Reliable yields of public water-supply wells in the fractured-rock aquifers of central Maryland, USA (original) (raw)
Related papers
Journal of Water Resource and Protection, 2014
Aquifer test methods have greatly improved in recent years with the advent of inverse analysis, derivative analysis, and diagnostic plots. Updated analyses of past aquifer tests allow for improved interpretations of the data to enhance the knowledge and the predictive capabilities of the flow system. This work thoroughly reanalyzes a series of pre-and post-hydraulic fracturing, single-well aquifer tests conducted in two crystalline rock wells in New Hampshire as part of an early 1970's study. Previous analyses of the data had relied on older manual type-curve methods for predicting the possible effects of hydraulic fracturing. This work applies inverse analysis, derivative analysis, and diagnostic plots to reanalyze the 1970's aquifer test data. Our results demonstrate that the aquifer tests were affected by changes in flow regimes, dewatering of the aquifer and discrete fractures, and changes due to well development. Increases in transmissivities are related to well development prior to hydraulic fracturing, propagation of a single, vertical fracture hydraulically connecting the two wells after stimulation and expansion of troughs of depression. After hydraulic fracturing, the estimated total yield of the individual wells increased by 2.5 times due to the hydraulic fracturing. However, the wells may be receiving water from the same source, and well interference may affect any significant increase in their combined yield. Our analyses demonstrate the value in applying inverse analysis, derivative analysis, and diagnostic plots over the conventional method of manual type-curve analysis. In addition, our improvement in the aquifer test interpretation of the 1970's test data has implications for more reliable estimates of sustained well yields.
Factors related to well yield in the fractured-bedrock aquifer of New Hampshire
Professional Paper
The New Hampshire Bedrock Aquifer Assessment was designed to provide information that can be used by communities, industry, profes sional consultants, and other interests to evaluate the groundwater development potential of the fractured-bedrock aquifer in the State. The assess ment was done at statewide, regional, and well field scales to identify relations that potentially could increase the success in locating high-yield water supplies in the fractured-bedrock aquifer. statewide, data were collected for well construc tion and yield information, bedrock lithology, surficial geology, lineaments, topography, and various derivatives of these basic data sets. Regionally, geologic, fracture, and lineament data were collected for the Pinardville and Windham quadrangles in New Hampshire. The regional scale of the study examined the degree to which predictive well-yield relations, developed as part of the statewide reconnaissance investigation, could be improved by use of quadrangle-scale geologic mapping. Beginning in 1984, water-well contractors in the State were required to report detailed information on newly constructed wells to the New Hampshire Department of Environmental Services (NHDES). The reports contain basic data on well construction, including six character istics used in this study-well yield, well depth, well use, method of construction, date drilled, and depth to bedrock (or length of casing). The NHDES has determined accurate georeferenced locations for more than 20,000 wells reported
Using Domestic Well Records to Determine Fractured Bedrock Watersheds and Recharge Rates
Groundwater, 2013
This study presents an approach for delineating groundwater basins and estimating rates of recharge to fractured crystalline bedrock. It entailed the use of completion report data (boring logs) from 2500 domestic wells in bedrock from the Coventry Quadrangle, which is located in northeastern Connecticut and characterized by metamorphic gneiss and schist. Completion report data were digitized and imported into ArcGIS ® for data analysis. The data were processed to delineate groundwater drainage basins for the fractured rock based on flow conditions and to estimate groundwater recharge to the bedrock. Results indicate that drainage basins derived from surface topography, in general, may not correspond with bedrock drainage basins due to scale. Estimates of recharge to the bedrock for the study area indicate that only a small fraction of the precipitation or the amount of water that enters the overburden recharges the rock. The approach presented here can be a useful method for water resource-related assessments that involve fractured rock aquifers.
High-capacity wells and baseflow decline in the Wolf River Basin, northeastern Wisconsin (USA)
Environmental Earth Sciences, 2016
The baseflow of the Wolf River (drainage area of 1,200 km 2) in northeastern Wisconsin has declined by over 30% during the last thirty years, whereas climatic, land cover, and soil characteristics of the basin have remained unchanged. Because groundwater basins do not always coincide with surface water basins, estimating groundwater discharge to streams using variables only pertinent to the surface water basin can be ineffective. The purpose of this study is to explain the decline in the baseflow of the Wolf River by developing a multiple regression model. To take into account variables pertaining to the groundwater basin, withdrawal rates from high capacity wells both inside the Wolf River basin and in two adjacent basins were included in the regression model. The other explanatory variables include annual precipitation and growing degree days. Groundwater discharge to the river was calculated using streamflow records with the computer program Groundwater Toolbox from the United States Geological Survey. Without the high capacity wells data, the model only explained 29.6% of the variability in the groundwater discharge. When the high capacity wells data within the Wolf River basin were included, r 2 improved to be 0.512. With the high capacity wells data in adjacent basins, r 2 improved to be 0.700. The study suggests that human activity taking place outside of the basin has had an effect on the baseflow, and should be taken into account when examining baseflow changes.
Prediction of Well Levels in the Alluvial Aquifer along the Lower Missouri River
Groundwater, 2011
Temporal variations in the head of wells in the alluvial aquifer along the lower Missouri River are accurately simulated by summation of linear differential terms involving daily variations in river stage and effective precipitation. Scaling parameters were optimized using a fourth order Adams-Bashforth-Moulton method, providing predictions for head that are typically accurate within ±1.5 feet (0.5 m) over intervals of 1 to 15 years. Parameter magnitudes represent the product of realistic aquifer properties and geometric factors.
2015
Groundwater modeling has been used since the 1970's as a way to analyze complex groundwater systems and to provide scientific evidence for management and policy determinations. The fundamental objective of this research was to develop a digital groundwater-flow model of the Rush Springs aquifer to assist in these determinations. The Rush Springs aquifer covers approximately 10,360 km 2 in westcentral Oklahoma and is the state's second most developed aquifer. This model will be used by government agencies to inform management decisions as well as gain insight about the aquifer's response to different scenarios such as policy determinations, changes in climate, or groundwater use. A steady-state simulation was first generated from the model. Hydraulic conductivity and recharge parameters were adjusted during calibration of the model to the 1956 head observations. The relationship between observed and simulated heads had a R 2 value of 0.97 and a mean residual of-11 m. A transient model was constructed for 1956 to 2013 with monthly time steps. Specific yield, recharge, and specific storage were adjusted for this simulation. The average residuals for the analyzed years ranged from-8 to-13 m. The second objective of this research was to utilize these models to analyze how groundwater use affects stream baseflow throughout the aquifer. Three different groundwater use scenarios from 2013-2023 were generated to compare how various management practices affect baseflow conditions including current groundwater use rates, assigning a 6093 m 3 /ha pumping rate out of every well in the model, as well as allowing for maximum irrigation use in the aquifer. Groundwater discharge to streams decreased for all three while recharge to the aquifer from the streams stayed relatively the same at approximately 1.5 m 3 /s. Recharge was also found to be a contributing factor in baseflow. Like the groundwater use scenarios, stream leakage out of the aquifer was larger than flow into the aquifer for all of these recharge scenarios. Unlike the groundwater use scenarios, stream leakage from the streams to the aquifer changed during the simulation period. This indicates that recharge has a greater effect on losing streams within this groundwater system than groundwater use. v
Estimation of Recharge to the Middle Trinity Aquifer of Central Texas Using Water-Level Fluctuations
2001
A 23-site monitoring well network located in the Trinity Aquifer region of Central Texas, with all wells penetrating the Middle Trinity Aquifer, was used with available values of aquifer storativity and specific yield to estimate recharge to the aquifer for 1999 and 2000. As part of the investigation, the Edwards Aquifer Research & Data Center (EARDC) staff worked with the Texas Water Development Board (TWDB) and local groundwater conservation districts to install five new recording well monitors in the study area, comprising about 4500 square miles. The results of the investigation yielded a method of recharge calculation different from the stream baseflow method now in use. The recharge values obtained by this study were somewhat less than representative results obtained by the stream baseflow method, perhaps due to inadequately defined aquifer storativity and low precipitation throughout much of 1999 and 2000. Texas Water Development Board (TWDB) grant from the Region J WPG through the San Antonio River Authority,. The grant enables the EARDC to install nine additional recording groundwater monitors within jurisdictions of groundwater conservation districts in the 10-county Trinity Aquifer region. The authors wish to acknowledge the staff support of the, without which this study could not have been performed. The TWDB Groundwater Availability Section, headed by Robert Mace provided valuable support, advice, and expertise during the course of this study. The TWDB also provided used equipment and installation support for continuous (analog) water-level monitoring equipment at well sites near Dripping Springs, Kerrville, Fredericksburg, and Blanco, TX, and assisted Edwards Aquifer Research & Data Center staff in the installation of new continuous (digital) water-level monitoring equipment at wells sites near Wimberley, Boerne, and Medina, TX. Because this study had a strong field measurement program, the TWDB field staff support of Doug Coker, Hydrologist Assistant, was critically important. Coker's careful training of graduate students and staff, encouragement, and ready assistance on all aspects of the field work is gratefully acknowledged. This study could not have been performed without the cooperation of landowners who volunteered the use of their wells for monitoring. The authors thank the landowners for their interest in groundwater research and conservation. Study Area The study area includes parts of 10-counties in central Texas (Fig. 1), comprises about 4,500 square miles, and includes some of the surface drainage area of the Pedernales River, Barton Creek, Onion Creek, the Blanco River, the Guadalupe River, Cibolo Creek, and the Medina River.
Evaluating Historical Well Data for Characterizing Regional Scale Aquifer Potential
2010
Summary The Geological Survey of Canada (GSC) is establishing a framework for characterizing regional scale aquifer potential. This is a data intensive task that requires a large amount of data from multiple sources. One key component in the project is the hydrogeologic characterization of mapped geologic units that currently host aquifers. The Groundwater Information Center (GIC) Groundwater Data from Alberta Environment is one data source that has extensive coverage across the province of Alberta and can be used for the project. The GIC data provides borehole and historical hydrogeologic data that is here evaluated to determine its suitability for characterizing regional scale aquifer potential. Findings show that historical hydrogeologic data associated with lithology data from boreholes grouped into two broad geology classes and three well completion types can successfully be used to distinguish distinct hydrogeologic properties for geologic units mapped at four different scales.