Page images
PDF
EPUB
[merged small][merged small][subsumed][graphic][subsumed]

consistent description of current waterquality conditions for a large part of the Nation's water resources; define longterm trends (or lack of trends) in water quality; and identify, describe, and explain the major factors that affect water-quality conditions and trends.

The program will focus on

water-quality conditions

that are prevalent or large

in scale and persistent

in time.

Determining the best method of conducting such an assessment is complicated by the many water-quality constituents that must be sampled for, the large water-quality variations in time and among locations, and the high cost of collecting and analyzing samples. At present, the program is in a pilot phase. Seven pilot projects, representing a range of hydrologic environments, were selected to test and further refine the assessment concepts; four projects focus primarily on surface water, and three projects focus primarily on ground water. A decision to proceed to a full-scale national program will be made in 1990.

The decision will be influenced by an ongoing evaluation of the design and potential utility of the program by a committee of the National Academy of Sciences.

The program will focus on waterquality conditions that are prevalent or large in scale and persistent in time. Regional degradation of water quality, such as occurs from nonpoint sources of pollution or from a high density of point sources, will be emphasized.

As presently envisioned, the national program will be accomplished through investigations of about 120 study unitsaquifer systems and river basins—that are distributed throughout the Nation and that incorporate about 80 percent of the Nation's water use. By using these discrete study units, the scientists will be able to examine the causes of observed water-quality conditions, which is vital if the program is to be useful to managers and policy makers at Federal, State, and local levels.

The collection of data and the interpretation and communication of findings will be conducted by small teams of individuals who are familiar with the study areas. Having the same team of individuals responsible for the collection and interpretation of data will help ensure that the data are of high quality and that they lead to relevant and meaningful interpretations. The 120 study units will

be linked together through a prescribed set of study approaches and protocols for sample collection, sample handling, laboratory analysis, and quality assurance. Data for the study units will be collected and interpreted on a nationally consistent set of water-quality constituents. Consistent records will be recorded on streamflow and basin characteristics, well and aquifer characteristics, and land use and other measures of human activity. In addition, written reports will contain similar information for each study unit; and finally, data will be stored in national data files, where they will be available to the user community upon request.

Assessment activities in each of the study units will be done on a rotational rather than continuous basis, and only a portion of the study units will be studied

in detail at a given time. For each study unit, 3- to 5-year periods of intensive data collection and analysis will be alternated with longer, less intensive periods of study.

Even a very effective National Water-Quality Assessment Program will not and should not eliminate the need for other water-quality data-collection activities. For some issues and questions, the sampling requirements and procedures may be different from those which this program is designed to address. By providing a strong, high-quality National Water-Quality Assessment Program, the USGS will help underpin and unify the Nation's water-quality activities. Such an assessment program should satisfy a significant share of the water-quality information needs of the country.

[merged small][ocr errors][ocr errors][ocr errors][ocr errors][ocr errors][ocr errors][ocr errors][graphic][graphic][graphic][graphic][ocr errors]

Geologic Investigations

Mission

The basic mission of the Geologic Division is to evaluate the Nation's geologic structure and the geologic processes that have shaped it, to assess the Nation's mineral and energy resources, and to identify and investigate geologic hazards.

• Investigations of geologic hazards provide information for predicting and delineating hazards from earthquakes and volcanoes and for identifying engineering problems related to ground failure hazards.

• Regional geologic studies provide geologic maps and regional syntheses of detailed geologic data essential to mineral, energy, and hazard assessments.

• Offshore geologic studies identify and describe the mineral and petroleum resources of the offshore areas of the United States, including the Exclusive Economic Zone, an area one-third larger than the land area of the United States.

• Mineral resource investigations assess the distribution, quantity, and quality of the Nation's mineral resources, with particular emphasis on strategic and critical minerals.

• Surveys of energy resources provide assessments of the Nation's coal, petroleum, uranium, and geothermal resources and enhance capabilities to explore for and develop new sources of energy.

[graphic][merged small]

Highlights

Erosion of Louisiana's
Coastal Barriers

By Asbury H. Sallenger, Jr.,
Bruce E. Jaffe, and
S. Jeffress Williams

Nearly three-quarters of the U.S. population lives within an hour of the Nation's coasts. Coastal erosion and wetland loss, therefore, are serious problems with long-term economic and social consequences. Developed areas face billions of dollars in property damage and potential loss of life as a result of long-term erosion and storm impacts, and valuable wetlands are being altered at rapid rates. Of the 30 States bordering the oceans, the Gulf of Mexico, or the Great Lakes, all are undergoing some erosion and 26 are presently experiencing an overall net erosion of their shorelines. The National Academy of Sciences has forecast increasing rates of sea-level rise, which means that erosion is likely to accelerate in the future.

Because of natural and manmade causes, Louisiana has the highest rates of coastal erosion and wetland loss of any region in the United States. In the Mississippi River delta plain, rates of wetland

[graphic]

Figure 1. Location of the Isles Deiuteres barrier islands,

STUDY AREA

50 100 MILES

n—i

0 50 100 KILOMETERS

loss exceed 80 square miles per year. Louisiana's barrier islands, which serve to protect wetlands, are eroding, in some places as much as 65 feet per year. The islands are decreasing in area as they migrate landward. For example, between 1890 and 1979, Louisiana barrier islands decreased in area by 37 percent. If this rate of land loss continues, the barrier islands will disappear, which in turn will accelerate the destruction of valuable wetlands. Louisiana contains 41 percent of the Nation's wetlands, which support a $1 billion annual fishery industry.

Many of the processes contributing to barrier island erosion are poorly understood and are not quantifiable with any degree of confidence. These processes must be better understood in order to predict the future shoreline response and, thus, allow better management of our coastal resources. In 1986, the U.S. Geological Survey and the Louisiana Geological Survey began a planned 5year study focused on the processes causing barrier island erosion.

Valuable wetlands are being altered at rapid rates.

Long-term erosion of Louisiana's barrier islands is due both to sea-level rise, relative to the land, and to diminishing sand supply. The primary objectives of the study are to better quantify processes related to sea-level rise and sand supply and to present the results in a form that can be applied to such practical problems as predicting future changes.

The study is divided into three main parts:

• Investigating the geologic framework within which the barriers have formed and migrated landward. This work uses cores and geophysical information to provide a broad regional understanding of the historical development of the barrier islands and a conceptual understanding of the processes of barrier island erosion.

• Developing a better quantitative understanding of the various processes responsible for erosion. We have focused on only a few of the many processes, including relative sea-level rise, overwash,

« PreviousContinue »