Geology topics

Dale J. Nyman

Publications and source records attributed to Dale J. Nyman.

4 recordsLinked to original sources

USGS1987

Louisiana ground-water map no. 1: Potentiometric surface, 1985, and water-level changes, 1983-85, of the Chicot aquifer in southwestern Louisiana

The Chicot aquifer is the principle source of groundwater in southwestern Louisiana and is the most extensively pumped (nearly 1 billion gallons per day) aquifer in the State. Withdrawals from the Chicot aquifer are used primarily for irrigation. Two maps show the generalized potentiometric surfaces of the upper sand unit ('200-ft ' sand in the Lake Charles area) and the ' 500-ft ' sand of the Chicot aquifer. General water level altitudes and flow directions may be inferred from these maps which were prepared in cooperation with the Louisiana Department of Transportation and Development, Office of Public Works. Previous studies of groundwater hydrology in southwestern Louisiana are included in selected references.

Louisiana↗

USGS1968

Flow pattern and related chemical quality of ground water in the "500-foot" sand in the Memphis area, Tennessee

The '500-foot' sand is the major source of water supply for the Memphis area. Thick layers of impervious clay above and below the sand confine the water in the aquifer under artesian pressure and also protect the aquifer from contamination. Recharge from rainfall enters the '500-foot' sand in the outcrop, or intake area south and east of Memphis. Recharge from other aquifers enters the sand wherever the confining beds are breached or absent. Some of the recharge that enters the '500-foot' sand in eastern Arkansas moves down the gradients created by pumping in the Memphis area. All discharge from the '500-foot' sand in the Memphis area results from well pumping. Since 1886 continuous withdrawals at gradually increasing rates of pumping have lowered water levels and altered hydraulic gradients in the area. These withdrawals have resulted in changes in direction and velocity of movement of water through the '500-foot' sand. Water in the sand in the southeaster n part of the Memphis area normally moves from the (outcrop area east and south of Memphis northwestward toward points of withdrawal. In the northwestern part of the area, water moves southeastward toward points of withdrawal. A flow-net analysis of the aquifer shows that the rate of water movement through the '500-foot' sand in 1964, toward the major cones of depression in the Memphis area, was about 350 feet per year, or 1 mile in 15 years. A flow-net analysis projected for the year 1975 indicates the rate will increase by about 20 percent in the 12-year period 1964-75. Water in the '500-foot' sand in the Memphis area is generally a calcium magnesium sodium bicarbonate type. It is soft, low in dissolved solids, high in concentrations of iron and carbon dioxide, and slightly to moderately corrosive. The softest and least mineralized water occurs in the southeastern part of the area, and the water becomes slightly harder and more mineralized as it moves downdip toward Memphis. The hardest and most mineralized water occurs in the northwestern part of the area. The variations in chemical quality of water en route through the '500-foot' sand are virtually proportional to increases or decreases of the major chemical constituents. The variations are chiefly attributed to the mixing or blending of water from different directions or sources of recharge as wells are pumped. As water levels are lowered by continuous pumping in the future, increasing rates of recharge from the outcrop areas and from shallow aquifers will probably cause little, if any, change in chemical quality of the water. Certainly, the effects on quality are not expected to be detrimental. Although future changes in chemical quality of water in the '500-foot' sand in the Memphis area will probably be neither intense nor extensive, some changes can be anticipated as a result of man's activities associated with the continued growth and development of the area. Increased pumping at existing pumping centers will deepen existing cones of depression and thereby increase gradients. These increases will not necessarily cause a change in chemical quality unless the increases in pumping are unevenly distributed. If a major well field were developed in the '500-foot' sand in the southwestern part of the Memphis area, little change in quality would result because water would be caused to move toward the well field from both the northwest and southeast. This movement would not affect the blending of updip and downdip water at other well fields If water were impounded in the Wolf River a few miles upstream from Memphis, the impoundment could furnish recharge, at least temporarily, to the '500-foot' sand. It is improbable that any detrimental effects on the chemical quality of the water supply of Memphis would result, because the water in the impoundment would probably be softer ,and less mineralized than the water in the '500-foot' sand in that area.

Water Supply Paper↗

USGS1965

Predicted hydrologic effects of pumping from the Lichterman Well Field in the Memphis Area, Tennessee

The Lichterman well field is scheduled to go into operation early in 1965 to supplement the municipal water-supply system for the city of Memphis, Tenn. Although the initial rate of withdrawal from the well field will be about 8 mgd (million gallons per day), the ultimate design capacity of the field is 20 mgd. A study of sand samples, drillers' logs, and geophysical logs collected during preliminary test drilling at the site for the Lichterman well field was used as a basis for defining three zones of sand favorable for the construction of high-capacity (1,000 gallons per minute or more) water wells. The three zones occur in the '500-foot' sand and are here designated (in descending order) as zone A, zone B, and zone C. The depth to the top of these zones below land surface has the following ranges: zone A, 125 to 225 feet; zone B, 200 to 350 feet; and zone C, 700 to 775 feet. Zones A and B range from 0 to 100 feet in thickness, and zone C ranges from 10 to 100 feet in thickness. Within the well field proper these zones are expected to react to the stress of pumping as separate hydrologic units, but outside the well field the three zones are expected to react as a single hydrologic unit. The '500-foot' sand in the Germantown-Collierville area is recharged chiefly by precipitation on the outcrop area of the sand to the east, but the evidence indicates that additional recharge is entering the aquifer from the Wolf River. In spite of this additional recharge, water levels in the '500-foot' sand are declining at an average rate of about two-thirds of a foot per year, owing to municipal and industrial pumpage in the Memphis area. However, this decline is not expected to alter the excellent quality of the water in the '500-foot' sand at the site of the Lichterman well field. Pumping in the Lichterman well field will create a cone of depression in the free-water (piezometric) surface of the '500-foot' sand. The decline in water levels will be directly proportional to the rate of pumping and inversely proportional to the distance from the well field. The resultant changes in hydraulic gradients will alter the direction of ground-water movement in the vicinity of the well field and increase the rate of movement toward the well field from areas of recharge. The lowering of water levels might also accelerate locally the changeover from artesian conditions to semiartesian or water-table conditions in the '500-foot' sand. Within the well field proper, water levels are expected to fluctuate as individual wells are turned on and off to accommodate the demand for water. The presence of clay beds in the aquifer will tend to limit the specific capacity of individual production wells, but could serve to limit interference between wells if adjacent wells are screened in different sections of the aquifer. Interference between wells might also be lessened by pumping those wells having the highest specific capacities for the longest periods of time.

Water Supply Paper↗

USGS1964

Hydrology of aquifer systems in the Memphis area, Tennessee

The Memphis area as described in .this report comprises about 1,300 square miles of the Mississippi embayment part of the Gulf Coastal Plain. The area is underlain by as much as 3,000 feet of sediments ranging in age from Cretaceous through Quaternary. In 1960, 150 mgd (million gallons per day) of water was pumped from the principal aquifers. Municipal pumpage accounted for almost half of this amount, and industrial pumpage a little more than half. About 90 percent of the water used in the area is derived from the '500-foot' sand, and most of the remainder is from the ?400-foot' sand; both sands are of Eocene age. A small amount of water for domestic use is pumped from the terrace deposits of Pliocene and Pleistocene age. Both the '500-foot' and the '1,400-foot' sands are artesian aquifers except in the southeastern part of the area; there the water level in wells in the '500-foot' sand is now below the overlying confining clay. Water levels in both aquifers have declined almost continuously since pumping began, but the rate of decline has increased rapidly since 1940. Water-level decline in the '1,400-foot' sand has been less pronounced since 1956. The cones of depression in both aquifers have expanded and deepened as a result of the annual increases in pumping, and an increase in hydraulic gradients has induced a greater flow of water into the area. Approximately 135 mgd entered the Memphis area through the '500-foot' sand aquifer in 1960, and, of this amount, 60 mgd originated as inflow from the east and about 75 mgd was derived from leakage from the terrace deposits, from the north, south, and west and from other sources. Of the water entering the '1,400-foot' sand, about 5 mgd was inflow from the east, and about half that amount was from each of the north, south, and west directions. The average rate of movement of water outside the area of heavy withdrawals is about 70 feet per year in the '500-foot' sand and about 40 feet per year in the '1,400-foot' sand. The average rate of depletion of storage in each aquifer since pumping began is about 1 mgd. Most of the recharge to the '500-foot' and '1,400-foot' sands occurs in outcrop areas about 30-80 miles east of Memphis. Also, water leaks from the terrace deposits to the '500-foot' sand in some places, and there may be some leakage from streams where the confining clay is thin or is breached by faults or streams. The quality of water from both the principal aquifers is very good. Iron, carbon dioxide, and hydrogen sulfide are the only constituents found in undesirable quantities. Water from the terrace deposits is hard but generally contains less iron and carbon dioxide than water from either of the principal aquifers. The hydraulic characteristics of both aquifers were determined by pumping tests and by applying the knowledge of the geology o# the area; these characteristics indicate that the aquifers are capable of producing more water than is currently being pumped from them. The '500-foot' sand will produce more water per unit decline of water level than will the '1,400-foot' sand. There appears to be no reason why the development of water supplies from both aquifers should not continue, but well spacing will remain a factor which could affect future development. Greater well spacing will tend to prolong the useful life of a well and the aquifers.

Water Supply Paper↗