Geohydrology

Search Results

Browse All Documents

2017 Salinas Valley Groundwater Level Contours & Seawater Intrusion Maps
$0.00
Bulk Download

2017 Salinas Valley Groundwater Level Contours & Seawater Intrusion Maps
Monterey County Water Resources Agency (MCWRA) | April 24, 2018...
Summary

View Document
Become a member to access this feature
Download NowEmail Details
A brief geologic and hydrologic reconnaissance of the Furnace Creek Wash area, Death Valley National Monument, California

Bulk Download

A brief geologic and hydrologic reconnaissance of the Furnace Creek Wash area, Death Valley National Monument, California
U.S. Geological Survey (USGS) | July 1, 1964...
Summary

View Document
Become a member to access this feature
Download NowEmail Details
A conceptual model for floodplains in the Sacramento-San Joaquin Delta

Bulk Download

A conceptual model for floodplains in the Sacramento-San Joaquin Delta
San Francisco Estuary & Watershed Science (UC Davis) | October 3, 2012...
Summary
Floodplains are among the most biologically productive and diverse ecosystems on Earth and they provide significant benefits to society such as attenuation of...
Floodplains are among the most biologically productive and diverse ecosystems on Earth and they provide significant benefits to society such as attenuation of floodwaters, groundwater recharge, filtration of nutrients and sediments, carbon sequestration, fisheries productivity and recreation. However, floodplains are also among the most converted and threatened ecosystems. Floodplain habitats in the Sacramento-San Joaquin Delta, and throughout California’s Central Valley, have been greatly reduced from their historic extent and key processes that create and maintain floodplains, such as flood flows and meander migration, have been greatly altered. These widespread alterations to habitats and processes have lead to declines in many species’ populations in California’s Central Valley and Delta, creating challenges for both environmental and water management. To address these challenges numerous entities and programs are now focused on restoring floodplains and other Delta habitats. This paper provides a conceptual model for floodplains that characterizes the key features and identifies the critical processes, drivers, and linkages that allow floodplains to produce a variety of functional outputs of management importance. These outputs include: (1) the floodplain habitat mosaic, including riparian vegetation and its associated wildlife; (2) spawning and rearing habitat for native fish; and (3) food-web productivity that can support native fish on the floodplain as well as be exported to downstream ecosystems. The model emphasizes that the production of these outputs from floodplains requires vertical and lateral hydrological connectivity across a broad range of flow conditions. For example, long-duration flooding in the spring promotes native fish spawning and food-web productivity that benefits native species.

View Document
Become a member to access this feature
Download NowEmail Details
A geohydrologic reconnaissance of the Saratoga Spring area, Death Valley National Monument, California

Bulk Download

A geohydrologic reconnaissance of the Saratoga Spring area, Death Valley National Monument, California
U.S. Geological Survey (USGS) | March 1, 1966...
Summary

View Document
Become a member to access this feature
Download NowEmail Details
A Guide for Using the Transient Ground-Water Flow Model of the Death Valley Regional Ground-Water Flow System, Nevada and California
$0.00
Bulk Download

A Guide for Using the Transient Ground-Water Flow Model of the Death Valley Regional Ground-Water Flow System, Nevada and California
U.S. Geological Survey (USGS), U.S. Department of Energy Office of Environmental Management | November 4, 2006...
Summary
This report is a guide for executing numerical simulations with the transient ground-water flow model of the Death Valley regional ground-water flow system,...
This report is a guide for executing numerical simulations with the transient ground-water flow model of the Death Valley regional ground-water flow system, Nevada and California using the U.S. Geological Survey modular finite-difference ground-water flow model, MODFLOW-2000. Model inputs, including observations of hydraulic head, discharge, and boundary flows, are summarized. Modification of the DVRFS transient ground-water model is discussed for two common uses of the Death Valley regional ground-water flow system model: predictive pumping scenarios that extend beyond the end of the model simulation period (1998), and model simulations with only steady-state conditions.

View Document
Become a member to access this feature
Download NowEmail Details
A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA
$0.00
Bulk Download

A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA
Science of the Total Environment | June 9, 2017...
Summary
Intense demand for water in the Central Valley of California and related increases in groundwater nitrate concentration threaten the sustainability of the groundwater...
Intense demand for water in the Central Valley of California and related increases in groundwater nitrate concentration threaten the sustainability of the groundwater resource. To assess contamination risk in the region, we developed a hybrid, non-linear, machine learning model within a statistical learning framework to predict nitrate contamination of groundwater to depths of approximately 500m below ground surface.

A database of 145 predictor variables representing well characteristics, historical and current field and landscape-scale nitrogen mass balances, historical and current land use, oxidation/reduction conditions, groundwater flow, climate, soil characteristics, depth to groundwater, and groundwater age were assigned to over 6000 private supply and public supply wells measured previously for nitrate and located throughout the study area. The boosted regression tree (BRT) method was used to screen and rank variables to predict nitrate concentration at the depths of domestic and public well supplies.

The novel approach included as predictor variables outputs from existing physically based models of the Central Valley. The top five most important predictor variables included two oxidation/reduction variables (probability of manganese concentration to exceed 50 ppb and probability of dissolved oxygen concentration to be below 0.5 ppm), field-scale adjusted unsaturated zone nitrogen input for the 1975 time period, average difference between precipitation and evapotranspiration during the years 1971–2000, and 1992 total landscape nitrogen input.

Twenty-five variables were selected for the final model for log-transformed nitrate. In general, increasing probability of anoxic conditions and increasing precipitation relative to potential evapotranspiration had a corresponding decrease in nitrate concentration predictions.

Conversely, increasing 1975 unsaturated zone nitrogen leaching flux and 1992 total landscape nitrogen input had an increasing relative impact on nitrate predictions.

Three-dimensional visualization indicates that nitrate predictions depend on the probability of anoxic conditions and other factors, and that nitrate predictions generally decreased with increasing groundwater age.

View Document
Become a member to access this feature
Download NowEmail Details
A multi-isotope (B, Sr, O, H, and C) and age dating (3H–3He and14C) study of groundwater from Salinas Valley, California: Hydrochemistry, dynamics, and contamination processes

Bulk Download

A multi-isotope (B, Sr, O, H, and C) and age dating (3H–3He and14C) study of groundwater from Salinas Valley, California: Hydrochemistry, dynamics, and contamination processes
American Geophysical Union (AGU) | January 31, 2002...
Summary
The chemical and isotope (11B/10B, 87Sr/86Sr, 18O/16O, 2H/H, 13C/12C, 14C, and 3He/3H) compositions of groundwater from the upper aquifer system of the Salinas Valley...
The chemical and isotope (11B/10B, 87Sr/86Sr, 18O/16O, 2H/H, 13C/12C, 14C, and 3He/3H) compositions of groundwater from the upper aquifer system of the Salinas Valley in coastal central California were investigated in order to delineate the origin and processes of groundwater contamination in this complex system. The Salinas Valley has a relatively deep, confined ‘‘400- foot’’ aquifer, overlain by a ‘‘180-foot’’ aquifer and a shallower perched aquifer, all made up of alluvial sand, gravel and clay deposits. Groundwater from the aquifers have different 14C ages: fossil (14C = 21.3 percent modern carbon (pmc) for the 400-foot aquifer and modern (14C = 72.2–98.2 pmc) for the 180-foot aquifer. Fresh groundwater in all aquifers is recharged naturally and artificially through the Salinas River. The two modes of recharge can be distinguished chemically.We identified several different saline components with distinguishable chemical and isotopic fingerprints. Saltwater intrusion in the northern basin has C1 concentrations up to 1700 mg/L, a Na/Cl ratio less than seawater, a marine Br/Cl ratio, a Ca/Cl ratio greater than seawater, d11B between +17 and +38% and 87Sr/86Sr between 0.7088 and 0.7096. Excess dissolved Ca, relative to the expected concentration for simple dilution of seawater, correlates with 87Sr/86Sr ratios, suggesting base exchange reaction with clay materials. (2) Agriculture return flow is high inNO3 and SO4, with a 87Sr/86Sr = 0.7082,d11B = 19% and d13C between 23 and 17%. The 3H–3He ages (5–17 years) and 14C data suggest vertical infiltration rates of irrigation water of 3–10 m/yr. (3) Nonmarine saline water in the southern part of the valley has high total dissolved solids up to 3800 mg/L, high SO4, Na/Cl ratio >1, d11B between +24 and +30%, and 87Sr/86Sr = 0.70852. This groundwater may have acquired its geochemical signature from leaching of sedimentary rocks associated with the Coast Range marine deposits of Mesozoic to early Cenozoic age. The combination of different geochemical and isotopic fingerprints enables us to delineate the impact of salt sources in different areas of the valley and to reconstruct the origin of the SO4-enriched NO3-depleted saline plume that is located west of the city of Salinas. We suggest that the latter is derived from a mixture of different natural saline waters rather than from anthropogenic contamination.

View Document
Become a member to access this feature
Download NowEmail Details
A New Technique for Modeling Land Subsidence Facilitates Better Groundwater Management

Bulk Download

A New Technique for Modeling Land Subsidence Facilitates Better Groundwater Management
Stanford Woods Institute for the Environment and the Bill Lane Center for the American West | December 1, 2019...
Summary
Land subsidence – the sudden sinking or gradual settling of Earth’s surface – can occur naturally or be triggered by human activity. One of...

Land subsidence – the sudden sinking or gradual settling of Earth’s surface – can occur naturally or be triggered by human activity. One of the most common human-affected factors is groundwater pumping, a practice that has been steadily increasing due to prolonged periods of drought. Groundwater pumping is so prevalent in some areas that it is severely compromising the quantity and quality of the groundwater as well as the physical structure of the land and aquifer capacity beneath it. Large-scale initiatives for putting water back into the ground, or groundwater recharge, are being implemented in some regions. However, groundwater resource managers still need better information to determine where the land is at greatest risk of subsidence as well as where recharge efforts would be the most effective. Integrating two reliable data gathering sources – helicopter-deployed systems (airborne electromagnetic or AEM technology) that measure electromagnetic fields and satellite-deployed systems (interferometric synthetic aperture radar or InSAR) to measure deformations – offers groundwater managers an improved method for more accurately modeling changes in the land surface related to the pumping and recharge of groundwater. Additionally, the ability to more precisely detect subsidence may offer an early warning system for declining groundwater levels.

View Document
Become a member to access this feature
Download NowEmail Details
A three-dimensional numerical model of predevelopment conditions in the Death Valley regional ground-water flow system, Nevada and California

Bulk Download

A three-dimensional numerical model of predevelopment conditions in the Death Valley regional ground-water flow system, Nevada and California
U.S. Geological Survey (USGS) | July 1, 2002...
Summary

View Document
Become a member to access this feature
Download NowEmail Details
A Water Resources Data Network Evaluation for Monterey County, California; Phase 1; South County
$0.00
Bulk Download

A Water Resources Data Network Evaluation for Monterey County, California; Phase 1; South County
U..S. Geological Survey (USGS), Monterey County Flood Control and Water Conservation District | July 12, 1986...
Summary
An evaluation made of rainfall, surface water, groundwater, and water quality monitoring networks in Salinas River basin in southern Monterey County, California, proposed...
An evaluation made of rainfall, surface water, groundwater, and water quality monitoring networks in Salinas River basin in southern Monterey County, California, proposed all long-term rain gages be continued for extending short-term records and suggested the installation of two additional recording gages. Eight new storage rain gages were suggested at midaltitudes of east and west sides of Salinas Valley where few data are available. The evaluation revealed some short-term gaging stations could be discontinued because of good regression relations between them and the long-term stations Arroyo Seco near Soledad.

Of 16 stations selected for the proposed network, 4 are new recording stations, 6 are new nonrecording streamflow and water quality sampling sites, 5 are existing stations, and the last is a station operated from 1969 to 1976; also included are water quality sampling stations on Lakes Nacimiento and San Antonio. The proposed groundwater network was developed from information on geology, geohydrology, and groundwater quality, high priority objectives for groundwater network, and consideration for providing good areal coverage of levels and water quality. Of 145 sites selected, 86 are existing monitoring wells.

View Document
Become a member to access this feature
Download NowEmail Details

Search

Geohydrology

Search

Browse All Documents

Type

Topic

Keywords

Publisher

Publication Year

Hydrologic Region

Index By

2017 Salinas Valley Groundwater Level Contours & Seawater Intrusion Maps

2017 Salinas Valley Groundwater Level Contours & Seawater Intrusion Maps

Become a member to access this feature

A brief geologic and hydrologic reconnaissance of the Furnace Creek Wash area, Death Valley National Monument, California

A brief geologic and hydrologic reconnaissance of the Furnace Creek Wash area, Death Valley National Monument, California

Become a member to access this feature

A conceptual model for floodplains in the Sacramento-San Joaquin Delta

A conceptual model for floodplains in the Sacramento-San Joaquin Delta

Become a member to access this feature

A geohydrologic reconnaissance of the Saratoga Spring area, Death Valley National Monument, California

A geohydrologic reconnaissance of the Saratoga Spring area, Death Valley National Monument, California

Become a member to access this feature

A Guide for Using the Transient Ground-Water Flow Model of the Death Valley Regional Ground-Water Flow System, Nevada and California

A Guide for Using the Transient Ground-Water Flow Model of the Death Valley Regional Ground-Water Flow System, Nevada and California

Become a member to access this feature

A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA

A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA

Become a member to access this feature

A multi-isotope (B, Sr, O, H, and C) and age dating (3H–3He and14C) study of groundwater from Salinas Valley, California: Hydrochemistry, dynamics, and contamination processes

A multi-isotope (B, Sr, O, H, and C) and age dating (3H–3He and14C) study of groundwater from Salinas Valley, California: Hydrochemistry, dynamics, and contamination processes

Become a member to access this feature

A New Technique for Modeling Land Subsidence Facilitates Better Groundwater Management

A New Technique for Modeling Land Subsidence Facilitates Better Groundwater Management

Become a member to access this feature

A three-dimensional numerical model of predevelopment conditions in the Death Valley regional ground-water flow system, Nevada and California

A three-dimensional numerical model of predevelopment conditions in the Death Valley regional ground-water flow system, Nevada and California

Become a member to access this feature

A Water Resources Data Network Evaluation for Monterey County, California; Phase 1; South County

A Water Resources Data Network Evaluation for Monterey County, California; Phase 1; South County

Become a member to access this feature