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A.G. Strickland

Publications and source records attributed to A.G. Strickland.

9 recordsLinked to original sources
USGS2010

Summary and statistical analysis of precipitation and groundwater data for Brunswick County, North Carolina, Water Year 2008

Groundwater conditions in Brunswick County, North Carolina, have been monitored continuously since 2000 through the operation and maintenance of groundwater-level observation wells in the surficial, Castle Hayne, and Peedee aquifers of the North Atlantic Coastal Plain aquifer system. Groundwater-resource conditions for the Brunswick County area were evaluated by relating the normal range (25th to 75th percentile) monthly mean groundwater-level and precipitation data for water years 2001 to 2008 to median monthly mean groundwater levels and monthly sum of daily precipitation for water year 2008. Summaries of precipitation and groundwater conditions for the Brunswick County area and hydrographs and statistics of continuous groundwater levels collected during the 2008 water year are presented in this report. Groundwater levels varied by aquifer and geographic location within Brunswick County, but were influenced by drought conditions and groundwater withdrawals. Water levels were normal in two of the eight observation wells and below normal in the remaining six wells. Seasonal Kendall trend analysis performed on more than 9 years of monthly mean groundwater-level data collected in an observation well located within the Brunswick County well field indicated there is a strong downward trend, with water levels declining at a rate of about 2.2 feet per year.

North Carolina↗
USGS1999

Water-level conditions in the upper Cape Fear Aquifer, 1994-98, in parts of Bladen and Robeson counties, North Carolina

Water-level measurements were made on a periodic basis from October 1994 through November 1998 in 17 wells that tap the upper Cape Fear aquifer. The approximately 730-square-mile study area in Bladen and Robeson Counties is in the southern Coastal Plain of North Carolina. Water-level declines occurred in the aquifer throughout much of the area as a result of pumping during this period. The greatest decline was about 42 feet in Bladen County. Water levels from the wells in the fall of 1998 were used to construct a map of the potentiometric surface of the upper Cape Fear aquifer. This map can be used to infer the direction of ground-water movement in the aquifer. Withdrawals from wells at pumping centers, such as in the Tar Heel and Elizabethtown areas in Bladen County, have caused ground water to flow toward pumped wells, resulting in cones of depression in the potentiometric surface.

North Carolina↗
USGS1994

Simulation of unsteady flow in the Roanoke River from near Oak City to Williamston, North Carolina

A one-dimensional, unsteady-flow model was calibrated, validated, and applied to a 30.4-mile reach of the Roanoke River between State Highway 42-11 bridge near Oak City (river mile 67.0) and the U.S. Highway 17-13 bridge at Williamston (river mile 36.6) North Carolina. The model was calibrated and validated for flows ranging from about 2,000 to 12,000 cubic feet per second. The model was used to compute daily mean flows at selected locations in the study reach for water years 1988-90. Flows were calculated for the range of conditions for which the model was calibrated and validated. Simulated monthly mean flows at river mile 67.0 were within 5 percent of measured flows at a gaging station at river mile 137.0, after adjustment of inflow from the intervening drainage area, for months having mean flows less than 14,000 cubic feet per second.

North Carolina↗
USGS1993

An interim report on flows in the lower Roanoke River, and water quality and hydrodynamics of Albermarle Sound, North Carolina, October 1989-April 1991

In 1990, a 3-year investigation was begun in North Carolina to: (1) develop a model for computing flows in the lower 67 mi of the Roanoke River; (2) characterize water-quality conditions in Albemarle Sound; and (3) describe the circulation regime of Albemarle Sound, particularly in relation to inflows. This report summarizes data and results obtained during the first year of the study. The water level in Albemarle Sound may affect flows in the Roanoke River as far as 60 mi upstream from the mouth of the river. The presence of higher water levels downstream relative to those upstream indicates that reverse flows likely occurred in the lower 20 mi of the Roanoke River in October and December 1990. A one-dimensional, unsteady flow model has been calibrated and validated for a 30-mi segment of the lower Roanoke River. Simulated and observed water levels typically differed by less than 0.5 ft, and simulated flows were generally within 10% of observed values. Near-surface and near-bottom specific conductances, near-surface water temperature, and near-surface, mid-depth, and near-bottom dissolved-oxygen concentrations were monitored at 10 locations in Albemarle Sound from October 1989 to April 1991. Observed salinities ranged from virtually 0 to more than 9 ppt, and maximum observed water temperatures were about 32C. Dissolved oxygen concentrations ranged from supersaturated to hypoxic conditions. The daily range in dissolved-oxygen concentrations was typically larger during the summer months than during the rest of the year, and the lowest dissolved-oxygen values were observed during the summer.

North Carolina↗
USGS1993

Simulation of unsteady flow in the Roanoke River from near Oak City to Williamston, North Carolina

A one-dimensional, unsteady-flow model was calibrated, validated, and applied to a 30.4-mile reach of the Roanoke River between State Highway 42-11 bridge near Oak City (river mile 67.0) and U.S. Highway 17-13 bridge (river mile 36.6) at Williamston, North Carolina. The model was calibrated and validated for water levels ranging from 5.62 to 16.44 feet at river mile 67.0, and for flows ranging from about 2,000 to 12,000 cubic feet per second. For model calibration, the mean absolute difference between 22 measured and simulated flows was 3.4 percent. The mean absolute difference between nine measured and simulated flows obtained in the validation process was 3.3 percent. The sensitivity of model results to small changes in computational time step, momentum coefficient, numerical scheme weighting factors, resistance coefficients, and boundary values was evaluated. The model, which was calibrated at a time step of 15 minutes, was unstable at a computational time step of 30 minutes, but results were insensitive to changes in the momentum coefficient and the numerical scheme weighting factors. Results were somewhat sensitive to small changes in the resistance coefficients and boundary values. The model was used to compute daily mean flows at river miles 67.0, 59.2, and 36.6 for water years 1988-90. Flows were calculated for the range of conditions for which the model was calibrated and validated. Simulated monthly mean flows at river mile 67.0 were within 5 percent of flows measured at Roanoke Rapids (river mile 137.0), after adjustment for inflow from the intervening drainage area between river miles 137.0 and 67.0, for months having mean flows less than about 14,000 cubic feet per second.

North Carolina↗
USGS1992

Ground-water level data for North Carolina, 1988-90

Continuous and periodic water-level measurements were made in 59 key wells throughout North Carolina. Additional measurements were made in 112 supplementary wells completed in Coastal Plain aquifers of the State. Changes in groundwater storage are shown in 3-year and 10-year hydrographs of selected wells in the State. The water table in the shallow aquifers was higher throughout most of 1989 and early 1990 than in 1988, indicating that these aquifers were sufficiently recharged by precipitation to replenish the late 1987-88 deficit in groundwater storage. Water levels in the heavily pumped Coastal Plain aquifers declined as a result of water being withdrawn from aquifer storage. Record low water levels were measured in 8 to 13 wells completed in the Castle Hayne aquifer and in 6 of 8 wells in the Peedee aquifer; the maximum annual declines during 1988-90 averaged 3.3 and 1.6 ft/yr, respectively, for these two aquifers. All wells in the Black Creek, upper Cape Fear, and lower Cape Fear aquifers had record low water levels during 1988-90, with maximum annual declines averaging 9.0, 2.2, and 2.6 ft/yr, respectively. Water levels in two of three wells in the Yorktown aquifer did not show a general downward trend during 1988-90, although water levels declined in the third well, reaching a record low in 1990. The effects of water withdrawals from major pumping centers in the North Carolina Coastal Plain are shown in potentiometric-surface maps of the Black Creek and lower Cape Fear aquifers.

North Carolina↗
USGS1989

Ground-water level data for North Carolina, 1987

Continuous and periodic measurements in 54 key wells and water-level measurements emplaced in Coastal Plain aquifers across North Carolina in 193 supplemental wells are presented in this report. Hydrographs of selected wells show changes in ground-water storage in the State. The water table in the shallow aquifers was higher throughout most of the State in 1987 than in 1986, indicating that rain had recharged these aquifers sufficiently to replenish the deficit in ground water storage that accumulated in the western and central parts of the State during 1986. Water levels in the heavily pumped Coastal Plain aquifers show a general downward trend for the year, indicating ground water is being withdrawn from aquifer storage. Record low water levels were measured in 4 of 13 wells in the Castle Hayne aquifer; the greatest decline measured during 1987 was 0.3 ft. Water levels in wells in the Peedee, Black Creek, upper Cape Fear, and lower Cape Fear aquifers generally show downward trends. Record low water levels were measured in 4 of 8 wells in the Peedee aquifer; the maximum decline measured during 1987 was 1.5 ft. All wells in the Black Creek, upper Cape Fear, and lower Cape Fear aquifers had record low water levels for 1987, with maximum measured declines in 1987 of 8.6, 3.1, and 3.1 ft., respectively. Record high water levels were measured in two wells, one each in the Castle Hayne and Peedee aquifers. Potentiometric surface maps show the effects of major centers of pumping for the Castle Hayne, Black Creek, and lower Cape Fear aquifers of the Coastal Plain.

North Carolina↗