English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Ground-water withdrawals from aquifers in the Memphis area average about 190 Mgal/d. Potential problems associated with increases in pumpage and urban development are lowered water levels, contamination of the aquifers, and land subsidence. Long-term water-level declines in the Memphis Sand, the principal artesian aquifer of the area, range from less than 0.1 foot per year near the outcrop area to about 1.8 feet per year near the center of pumping. A 1980 potentiometric map shows that small cones of depression around major pumping centers are superimposed on a regional cone. Except for increased pumping lift, few problems are expected from water-level declines in the Memphis Sand. There is at present very little pumpage from other aquifers in the area the alluvium, the fluvial deposits, and the Fort Pillow Sand and no long-term water-level declines are expected unless pumpage is increased significantly. Low concentrations of leachates from waste-disposal sites in the area have been detected in the water-table aquifers near these sites, but no indication of contamination of the underlying artesian aquifers has yet been found. Seasonal land-surface elevation changes of less than 0.03 foot have been recorded by an extensometer near the center of the major cone of depression of the Memphis Sand. These changes correlate with seasonal changes in artesian pressure in the Memphis Sand. Over the period of record no significant net change in land-surface elevation has been recorded, indicating that no permanent land subsidence due to declining water level is occurring. INTRODUCTION Ground water is the only source of potable water being used fen municipal and industrial supplies in the Memphis area. Although a sufricient quantity of water that meets most water-quality criteria is available from depths of less than 2,000 feet, problems associated with resource development and management may occur as withdrawals are increased to meet the demands of a growing metropolitan area. Potential problems are: (l) the effects of the lowering of water levels, (2) possible contamination of the aquifer system as a result of man's activities, and (3) possible land subsidence caused by reductions in artesian pressures. The term "Memphis area", as used in this report, refers to a 1,300 mi^ area in the Mississippi embayment comprising parts of three states (fig. 1). It includes all of Shelby and parts of Fayette and Tipton Counties in Tennessee, DeSoto and Marshall Counties in Mississippi, and Crittenden and Mississippi Counties in Arkansas (fig. 2). The locations of wells discussed in the text are also shown in figure 2. k Purpose and Scope A large amount 'of information has been and is being collected from the aquifers in the Memphis area. Much of this information has been published in several previous reports. The purpose of this report is to update some of this published information and present additional information pertinent to the potential problems associated with the increasing development of the groundwater resource. To provide the background information necessary for evaluating changes that are occurring or might occur in the ground-water system, the Geological Survey, in cooperation with the City of Memphis, Memphis Light, Gas and Water Division (MLGW), currently is conducting the following data-collection activities: (1) a network of observation wells is maintained to define water-level trends and provide data necessary for the preparation of potentiometric surface maps, (2) a yearly inventory is conducted to provide information about the distribution and amounts of pumpage, (3) key wells are sampled yearly to monitor changes in water quality in the principal artesian aquifer, (4) wells close to areas of potential contamination from waste-disposal sites are sampled to determine the presence and quantities of hazardous constituents that have entered or might be entering the shallow water-table aquifer, and (5) two recording extensometers are operated to monitor possible land subsidence. Additionally, the Geological Survey makes geophysical logs in new municipal supply wells and other wells in the area to obtain information for use in further defining the subsurface geology. Previous Investigations The general hydrology and geology of the Memphis aquifer systems are described in reports by Schneider and Gushing (1948), Criner and Armstrong (1958), Criner and others (1964), and Bell and Nyman (1968). A series of potentiometric maps and a description of historic water-level changes and pumpage from the Memphis Sand and the Fort Pillow Sand are given in Criner and Parks (1976). The configuration of the potentiometric surface of the Memphis Sand for the year 1978 is shown in Graham (1979). Records of water levels

Effects of urban development on the aquifers in the Memphis area, Tennessee