Geology topics

Research about Arkansas

Source-linked reports with geographic coverage including Arkansas.

At least 127 records · Page 7Linked to original sources

USGS2012

Autumn migration of of Mississippi Flyway mallards as determined by satellite telemetry

We used satellite telemetry to study autumn migration timing, routes, stopover duration, and final destinations of mallards Anas platyrhynchos captured the previous spring in Arkansas from 2004 to 2007. Of those mallards that still had functioning transmitters on September 15 ( n = 55), the average date when autumn migration began was October 23 (SE = 2.62 d; range = September 17–December 7). For those mallards that stopped for >1 d during migration, the average stopover length was 15.4 d (SE = 1.47 d). Ten mallards migrated nonstop to wintering sites. The eastern Dakotas were a heavily utilized stopover area. The total distance migrated per mallard averaged 1,407 km (SE = 89.55 km; range = 142–2,947 km). The average time spent on migration per individual between September 15 and December 15 was 27 d (SE = 2.88 d; range = 2–84 d). The state where most mallards were located on December 15 was Missouri (11) followed by Arkansas (8), while 5 mallards were still in Canada, and only 8 of 43 females and 0 of 10 males were present in Arkansas. The eastern Dakotas are a heavily utilized migration stopover for midcontinent mallards that may require more attention for migration habitat management. The reasons for so few mallards, especially male mallards, returning to Arkansas the following year deserves further research. .

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USGS2011

Surface complexation modeling for predicting solid phase arsenic concentrations in the sediments of the Mississippi River Valley alluvial aquifer, Arkansas, USA

The potential health impact of As in drinking water supply systems in the Mississippi River Valley alluvial aquifer in the state of Arkansas, USA is significant. In this context it is important to understand the occurrence, distribution and mobilization of As in the Mississippi River Valley alluvial aquifer. Application of surface complexation models (SCMs) to predict the sorption behavior of As and hydrous Fe oxides (HFO) in the laboratory has increased in the last decade. However, the application of SCMs to predict the sorption of As in natural sediments has not often been reported, and such applications are greatly constrained by the lack of site-specific model parameters. Attempts have been made to use SCMs considering a component additivity (CA) approach which accounts for relative abundances of pure phases in natural sediments, followed by the addition of SCM parameters individually for each phase. Although few reliable and internally consistent sorption databases related to HFO exist, the use of SCMs using laboratory-derived sorption databases to predict the mobility of As in natural sediments has increased. This study is an attempt to evaluate the ability of the SCMs using the geochemical code PHREEQC to predict solid phase As in the sediments of the Mississippi River Valley alluvial aquifer in Arkansas. The SCM option of the double-layer model (DLM) was simulated using ferrihydrite and goethite as sorbents quantified from chemical extractions, calculated surface-site densities, published surface properties, and published laboratory-derived sorption constants for the sorbents. The model results are satisfactory for shallow wells (10.6 m below ground surface), where the redox condition is relatively oxic or mildly suboxic. However, for the deep alluvial aquifer (21–36.6 m below ground surface) where the redox condition is suboxic to anoxic, the model results are unsatisfactory.

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USGS2011

Geophysical characterization of the Lollie Levee near Conway, Arkansas, using capacitively coupled resistivity, coring, and direct push logging

A geophysical characterization of Lollie Levee near Conway, Arkansas, was conducted in February 2011. A capacitively coupled resistivity survey (using Geometric's OhmMapper) was completed along the top and toe of the 6.7-mile levee. Two-dimensional inversions were conducted on the geophysical data. As a quality-control measure, cores and direct push logs were taken at approximately 1-mile intervals along the levee. The capacitively coupled resistivity survey, the coring, and the direct push logs were used to characterize the geologic materials. Comparison of the cores and the direct push log data, along with published resistivity values, indicates that resistivity values of 200 Ohm-meters or greater represent relatively clean sand, with decreasing resistivity values occurring with increasing silt and clay content. The cores indicated that the levee is composed of a heterogeneous mixture of sand, silt, and clay. The capacitively coupled resistivity sections confirm that the levee is composed of a heterogeneous mixture of high and low resistivity materials and show that the composition of the levee varies spatially. The geologic materials underlying the levee vary spatially as a result of the geologic processes that deposited them. In general, the naturally deposited geologic materials underlying the levee contain a greater amount of low resistivity materials in the southern extent of the levee.

Faulkner, Arkansas↗

USGS2011

Flood of June 11, 2010, in the Upper Little Missouri River watershed, Arkansas

Catastrophic flash flooding occurred in the early morning hours of June 11, 2010, in the upper Little Missouri River and tributary streams in southwest Arkansas. The flooding, which resulted in 20 fatalities and substantial property damage, was caused by as much as 4.7 inches of rain falling in the upper Little Missouri River watershed in 3 hours. The 4.7 inches of rain in 3 hours corresponds to estimated annual exceedance probability of approximately 2 percent for a 3-hour duration storm. The maximum total estimated rainfall in the upper Missouri River watershed was 5.3 inches in 6 hours. Peak streamflows and other hydraulic properties were determined at five ungaged locations and one gaged location in the upper Little Missouri River watershed.The peak streamflow for the Little Missouri River at Albert Pike, Arkansas was 40,100 cubic feet per second, estimated to have occurred between 4:00 AM and 4:30 AM the morning of June 11, 2010. The peak streamflow resulted in average water depths in the nearby floodplain (Area C of the Albert Pike Campground) of 7 feet flowing at velocities potentially as great as 11 feet per second. Peak streamflow 9.1 miles downstream on the Little Missouri at the U.S. Geological Survey streamgage near Langley, Arkansas was 70,800 cubic feet per second, which corresponds to an estimated annual exceedance probability of less than 1 percent.

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USGS2011

Simulation of the effects of groundwater withdrawals on water-level altitudes in the Sparta aquifer in the Bayou Meto-Grand Prairie area of eastern Arkansas, 2007-37

A groundwater-flow model of the Mississippi embayment was used to evaluate changes in water-level altitudes before (scenario 1) and after (scenario 2) the addition of wells that simulate potential future pumping from the Sparta aquifer in the Bayou Meto-Grand Prairie area of eastern Arkansas for the 30-year period from 2007 through 2037. Water-level altitudes at six model cell locations from the two different scenarios were compared for the period 2007 through 2037. Potential future pumping wells were added to the Mississippi Embayment Regional Aquifer Study model at a rate of 13 wells per year within areas of potential future pumping. Change maps for the Bayou Meto-Grand Prairie area were constructed for each scenario and water-level hydrographs were constructed for each scenario for each of the six model cell locations. The additional pumping from wells in the Sparta aquifer created greater water-level declines in the Bayou Meto-Grand Prairie area. In scenario 1, simulated water-level altitude declines range from 20 to 40 feet from 2007 through 2037. In scenario 2, the cone of depression in Lonoke County is the deepest, with a maximum water-level decline of approximately 102 feet. Water-level altitude declines range from 40 to 50 feet over most of the remainder of the Bayou Meto-Grand Prairie area in scenario 2. Simulated water-level altitudes across the Bayou Meto-Grand Prairie area and at all six model cell locations indicate substantial declines when additional wells pumping from the Sparta aquifer are introduced into the model from 2007 through 2037.

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USGS2011

A review of the lignite resources of Arkansas

This review of the lignite resources of Arkansas is a part of the U.S. Geological Survey's (USGS) National Coal Resource Assessment (NCRA) of the Gulf Coastal Plain Coal Province, which also includes coal-bearing areas in the states of Texas, Louisiana, Alabama, Mississippi, Tennessee, and Kentucky (see Ruppert et al., 2002 ; Dennen, 2009 ; and other chapters of this publication). Lignite mining is not planned in Arkansas in the immediate future, and the lignite resources of the state were not assessed in detail as part of the NCRA. This chapter includes reviews of the geology of the lignite-bearing units, historical mining, previous investigations of lignite resources, and coal quality. Palynological data for lignite samples collected in Arkansas as part of this work are presented in Table 1 .

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USGS2010

Identifying sites for elk restoration in Arkansas

We used spatial data to identify potential areas for elk ( Cervus elaphus ) restoration in Arkansas. To assess habitat, we used locations of 239 elk groups collected from helicopter surveys in the Buffalo National River area of northwestern Arkansas, USA, from 1992 to 2002. We calculated the Mahalanobis distance ( D 2 ) statistic based on the relationship between those elk-group locations and a suite of 9 landscape variables to evaluate winter habitat in Arkansas. We tested model performance in the Buffalo National River area by comparing the D 2 values of pixels representing areas with and without elk pellets along 19 fixed-width transects surveyed in March 2002. Pixels with elk scat had lower D 2 values than pixels in which we found no pellets (logistic regression: Wald χ 2 = 24.37, P < 0.001), indicating that habitat characteristics were similar to those selected by the aerially surveyed elk. Our D 2 model indicated that the best elk habitat primarily occurred in northern and western Arkansas and was associated with areas of high landscape heterogeneity, heavy forest cover, gently sloping ridge tops and valleys, low human population density, and low road densities. To assess the potential for elk–human conflicts in Arkansas, we used the analytical hierarchy process to rank the importance of 8 criteria based on expert opinion from biologists involved in elk management. The biologists ranked availability of forage on public lands as having the strongest influence on the potential for elk–human conflict (33%), followed by human population growth rate (22%) and the amount of private land in row crops (18%). We then applied those rankings in a weighted linear summation to map the relative potential for elk–human conflict. Finally, we used white-tailed deer ( Odocoileus virginianus ) densities to identify areas where success of elk restoration may be hampered due to meningeal worm ( Parelaphostrongylus tenuis ) transmission. By combining results of the 3 spatial data layers (i.e., habitat model, elk–human conflict model, deer density), our model indicated that restoration sites located in west-central and north-central Arkansas were most favorable for reintroduction.

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USGS2010

Woodpecker densities in the big woods of Arkansas

Sightings of the now-feared-extinct ivory-billed woodpecker Campephilus principalis in 2004 in the Big Woods of Arkansas initiated a series of studies on how to best manage habitat for this endangered species as well as all woodpeckers in the area. Previous work suggested that densities of other woodpeckers, particularly pileated Dryocopus pileatus and red-bellied Melanerpes carolinus woodpeckers, might be useful in characterizing habitat use by the ivory-billed woodpecker. We estimated densities of six woodpecker species in the Big Woods during the breeding seasons of 2006 and 2007 and also during the winter season of 2007. Our estimated densities were as high as or higher than previously published woodpecker density estimates for the Southeastern United States. Density estimates ranged from 9.1 to 161.3 individuals/km 2 across six woodpecker species. Our data suggest that the Big Woods of Arkansas is attractive to all woodpeckers using the region, including ivory-billed woodpeckers.

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USGS2010

Tree growth and mortality during 20 years of managing a Green-Tree Reservoir in Arkansas, USA

Green-Tree Reservoirs (GTR) are bottomland hardwood forests that are flooded during late fall and winter to provide waterfowl habitat. Early reports suggested that increased moisture improved tree growth and mast production; however, recent reports showed reduced vigor and growth. This study examines the effects of 20 years of GTR management practices in the Felsenthal National Wildlife Refuge, Crossett, Arkansas. Tree species composition, size characteristics, and vigor classes were measured in 1990, 1995, 2001, and 2006. The overall annual tree mortality rate was 2.6%, with high elevations at 1.7% and low elevations at 3.1%. Annual mortality rates exceeded 3% for willow oak ( Quercus phellos ) and water hickory ( Carya aquatica ), while rates for Nuttall oak ( Q. texana ), overcup oak ( Q. lyrata ), and sweetgum ( Liquidambar styraciflua .) were lower at 2.8, 2.4, and 1.5%, respectively. Tree health (vigor) has degraded substantially for over 60% of trees initially rated in good or fair condition. Statistical probit models were generated to predict short-term (5 years) and long-term (15 years) vigor degradation. Low numbers of saplings and little advanced regeneration indicated lack of tree replacement, suggesting that inundation strategies of the GTR management may have long-term impacts on forest structure and composition in the southeastern United States.

Arkansas↗

USGS2010

Antibiotic fate and transport in three effluent-dominated Ozark streams

Antibiotic transport downstream from a wastewater treatment plant effluent discharge was evaluated along stream reaches on Mud Creek, Spring Creek, and Decatur Branch in northwestern Arkansas, USA. Water and streambed samples were collected during August and September 2006 and analyzed for multiple antibiotics representing five classes (beta-lactams, macrolides, quinolones, sulfonamides, and tetracyclines). Antibiotics within the classes macrolides, quinolones, and sulfonamides were detected in the water column at all three stream reaches. Several of these same antibiotics, as well as antibiotics from the class tetracycline, were measured in streambed material at quantities significantly greater than those observed in the water column. Pseudo-partitioning coefficients ranged from 4 to >8000 L kg −1 . Most of the antibiotics studied were significantly retained in the reaches at Mud Creek and Spring Creek and traveled kilometer-scale distances ( S net , 3.3–20.2 km) with low uptake velocities ( v f-net "> vf-net , 2.9–16.1 × 10 −6 m s −1 ) and rates ( U net 0.01–37.9 × 10 −6 μg m −2 s −1 ). Some antibiotics increased in concentration downstream from the effluent discharge at Decatur Branch, suggesting possible release from within the fluvial channel or additional sources along the stream reach. In general, antibiotics traveled kilometer-scale distances before significant dilution occurred through in-stream processes (e.g., advection, dispersion, sorption, uptake and/or degradation) within the fluvial channel of these effluent-dominated streams.

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USGS2010

Effects of exploitation on black bear populations at White River National Wildlife Refuge

We live-trapped American black bears ( Ursus americanus ) and sampled DNA from hair at White River National Wildlife Refuge, Arkansas, USA, to estimate annual population size ( N ), growth (λ), and density. We estimated N and λ with open population models, based on live-trapping data collected from 1998 through 2006, and robust design models for genotyped hair samples collected from 2004 through 2007. Population growth was weakly negative (i.e., 95% CI included 1.0) for males (0.901, 95% CI = 0.645–1.156) and strongly negative (i.e., 95% CI excluded 1.0) for females (0.846, 95% CI = 0.711–0.981), based on live-trapping data, with N from 1999 to 2006 ranging from 94.1 (95% CI = 70.3–137.1) to 45.2 (95% CI = 27.1–109.3), respectively, for males and from 151.4 (95% CI = 127.6–185.8) to 47.1 (95% CI = 24.4–140.4), respectively, for females. Likewise, mean annual λ based on hair-sampling data was weakly negative for males (0.742, 95% CI = 0.043–1.441) and strongly negative for females (0.782, 95% CI = 0.661–0.903), with abundance estimates from 2004 to 2007 ranging from 29.1 (95% CI = 21.2–65.8) to 11.9 (95% CI = 11.0–26.9), respectively, for males and from 54.4 (95% CI = 44.3–77.1) to 27.4 (95% CI = 24.9–36.6), respectively, for females. We attribute the decline in the number of females in this isolated population to a decrease in survival caused by a past translocation program and by hunting adjacent to the refuge. We suggest that managers restructure the quota-based harvest limits until these growth rates recover.

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USGS2009

Plant community establishment following drawdown of a reservoir in southern Arkansas, USA

Wetland area, function and wildlife habitat value are extensively altered by the construction of freshwater reservoirs. We studied the effects of a temporary drawdown on shoreline vegetation communities of Felsenthal Navigation Pool (“the pool”), an impoundment at Felsenthal National Wildlife Refuge in southern Arkansas that is managed as a greentree reservoir. The pool was permanently flooded from 1985 until the summer of 1995 when the water level was dropped 0.3 m for about 16 weeks, exposing about 1,591 ha of soil. To document plant succession on the sediments exposed, we recorded plant species composition and cover at 14 transects along the pool margin prior to the drawdown, during the drawdown, and in the following summer. A soil disturbance treatment was applied near five transects following the drawdown, and soil was collected at each transect for seed bank and soil analyses. Plants colonized the drawdown zone quickly and high vegetation cover was present at some transects 4 weeks after the drawdown was initiated. Plants included species that are high quality food sources for waterfowl, including Cyperus erythrorhizos and Leptochloa fascicularis var. fascicularis . Vegetation response, measured by species richness, total cover, and cover of Cyperus species, was often greater at low compared to high elevations in the drawdown zone; this effect was probably intensified by low summer rainfall. Response on the disturbed transects was lower than that on the undisturbed transects. This effect was attributed to two factors: (1) removal of the existing seed bank by the disturbance applied and (2) reduced incorporation of seeds recruited during the drawdown because of unusually low rainfall. Seed bank studies demonstrated that several species persisted despite 10 years of continual flooding, and that seed bank species richness increased during the drawdown. Although conclusions are limited by the 1-year time frame of the study, it is unlikely that permanent change to plant community structure in the drawdown zone resulted from the lowered water level.

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USGS2009

Hydrogeologic characteristics and water levels of Wilcox aquifer in southwestern and northeastern Arkansas

The Wilcox Group of Eocene and Paleocene age is located throughout most of southern and eastern Arkansas. The Wilcox Group in southern Arkansas is undifferentiated, while in northeastern Arkansas, the Wilcox Group is subdivided into three units: Flour Island, Fort Pillow Sand, and Old Breastworks Formation. The Wilcox Group crops out in southwestern Arkansas in discontinuous, 1 to 3 mi wide bands. In northeastern Arkansas, the Wilcox Group crops out along a narrow, discontinuous, band along the western edge of Crowleys Ridge. The Wilcox aquifer provides sources of groundwater in southwestern and northeastern Arkansas. In 2005, reported withdrawals from the Wilcox aquifer in Arkansas totaled 27.0 million gallons per day, most of which came from the northeastern area. Major withdrawals from the aquifer were for public supplies with lesser but locally important withdrawals for commercial, domestic, and industrial uses. A study was conducted by the U.S. Geological Survey in cooperation with the Arkansas Natural Resources Commission and the Arkansas Geological Survey to determine the water levels associated with the Wilcox aquifer in southwestern and northeastern Arkansas. During February 2009, 58 water-level measurements were made in wells completed in the Wilcox aquifer. The results from this study and previous studies are presented as potentiometric-surface maps, water-level difference maps, and long-term hydrographs. The direction of groundwater flow in the southwestern area is affected by two potentiometric-surface mounds, one in the north and the other in the southwest, and a cone of depression in the center. The direction of water flowing off of the northern mound of water is generally to the south and east with some to the north. The direction of water flowing off of the southwestern mound is generally to the south and east. The direction of water flowing into the cone of depression is generally from the north, west, and south. The direction of groundwater flow in the northeastern area is generally to the south and southeast, except in the northwestern part of the area where the flow is in a westerly direction towards Paragould. Large groundwater withdrawals have altered the natural direction of flow near centers of pumping at Paragould and West Memphis. Water-level difference maps for the Wilcox aquifer in Arkansas were constructed using the differences between water-level measurements made during 2003 and 2009 from 52 wells. The difference in water levels between 2003 and 2009 in the southwestern area ranged from -36.4 to 16.0 ft. Water levels rose in the northern parts of the southwestern area, while the water levels in the southern part of the area declined with the exception of one well. The differences in water levels between 2003 and 2009 in the northeastern area ranged from -21.7 to 1.3 ft. Water levels declined throughout the northeastern area with the exception of two wells. Hydrographs from 42 wells with a minimum of 20 yr of water-level measurements were constructed. Trend lines using linear regression were calculated for the period from 1990 to 2009 to determine the slope in ft/yr for water levels in each well. In the southwestern area, the county mean annual water level rose 0.15 ft/yr in Hot Spring County. County mean annual water levels declined between 0.71 ft/yr and 0.03 ft/yr in Clark, Hempstead, and Nevada counties. In the northeastern area, the county mean annual water level rose 0.46 ft/yr in Greene County. County mean annual water levels declined between 0.03 ft/yr and 2.12 ft/yr in Clay, Craighead, Crittenden, Lee, Mississippi, Poinsett, and St. Francis counties.

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USGS2008

Geomorphic characterization of the Middle Fork Saline River: Garland, Perry, and Saline Counties, Arkansas

This report was prepared to help address concerns raised by local residents, State, and Federal agencies about the current geomorphic conditions of the Middle Fork Saline River. Over the past 30 years the Middle Fork Saline River Basin has experienced a marked increase in urbanization. The report summarizes the Middle Fork?s current (2003) channel characteristics at nine stream reaches in the upper 91 square miles of the basin. Assessments at each study reach included comparing measured stream geometry dimensions (cross-sectional area, top width, and mean depth) at bankfull stage to regional hydraulic geometry curves for the Ouachita Mountains Physiographic Province of Arkansas and Oklahoma, evaluations of streambed materials and sinuosity, and classification of individual stream reach types. When compared to the Ouachita Mountains? regional hydraulic geometry curves for natural, stable, stream reaches, five of the nine study reaches had slightly smaller crosssectional areas, longer top widths, and shallower depths. Streambed material analysis indicates that the Middle Fork is a bedrock influenced, gravel dominated stream with lesser amounts of sand and cobbles. Slight increases in sinuosity from 1992 to 2002 at seven of the nine study reaches indicate a slight decrease in stream channel slope. Analyses of the Middle Fork?s hydraulic geometry and sinuosity indicate that the Middle Fork is currently overly wide and shallow, but is slowly adjusting towards a deeper, narrower hydraulic geometry. Using the Rosgen system of channel classification, the two upstream study reaches classified as B4c/1 stream types; which were moderately entrenched, riffle dominated channels, with infrequently spaced pools. The downstream seven study reaches classified as C4/1 stream types; which were slightly entrenched, meandering, gravel-dominated, riffle/ pool channels with well developed flood plains. Analyses of stream reach types suggest that the downstream reaches of the Middle Fork are more vulnerable to streambank failure than the upstream reaches of the stream.

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USGS2008

Low-flow characteristics and regionalization of low-flow characteristics for selected streams in Arkansas

Water use in Arkansas has increased dramatically in recent years. Since 1990, the use of water for all purposes except power generation has increased 53 percent (4,004 cubic feet per second in 1990 to 6,113 cubic feet per second in 2005). The biggest users are agriculture (90 percent), municipal water supply (4 percent) and industrial supply (2 percent). As the population of the State continues to grow, so does the demand for the State’s water resources. The low-flow characteristics of a stream ultimately affect its utilization by humans. Specific information on the low-flow characteristics of streams is essential to State water-management agencies such as the Arkansas Department of Environmental Quality, the Arkansas Natural Resources Commission, and the Arkansas Game and Fish Commission when dealing with problems related to irrigation, municipal and industrial water supplies, fish and wildlife conservation, and dilution of waste. Low-flow frequency data are of particular value to management agencies responsible for the development and management of the State’s water resources. This report contains the low-flow characteristics for 70 active continuous-streamflow record gaging stations, 59 inactive continuous-streamflow record stations, and 101 partial-record gaging stations. These characteristics are the annual 7-day, 10-year low flow and the annual 7-day, 2-year low flow, and the seasonal, bimonthly, and monthly 7-day, 10-year low flow for the 129 active and inactive continuous-streamflow record and 101 partial-record gaging stations. Low-flow characteristics were computed on the basis of streamflow data for the period of record through September 2005 for the continuous-streamflow record and partial-record streamflow gaging stations. The low-flow characteristics of these continuous- and partial-record streamflow gaging stations were utilized in a regional regression analysis to produce equations for estimating the annual, seasonal, bimonthly, and monthly (November through April) 7-day, 10-year low flows and the annual 7-day, 2-year low flow for ungaged streams in the western two-thirds of Arkansas.

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USGS2008

Evaluation of selected model constraints and variables on simulated sustainable yield from the Mississippi River Valley alluvial aquifer system in Arkansas

An existing conjunctive use optimization model of the Mississippi River Valley alluvial aquifer was used to evaluate the effect of selected constraints and model variables on ground-water sustainable yield. Modifications to the optimization model were made to evaluate the effects of varying (1) the upper limit of ground-water withdrawal rates, (2) the streamflow constraint associated with the White River, and (3) the specified stage of the White River. Upper limits of ground-water withdrawal rates were reduced to 75, 50, and 25 percent of the 1997 ground-water withdrawal rates. As the upper limit is reduced, the spatial distribution of sustainable pumping increases, although the total sustainable pumping from the entire model area decreases. In addition, the number of binding constraint points decreases. In a separate analysis, the streamflow constraint associated with the White River was optimized, resulting in an estimate of the maximum sustainable streamflow at DeValls Bluff, Arkansas, the site of potential surface-water withdrawals from the White River for the Grand Prairie Area Demonstration Project. The maximum sustainable streamflow, however, is less than the amount of streamflow allocated in the spring during the paddlefish spawning period. Finally, decreasing the specified stage of the White River was done to evaluate a hypothetical river stage that might result if the White River were to breach the Melinda Head Cut Structure, one of several manmade diversions that prevents the White River from permanently joining the Arkansas River. A reduction in the stage of the White River causes reductions in the sustainable yield of ground water.

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USGS2008

Summary of aquifer test data for Arkansas – 1940-2006

As demands on Arkansas's ground water continue to increase, decision-makers need all available information to ensure the sustainability of this important natural resource. From 1940 through 2006, the U.S. Geological Survey has conducted over 300 aquifer tests in Arkansas. Much of these data never have been published. This report presents the results from 206 of these aquifer tests from 21 different hydrogeologic units spread across 51 Arkansas counties. Ten of the hydrogeologic units are within the Atlantic Plain of Arkansas and consist mostly of unconsolidated and semi-consolidated deposits. The remaining 11 units are within the Interior Highlands consisting mainly of consolidated rock. Descriptive statistics are reported for each hydrologic unit with two or more tests, including the mean, minimum, median, maximum and standard deviation values for specific capacity, transmissivity, hydraulic conductivity, and storage coefficient. Hydraulic conductivity values for the major water-bearing hydrogeologic units are estimated because few conductivity values are recorded in the original records. Nearly all estimated hydraulic conductivity values agree with published hydraulic conductivity values based on the hydrogeologic unit material types. Similarly, because few specific capacity values were available in the original aquifer test records, specific capacity values are estimated for individual wells.

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USGS2007

Status of water levels in aquifers in the Nacatoch Sand of southwestern and northeastern Arkansas and the Tokio Formation of southwestern Arkansas, February 2005

The Nacatoch Sand and Tokio Formation aquifers in southwestern Arkansas and the Nacatoch Sand aquifer in northeastern Arkansas are sources of water for industrial, public supply, domestic, and agricultural uses. Potentiometric-surface maps were constructed from water-level measurements made in 60 wells completed in the Nacatoch Sand and 50 wells completed in the Tokio Formation during February 2005. Aquifers in the Nacatoch Sand and Tokio Formation are hereafter referred to as the Nacatoch aquifer and Tokio aquifer, respectively. The direction of ground-water flow in the Nacatoch aquifer in northeastern Arkansas generally is towards the southeast. The potentiometric high is located along the north and northwestern boundaries of the area. The direction of ground-water flow in the Nacatoch aquifer in southwestern Arkansas is towards the south-southeast in Little River, Miller, and Hempstead Counties and to the east-southeast in Nevada and Clark Counties. The potentiometric high is located within the outcrop area in north-central Hempstead County. A cone of depression exists in the Nacatoch aquifer at Hope in southeastern Hempstead County. The direction of ground-water flow in the Tokio aquifer in southwestern Arkansas generally is towards the south or southeast. The potentiometric high is within the outcrop area. An area of artesian flow exists in southeastern Pike, northeastern Hempstead, and northwestern Nevada Counties. One apparent cone of depression might exist northwest of Hope in Hempstead County. In northeastern Arkansas, withdrawals from the Nacatoch aquifer increased by 516 percent from 1965 to 2000. In southwestern Arkansas, withdrawals from Nacatoch aquifer and Tokio aquifer increased by 125 percent and 201 percent, respectively, from 1965 to 1980 and decreased by 93 percent and 80 percent, respectively, from 1980 to 2000. Long-term hydrographs were prepared for 10 wells in the study areas. Changes in water levels in some wells may be associated with changes in withdrawals from the respective aquifers.

Arkansas↗