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O. Lehn Franke

Publications and source records attributed to O. Lehn Franke.

10 recordsLinked to original sources
USGS2010

Nitrate Loads and Concentrations in Surface-Water Base Flow and Shallow Groundwater for Selected Basins in the United States, Water Years 1990-2006

Hydrograph separation was used to determine the base-flow component of streamflow for 148 sites sampled as part of the National Water-Quality Assessment program. Sites in the Southwest and the Northwest tend to have base-flow index values greater than 0.5. Sites in the Midwest and the eastern portion of the Southern Plains generally have values less than 0.5. Base-flow index values for sites in the Southeast and Northeast are mixed with values less than and greater than 0.5. Hypothesized flow paths based on relative scaling of soil and bedrock permeability explain some of the differences found in base-flow index. Sites in areas with impermeable soils and bedrock (areas where overland flow may be the primary hydrologic flow path) tend to have lower base-flow index values than sites in areas with either permeable bedrock or permeable soils (areas where deep groundwater flow paths or shallow groundwater flow paths may occur). The percentage of nitrate load contributed by base flow was determined using total flow and base flow nitrate load models. These regression-based models were calibrated using available nitrate samples and total streamflow or base-flow nitrate samples and the base-flow component of total streamflow. Many streams in the country have a large proportion of nitrate load contributed by base flow: 40 percent of sites have more than 50 percent of the total nitrate load contributed by base flow. Sites in the Midwest and eastern portion of the Southern Plains generally have less than 50 percent of the total nitrate load contributed by base flow. Sites in the Northern Plains and Northwest have nitrate load ratios that generally are greater than 50 percent. Nitrate load ratios for sites in the Southeast and Northeast are mixed with values less than and greater than 50 percent. Significantly lower contributions of nitrate from base flow were found at sites in areas with impermeable soils and impermeable bedrock. These areas could be most responsive to nutrient management practices designed to reduce nutrient transport to streams by runoff. Conversely, sites with potential for shallow or deep groundwater contribution (some combination of permeable soils or permeable bedrock) had significantly greater contributions of nitrate from base flow. Effective nutrient management strategies would consider groundwater nitrate contributions in these areas. Mean annual base-flow nitrate concentrations were compared to shallow-groundwater nitrate concentrations for 27 sites. Concentrations in groundwater tended to be greater than base-flow concentrations for this group of sites. Sites where groundwater concentrations were much greater than base-flow concentrations were found in areas of high infiltration and oxic groundwater conditions. The lack of correspondingly high concentrations in the base flow of the paired surface-water sites may have multiple causes. In some settings, there has not been sufficient time for enough high-nitrate shallow groundwater to migrate to the nearby stream. In these cases, the stream nitrate concentrations lag behind those in the shallow groundwater, and concentrations may increase in the future as more high-nitrate groundwater reaches the stream. Alternatively, some of these sites may have processes that rapidly remove nitrate as water moves from the aquifer into the stream channel. Partitioning streamflow and nitrate load between the quick-flow and base-flow portions of the hydrograph coupled with relative scales of soil permeability can infer the importance of surface water compared to groundwater nitrate sources. Study of the relation of nitrate concentrations to base-flow index and the comparison of groundwater nitrate concentrations to stream nitrate concentrations during times when base-flow index is high can provide evidence of potential nitrate transport mechanisms. Accounting for the surface-water and groundwater contributions of nitrate is crucial to effective management and remediat

Scientific Investigations Report↗
USGS2007

Water Budgets: Foundations for Effective Water-Resources and Environmental Management

INTRODUCTION Water budgets provide a means for evaluating availability and sustainability of a water supply. A water budget simply states that the rate of change in water stored in an area, such as a watershed, is balanced by the rate at which water flows into and out of the area. An understanding of water budgets and underlying hydrologic processes provides a foundation for effective water-resource and environmental planning and management. Observed changes in water budgets of an area over time can be used to assess the effects of climate variability and human activities on water resources. Comparison of water budgets from different areas allows the effects of factors such as geology, soils, vegetation, and land use on the hydrologic cycle to be quantified. Human activities affect the natural hydrologic cycle in many ways. Modifications of the land to accommodate agriculture, such as installation of drainage and irrigation systems, alter infiltration, runoff, evaporation, and plant transpiration rates. Buildings, roads, and parking lots in urban areas tend to increase runoff and decrease infiltration. Dams reduce flooding in many areas. Water budgets provide a basis for assessing how a natural or human-induced change in one part of the hydrologic cycle may affect other aspects of the cycle. This report provides an overview and qualitative description of water budgets as foundations for effective water-resources and environmental management of freshwater hydrologic systems. Perhaps of most interest to the hydrologic community, the concepts presented are also relevant to the fields of agriculture, atmospheric studies, meteorology, climatology, ecology, limnology, mining, water supply, flood control, reservoir management, wetland studies, pollution control, and other areas of science, society, and industry. The first part of the report describes water storage and movement in the atmosphere, on land surface, and in the subsurface, as well as water exchange among these compartments. Our ability to measure these phenomena and inherent uncertainties in measurement techniques also are discussed. The latter part of the report presents a number of case studies that illustrate how water-budget studies are conducted, documents how human activities affect water budgets, and describes how water budgets are used to address water and environmental issues.

Circular↗
USGS1999

Sustainability of ground-water resources

The pumpage of fresh ground water in the United States in 1995 was estimated to be approximately 77 billion gallons per day (Solley and others, 1998), which is about 8 percent of the estimated 1 trillion gallons per day of natural recharge to the Nation's ground-water systems (Nace, 1960). From an overall national perspective, the ground-water resource appears ample. Locally, however, the availability of ground water varies widely. Moreover, only a part of the ground water stored in the subsurface can be recovered by wells in an economic manner and without adverse consequences.

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USGS1998

Ground water and surface water: A single resource

The importance of considering ground water and surface water as a single resource has become increasingly evident. Issues related to water supply, water quality, and degradation of aquatic environments are reported on frequently. The interaction of ground water and surface water has been shown to be a significant concern in many of these issues. Contaminated aquifers that discharge to streams can result in long-term contamination of surface water; conversely, streams can be a major source of contamination to aquifers. Surface water commonly is hydraulically connected to ground water, but the interactions are difficult to observe and measure. The purpose of this report is to present our current understanding of these processes and activities as well as limitations in our knowledge and ability to characterize them.

Circular↗
USGS1998

Estimating areas contributing recharge to wells, lessons from previous studies

Factors relating to the estimation of areas contributing recharge to wells, such as complexity of the ground-water flow system, effects of changing hydrologic conditions, and effects of well-screen locations and pumping rates, are reviewed. The point of view that simulation is the best means to obtain physically based estimates of contributing areas is emphasized. An extensive list of USGS reports that include estimation of contributing areas is provided.

Circular↗
USGS1989

Bias in groundwater samples caused by wellbore flow

Design of physical installations and sampling procedures for ground-water monitoring networks, particularly for detection and analysis of possible contaminants, is a topic of great scientific and practical interest at the present time. Recent practice in the design of monitoring networks associated with known contaminant sources sometimes includes an array of monitoring wells with long well screens (up to 50 feet or more). Numerical experiments with a detailed three-dimensional ground-water flow model indicate that significant wellbore flow can occur in contaminant monitoring wells with long well screens that are embedded in homogeneous aquifers with very small vertical head differences in the aquifer. This ``short circuiting'' of flow through boreholes should exist at some level on all scales. Consideration of the general flow pattern within the borehole, the flow pattern in the aquifer adjacent to the borehole, and the process of obtaining water samples from the borehole suggests that in many situations the practice of installing long well screens in contaminant monitoring wells should be abandoned.

Journal of Hydraulic Engineering↗
USGS1988

Quantitative assessment of the shallow ground-water flow system associated with Connetquot Brook, Long Island, New York

Streamflow on Long Island is derived principally from shallow ground water that flows above the deeper regional flow system. The movement of shallow ground water was studied during 1975-82 at Connetquot Brook, an undisturbed stream in Connetquot River State Park, in south-central Long Island, New York. The investigation encompassed (1) field studies of streamflow, ground-water levels, and age of water as indicated by tritium and dissolved-oxygen concentrations and (2) numerical simulation of the shallow flow system to evaluate the hydraulic factors that govern the direction of shallow ground-water flow near and beneath the stream. Analysis of water-level data indicates that ground water flows essentially horizontally throughout the drainage basin except near and beneath the stream, where it moves vertically upward toward the stream discharge boundary. Water levels in wells driven directly into the streambed and into the streambank at three sites were 1 to 2 feet higher than stream stage in the first 5 feet of penetration. Increases in head, which were detected to depths of 30 feet beneath the streambed, indicate upward movement of water above that depth. Hydraulic conductivity of the streambed sediments was calculated from head gradients in the streambed and from measured stream seepage; values were between 11 and 15 feet per day. Water samples from selected wells were analyzed for dissolved-oxygen and tritium concentrations to determine the relative age of the water in an attempt to locate the bottom boundary of the shallow flow system. Dissolved oxygen showed no pattern, but tritium concentrations about 1,000 feet from the stream were lower than those near the stream. The tritium concentrations indicate that the lower flow boundary was between 45 and 100 feet below the water table. A two-dimensional cross-sectional flow model of the shallow flow system was developed. The near-stream model response compared well with field data when the streambed discharge boundary was simulated as a uniform leaky bed. A systematic sensitivity analysis was done to determine which factors have the greatest influence on hydraulic head in the system. Ten dimensional parameters that describe the important aspects of the flow system were combined into a series of dimensionless parameters to simplify analysis. Results indicate that (1) streambed factors (width and hydraulic conductivity) are most influential upon heads near the stream, (2) factors representing thickness of the shallow flow system influence heads distant from the stream but have a negligible effect near the stream, and (3) factors that represent the quantity of water entering the system (recharge) influence the heads throughout the area. Field measurements of hydraulic head indicate that the thickness of the shallow flow system below the stream channel is about 30 feet. However, results of the sensitivity analysis indicate that the shallow system's thickness has a negligible effect on head distribution beneath the stream.

Water Supply Paper↗
USGS1987

The principle of superposition and its application in ground-water hydraulics

The principle of superposition, a powerful mathematical technique for analyzing certain types of complex problems in many areas of science and technology, has important applications in ground-water hydraulics and modeling of ground-water systems. The principle of superposition states that problem solutions can be added together to obtain composite solutions. This principle applies to linear systems governed by linear differential equations. This report introduces the principle of superposition as it applies to ground-water hydrology and provides background information, discussion, illustrative problems with solutions, and problems to be solved by the reader.

Techniques of Water-Resources Investigations↗
USGS1987

A conceptual framework for ground-water solute-transport studies with emphasis on physical mechanisms of solute movement

Analysis of solute transport in groundwater systems involves a complex, multi-discipline study that requires intensive and costly investigation. Groundwater contamination, particularly from point sources, has been growing in importance in recent years. This report examines the physical mechanisms of solute transport, advection and dispersion, and explains how they relate to one another and the scale of study. The approach uses a preliminary analysis prior to collection of new data to focus on the technical problems to be addressed and to direct the initial collection of new data if warranted. The field investigation (collection of new data) progresses in stages that use the new knowledge and understanding gained from the preceding data collection to aid in further data collection as the study proceeds. A major premise of the approach is that the foundation of any analysis is a detailed quantitative definition of: (1) the groundwater flow field in three dimensions, and (2) the distribution of solutes in the contaminant plume in three dimensions at one point in time, or preferably at more than features of the groundwater flow field, and is an important tool for analysis. However, the scale of analysis for solute transport studies is usually much finer than the scale of analysis for groundwater flow alone. Therefore, an increase in detail of the velocity field is needed to provide for accurate calculations of pathlines in three-dimensional heterogeneous groundwater systems. (Lantz-PTT)

Water-Resources Investigations Report↗