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Lari A. Knochenmus

Publications and source records attributed to Lari A. Knochenmus.

12 recordsLinked to original sources
USGS2011

Data network, collection, and analysis in the Diamond Valley flow system, central Nevada

Future groundwater development and its effect on future municipal, irrigation, and alternative energy uses in the Diamond Valley flow system are of concern for officials in Eureka County, Nevada. To provide a better understanding of the groundwater resources, the U.S. Geological Survey, in cooperation with Eureka County, commenced a multi-phase study of the Diamond Valley flow system in 2005. Groundwater development primarily in southern Diamond Valley has resulted in water-level declines since the 1960s ranging from less than 5 to 100 feet. Groundwater resources in the Diamond Valley flow system outside of southern Diamond Valley have been relatively undeveloped. Data collected during phase 2 of the study (2006-09) included micrometeorological data at 4 evapotranspiration stations, 3 located in natural vegetation and 1 located in an agricultural field; groundwater levels in 95 wells; water-quality constituents in aquifers and springs at 21 locations; lithologic information from 7 recently drilled wells; and geophysical logs from 3 well sites. This report describes what was accomplished during phase 2 of the study, provides the data collected, and presents the approaches to strengthen relations between evapotranspiration rates measured at micrometeorological stations and spatially distributed groundwater discharge. This report also presents the approach to improve delineation of areas of groundwater discharge and describes the current methodology used to improve the accuracy of spatially distributed groundwater discharge rates in the Diamond Valley flow system.

Open-File Report↗
USGS2008

Water Resources of the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah

INTRODUCTION This report summarizes results of a water-resources study for White Pine County, Nevada, and adjacent areas in east-central Nevada and western Utah. The Basin and Range carbonate-rock aquifer system (BARCAS) study was initiated in December 2004 through Federal legislation (Section 301(e) of the Lincoln County Conservation, Recreation, and Development Act of 2004; PL108-424) directing the Secretary of the Interior to complete a water-resources study through the U.S. Geological Survey, Desert Research Institute, and State of Utah. The study was designed as a regional water-resource assessment, with particular emphasis on summarizing the hydrogeologic framework and hydrologic processes that influence ground-water resources. The study area includes 13 hydrographic areas that cover most of White Pine County; in this report however, results for the northern and central parts of Little Smoky Valley were combined and presented as one hydrographic area. Hydrographic areas are the basic geographic units used by the State of Nevada and Utah and local agencies for water-resource planning and management, and are commonly defined on the basis of surface-water drainage areas. Hydrographic areas were further divided into subbasins that are separated by areas where bedrock is at or near the land surface. Subbasins are the subdivisions used in this study for estimating recharge, discharge, and water budget. Hydrographic areas are the subdivision used for reporting summed and tabulated subbasin estimates.

Scientific Investigations Report↗
USGS2006

Regional evaluation of the hydrogeologic framework, hydraulic properties, and chemical characteristics of the intermediate aquifer system underlying southern west-central Florida

Three major aquifer systems-the surficial aquifer system, the intermediate aquifer system, and the Floridan aquifer system-are recognized in the approximately 5,100-square-mile southern west-central Florida study area. The principal source of freshwater for all uses is ground water supplied from the three aquifer systems. Ground water from the intermediate aquifer system is considered only moderately abundant compared to the Upper Floridan aquifer, but it is an important source of water where the Upper Floridan aquifer contains water too mineralized for most uses. In the study area, the potential ground-water resources of the intermediate aquifer system were evaluated by regionally assessing the vertical and lateral distribution of hydrogeologic, hydraulic, and chemical characteristics. Although the intermediate aquifer system is considered a single entity, it is composed of multiple water-bearing zones separated by confining units. Deposition of a complex assemblage of carbonate and siliciclastic sediments during the late Oligocene to early Pliocene time resulted in discontinuities that are reflected in transitional and abrupt contacts between facies. Discontinuous facies produce water-bearing zones that may be locally well-connected or culminate abruptly. Changes in the depositional environment created the multilayered intermediate aquifer system that contains as many as three zones of enhanced water-bearing capacity. The water-bearing zones consist of indurated limestone and dolostone and in some places unindurated sand, gravel, and shell beds, and these zones are designated, in descending order, as Zone 1, Zone 2, and Zone 3. Zone 1 is thinnest (<80 feet thick) and is limited to <20 percent (southern part) of the study area. Zone 2, the only regionally extensive zone, is characterized by moderately low permeability. Zone 3 is found in about 50 percent of the study area, has the highest transmissivities, and generally is in good hydraulic connection with the underlying Upper Floridan aquifer. In parts of the study area, particularly in southwestern Hillsborough County and southeastern De Soto and Charlotte Counties, Zone 3 likely is contiguous with and part of the Upper Floridan aquifer. Transmissivity of the intermediate aquifer system ranges over five orders of magnitude from about 1 to more than 40,000 feet squared per day (ft2/d), but rarely exceeds 10,000 ft2/d. The overall transmissivity of the intermediate aquifer system is substantially lower (2 to 3 orders of magnitude) than the underlying Upper Floridan aquifer. Transmissivity varies vertically among the zones within the intermediate aquifer system; Zone 2 has the lowest median transmissivity (700 ft2/d), Zone 1 has a moderate median transmissivity (2,250 ft2/d), and Zone 3 has the highest median transmissivity (3,400 ft2/d). Additionally, the transmissivity varies geographically (from site to site) within a zone. Specifically, a region of relatively low transmissivity (<100 ft2/d) throughout the vertical extent of the intermediate aquifer system is present in the central part of the study area. This low transmissivity region is encompassed by a larger region of moderately low transmissivity (<1,000 ft2/d) that covers a large part of the study area. Clay beds and fine-grained carbonates form the confining units between the water-bearing zones and are characterized by low leakance. Leakance through the intermediate aquifer system confining units ranges over 4 orders of magnitude from 4.2x10-7 to 6.0x10-3 feet per day per foot [(ft/d)/ft]. Despite the large range, the geometric mean and median leakances of individual confining units are within the same order of magnitude, 10-5 (ft/d)/ft, which is 2 orders of magnitude less than the median leakance of the semiconfining unit within the Upper Floridan aquifer. Major ion concentrations in water from the intermediate aquifer system, and throughout the ground-water flow system, generally increase with depth. T

Scientific Investigations Report↗
USGS2001

Hydrology of the coastal springs ground-water basin and adjacent parts of Pasco, Hernando, and Citrus Counties, Florida

The coastal springs in Pasco, Hernando, and Citrus Counties, Florida consist of three first-order magnitude springs and numerous smaller springs, which are points of substantial ground-water discharge from the Upper Floridan aquifer. Spring flow is proportional to the water-level altitude in the aquifer and is affected primarily by the magnitude and timing of rainfall. Ground-water levels in 206 Upper Floridan aquifer wells, and surface-water stage, flow, and specific conductance of water from springs at 10 gaging stations were measured to define the hydrologic variability (temporally and spatially) in the Coastal Springs Ground-Water Basin and adjacent parts of Pasco, Hernando, and Citrus Counties. Rainfall at 46 stations and ground-water withdrawals for three counties, were used to calculate water budgets, to evaluate long-term changes in hydrologic conditions, and to evaluate relations among the hydrologic components. Predictive equations to estimate daily spring flow were developed for eight gaging stations using regression techniques. Regression techniques included ordinary least squares and multiple linear regression techniques. The predictive equations indicate that ground-water levels in the Upper Floridan aquifer are directly related to spring flow. At tidally affected gaging stations, spring flow is inversely related to spring-pool altitude. The springs have similar seasonal flow patterns throughout the area. Water-budget analysis provided insight into the relative importance of the hydrologic components expected to influence spring flow. Four water budgets were constructed for small ground-water basins that form the Coastal Springs Ground-Water Basin. Rainfall averaged 55 inches per year and was the only source of inflow to the Basin. The pathways for outflow were evapotranspiration (34 inches per year), runoff by spring flow (8 inches per year), ground-water outflow from upward leakage (11 inches per year), and ground-water withdrawal (2 inches per year). Recharge (rainfall minus evapotranspiration) to the Upper Floridan aquifer consists of vertical leakage through the surficial deposits. Discharge is primarily through springs and diffuse upward leakage that maintains the extensive swamps along the Gulf of Mexico. The ground-water basins had slightly different partitioning of hydrologic components, reflecting variation among the regions. Trends in hydrologic data were identified using nonparametric statistical techniques to infer long-term changes in hydrologic conditions, and yielded mixed results. No trend in rainfall was detected during the past century. No trend in spring flow was detected in 1931-98. Although monotonic trends were not detected, rainfall patterns are naturally variable from month to month and year to year; this variability is reflected in ground-water levels and spring flows. A decreasing trend in ground-water levels was detected in the Weeki Wachee well (1966-98), but the trend was statistically weak. At current ground-water withdrawal rates, there is no discernible affect on ground-water levels and spring flows. Sporadic data records, lack of continuous data, and inconsistent periods of record among the hydrologic components impeded analysis of long-term changes to the hydrologic system and interrelations among components. The ongoing collection of hydrologic data from index sites could provide much needed information to assess the hydrologic factors affecting the quantity and quality of spring flow in the Coastal Springs Ground-Water Basin.

Water-Resources Investigations Report↗
USGS1996

Descriptions of anisotropy and heterogeneity and their effect on ground-water flow and areas of contribution to public supply wells in a karst carbonate aquifer system

Delineation of areas of contribution to wells tapping a karst carbonate aquifer system can be extremely difficult using conventional approaches designed for isotropic and homogeneous aquifers, because ground-water flow tends to be through solution-enhanced conduits. Nonradial flow along preferential zones can result in inaccurate estimates of flow paths and traveltimes. Because of the large variability in factors affecting contributing areas and an imperfect understanding of how these factors can vary, the estimation of contributing areas is an approximation at best. To better understand the effects of aquifer anisotropy and heterogeneity on areas of contribution, an exploratory modeling approach was used. MODFLOW, a numerical flow model, and MODPATH, a particle tracking program, were used to generate time-related areas of contribution for six hypothetical carbonate aquifer system types. The six types were conceptualized to approximate different types of aquifer anisotropy and heterogeneity. These include: (1) an isotropic and homogeneous single-layer system; (2) an anisotropic in a horizontal plane single layer system; (3) a discrete vertically fractured single-layer system; (4) a multilayered system; (5) a doubly porous single-layer system; and (6) a vertically and horizontally interconnected heterogeneous system. The simulated aquifer anisotropy was 5:1 (Kxx/Kyy) determined from TENSOR2D results. The simulated discrete vertical fracture network represents locations inferred from mapped photolineaments. The simulated enhanced flow zones were determined from borehole video and geophysical logs. Areas of contribution were simulated for two prototype regions. The two prototypes were selected to be representative of the hydrologic diversity within the study area and were designated the Central Swamp and Lake Terrace regions. Localized conditions in pumping, production well distribution, and aquifer transmissivity affect the size, shape, and orientation of areas of contribution to public supply wells. The simulated areas of contribution are 60 percent larger in the Central Swamp region where pumpage is more than double and transmissivity is about half that of the Lake Terrace region. Although these factors are important, this study focused on the effects from hydrogeologic factors common to karst carbonate aquifer systems. This study indicates that the distribution and type of aquifer anisotropy and heterogeneity will affect the size, shape, and orientation of areas of contribution in a karst carbonate aquifer system. The size of the 50-year time-related areas of contribution ranged from 8.2 to 39.1 square miles in the Central Swamp region and from 4.0 to 18.3 square miles in the Lake Terrace region. Simulations showed that the size of areas of contribution is primarily affected by simulated withdrawal rates, effective porosity of the carbonate rock, and transmissivity. The shape and orientation of the simulated areas of contribution primarily result from aquifer anisotropy, well distribution, flow along solution-enhanced zones, and short-circuiting of flow through fracture networks. Comparisons also were made between protection zones delineated using analytical models and areas of contribution delineated using numerical models. The size of the 5-year time-related protection zone in the Central Swamp region using an analytical model was almost twice as large as the numerically simulated area of contribution, and more than eight times larger than the numerically simulated area of contribution in the Lake Terrace region. The differences in size are primarily the result of how the flow field is approximated. The analytical method assumes only lateral flow to wells but numerical methods allow particles to move laterally and vertically. Additionally, multiple-well-interference effects resulting from the close proximity of several pumping wells cause individual capture zones to converge or diverge, depending on the difference in pumping rates and orientation among the wells. Such an interpretation is not available from analytical methods. The simulated distributions of aquifer anisotropy and heterogeneity, in this study, were highly conceptualized, but were based on plausible occurrences of anisotropy and heterogeneity inherent in carbonate aquifer systems.

Florida↗