient braided streams deposited longitudinal bars and channel fills across the Norfolk arch subarea. By contrast, across the Salisbury and Albemarle embayment subareas, mature, medium- to low-gradient meandering streams deposited medium- to coarse-grained channel fills and point bars segregated from fine-grained overbank deposits. The Virginia depositional complex merged northward across the Salisbury embayment subarea with another complex in Maryland. Here, additional sediments were received from schist source rocks that underwent three cycles of initial uplift and rapid erosion followed by crustal stability and erosional leveling. Because of the predominance of coarse-grained sediments, transmissivity, hydraulic conductivity, and regional velocities of lateral flow through the Potomac aquifer are greatest across the Norfolk arch depositional subarea, but decrease progressively northward with increasingly fine-grained sediments. Confining units hydraulically separate the Potomac aquifer from overlying aquifers, as indicated by large vertical hydraulic gradients. By contrast, most of the Potomac aquifer internally functions hydraulically as a single interconnected aquifer, as indicated by uniformly small vertical gradients. Most fine-grained sediments within the aquifer do not hydraulically separate overlying and underlying coarse-grained sediments. Across the Salisbury embayment depositional subarea, however, hydraulic separation among the vertically spaced subaquifers is imposed by the intervening confining units. The Potomac aquifer is the largest and most heavily used source of groundwater in the Virginia Coastal Plain. Water-level declines as great as 200 feet create the potential for saltwater intrusion. Conventional stratigraphic correlation has been generally ineffective at accurately characterizing complexly distributed fluvial sediments that compose the Potomac aquifer. Consequently, the aquifer’s internal hydraulic connectivity and overall hydrologic function have not been well understood. Water-supply planning and development efforts have been hampered, and interpretations of regulatory criteria for allowable water-level declines have been ambiguous. An investigation undertaken during 2010–11 by the U.S. Geological Survey, in cooperation with the Virginia Department of Environmental Quality, provides a comprehensive regional description of the spatial distribution of Potomac aquifer sediments and their relation to hydrologic conditions. Altitudes and thicknesses of 2,725 vertical sediment intervals represent the spatial distribution of Potomac aquifer sediments in the Virginia Coastal Plain and adjacent parts of Maryland and North Carolina. Sediment intervals are designated as either dominantly coarse or fine grained and were determined by interpretation of geophysical logs and ancillary information from 456 boreholes. Sediment-interval and borehole summary statistical data indicate regional trends in sediment lithology and stratigraphic continuity, upon which three structurally based and hydrologically distinct sediment depositional subareas are designated. Broad patterns of sediment deposition over time are inferred from published sediment pollen-age data. Discrepancies in previously drawn hydrostratigraphic relations between southeastern Virginia and northeastern North Carolina are partly resolved based on borehole geophysical logs and a recently documented geologic map and corehole. A conceptual model theorizes the depositional history of the sediments and geologically accounts for their distribution. Documented pumping tests of the Potomac aquifer at 197 locations produced 336 values of transmissivity and 127 values of storativity. Based on effective aquifer thicknesses, 296 values of sediment hydraulic conductivity and 113 values of sediment specific storage are calculated. Vertical hydraulic gradients are calculated from 9,479 pairs of water levels measured between November 17, 1953, and October 4, 2011, in 129 closely spaced pairs of wells. Borehole sediment-interval and related data provide a means to achieve high yielding production wells in the Potomac aquifer by site-specific targeting of drilling operations toward water-bearing coarse-grained sand and gravel. Advance knowledge of the potential of different parts of the aquifer also aids in planning optimal groundwater-development areas. Depositional subareas further provide a possible context for resource management. Current (2013) regulatory limits on water-level declines are relative to top surfaces of subdivided upper, middle, and lower Potomac aquifers across the entire Virginia Coastal Plain, but have the potential to exceed the same limit relative to a single undivided Potomac aquifer. By contrast, designation of the sediments as a single aquifer in the Norfolk arch and Albemarle embayment subareas—and as a series of vertically spaced subaquifers and intervening confining units in the Salisbury embayment subarea—best reflects understanding of the Potomac aquifer and can avoid the potential for excessive water-level declines. Simulation modeling to evaluate effects of groundwater withdrawals could be designed similarly, including vertical discretization and (or) zonation of the Potomac aquifer based on depositional subareas and a geostatistical distribution of aquifer properties derived from borehole sediment-interval data. Further resource-management information needs extend beyond the developed part of the Potomac aquifer, particularly across the Northern Neck and Middle Peninsula where only the shallowest part of the aquifer is known, and include structural aspects such as faults, basement bedrock, and the Chesapeake Bay impact crater.

Maryland, North Carolina, Virginia↗

USGS2014

U.S. Geological Survey Karst Interest Group Proceedings, Carlsbad, New Mexico, April 29-May 2, 2014

Karst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tectonic events, and geochemical weathering processes that form karst aquifers are varied and complex, and involve biological, chemical, and physical changes. These factors, combined with the diverse climatic regimes under which karst development in these rocks has taken place, result in the unique dual- or triple-porosity nature of karst aquifers. These complex hydrogeologic systems typically represent challenging and unique conditions to scientists attempting to study groundwater flow and contaminant transport in these terrains. The dissolution of carbonate rocks and the subsequent development of distinct and beautiful landscapes, caverns, and springs has resulted in the most exceptional karst areas of the United States being designated as national or state parks; commercial caverns and known privately owned caves number in the tens of thousands. Both public and private properties provide access for scientists to study the flow of groundwater in situ. Likewise, the range and complexity of landforms and groundwater flow systems associated with karst terrains are enormous, perhaps more than for any other aquifer type. Karst aquifers and landscapes that form in tropical areas, such as the cockpit karst along the north coast of Puerto Rico, differ greatly from karst landforms in more arid climates, such as the Edwards Plateau in west-central Texas or the Guadalupe Mountains near Carlsbad, New Mexico, where hypogenic processes have played a major role in speleogenesis. Many of these public and private lands also contain unique flora and fauna associated with these karst hydrogeologic systems. As a result, numerous federal, state, and local agencies have a strong interest in the study of karst terrains. Many of the major springs and aquifers in the United States have developed in carbonate rocks, such as the Floridan aquifer system in Florida and parts of Alabama, Georgia, and South Carolina; the Ozark Plateaus aquifer system in parts of Arkansas, Kansas, Missouri, and Oklahoma; and the Edwards-Trinity aquifer system in west-central Texas. These aquifers, and the springs that discharge from them, serve as major water-supply sources and as unique ecological habitats. Competition for the water resources of karst aquifers is common, and urban development and the lack of attenuation of contaminants in karst areas can impact the ecosystem and water quality of these aquifers. The concept for developing a platform for interaction among scientists within the U.S. Geological Survey (USGS) working on karst-related studies evolved from the November 1999 National Ground-Water Meeting of the USGS. As a result, the Karst Interest Group (KIG) was formed in 2000. The KIG is a loose-knit, grass-roots organization of USGS and non-USGS scientists and researchers devoted to fostering better communication among scientists working on, or interested in, karst science. The primary mission of the KIG is to encourage and support interdisciplinary collaboration and technology transfer among scientists working in karst areas. Additionally, the KIG encourages collaborative studies between the different mission areas of the USGS as well as other federal and state agencies, and with researchers from academia and institutes. The KIG also encourages younger scientists by participation of students in the poster and oral sessions. To accomplish its mission, the KIG has organized a series of workshops that are held near nationally important karst areas. To date (2014) six KIG workshops, including the workshop documented in this report, have been held. The workshops typically include oral and poster sessions on selected karst-related topics and research, as well as field trips to local karst features. Proceedings of the workshops are published by the USGS and are available online at http://water.usgs.gov/ogw/karst/kig . The first KIG workshop was held in St. Petersburg, Florida, February 13–16, 2001, in the vicinity of the large springs and other karst features of the Floridan aquifer system. The second KIG workshop was held August 20–22, 2002, in Shepherdstown, West Virginia, in proximity to the carbonate aquifers of the northern Shenandoah Valley and highlighted an invited presentation on karst literature by the late Barry F. Beck of P.E. LaMoreaux and Associates. The third KIG workshop was held September 12–15, 2005, in Rapid City, South Dakota, nearby to karst features in evaporites and limestones of the Madison Group in the Black Hills of South Dakota, including Wind Cave National Park and Jewel Cave National Monument. The workshop also included a featured presentation by Thomas Casadevall, Central Region Director, USGS, on the status of earth science at the USGS and evening trips to Jewel Cave led by Mike Wiles, National Park Service (NPS) and Wind Cave led by Rod Horrocks, NPS. The fourth KIG workshop was held May 27–29, 2008, and hosted by the Hoffman Environmental Research Institute and Center for Cave and Karst Studies at Western Kentucky University in Bowling Green, Kentucky, near Mammoth Cave National Park and karst features of the Chester Upland and Pennyroyal Plateau. The workshop featured a late-night field trip into Mammoth Cave with Rickard Toomey and Rick Olsen, NPS. The fifth workshop was held April 26–29, 2011, and was a joint meeting of the USGS KIG and University of Arkansas HydroDays, hosted by the Department of Geosciences at the University of Arkansas in Fayetteville. The workshop featured an outstanding field trip to the unique karst terrain along the Buffalo National River of the southern Ozarks and a keynote presentation on paleokarst in the United States by Art and Peggy Palmer. This sixth and current 2014 KIG workshop is hosted by the National Cave and Karst Research Institute (NCKRI) in Carlsbad, New Mexico, with Director of NCKRI, George Veni, serving as co-chair of the workshop with Eve Kuniansky, USGS. The session planning committee for this sixth workshop includes Van Brahana, USGS retired and University of Arkansas Professor Emeritus; Tom Byl, USGS and Tennessee State University; Zelda Bailey, former Director of NCKRI and retired Director, National Institute of Standards and Technology, Boulder Laboratory, Colorado; Patrick Tucci, USGS retired; and Mike Bradley, Allan Clark, Geoff Delin, Daniel Doctor, James Kaufmann, Eve Kuniansky, Randy Orndorff, Larry Spangler, and Dave Weary of the USGS. The karst hydrology field trip on Thursday will be led by Lewis Land (NCKRI karst hydrologist) and the optional Friday field trip on the geology of Carlsbad Caverns National Park will be led by George Veni. The keynote speaker is Dr. Penelope Boston, Director of Cave and Karst Studies at New Mexico Tech, Socorro, and Academic Director at NCKRI, who will address the future of karst research. Additionally, there is a featured presentation “Irish karst and its management,” by Caoimhe Hickey, The Geological Survey of Ireland, preceding a panel discussion on “Collaboration During Times of Limited Resources.” The extended abstracts of USGS authors were peer reviewed and approved for publication by the U.S. Geological Survey. Articles submitted by university researchers and other federal and state agencies did not go through the formal USGS peer review and approval process, and therefore may not adhere to our editorial standards or stratigraphic nomenclature and is not research conducted or data collected by the USGS. However, all articles had at a minimum of two peer reviews, and all articles were edited for consistency of appearance in the published Proceedings. The use of trade, firm or product names in any article is for descriptive purposes only and does not imply endorsement by the U.S. Government. The USGS, Office of Groundwater, provides technical support for the Karst Interest Group website and public availability of the Proceedings from these workshops, and the USGS Groundwater Resources Program funds the publication costs. Finally, the cover illustration is the work of Ann Tihansky, USGS, used since the first KIG workshop in 2000.

Scientific Investigations Report↗

USGS2014

Hydrogeologic framework and groundwater/surface-water interactions of the upper Yakima River Basin, Kittitas County, central Washington

The hydrogeology, hydrology, and geochemistry of groundwater and surface water in the upper (western) 860 square miles of the Yakima River Basin in Kittitas County, Washington, were studied to evaluate the groundwater-flow system, occurrence and availability of groundwater, and the extent of groundwater/surface-water interactions. The study area ranged in altitude from 7,960 feet in its headwaters in the Cascade Range to 1,730 feet at the confluence of the Yakima River with Swauk Creek. A west-to-east precipitation gradient exists in the basin with the western, high-altitude headwaters of the basin receiving more than 100 inches of precipitation per year and the eastern, low-altitude part of the basin receiving about 20 inches of precipitation per year. From the early 20th century onward, reservoirs in the upper part of the basin (for example, Keechelus, Kachess, and Cle Elum Lakes) have been managed to store snowmelt for irrigation in the greater Yakima River Basin. Canals transport water from these reservoirs for irrigation in the study area; additional water use is met through groundwater withdrawals from wells and surface-water withdrawals from streams and rivers. Estimated groundwater use for domestic, commercial, and irrigation purposes is reported for the study area. A complex assemblage of sedimentary, metamorphic, and igneous bedrock underlies the study area. In a structural basin in the southeastern part of the study area, the bedrock is overlain by unconsolidated sediments of glacial and alluvial origin. Rocks and sediments were grouped into six hydrogeologic units based on their lithologic and hydraulic characteristics. A map of their extent was developed from previous geologic mapping and lithostratigraphic information from drillers’ logs. Water flows through interstitial space in unconsolidated sediments, but largely flows through fractures and other sources of secondary porosity in bedrock. Generalized groundwater-flow directions within the unconfined part of the aquifers in unconsolidated sediments indicate generalized groundwater movement toward the Yakima River and its tributaries and the outlet of the study area. Groundwater movement through fractures within the bedrock aquifers is complex and varies over spatial scales depending on the architecture of the fracture-flow system and its hydraulic properties. The complexity of the fracturedbedrock groundwater-flow system is supported by a wide range of groundwater ages determined from geochemical analyses of carbon-14, sulfur hexafluoride, and tritium in groundwater. These geochemical data also indicate that the shallow groundwater system is actively flushing with young, isotopically heavy groundwater, but isotopicallylight, Pleistocene-age groundwater with a geochemicallyevolved composition occurs at depth within the fracturedbedrock aquifers of upper Kittitas County. An eastward depletion of stable isotopes in groundwater is consistent with hydrologically separate subbasins. This suggests that groundwater that recharges in one subbasin is not generally available for withdrawal or discharge into surface-water features within other subbasins. Water budget components were calculated for 11 subbasins using a watershed model and varied based on the climate, land uses, and geology of the subbasin. Synoptic streamflow measurements made in August 2011 indicate that groundwater discharges into several tributaries of the Yakima River with several losses of streamflow measured where the streams exit bedrock uplands and flow over unconsolidated sediments. Profiles of stream temperature during late summer suggest cool groundwater inflow over discrete sections of streams. This groundwater/surfacewater connection is further supported by the stable-isotope composition of stream water, which reflects the local stableisotope composition of groundwater measured at some wells and springs. Collectively, these hydrogeologic, hydrologic, and geochemical data support a framework for evaluating the potential effects of future groundwater appropriations on senior surface-water and groundwater rights and streamflows. Although total pumping rates in upper Kittitas County of about 3.5 cubic feet per second are small relative to other components of the water budget, the magnitude, timing, and location of withdrawals may have important effects on the hydrologic system. The heterogeneous and variably fractured bedrock in the study area precluded a detailed evaluation of localized effects of pumping, but several generalizations about the groundwater and surface-water systems can be made. These generalizations include evidence for the continuity between the groundwater and surface-water system apparent from synoptic streamflow measurements, stream-temperature profiles, and stable-isotope data of groundwater and surface waters.

Washington↗

USGS2015

Assessing geomorphic change along the Trinity River downstream from Lewiston Dam, California, 1980-2011

The Trinity River Restoration Program, one of the nation’s largest adaptively managed river restoration programs, requires periodic assessment to determine the effectiveness of management actions in restoring channel dynamics and habitat features. This study documents riparian and channel changes along an intensively managed 65-kilometer reach of the Trinity River in California, downstream from Lewiston Dam. The two primary periods of interest, from 1980 to 2001 and from 2001 to 2011, are separated by a shift in restoration activities mandated by the U.S. Department of the Interior December 2000 Record of Decision. The post-2001 restoration strategy increased managed-flow releases, gravel augmentation, watershed restoration, and mechanical channel rehabilitation. We assessed the nature and extent of geomorphic change and a series of ecological performance measures (channel complexity, shoreline length, and channel–floodplain connectivity) by using a series of maps digitized from available rectified orthophotography acquired during low-flow conditions in 1980, 1997, 2001, 2006, 2009, and 2011. Lateral changes in riparian and channel features were used to quantify alluvial processes, and a review of existing streamflow, sediment, and restoration records was used to assess causal mechanisms. During the study period, natural bank erosion and mechanical rehabilitation of channel margins converted riparian features to channel features and expanded the active-channel area. The primary period of bank erosion and expansion of the active channel was from 1980 to 1997. Subsequent bar accretion from 1997 to 2001, followed by slightly greater bar scour from 2001 to 2006, took place primarily in the central and lower reaches of the study area, downstream of Indian Creek. In comparison, post‑2006 bank and bar changes were spatially limited to reaches that had sufficient local transport capacity or sediment supply supported by gravel augmentation, mechanical channel rehabilitation, and tributary contributions. The highest rates of change in the areal extents of channel and riparian features were observed during the pre‑2001 period, which was longer and relatively wetter than the post-2001 period. A series of tributary floods in 1997, 1998, and 2006 increased channel complexity and floodplain connectivity. During the post-2006 period, managed-flow releases, in the absence of tributary flooding, combined with gravel augmentation and mechanical restoration, caused localized increases in sediment supply and transport capacity that led to smaller, but measurable, increases in channel complexity and floodplain connectivity in the upper river near Lewiston Dam. Extensive pre-2001 channel widening and the muted geomorphic response of channel rehabilitation sites to post-2001 managed flows highlight the need for continued monitoring and assessment of the magnitude, duration, and timing of prescriptive flows and associated geomorphic responses.

California↗

USGS2015

Hydrology of and Current Monitoring Issues for the Chicago Area Waterway System, Northeastern Illinois

The Chicago Area Waterway System (CAWS) consists of a combination of natural and manmade channels that form an interconnected navigable waterway of approximately 90-plus miles in the metropolitan Chicago area of northeastern Illinois. The CAWS serves the area as the primary drainage feature, a waterway transportation corridor, and recreational waterbody. The CAWS was constructed by the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC). Completion of the Chicago Sanitary and Ship Canal (initial portion of the CAWS) in 1900 breached a low drainage divide and resulted in a diversion of water from the Lake Michigan Basin. A U.S. Supreme Court decree (Consent Decree 388 U.S. 426 [1967] Modified 449 U.S. 48 [1980]) limits the annual diversion from Lake Michigan. While the State of Illinois is responsible for the diversion, the MWRDGC regulates and maintains water level and water quality within the CAWS by using several waterway control structures. The operation and control of water levels in the CAWS results in a very complex hydraulic setting characterized by highly unsteady flows. The complexity leads to unique gaging requirements and monitoring issues. This report provides a general discussion of the complex hydraulic setting within the CAWS and quantifies this information with examples of data collected at a range of flow conditions from U.S. Geological Survey streamflow gaging stations and other locations within the CAWS. Monitoring to address longstanding issues of waterway operation, as well as current (2014) emerging issues such as wastewater disinfection and the threat from aquatic invasive species, is included in the discussion.

Illinois↗