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At least 487 records · Page 27Linked to original sources
USGS1996

Water Budget for the Lahaina District, Island of Maui, Hawaii

Ground-water recharge is estimated as the residual component of a monthly water budget calculated using long-term average rainfall, streamflow, irrigation, pan-evaporation data, and soil characteristics. The water-budget components are defined seasonally, through the use of monthly data, and spatially by topographic and geologic areas, through the use of a geographic information system model. The long-term average ground-water recharge for the Lahaina District was estimated for three scenarios using 1923-78 land-use and irrigation data, 1986-93 land-use and irrigation data, and natural conditions. The average annual ground-water recharge rate for 1923-78 conditions is 190 million gallons per day, which is 45 percent of the sum of rainfall and irrigation. The recharge rate for 1986-93 conditions is 163 million gallons per day, which is 42 percent of rainfall plus irrigation. The recharge rate for natural conditions is 145 million gallons per day, which is 44 percent of rainfall.

Water-Resources Investigations Report↗
USGS1977

Ground water in the Lajas Valley, Puerto Rico

Lajas Valley is plagued with salinity and waterlogging problems of the soils. Use of brackish (500 milligrams per liter) ground water for irrigation compounded the problem until an irrigation-drainage system was constructed in 1955. Lajas Valley is an alluvium-filled trough between volcanic and limestone highlands. The alluvium, mostly clay and as much as 300 feet (90 meters) thick, contains brackish ground water except in the recharge areas located along the foothills. Artesian conditions exist in the eastern part of the valley where upward hydraulic gradients have increased due to the addition of irrigation water in the recharge areas. Wells yield up to 200 gallons per minute (13 liters per second) from alluvial fan deposits in the recharge areas. Wells tapping the buried limestone aquifer in the northwest will yield as much as 2,000 gallons per minute (126 liters per second). Results from a digital models show that a network of discharge wells could alleviate waterlogging of the soils in the artesians

Water-Resources Investigations Report↗
USGS1985

Management of ground water and evolving hydrogeologic studies in New Jersey : a heavily urbanized and industrialized state in the northeastern United States

New Jersey is the most densely populated and one of the most industrialized states in the United States. An abundance of freshwater and proximity to major northeastern metropolitan centers has facilitated this development. Pumpage of freshwater from all aquifers in the State in 1980 was 730 million gallons per day (2.76 million cubic meters per day). Management and efficient development of the ground-water resources of the State are the responsibility of the New Jersey Department of Environmental Protection. Laws have been enacted and updated by the State legislature to manage water allocation and to control the disposal of hazardous wastes. Present resource management is guided by the New Jersey Water-Supply Master Plan of 1981. Funding for management activities is partially derived from the sale of state-approved bonds. Effective planning and regional management require accurate and up-to-date hydrologic information and analyses. The U.S. Geological Survey, in cooperation with the New Jersey Geological Survey, is conducting three intensive ground-water studies involving the collection and interpretation of hydrologic data to meet the urgent water-management needs of New Jersey. These studies are part of a long-term cooperative program and are funded through the Water-Supply Bond Act of 1981. They began in 1983 and are scheduled to be completed in 1988. The project areas are situated in the New Jersey part of the Atlantic Coastal Plain in and near Atlantic City, Camden, and South River. They range in size from 400 to 1,200 mil (1,040 to 3,120 km2). The studies are designed to define the geology, hydrology, and geochemistry of the local ground-water systems. The results of these studies will enable the State to address more effectively major problems in these areas such as declining water levels, overpumping, saltwater intrusion, and ground-water contamination resulting from the improper disposal of hazardous wastes. Specific objectives of these studies by the U.S. Geological Survey are to (1) develop an accurate and up-to-date hydrogeologic data base, (2) design and implement a data-collection program and establish a computerized information management system, (3) refine the conceptualization of the ground-water flow system, and (4) define the geochemistry of the aquifer system by conducting a water-quality appraisal. The objectives are accomplished by standard hydrogeologic methods. Information concerning hydrogeologic framework, ground-water levels, water use, hydraulic characteristics, and water quality in the study areas is compiled from all available sources. Additional data needed are collected through well inventories, surface geophysical surveys, water-quality samplings, water-level measurements, and a well-drilling program. Interpretation of the flow system is based on the use of standard analytical techniques and digital flow modeling. Calibrated flow models will provide ground-water managers with a mechanism to develop and test regional water-supply strategies. Definition of the geochemistry of the aquifer system is accomplished through a variety of methods which depend on the problems and available data in the particular study area. The approach includes statistical analysis of water-quality data, reaction-path modeling, and determination of the movement of chemical constituents using analytical and numerical modeling techniques. A combined staff of 25 to 30 professionals and technicians from the New Jersey District office of the U.S. Geological Survey is committed to the three studies. The staff has specialists in geohydrology, numerical modeling, geochemistry, geophysics, and computer science. The findings of these studies will be published in data reports, interpretive reports, instructional manuals and journal articles.

New Jersey↗
USGS1982

Modifications and corrections to the finite-difference model for simulation of three-dimensional ground-water flow

This report describes modifications incorporated into the finite-difference model for simulation of groundwater flow in three dimensions. These modifications extend the application of this model to simulations involving head-dependent sources and sinks (i.e., rivers, evapotranspiration, and springs or drains). Other modifications are made that enhance the iterative-solution process of the Strongly Implicit Procedure (SIP). An acceleration (or dampening) factor is introduced to the matrix equation that is to be solved, and optional methods of computing iteration parameters are incorporated into the original model. This report also describes corrections to the model that eliminate errors in the equation formulation and in mass-balance computations of certain types of simulations. Additional data-input instructions, definitions of new variables, and a list of program-statement changes are given in an appendix. (USGS)

Water-Resources Investigations Report↗
USGS2005

Water quality and ground-water/surface-water interactions along the John River near Anaktuvuk Pass, Alaska, 2002-2003

The headwaters of the John River are located near the village of Anaktuvuk Pass in the central Brooks Range of interior Alaska . With the recent construction of a water -supply system and a wastewater-treatment plant, most homes in Anaktuvuk Pass now have modern water and wastewater systems. The effluent from the treatment plant discharges into a settling pond near a tributary of the John River . The headwaters of the John River are adjacent to Gates of the Arctic National Park and Preserve, and the John River is a designated Wild River . Due to the concern about possible water - quality effects from the wastewater effluent, the hydrology of the John River near Anaktuvuk Pass was studied from 2002 through 2003 . Three streams form the John River at Anaktuvuk Pass : Contact Creek, Giant Creek, and the John River Tributary. These streams drain areas of 90.3 km (super 2) , 120 km (super 2) , and 4.6 km (super 2) , respectively. Water - quality data collected from these streams from 2002 -03 indicate that the waters are a calcium-bicarbonate type and that Giant Creek adds a sulfate component to the John River. The highest concentrations of bicarbonate, calcium, sodium, sulfate, and nitrate were found at the John River Tributary below the wastewater-treatment lagoon. These concentrations have little effect on the water quality of the John River because the flow of the John River Tributary is only about 2 percent of the John River flow. To better understand the ground-water/surface-water interactions of the upper John River, a numerical groundwater-flow model of the headwater area of the John River was constructed. Processes that occur during spring break-up, such as thawing of the active layer and the frost table and the resulting changes of storage capacity of the aquifer, were difficult to measure and simulate. Application and accuracy of the model is limited by the lack of specific hydrogeologic data both spatially and temporally. However, during the mid-winter and open-water periods, the model provided acceptable results and was coupled with a particle-movement model to simulate the movement and possible extent of conservative particles from the wastewater-treatment-plant lagoon.

Scientific Investigations Report↗
USGS2004

Virus fate and transport during recharge using recycled water at a research field site in the Montebello Forebay, Los Angeles County, California, 1997-2000

Total and fecal coliform bacteria distributions in subsurface water samples collected at a research field site in Los Angeles County were found to increase from nondetectable levels immediately before artificial recharge using tertiary-treated municipal wastewater (recycled water). This rapid increase indicates that bacteria can move through the soil with the percolating recycled water over intervals of a few days and vertical and horizontal distances of about 3 meters. This conclusion formed the basis for three field-scale experiments using bacterial viruses (bacteriophage) MS2 and PRD1 as surrogates for human enteric viruses and bromide as a conservative tracer to determine the fate and transport of viruses in recycled water during subsurface transport under actual recharge conditions. The research field site consists of a test basin constructed adjacent to a large recharge facility (spreading grounds) located in the Montebello Forebay of Los Angeles County, California. The soil beneath the test basin is predominantly medium to coarse, moderately sorted, grayish-brown sand. The three tracer experiments were conducted during August 1997, August-September 1998, and August 2000. For each experiment, prepared solutions of bacteriophage and bromide were sprayed on the surface of the water in the test basin and injected, using peristaltic pumps, directly into the feed pipe delivering the recycled water to the test basin. Extensive data were obtained for water samples collected from the test basin itself and from depths of 0.3, 0.6, 1.0, 1.5, 3.0, and 7.6 meters below the bottom of the test basin. The rate of bacteriophage inactivation in the recycled water, independent of any processes occurring in the subsurface, was determined from measurements on water samples from the test basin. Regression analysis of the ratios of bacteriophage to bromide was used to determine the attenuation rates for MS2 and PRD1, defined as the logarithmic reduction in the ratio during each experiment. Although the inactivation rates increased during the third tracer experiment, they were nearly two orders of magnitude less than the attenuation rates. Therefore, adsorption, not inactivation, is the predominant removal mechanism for viruses during artificial recharge. Using the colloid-filtration model, the collision efficiency was determined for both bacteriophage during the second and third field-scale tracer experiments. The collision efficiency confirms that more favorable attachment conditions existed for PRD1, especially during the third tracer experiment. The different collision efficiencies between the second and third tracer experiments possibly were due to changing hydraulic conditions at the research field site during each experiment. The field data suggest that an optimal management scenario might exist to maximize the amount of recycled water that can be applied to the spreading grounds while still maintaining favorable attachment conditions for virus removal and thereby ensuring protection of the ground-water supply.

Scientific Investigations Report↗
USGS2013

Simulating stream transport of nutrients in the eastern United States, 2002, using a spatially-referenced regression model and 1:100,000-scale hydrography

Existing Spatially Referenced Regression on Watershed attributes (SPARROW) nutrient models for the northeastern and southeastern regions of the United States were recalibrated to achieve a hydrographically consistent model with which to assess nutrient sources and stream transport and investigate specific management questions about the effects of wetlands and atmospheric deposition on nutrient transport. Recalibrated nitrogen models for the northeast and southeast were sufficiently similar to be merged into a single nitrogen model for the eastern United States. The atmospheric deposition source in the nitrogen model has been improved to account for individual components of atmospheric input, derived from emissions from agricultural manure, agricultural livestock, vehicles, power plants, other industry, and background sources. This accounting makes it possible to simulate the effects of altering an individual component of atmospheric deposition, such as nitrate emissions from vehicles or power plants. Regional differences in transport of phosphorus through wetlands and reservoirs were investigated and resulted in two distinct phosphorus models for the northeast and southeast. The recalibrated nitrogen and phosphorus models account explicitly for the influence of wetlands on regional-scale land-phase and aqueous-phase transport of nutrients and therefore allow comparison of the water-quality functions of different wetland systems over large spatial scales. Seven wetland systems were associated with enhanced transport of either nitrogen or phosphorus in streams, probably because of the export of dissolved organic nitrogen and bank erosion. Six wetland systems were associated with mitigating the delivery of either nitrogen or phosphorus to streams, probably because of sedimentation, phosphate sorption, and ground water infiltration.

Scientific Investigations Report↗
USGS2008

Hydrochemical Regions of the Glacial Aquifer System, Northern United States, and Their Environmental and Water-Quality Characteristics

The glacial aquifer system in the United States is a large (953,000 square miles) regional aquifer system of heterogeneous composition. As described in this report, the glacial aquifer system includes all unconsolidated geologic material above bedrock that lies on or north of the line of maximum glacial advance within the United States. Examining ground-water quality on a regional scale indicates that variations in the concentrations of major and minor ions and some trace elements most likely are the result of natural variations in the geologic and physical environment. Study of the glacial aquifer system was designed around a regional framework based on the assumption that two primary characteristics of the aquifer system can affect water quality: intrinsic susceptibility (hydraulic properties) and vulnerability (geochemical properties). The hydrochemical regions described in this report were developed to identify and explain regional spatial variations in ground-water quality in the glacial aquifer system within the hypothetical framework context. Data analyzed for this study were collected from 1991 to 2003 at 1,716 wells open to the glacial aquifer system. Cluster analysis was used to group wells with similar ground-water concentrations of calcium, chloride, fluoride, magnesium, potassium, sodium, sulfate, and bicarbonate into five unique groups. Maximum Likelihood Classification was used to make the extrapolation from clustered groups of wells, defined by points, to areas of similar water quality (hydrochemical regions) defined in a geospatial model. Spatial data that represented average annual precipitation, average annual temperature, land use, land-surface slope, vertical soil permeability, average soil clay content, texture of surficial deposits, type of surficial deposit, and potential for ground-water recharge were used in the Maximum Likelihood Classification to classify the areas so the characteristics of the hydrochemical regions would resemble the characteristics of the clusters. The result of the Maximum Likelihood Classification is a map showing five hydrochemical regions of the glacial aquifer system. Statistical analysis of ion concentrations (calcium, chloride, fluoride, magnesium, sodium, potassium, sulfate, and bicarbonate) in samples collected from wells completed in the glacial aquifer system illustrates that variations in water quality can be explained, in part, by related environmental characteristics that control the movement of ground water through the aquifer system. A comparison of median concentrations of chemical constituents in ground water among the five hydrochemical regions indicates that ground water in the Midwestern Agricultural Region, the Urban-Influenced Region, and the Western Agriculture and Grassland Region has the highest concentrations of major and minor ions, whereas ground water in the Northern and Great Lakes Forested Region and the Mountain and Coastal Forested Region has the lowest concentrations of these ions. Median concentrations of barium, arsenic, lithium, boron, strontium, and nitrite plus nitrate as nitrogen also are significantly different among the hydrochemical regions.

Scientific Investigations Report↗
USGS1983

Numerical simulation of the alluvium and terrace aquifer along the North Canadian River from Canton Lake to Lake Overholser, central Oklahoma

Alluvium and terrace deposits of Quaternary age, which cover an area of about 400 square miles along the North Canadian River between Canton Lake and Lake Overholser, locally yield as much as 500 gallons per minute to wells. The deposits are as much as 100 feet thick and consist of clay, silt, sand, and gravel, with sand-sized material dominating. The underlying bedrock is Permian sandstone and shale. The amount of water stored in the aquifer during 1980 was estimated to be 4.00 x 1010 cubic feet. A digital model was used to estimate the ability of the aquifer to continue to supply water for irrigation, industry, and domestic use. A block-centered, finite-difference model with 1 mile node spacing was used to project the amount and distribution of water in the aquifer in the future. The model was calibrated using the aquifer discharge to the North Canadian River and the difference between computed and measured heads. The model was calibrated using recharge rate of 1 inch per year, a horizontal hydraulic conductivity of 4.5 x 10 -4 feet per second and a specific yield of 0.16. Model simulations using the 1979 pumping rate, a projected pumping rate (based on expected increases in water use), and double the projected increase in pumping rate were made to 1993. With the 1979 pumping rate, the volume of water in storage in 1993 is 3.88 x 10 10 cubic feet and ground-water discharge to the North Canadian River is 10.9 cubic feet per second. With the projected pumping increase, the volume of water in storage is 3.81 x 1010 cubic feet and ground-water discharge to the stream is 6.91 cubic feet per second. At double the projected increase in pumping rate, the volume of water in storage is 3.74 x 1010 cubic feet and the ground-water discharge is 2.93 cubic feet per second.

Water-Resources Investigations Report↗
USGS1993

Geohydrology and simulation of flow and water levels in the aquifer system in the Mud Lake area of the eastern Snake River plain, eastern Idaho

Water users rely on surface water and ground water to irrigate crops and to maintain lakes on wildlife refuges in the 2,200-square-mile Mud Lake study area. Ground-water development between the late 1970's and 1989 increased withdrawals from about 240,000 acre-feet in 1983 to about 370,000 acre-feet in 1990. Concurrent with ground-water development, change from subirrigation to sprinkler irrigation was predicted to reduce recharge by 95,000 acre-feet, according to an independent study. Of the 660,000 acre-feet total estimated recharge from precipitation and irrigation in the study area in 1980, half was in the area in which irrigation methods were changed. Water managers need the ability to evaluate the effects of water-use changes on the future supply of surface water and ground water. Basalt and rhyolite predominate on the surface and in the subsurface of the study area. Total basalt thickness is less than 4,000 feet; total sediment thickness (clay, silt, sand, and gravel) is less than 1,000 feet. Basalt and sediment interbeds contribute to confined ground-water conditions and affect movement and supply of water in parts of the aquifer system. Estimated losses from and gains to perennial streams and lakes in 1980 were each about 110,000 acre-feet. Water-table altitudes ranged from about 4,500 to 6,200 feet above sea level, and water-table gradients were 3 to 120 feet per mile. Underflow from basins tributary to the study area was estimated to be about 450,000 acre-feet in 1980; measured discharge from flowing wells was about 10,000 acre-feet. A five-layer, three-dimensional, finite-difference, numerical ground-water flow model was calibrated by trial-and-error to assumed 1980 steady-state hydrologic conditions to obtain a better understanding of the geohydrology and provide a tool to evaluate water-use alternatives. Water-level gradients simulated by the model were similar to gradients measured in 1980. Simulated underflow across model boundaries for 1980 was 932,000 acre-feet. Simulated losses from and gains to most streams and lakes were within 2 percent of estimated values. Simulated discharge from flowing wells matched measurements for 1980. An attempt to calibrate the numerical model to transient hydrologic conditions in monthly increments from 1981 to 1990 was discontinued because available data did not justify changes that were indicated by model simulations.

Idaho↗
USGS2002

Geohydrology and Numerical Simulation of Alternative Pumping Distributions and the Effects of Drought on the Ground-Water Flow System of Tinian, Commonwealth of the Northern Mariana Islands

Ground water in a freshwater lens is the main source of freshwater on Tinian, Commonwealth of the Northern Mariana Islands. Four major geologic units make up the island with high-permeability limestone units overlying low-permeability volcanic rocks. Estimates of limestone hydraulic conductivity range from 21 to 23,000 feet per day. Estimates of water-budget components for Tinian are 82 inches per year of rainfall, about 6 inches per year of runoff, 46 inches per year of evapotranspiration, and 30 inches per year of recharge. From 1990?97, ground-water withdrawal from the Municipal well, the major source of water, averaged about 780 gallons per minute. A two-dimensional, steady-state, ground-water flow model using the computer code SHARP was developed for Tinian, to enhance the understanding of (1) the distribution of aquifer hydraulic properties, (2) the conceptual framework of the ground-water flow system, and (3) the effects of various pumping distributions and drought on water levels and the freshwater/saltwater transition zone. For modeling purposes, Tinian was divided into three horizontal hydraulic-conductivity zones: (1) highly permeable limestone, (2) less-permeable, clay-rich limestone, and (3) low-permeability volcanic rocks. The following horizontal hydraulic conductivities were estimated: (1) 10,500 feet per day for the highly permeable limestone, (2) 800 feet per day for the less-permeable clay-rich limestone, and (3) 0.2 foot per day for the volcanic rocks. To estimate the hydrologic effects of different pumping distributions on the aquifer, three different steady-state pumping scenarios were simulated, (1) a scenario with no ground-water pumping, (2) a 2001-pumping scenario, and (3) a maximum-pumping scenario. The results of the no-pumping scenario showed that the freshwater/saltwater interface beneath the Municipal well would be about 7 feet deeper and ground-water discharge to the coast would be higher along both the east and west coasts of the island when compared with 1990-97 pumping conditions. For the maximum pumping scenario, the model-calculated freshwater/saltwater interface is about 7 feet shallower than the position calculated in the base-case scenario. To estimate the hydrologic effects of drought on the freshwater lens, the 2001- and maximum-pumping scenarios were simulated using three combinations of aquifer porosity values covering a range of possible limestone properties. In all scenarios, recharge was reduced to 10 percent of average estimated recharge and the transient response was simulated for 1 year. These simulations demonstrated that the ground-water resource is adequate to withstand a drought similar to that experienced in 1998 using existing infrastructure.

Water-Resources Investigations Report↗
USGS1984

Application of the conjugate-gradient method to ground-water models

The conjugate-gradient method can solve efficiently and accurately finite-difference approximations to the ground-water flow equation. An aquifer-simulation model using the conjugate-gradient method was applied to a problem of ground-water flow in an alluvial aquifer at the Rocky Mountain Arsenal, Denver, Colorado. For this application, the accuracy and efficiency of the conjugate-gradient method compared favorably with other available methods for steady-state flow. However, its efficiency relative to other available methods depends on the nature of the specific problem. The main advantage of the conjugate-gradient method is that it does not require the use of iteration parameters, thereby eliminating this partly subjective procedure. (USGS)

Water-Resources Investigations Report↗
USGS1981

Hydrogeology, estimated impact, and regional well monitoring of effects of subsurface wastewater injection, Tampa Bay area, Florida

Six proposed injection sites are located in Pinellas County, Fla., and the city of St. Petersburg. Projected maximum injection rate, if all sites become operational, will be about 40 million gallons per day. The injection zone at the proposed sites is in a consistently dolomitized section of the Avon Park Limestone in the lower part of the Floridan aquifer. The injection zone contains saline ground water that has a chloride concentration of 19,000 to 20,000 milligrams per liter. Pressure and velocity changes were computed at selected regional locations in the upper and lower parts of the Floridan aquifer. Results of the model computations suggest that the regional impact after 20 years of injection will be small. Three locations are proposed for regional monitoring of subsurface injection. They are in the vicinity of the intersection of highways U.S. 19 and U.S. 60 in Pinellas County, Sun City in Hillsborough County, and the intersection of Sheldon Road and Gunn Highway in Hillsborough County. (USGS)

Water-Resources Investigations Report↗
USGS1990

Geohydrology and water quality of confined-drift aquifers in the Brooten-Belgrade area, west-central Minnesota

Confined-drift aquifers in six aquifer zones identified in a 1,300-square-mile area of west-central Minnesota near Brooten and Belgrade range in thickness from 5 to 110 feet. Transmissivities generally range from 500 to 10,000 feet squared per day, and theoretical well yields generally range from 100 to 900 gallons per minute. Regional ground-water flow in the confined-drift aquifers is to the southeast with local discharge to the East and Middle Branches of the Chippewa River, the North Fork Crow and Sauk Rivers, and to smaller streams, lakes, wetlands, and wells. Water levels near high-capacity pumped wells generally fluctuate 5 to 40 feet annually, compared to annual fluctuations of less than 5 feet in the unconfined aquifer. Water from confined-drift aquifers generally is suitable for most uses. The water is hard to very hard and contains locally elevated concentrations of iron, manganese, and dissolved solids. Results from a ground-water-flow model indicate that increased pumping from confined aquifers in the area would not adversely affect water levels. The addition of 10 to 20 hypothetical wells, pumping 123 to 246 million gallons per year, generally resulted in regional water-level declines of 0.1 to 1.0 feet. Simulations showed that the reduced recharge and increased pumping resulting from a 3-year drought probably would lower water levels between 5 and 10 feet regionally in the confined-drift aquifers and as much as 20 feet locally in the unconfined aquifer. Ground-water discharge to the East Branch Chippewa and North Fork Crow Rivers during the simulated drought would be reduced by 38 percent of 1984 conditions.

Minnesota↗
USGS1977

Simulated changes in ground-water levels resulting from proposed phosphate mining, west-central Florida; preliminary results

A digital model of two-dimensional ground-water flow was used to simulate projected changes in the Floridan aquifer potentiometric surface in 1985 and 2000, resulting from proposed ground-water developments by the phosphate mining industry in west-central Florida. The .model was calibrated under steady-state conditions to simulate the September 1975 potentiometric surface. Under one development plan, existing phosphate mines in Polk County would continue to withdraw ground water at 1975 rates, until phased out as the ore is depleted; no new mines would be introduced. Preliminary results indicate that under this plan, maximum simulated recovery of the potentiometric surface is 11.9 feet by 1985 and 36.5 feet by 2000. Under an alternative plan, all proposed mines in Polk, Hardee, DeSoto, Hillsborough and Manatee Counties would begin operations: in addition to the continuation and phasing out of existing mines. Preliminary results indicate that the potentiometric surface would generally recover in Polk County and decline elsewhere in the modeled area. Maximum simulated recovery is 4.5 feet by 1985 and 29.6 feet by 2000; maximum simulated drawdown is 15.1 feet by 1985 and feet by 2000. All results are preliminary and subject to revision as the investigation continues.

Open-File Report↗
USGS2009

Processing, Analysis, and General Evaluation of Well-Driller Logs for Estimating Hydrogeologic Parameters of the Glacial Sediments in a Ground-Water Flow Model of the Lake Michigan Basin

In 2005, the U.S. Geological Survey began a pilot study for the National Assessment of Water Availability and Use Program to assess the availability of water and water use in the Great Lakes Basin. Part of the study involves constructing a ground-water flow model for the Lake Michigan part of the Basin. Most ground-water flow occurs in the glacial sediments above the bedrock formations; therefore, adequate representation by the model of the horizontal and vertical hydraulic conductivity of the glacial sediments is important to the accuracy of model simulations. This work processed and analyzed well records to provide the hydrogeologic parameters of horizontal and vertical hydraulic conductivity and ground-water levels for the model layers used to simulated ground-water flow in the glacial sediments. The methods used to convert (1) lithology descriptions into assumed values of horizontal and vertical hydraulic conductivity for entire model layers, (2) aquifer-test data into point values of horizontal hydraulic conductivity, and (3) static water levels into water-level calibration data are presented. A large data set of about 458,000 well driller well logs for monitoring, observation, and water wells was available from three statewide electronic data bases to characterize hydrogeologic parameters. More than 1.8 million records of lithology from the well logs were used to create a lithologic-based representation of horizontal and vertical hydraulic conductivity of the glacial sediments. Specific-capacity data from about 292,000 well logs were converted into horizontal hydraulic conductivity values to determine specific values of horizontal hydraulic conductivity and its aerial variation. About 396,000 well logs contained data on ground-water levels that were assembled into a water-level calibration data set. A lithology-based distribution of hydraulic conductivity was created by use of a computer program to convert well-log lithology descriptions into aquifer or nonaquifer categories and to calculate equivalent horizontal and vertical hydraulic conductivities (K and KZ, respectively) for each of the glacial layers of the model. The K was based on an assumed value of 100 ft/d (feet per day) for aquifer materials and 1 ft/d for nonaquifer materials, whereas the equivalent KZ was based on an assumed value of 10 ft/d for aquifer materials and 0.001 ft/d for nonaquifer materials. These values were assumed for convenience to determine a relative contrast between aquifer and nonaquifer materials. The point values of K and KZ from wells that penetrate at least 50 percent of a model layer were interpolated into a grid of values. The K distribution was based on an inverse distance weighting equation that used an exponent of 2. The KZ distribution used inverse distance weighting with an exponent of 4 to represent the abrupt change in KZ that commonly occurs between aquifer and nonaquifer materials. The values of equivalent hydraulic conductivity for aquifer sediments needed to be adjusted to actual values in the study area for the ground-water flow modeling. The specific-capacity data (discharge, drawdown, and time data) from the well logs were input to a modified version of the Theis equation to calculate specific capacity based horizontal hydraulic conductivity values (KSC). The KSC values were used as a guide for adjusting the assumed value of 100 ft/d for aquifer deposits to actual values used in the model. Water levels from well logs were processed to improve reliability of water levels for comparison to simulated water levels in a model layer during model calibration. Water levels were interpolated by kriging to determine a composite water-level surface. The difference between the kriged surface and individual water levels was used to identify outlier water levels. Examination of the well-log lithology data in map form revealed that the data were not only useful for model input, but also were useful for understanding th

Scientific Investigations Report↗
USGS2020

Changing storm conditions in response to projected 21st century climate change and the potential impact on an arctic barrier island–lagoon system—A pilot study for Arey Island and Lagoon, eastern Arctic Alaska

Executive Summary Arey Lagoon, located in eastern Arctic Alaska, supports a highly productive ecosystem, where soft substrate and coastal wet sedge fringing the shores are feeding grounds and nurseries for a variety of marine fish and waterfowl. The lagoon is partially protected from the direct onslaught of Arctic Ocean waves by a barrier island chain (Arey Island) which in itself provides important habitat for migratory shorebirds and waterfowl. In this work, numerically modeled waves and water levels are computed under the provision of sea-level rise and changing conditions brought about by 21st century climate variability. Model results, supported by observations, are used to assess the stability of the barrier chain and spatiotemporal changes in flood patterns across fringing coastal wet sedge areas. The results aim to support studies that investigate the possibility of new biological succession trajectories and loss or increase of habitat areas.

Alaska↗
USGS1982

A Numerical model to evaluate proposed ground-water allocations in southwest Kansas

A computer model was developed to assist the Southwest Kansas Groundwater Management District No. 3 in the evaluation of applications to appropriate ground water. The model calculated the drawdown due from a proposed well at all existing wells in the section of the proposed well and at all wells in the adjacent eight sections. The depletion expected in the 9-square-mile area due to all existing wells and the proposed well is computed and compared with allowable limits defined by the management district. An optional program permits the evaluation of allowable depletion for one or more townships. All options are designed to run interactively, thus allowing for immediate evaluation of proposed ground-water withdrawals. (USGS)

Water-Resources Investigations Report↗