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USGS2020

Altitude of the potentiometric surface in the Mississippi River Valley alluvial aquifer, spring 2018

A potentiometric-surface map for spring 2018 was created for the Mississippi River Valley alluvial (MRVA) aquifer using available groundwater-altitude data from 1,126 wells completed in the MRVA aquifer and from the altitude of the top of the water surface in area rivers from 66 streamgages. Personnel from Arkansas Natural Resources Commission, Arkansas Department of Health, Arkansas Geological Survey, Illinois Department of Agriculture, Illinois State Water Survey, Louisiana Department of Natural Resources, Louisiana Department of Transportation and Development, Mississippi Department of Environmental Quality, Missouri Department of Natural Resources, Yazoo Mississippi Delta Joint Water Management District, U.S. Department of Agriculture-Natural Resources Conservation Service, and U.S. Geological Survey (USGS) routinely collect groundwater-level data from wells screened in the MRVA aquifer. The USGS and the U.S. Army Corps of Engineers routinely collect data on river stage and streamflow for the rivers overlying the MRVA aquifer area. The potentiometric-surface map for 2018 was created utilizing existing groundwater and surface-water altitudes to support investigations to characterize the MRVA aquifer as part of the USGS Water Availability and Use Science Program. Sufficient data were available to map the potentiometric surface of the MRVA aquifer for spring 2018 for about 87 percent of the aquifer area. The potentiometric contours ranged from 10 to 340 feet above North American Vertical Datum of 1988. The regional direction of groundwater flow was generally to the south-southwest, except in areas of groundwater-altitude depressions, where groundwater flowed into the depression, and near rivers, where flow can be from aquifer to the river or from the river into the aquifer. There are large depressions in the potentiometric-surface map in the lower one-half of the Cache region and in most of the Grand Prairie and Delta regions.

Mississippi River Valley alluvial aquifer↗

USGS1985

Contaminant residues in fish and sediments from lakes in the Atchafalaya River Basin (Louisiana)

Conversion of bottomland hardwood forests ℴ agricultural land has reduced habitat and water quality in many lakes in the floodplain of the lower Mississippi River. The objectives of this study were to ascertain current contaminant residue concentrations in fish and sediment from lakes in the Atchafalaya River Basin and to determine the influence of overflow and agricultural land use on contaminant levels. Fish and sediment samples were collected from eight lakes that differed in overflow (no overflow, headwater overflow, backwater overflow) and land-use characteristics (presence or absence of agricultural land). Residue analysis of 24 sediment and 82 fish samples collected from the study lakes showed that contaminant residues were uniformly low. Total DDT concentrations, consisting mainly of DDE, were found in 98% of the fish samples and generally were the highest residues though they rarely exceeded 0.50 μg/g. Dieldrin, α-BHC and γ-BHC, in concentrations rarely exceeding 0.05 μg/g, were detected in about 50% of the fish samples. Total organochlorine pesticide and PCB residues were less than 2.00 μg/g in all fish from all lakes, except for a 3.46 μg/g total in spotted gar ( Lepisosteus oculatus ) from one lake. Sediments were free from pesticide residues except for occasional traces (0.01 μg/g) of α-BHC. Metal residue concentrations in fish and sediment samples were typical of uncontaminated areas. Lake systems in the Atchafalaya River Basin appeared to be relatively uncontaminated by agricultural pesticides, but metal and organic residues in fish were similar from lakes with the same land-use and overflow characteristics.

Louisiana↗

USGS2002

Avian response to bottomland hardwood reforestation: The first 10 years

Bottomland hardwood forests were planted on agricultural fields in Mississippi and Louisiana predominantly using either Quercus species (oaks) or Populus deltoides (eastern cottonwood). We assessed avian colonization of these reforested sites between 2 and 10 years after planting. Rapid vertical growth of cottonwoods (circa 2–3 m/year) resulted in sites with forest structure that supported greater species richness of breeding birds, increased Shannon diversity indices, and supported greater territory densities than on sites planted with slower-growing oak species. Grassland birds ( Spiza americana [Dickcissel] and Sturnella magna [Eastern Meadowlark]) were indicative of species breeding on oak-dominated reforestation no more than 10 years old. Agelaius phoeniceus (Red-winged Blackbird) and Colinus virginianus (Northern Bobwhite) characterized cottonwood reforestation no more than 4 years old, whereas 14 species of shrub-scrub birds (e.g., Passerina cyanea [Indigo Bunting]) and early-successional forest birds (e.g., Vireo gilvus [Warbling vireo]) typified cottonwood reforestation 5 to 9 years after planting. Rates of daily nest survival did not differ between reforestation strategies. Nest parasitism increased markedly in older cottonwood stands but was overwhelmed by predation as a cause of nest failure. Based on Partners in Flight prioritization scores and territory densities, the value of cottonwood reforestation for avian conservation was significantly greater than that of oak reforestation during their first 10 years. Because of benefits conferred on breeding birds, we recommend reforestation of bottomland hardwoods should include a high proportion of fast-growing early successional species such as cottonwood.

Restoration Ecology↗

USGS2023

Diurnal time–activity budget and habitat use of Whooping Cranes (Grus americana) in the reintroduced Louisiana nonmigratory population

Time–activity budget studies provide valuable insights for better understanding animal behavior relative to spatial and temporal habitat use. We examined a reintroduced, nonmigratory Whooping Crane ( Grus americana ) population to determine how time–activity budgets change relative to crane age, sex, habitat type, and season. Our study area encompassed natural marshes and working wetlands primarily in southwestern Louisiana. From June 2012 to January 2016, we conducted continuous focal sampling on individuals ( n = 27) from the first 4 captive-reared cohorts released in the state. We classified age groups as juveniles, subadults, and adults, and identified 5 main habitat types utilized by cranes in Louisiana: crawfish ponds, rice fields, agricultural levees/farm roads, fallow fields, and natural wetlands. On average, cranes spent approximately 53% of their diurnal time–activity budget foraging. Maintenance/rest (28%), vigilance (12%), locomotion (6%), and other/unknown (2%) behaviors accounted for the remainder of the time observed. Foraging most frequently occurred in fallow fields and crawfish ponds where cranes likely encountered greater invertebrate biomass and density. Cranes tended to spend less time foraging and more time on maintenance as they aged, which could indicate age-dependent differences based on experience on the landscape. Vigilance levels were not significantly affected by age, but males tended to be more vigilant than females. As this young population continues to mature, additional study of breeding pairs and family groups may elucidate other behavioral differences in response to the dynamic habitat conditions in the region.

The Wilson Journal of Ornithology↗

USGS1998

Survival of female northern pintails wintering in southwestern Louisiana

The North American breeding population of northern pintails ( Anas acuta ) has reached previously unprecedented low numbers 4 times since 1983. Because pintails show high fidelity to wintering areas, regional survival estimates and identification of factors influencing survival are needed to guide management of wintering pintails. We used radiotelemetry to estimate survival rates of female pintails wintering in southwestern Louisiana. We tested for variation in survival and hunting mortality rates in relation to age (immature or adult), winter (1990-91, 1991-92, 1992-93), time period (prehunting season, first hunting season, time between split hunting seasons, second hunting season, posthunting season), body condition (body mass when released, adjusted for body size), and region (southwestern Louisiana or elsewhere on the Texas-Louisiana Gulf Coast or Mississippi Alluvial Valley). Within southwestern Louisiana, the 147-day (5 Oct-28 Feb) survival rate of adults (0.714 ± 0.045; x̅ ± SE) was greater ( P = 0.02) than that of immatures (0.550 ± 0.068), primarily because immatures had higher hunting mortality. Female survival was lower ( P s < 0.01) during hunting than during nonhunting seasons but did not differ between first and second hunting seasons ( P = 0.58) or among non-hunting seasons ( P s >0.25). Survival did not differ in relation to winter or condition ( P s > 0.12). Hunting mortality did not differ ( P s > 0.13) in relation to winter, condition, or region, but hunting mortality of immatures (0.287 ± 0.046) was greater ( P < 0.001) than that of adults (0.130 ± 0.025). Despite conservative hunting regulations (30-day seasons and 1 pintail daily), hunting mortality rates of pintails in southwestern Louisiana were high. Pintails in southwestern Louisiana rely on a small number of key refuges for protection but feed almost exclusively in privately owned agricultural fields. If increased winter survival of female pintails in southwestern Louisiana is desired, we recommend that managers increase food available.

Louisiana↗

USGS2015

Potentiometric surface, 2013, and water-level differences, 1991-2013, of the Carrizo-Wilcox aquifer in northwest Louisiana

The Carrizo-Wilcox aquifer is the primary source of fresh groundwater for public supply as well as industrial, agricultural, and domestic uses in several parishes in northwestern Louisiana, including Bienville, Bossier, Caddo, De Soto, Natchitoches, Red River, Sabine, and Webster. In 2010, about 19 million gallons per day (Mgal/d) were withdrawn from the Carrizo-Wilcox aquifer in Louisiana. This is an increase of over 6 Mgal/d from 1990 withdrawal amounts. The largest increase in withdrawals occurred in Caddo (3.79 Mgal/d) and De Soto Parishes (2.32 Mgal/d), whereas the largest decrease in withdrawals occurred in Natchitoches Parish (1.17 Mgal/d). Groundwater withdrawals from the Carrizo-Wilcox aquifer have caused water-level declines throughout much of the aquifer in the study area. Additional knowledge about the effects of withdrawals on water levels and flow directions in the Carrizo-Wilcox aquifer are needed to assess current conditions in the aquifer. In 2012, the U.S. Geological Survey (USGS) in cooperation with the Louisiana Department of Natural Resources began a study to document current water levels and water-level changes in selected aquifers. This report presents data and maps that illustrate the potentiometric surface of the Carrizo-Wilcox aquifer during March–May 2013 and water-level differences from 1991 to 2013. The potentiometric surface map can be used for determining the direction of groundwater flow, hydraulic gradients, and effects of withdrawals on the groundwater resource. The rate of groundwater movement also can be estimated from the gradient when the hydraulic conductivity is applied. Water-level data collected for this study are stored in the USGS National Water Information System (NWIS) ( http://waterdata.usgs.gov/nwis ) and are on file at the USGS office in Baton Rouge, La.

Louisiana↗

USGS2003

Trace elements in lesser scaup (Aythya affinis) from the Mississippi flyway

Previous research reported that concentrations of selenium in the livers of 88a??95% of lesser scaup from locations in Lake Erie, Lake St. Clair, and Lake Michigan, USA were either elevated (10a??33 A?g/g dry weight [dw]) or in the potentially harmful range (>33 A?g/g dw). In order to determine the geographic extent of these high selenium concentrations, we collected lesser scaup in Louisiana, Arkansas, Illinois, Minnesota, Wisconsin, and Manitoba and analyzed the livers for 19 trace elements. We found that all trace element concentrations, except for selenium, generally were low. Arsenic, which usually is not detected in liver samples, was detected in Louisiana and may be related to past agricultural usages. Chromium, which also is not usually detected, was only present in lesser scaup from Arkansas and may be related to fertilizer applications. Cadmium and mercury concentrations did not differ among locations and concentrations were low. Selenium concentrations in Arkansas (geometric mean=4.2 A?g/g dw) were significantly lower than those in Louisiana (10.7 A?g/g dw), Illinois (10.5 A?g/g dw), and Minnesota (8.0 A?g/gdw); concentrations in Wisconsin and Manitoba were intermediate (6.6 and 6.5 A?g/g dw). About 25% of lesser scaup livers contained elevated selenium concentrations; however, none were in the harmful range. We concluded that selenium concentrations in lesser scaup in the Mississippi Flyway are elevated in some individuals, but not to the extent that has been documented in the industrial portions of the Great Lakes.

Ecotoxicology↗

USGS2015

Connectivity among subpopulations of Louisiana black bears as estimated by a step selection function

Habitat fragmentation is a fundamental cause of population decline and increased risk of extinction for many wildlife species; animals with large home ranges and small population sizes are particularly sensitive. The Louisiana black bear ( Ursus americanus luteolus ) exists only in small, isolated subpopulations as a result of land clearing for agriculture, but the relative potential for inter-subpopulation movement by Louisiana black bears has not been quantified, nor have characteristics of effective travel routes between habitat fragments been identified. We placed and monitored global positioning system (GPS) radio collars on 8 female and 23 male bears located in 4 subpopulations in Louisiana, which included a reintroduced subpopulation located between 2 of the remnant subpopulations. We compared characteristics of sequential radiolocations of bears (i.e., steps) with steps that were possible but not chosen by the bears to develop step selection function models based on conditional logistic regression. The probability of a step being selected by a bear increased as the distance to natural land cover and agriculture at the end of the step decreased and as distance from roads at the end of a step increased. To characterize connectivity among subpopulations, we used the step selection models to create 4,000 hypothetical correlated random walks for each subpopulation representing potential dispersal events to estimate the proportion that intersected adjacent subpopulations (hereafter referred to as successful dispersals). Based on the models, movement paths for males intersected all adjacent subpopulations but paths for females intersected only the most proximate subpopulations. Cross-validation and genetic and independent observation data supported our findings. Our models also revealed that successful dispersals were facilitated by a reintroduced population located between 2 distant subpopulations. Successful dispersals for males were dependent on natural land cover in private ownership. The addition of hypothetical 1,000-m- or 3,000-m-wide corridors between the 4 study areas had minimal effects on connectivity among subpopulations. For females, our model suggested that habitat between subpopulations would probably have to be permanently occupied for demographic rescue to occur. Thus, the establishment of stepping-stone populations, such as the reintroduced population that we studied, may be a more effective conservation measure than long corridors without a population presence in between.

Louisiana↗

USGS1998

Natural establishment of woody species on abandoned agricultural fields in the lower Mississippi Valley: first- and second-year results

The natural establishment of woody seedlings on abandoned agricultural fields was investigated at sites in Louisiana and Mississippi. Series of disked and undisked plots originating at forest edges and oriented in cardinal directions were established on fields at each site. During the firest 2 years, seedling recruitment was dominated by sweetgum, sugarberry, and elms at both sites. Seedling establishment was strongly affected by direction from mature forest and disking, and to a slightly lesser degree by distance from mature forest. Slightly under half of the variation in seedling numbers per plot was explained by the effects of direction, distance, and disking, indicating that other factors also may play an important role in seedling recruitment.

General Technical Report SRS↗

USGS1998

Use of mini-refuges by female northern pintails wintering in southwestern Louisiana

The Gulf Coast Joint Venture of the North American Waterfowl Management Plan began contracting private agricultural lands (hereafter mini-refuges) in 1988 to expand existing sanctuaries for northern pintails ( Anas acuta ) in southwestern Louisiana. Previous research suggested that mini-refuges may prove more attractive to pintails than permanent, open-water pools (pools) on refuges because mini-refuges provide sanctuary and food during the day, whereas pools generally provide only sanctuary (Rave and Cordes 1993). We used radiotelemetry to compare diel use of mini-refuges and pools (Lacassine Pool and Amoco Pool) by female pintails in southwestern Louisiana during winters of 1991-1992 and 1992-1993. We examined variation in use of these areas in relation to female age (immature or adult), time period (prehunting season, first hunting season, time between split hunting seasons, second hunting season, and posthunting season), and winter (1991-1992 and 1992-1993). Diurnal use of min-refuges and pools differed among time periods, but differences were not consistent between winters. Mini-refuges accounted for <2% of diurnal use by pintails in 7 of 10 time-period and winter comparisons. Diurnal use of mini-refuges was lower than that of Lacassine Pool in 8 of 10 time-period and winter comparisons. Diurnal use of mini-refuges was lower than tha of Amoco pool during first hunting season in 1992-1993, but use of these areas did not differ within other time periods and winters. Nocturnal use of mini-refuges and pools did not differ in relation to female age, time period, winter, or individual bird. Nocturnal use of mini-refuges did not differ from that of Lacassine Pool. In contrast to predictions and findings by Rave and Cordes (1993), we found that: (1) female pintails did not use mini-refuges more than pools, and (2) female pintails used mini-refuges at night. We believe that use of mini-refuges by pintails could be increased if mini-refuges were (1) located in areas of traditionally high pintail use, (2) increased in size, (3) flooded immediately prior to hunting season, and (4) cleared of dense vegetation by rolling, disking, or burning.

Louisiana↗

USGS2004

Withdrawals, water levels, and specific conductance in the Chicot aquifer system in southwestern Louisiana, 2000-03

The Chicot aquifer system is the principal source of fresh ground-water supplies in southwestern Louisiana. Much of the area is rural and rice cultivation is the primary agricultural activity. About 540 million gallons per day were withdrawn from the aquifer system in southwestern Louisiana in 2000. Potentiometric-surface maps of the aquifer system were created for June 2002 and January 2003 to determine where water-level declines occur due to seasonal ground-water withdrawals. During June 2002, water levels in the aquifer system were more than 40 feet below the National Geodetic Vertical Datum of 1929 (NGVD 29) in parts of Acadia, Calcasieu, Evangeline, and Jefferson Davis Parishes, in an area that generally coincides with rice-farming areas. During January 2003, water levels were more than 30 feet below NGVD 29 in these areas. From June 2002 to January 2003, water levels generally recovered between 5 and 20 feet in the Chicot aquifer system in most of Acadia and Jefferson Davis Parishes, southeastern Calcasieu Parish, and southern Evangeline Parish, in an area that generally coincides with rice-farming areas. These water-level changes are representative of the areal extent and magnitude of typical seasonal water-level fluctuations that occur in the aquifer system in response to seasonal ground-water withdrawals for rice irrigation. The presence of saltwater has been documented in the Chicot aquifer system beneath coastal parishes and in some areas where the aquifer system merges with the stratigraphically adjacent Atchafalaya aquifer. Data collected during the period 1943 to 2003 from 1,355 wells screened in the massive, upper, and "200-foot" sands of the Chicot aquifer system and the Atchafalaya aquifer were used to delineate areas having similar specific conductance values and determine areas where wells are affected by saltwater. Near the outcrop area, specific conductance values in the Chicot aquifer system generally are less than 150 µS/cm (microsiemens per centimeter at 25 degrees Celsius). Specific conductance values increase south and east of the outcrop area. Specific conductance values generally range from 151 to 500 µS/cm in rice-farming areas of northwestern Acadia Parish, southeastern Allen Parish, western Evangeline Parish, and northern and central Jefferson Davis Parish. Specific conductance values generally range from 501 to 1,000 µS/cm in most of the remaining rice-farming areas. Specific conductance values often exceed 1,000 µS/cm in an area along the border between Calcasieu and Jefferson Davis Parishes near Iowa, Louisiana, parts of northeastern Cameron Parish, an area of northwestern and central St. Landry Parish; parts of Vermilion Parish, and several areas along the eastern boundary of the study area where the Chicot aquifer system merges with the Atchafalaya aquifer. The maximum specific conductance value, 12,100 µS/cm, is from a well in Cameron Parish. During 2000-03, specific conductance was measured in 521 water samples from 166 wells screened in the Chicot aquifer system or the Atchafalaya aquifer. Specific conductance values exceeded 1,000 µS/cm in water samples from wells in Calcasieu, Cameron, Jefferson Davis, St. Landry, St. Martin, St. Mary, and Vermilion Parishes. Specific conductance values exceeded 2,000 µS/cm in only two wells—an irrigation well located about 2 miles south of Iowa and a USGS observation well used to monitor saltwater encroachment in east-central Vermilion Parish. Specific conductance values increased steadily at one well, from 1,090 µS/cm in April 2000 to 2,860 µS/cm in April 2003. Nearby wells did not show similar increases. Specific conductance was measured hourly during pumping at two irrigation wells between 2000 and 2003. Specific conductance values were greater than 1,000 µS/cm in both wells, indicating the presence of saltwater near the wells. Specific conductance values generally fluctuated about 150 µS/cm at both wells, but no long-term trends in the specific conductance were evident in either well.

Louisiana↗

USGS1994

Guide to Louisiana's ground-water resources

Ground water is one of the most valuable and abundant natural resources of Louisiana. Of the 4-.4 million people who live in the State, 61 percent use ground water as a source for drinking water. Most industrial and rural users and half of the irrigation users in the State rely on ground water. Quantity, however, is not the only aspect that makes ground water so valuable; quality also is important for its use. In most areas, little or no water treatment is required for drinking water and industrial purposes. Knowledge of Louisiana's ground-water resources is needed to ensure proper development and protection of this valuable resource. This report is designed to inform citizens about the availability and quality of ground water in Louisiana. It is not intended as a technical reference; rather, it is a guide to ground water and the significant role this resource plays in the state. Most of the ground water that is used in the State is withdrawn from 13 aquifers and aquifer systems: the Cockfield, Sparta, and Carrizo-Wilcox aquifersin northern Louisiana; Chicot aquifer system, Evangeline aquifer, Jasper aquifer system, and Catahoula aquifer in central and southwestern Louisiana; the Chicot equivalent, Evangeline equivalent, and Jasper equivalent aquifer systems in southeastern Louisiana; and the MississippiRiver alluvial, Red River alluvial, and upland terrace aquifers that are statewide. Ground water is affected by man's activities on the land surface, and the major ground-water concerns in Louisiana are: (1) contamination from surface disposal of hazardous waste, agricultural chemicals, and petroleum products; (2) contamination from surface wastes and saltwater through abandoned wells; (3) saltwater encroachment; and (4) local overdevelopment. Information about ground water in Louisiana is extensive and available to the public. Several State and Federal agencies provide published and unpublished material upon request.

Water-Resources Investigations Report↗

USGS2024

Inset groundwater-flow models for the Cache and Grand Prairie Critical Groundwater Areas, northeastern Arkansas

The water resources in the Mississippi alluvial plain, located in parts of Missouri, Kentucky, Tennessee, Mississippi, Louisiana, and Arkansas, supports a multibillion-dollar agricultural industry that relies heavily on pumping of groundwater for irrigation of crops and aquaculture. The primary source of groundwater for agricultural-related pumping is the Mississippi River Valley alluvial aquifer, which has declined in storage for decades; secondary groundwater sources include the middle Claiborne aquifer and Wilcox aquifer system. Two areas in northeastern Arkansas that lie within the Mississippi alluvial plain, part of the Cache and Grand Prairie regions, have been designated as Critical Groundwater Areas owing to decades of groundwater declines that resulted from past and current water use. The multidisciplinary Mississippi Alluvial Plain project, led by the U.S. Geological Survey, and funded by their Water Availability and Use Science Program, included objectives to develop numerical groundwater models in focus regions, including the part of the Cache and Grand Prairie regions of northeastern Arkansas. Two inset models were developed using the child model capabilities of MODFLOW 6, the U.S. Geological Survey’s Modular Hydrologic Model simulation software. Both models, called the Cache model and Grand Prairie model, simulated the groundwater system and surface-water/groundwater interactions for the Mississippi River Valley alluvial aquifer and underlying Tertiary-age aquifers and confining units to the Midway confining unit. Each model was spatially discretized into 500-meter x 500-meter orthogonal cells on a grid with 5-meter constant-thickness vertical layers that represented the Mississippi River Valley alluvial aquifer and increasing thickness layers for the aquifers and confining units below the alluvial aquifer. The Cache and Grand Prairie models were calibrated with the PEST++ iterative ensemble smoother Version 5 and employed high dimensional parameterization schemes of 13,740 and 30,436 parameters, respectively. The Cache mean absolute residual for groundwater-level observations within each model domain for the priority well was 1.58 meters. Grand Prairie mean absolute residuals for the alluvial aquifer and middle Claiborne aquifer groundwater-level observations were 2.71 and 10.78 meters, respectively. The groundwater budgets for the Cache and Grand Prairie models were characterized by substantial outflows to irrigation wells, which constituted about 52 and 54 percent of all outflows, with the primary source of water to those wells being releases from unconfined aquifer storage.

Arkansas↗

USGS1956

Water resources of southwestern Louisiana

In southwestern Louisiana large quantities of fresh water are available for agricultural, municipal, domestic, and industrial purposes. However, local and regional problems resulting from salt-water encroachment in the streams and persistent declines of the groundwater levels in certain areas during . drought periods have caused some concern regarding the future water supply of the region. · In order to appraise the situation, to provide hydrologic information basic to development of the area, and to provide a basis for sound plans for alleviating recurrent dry-year losses, a study of the ground-water resources of the area was begun in 1938 through cooperation with the Louisiana Geological Survey, Department of Conservation. An intensive investigation comprising ground-water, surface-water, and quality-of-water studies was authorized in 1948 in cooperation with the Louisiana Department of Public Works, and was completely under' way before the 1949 irrigation season. The studies were carried through the irrigation season of 1951.

Louisiana↗

USGS2012

Occurrence of pesticides in water and sediment collected from amphibian habitats located throughout the United States, 2009-10

Water and bed-sediment samples were collected by the U.S. Geological Survey (USGS) in 2009 and 2010 from 11 sites within California and 18 sites total in Colorado, Georgia, Idaho, Louisiana, Maine, and Oregon, and were analyzed for a suite of pesticides by the USGS. Water samples and bed-sediment samples were collected from perennial or seasonal ponds located in amphibian habitats in conjunction with research conducted by the USGS Amphibian Research and Monitoring Initiative and the USGS Toxic Substances Hydrology Program. Sites selected for this study in three of the states (California, Colorado, and Orgeon) have no direct pesticide application and are considered undeveloped and remote. Sites selected in Georgia, Idaho, Louisiana, and Maine were in close proximity to either agricultural or suburban areas. Water and sediment samples were collected once in 2009 during amphibian breeding seasons. In 2010, water samples were collected twice. The first sampling event coincided with the beginning of the frog breeding season for the species of interest, and the second event occurred 10-12 weeks later when pesticides were being applied to the surrounding areas. Additionally, water was collected during each sampling event to measure dissolved organic carbon, nutrients, and the fungus, Batrachochytrium dendrobatidis , which has been linked to amphibian declines worldwide. Bed-sediment samples were collected once during the beginning of the frog breeding season, when the amphibians are thought to be most at risk to pesticides. Results of this study are reported for the following two geographic scales: (1) for a national scale, by using data from the 29 sites that were sampled from seven states, and (2) for California, by using data from the 11 sampled sites in that state. Water samples were analyzed for 96 pesticides by using gas chromatography/mass spectrometry. A total of 24 pesticides were detected in one or more of the 54 water samples, including 7 fungicides, 10 herbicides, 4 insecticides, 1 synergist, and 2 pesticide degradates. On a national scale, aminomethylphosphonic acid (AMPA), the primary degradate of the herbicide glyphosate, which is the active ingredient in Roundup®, was the most frequently detected pesticide in water (16 of 54 samples) followed by glyphosate (8 of 54 samples). The maximum number of pesticides observed at a single site was nine compounds in a water sample from a site in Louisiana. The maximum concentration of a pesticide or degradate observed in water was 2,880 nanograms per liter of clomazone (a herbicide) at a site in Louisiana. In California, a total of eight pesticides were detected among all of the low and high elevation sites; AMPA was the most frequently detected pesticide, but glyphosate was detected at the highest concentrations (1.1 micrograms per liter). Bed-sediment samples were analyzed for 94 pesticides by using accelerated solvent extraction, gel permeation chromatography for sulfur removal, and carbon/alumina stacked solid-phase extraction cartridges to remove interfering sediment matrices. In bed sediment, 22 pesticides were detected in one or more of the samples, including 9 fungicides, 3 pyrethroid insecticides, p,p' -dichlorodiphenyltrichloroethane ( p,p' -DDT) and its major degradates, as well as several herbicides. Pyraclostrobin, a strobilurin fungicide, and bifenthrin, a pyrethroid insecticide, were detected most frequently. Maximum pesticide concentrations ranged from less than their respective method detection limits to 1,380 micrograms per kilogram (tebuconazole in California). The number of pesticides detected in samples from each site ranged from zero to six compounds. The sites with the greatest number of pesticides were in Maine and Oregon with six pesticides detected in one sample from each state, followed by Georgia with four pesticides in one sample. For California, a total of 10 pesticides were detected among all sites, and 4 pesticides were detected at both low and high elevation sites; tebuconazole and pyraclostrobin were the two most frequently detected pesticides in California. For the other six selected states, the most frequently detected pesticides in bed sediment were pyraclostrobin (detected in 17 of 42 samples), bifenthrin (detected in 14 of 42 samples), and tebuconazole (detected in 10 of 42 samples). The fungus, Batrachochytrium dendrobatidis (Bd), was detected in water samples in sites from four of the seven states during 2009 and 2010, and the number of zoospore equivalents per liter of water in samples where Bd was detected ranged from 1.6 to 343. Bd was not detected in water samples from sites in Georgia, Louisiana, and Oregon.

Data Series↗

USGS1998

Simulated response to pumping stress in the Sparta aquifer of southeastern Arkansas and north-central Louisiana, 1998-2027

The Sparta aquifer in southeastern Arkansas and north-central Louisiana is a major water resource for municipal, industrial, and agricultural uses. In recent years, the demand for water in some areas has resulted in withdrawals from the Sparta that significantly exceed recharge to the aquifer. Considerable drawdown has occurred in the potentiometric surface, and water users and managers alike have begun to question the ability of the aquifer to supply water for the long term. Large cones of depression are centered beneath the Grand Prairie area and the cities of Pine Bluff and El Dorado in Arkansas, and Monroe in Louisiana. Water levels in the aquifer have declined at rates greater than 1 foot per year for more than a decade in much of southern Arkansas and northern Louisiana and are now below the top of the formation in parts of Union and Columbia Counties, Arkansas, and in several areas of Louisiana. Problems related to over draft in the Sparta could result in increased drilling and pumping costs, loss of yield, salt-water intrusion, and decrease in water quality in areas of large drawdown. The effects of current ground-water withdrawals and potential future withdrawals on water availability are major concerns of water managers and users as well as the general public in the two States. The Sparta model-a regional scale, digital ground-water flow model-was first calibrated in the mid-1980's. The model was updated and reverified using 1995-97 data. Visual inspection of the observed (1996-97) and simulated potentiometric surfaces, statistical analysis of the error for the original calibration and current reverification, and comparison of observed versus simulated hydro graphs indicates that the model is simulating conditions in the aquifer within acceptable error, and the quality of current (1998) model results is similar to the original model calibration results. When stressed with current withdrawal volumes and distributions, the model is able to simulate currently observed heads effectively as heads were simulated in the original calibration period. Five pumping scenarios were simulated over a 30-year period based on (1) current pumping rates, (2) current rates of change in pumping, (3) decreased pumping in selected areas, (4) increased pumping in selected areas, and (5) redistribution and increase of pumping in selected areas. Model results show that although continued pumping at current rates will result in relatively minor declines in water levels (scenario 1 above), continued pumping at currently observed rates of change will result in drastic declines across large areas of focused withdrawals (scenario 2). Under the first scenario-in which current pumping rates are input to the model for the 30-year simulation period-water levels in the middle of the cones of depression centered on El Dorado and Monroe decrease less than 10 feet. In the second scenario-in which the current rate of change in pumpage is applied to the model-substantial declines occur in the proximity of most major pumpage centers. During the 1998-2027 model period, predicted water levels decline from 307 feet below sea level to 438 feet below sea level near El Dorado, from 58 feet below sea level to 277 feet below sea level near Pine Bluff, but only by about 25 feet-from 202 feet below sea level to 225 feet below sea level near Monroe. In the third scenario-in which minimum predicted water use figures supplied by selected facilities in Arkansas and decreased pumping estimates for Louisiana are applied to the model-simulated water levels are substantially higher at cones of depression around the major pumping centers of Monroe and El Dorado as compared to initial (1997) values. During the 1998-2027 model period, predicted water levels near Monroe increase from 202 feet below sea level to 133 feet below sea level; water levels near El Dorado increase from 307 feet below sea level to 123 feet below sea level. For the fourth scenario-in which maxi mum pr

Water-Resources Investigations Report↗

USGS2003

Comparing regeneration techniques for afforesting previously farmed bottomland hardwood sites in the Lower Mississippi Alluvial Valley, USA

A study was implemented to test site preparation methods and artificial regeneration of three oak (Quercus spp.) species on four agricultural fields in the Lower Mississippi Alluvial Valley in Louisiana, USA. Six years after establishment, few consistent differences were found in oak density between sowing acorn methods (seed drill versus broadcast seeding), autumn sowing versus spring sowing, and sowing acorns versus planting oak seedlings. Results indicated that some degree of site preparation is needed to establish oak seedlings but few differences were found between site preparation treatments. These results indicate that no one prescription for oak regeneration fits all potential afforestation projects in the Lower Mississippi Alluvial Valley. Successful bottomland hardwood afforestation projects will require plans that include specific objectives, site evaluation, and a regeneration prescription prior to sowing the first seed or planting the first seedling.

Conference Paper↗

USGS2006

Monitoring the Recovery of the Sparta Aquifer in Southern Arkansas and Northern Louisiana

The Sparta aquifer supplies the majority of water for industrial, municipal, and agricultural uses in Union County, Arkansas, and the surrounding area. In Union County, the Sparta aquifer has been used increasingly since development began in the early 1920s, resulting in water-level declines of more than 360 feet (ft) in some areas. In addition, water quality of the Sparta aquifer has degraded in some areas as usage has increased. In response to the declining water levels and degraded water quality, the Arkansas Natural Resources Commission designated the Sparta aquifer as a Critical Ground-Water Area in five counties of southern Arkansas in 1996. Ground-water flow models developed by the U.S. Geological Survey (USGS) indicate that withdrawals from the Sparta aquifer in Union County must be reduced to 28 percent of 1997 withdrawals (about 6 million gallons per day (Mgal/d)) to maintain water levels at or above the top of the Sparta Sand (Hays, 2000).

Fact Sheet↗