Geology topics
P. Patrick Leahy
Publications and source records attributed to P. Patrick Leahy.
Geology for a changing world: Summary of USGS Circular 1172: A science strategy for the Geologic Division of the U.S. Geological Survey, 2000-2010
The U.S. Geological Survey (USGS) provides the Nation with reliable and timely earth science information that is used to minimize loss of life and property from natural disasters; to manage energy, mineral, water, and biological resources; to enhance and protect the quality of life; and to contribute to wise economic development and a sustainable future. USGS Circular 1172, "Geology for a Changing World-- A Science Strategy for the Geologic Division of the U.S. Geological Survey, 2000-2010," presents a science strategy describing how the Geologic Division will carry out its share of this mission for the years 2000-2010. Acquisition of scientific knowledge through research, assessment, and insightful monitoring and the effective communication of this knowledge to planners and decisionmakers will allow the Geologic Division and its partners to assist the Nation in meeting a complex, challenging, and promising future.
National Water-Quality Assessment (NAWQA) program. A basis for water-resource policy development
The concepts that are the basis for the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) program began forming in the early 1980's. By 1986, a pilot phase was initiated to test and refine assessment concepts and in 1991, the NAWQA program began a multi-year transition to a fully operational program. The goals of the program are to describe the status and trends in the quality of a large representative part of the Nation's ground- and surface-water resources and to develop an understanding of the natural and human factors affecting the quality of these resources. This information will provide a sound scientific basis upon which water resources decision making at all governmental levels can be based. To meet its goals, the program will integrate water-quality information at local, regional, and national scales. The program will be perennial and consist of two major components -- study-unit investigations and national assessment activities. Investigations of surface- and ground-water resources of major regional hydrologic systems (river basins and aquifer systems) each covering 1200 to about 60,000 square miles, will be conducted on a rotating basis for 60 study units located throughout the Nation. Key findings from these study-unit investigations will be used along with other information to provide issue-oriented water-quality assessments of regional and national interest.
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.
Combined use of digital aquifer models and field base-flow data to identify recharge-leakage areas of artesian aquifers
As a result of continuous pumping since the 1890's, a regional cone of depression encompassing 363 km 2 has developed within the artesian Miocene Cheswold aquifer at Dover, Del. The aquifer is not being recharged significantly by leakage near the center of the cone, nor is major recharge induced in the updip subcrop area. The source of pumped water is apparently an area of about 65 km 2 northwest of Dover, where vertical leakage is substantial. This area was delineated by use of a digital aquifer model and streamflow data. A model of the unconfined aquifer was used to compute the unconfined aquifer's natural discharge to streams, assuming no leakage to underlying artesian aquifers. The area of substantial leakage to the underlying Cheswold was delineated as being coincident with that area where model-computed values of stream discharge were substantially larger than actual values of stream discharge determined in the field.