Geochemistry of ground water in the Gulf Coast Aquifer systems, south-central United States

Pettijohn, Robert A.

doi:10.3133/wri964107

Cited by 2 publications

(2 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In particular, the southern extent of the study area has highly saline groundwater at depth that precluded groundwater-flow modeling for Tertiary units in Clark and Hart (2009). The effects of this wedge of saline water can be observed in the prediction maps for the MCAQ and LCAQ where Cl is highest near the southern boundary of the active model cells ( Figure 8); concentrations in the inactive cells are generally greater than 10,000 mg/L TDS (not shown in Figure 7) owing to dissolution of halite in salt domes (Pettijohn 1996). SC model predictions were more accurate (higher r 2 and lower RMSE) than for Cl.…”

Section: Important Explanatory Variablesmentioning

confidence: 99%

“…The difference in the partial dependence plots for ageMin between SC and Cl (Figure S5), with some high Cl concentrations where young water is present, but SC is low, likely reflects the anthropogenic contribution of Cl. Areas of higher salinity in the MRVA have been hypothesized to be controlled by (1) deeper sources of salinity (whether saline groundwater from dissolution of salt domes or connate seawater) moving upward from underlying aquifers (e.g., along faults, wells, or where confining units are thin or absent) or (2) accumulation of salts during evaporation when recharge is slowed by surficial clays (Pettijohn 1996;Kresse and Clark 2008;Paul et al 2018). Because of the physiography of the alluvial plain footprint, many surficial explanatory variables (especially soils and land use) strongly reflect that footprint.…”

Section: Important Explanatory Variablesmentioning

confidence: 99%

See 1 more Smart Citation

Using Boosted Regression Tree Models to Predict Salinity in Mississippi Embayment Aquifers, Central United States

Knierim

Kingsbury

Haugh

et al. 2020

J American Water Resour Assoc

View full text Add to dashboard Cite

High salinity limits groundwater use in parts of the Mississippi embayment. Machine learning was used to create spatially continuous and three‐dimensional predictions of salinity across drinking‐water aquifers in the embayment. Boosted regression tree (BRT) models, a type of machine learning, were used to predict specific conductance (SC) and chloride (Cl), and total dissolved solids (TDS) was calculated from a correlation with SC. Explanatory variables for BRT models included well location and construction, surficial variables (e.g., soils and land use), and variables extracted from a groundwater‐flow model, including simulated groundwater ages. BRT model fits (r2) were 0.74 (SC and Cl) and 0.62 (TDS). BRT models provided spatially continuous salinity predictions across surficial and deeper aquifers where discrete water‐quality samples were missing. Uncertainty was smaller where salinity was lower, and models tended to underpredict in areas of highest salinity. Despite this, BRT models were able to capture areas of documented high salinity that exceed the TDS secondary maximum contaminant level for drinking water of 500 mg/L. Variables that served as surrogates for position along groundwater flowpaths were the most important predictors, indicating that much of the control on dissolved solids is related to rock‐water interaction as residence time increases. BRT models additionally support hypotheses of both surficial and deep sources of salinity.

show abstract

Section: Important Explanatory Variablesmentioning

confidence: 99%

Section: Important Explanatory Variablesmentioning

confidence: 99%

Using Boosted Regression Tree Models to Predict Salinity in Mississippi Embayment Aquifers, Central United States

Knierim

Kingsbury

Haugh

et al. 2020

J American Water Resour Assoc

View full text Add to dashboard Cite

show abstract

Quality of Shallow Groundwater and Drinking Water in the Mississippi Embayment-Texas Coastal Uplands Aquifer System and the Mississippi River Valley Alluvial Aquifer, South-Central United States, 1994-2004

Welch¹,

Kingsbury²,

Tollett³

et al. 2009

Scientific Investigations Report

View full text Add to dashboard Cite

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 888-ASK-USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. ForewordThe U.S. Geological Survey (USGS) is committed to providing the Nation with reliable scientific information that helps to enhance and protect the overall quality of life and that facilitates effective management of water, biological, energy, and mineral resources (http://www.usgs. gov/). Information on the Nation's water resources is critical to ensuring long-term availability of water that is safe for drinking and recreation and is suitable for industry, irrigation, and fish and wildlife. Population growth and increasing demands for water make the availability of that water, measured in terms of quantity and quality, even more essential to the long-term sustainability of our communities and ecosystems.The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to support national, regional, State, and local information needs and decisions related to water-quality management and policy (http://water.usgs.gov/nawqa). The NAWQA Program is designed to answer: What is the quality of our Nation's streams and ground water? How are conditions changing over time? How do natural features and human activities affect the quality of streams and ground water, and where are those effects most pronounced? By combining information on water chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities. From 1991 to 2001, the NAWQA Program completed interdisciplinary assessments and established a baseline understanding of water-quality conditions in 51 of the Nation's river basins and aquifers, referred to as Study Units (http://water.usgs.gov/nawqa/studyu.html).In the second decade of the Program (2001Program ( -2012, a major focus is on regional assessments of water-quality conditions and trends. These regional assessments are based on major river basins and principal aquifers, which encompass larger regions of the country than the Study Units. Regional assessments extend the findings in the Study Units by filling critical gaps in characterizing the quality of surface water and ground water, and by determining water-quality status and trends at sites that have been consistently monitored for more than a decade. In addition, the regional assessments continue to build an understanding o...

show abstract

Geochemistry of ground water in the Gulf Coast Aquifer systems, south-central United States

Abstract: Median value of selected chemical constituents and properties of water, median sampling depth, water types, and number of analyses for each subarea of permeable zone C

Cited by 2 publications

References 10 publications

Using Boosted Regression Tree Models to Predict Salinity in Mississippi Embayment Aquifers, Central United States

Using Boosted Regression Tree Models to Predict Salinity in Mississippi Embayment Aquifers, Central United States

Quality of Shallow Groundwater and Drinking Water in the Mississippi Embayment-Texas Coastal Uplands Aquifer System and the Mississippi River Valley Alluvial Aquifer, South-Central United States, 1994-2004

Contact Info

Product

Resources

About