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Introduction

Ground water is one of the Nations most important natural resources. It is the principal source of drinking water for about 50 percent of the United States population, providing approximately 96 percent of the water used for rural domestic supplies and 40 percent of the water used for public supplies. In addition, more than 30 percent of the water used for agricultural purposes is withdrawn from wells. Ground water also is a significant, but often unrecognized, component of the Nations surface-water resources. Much of the flow in streams and the water in lakes and wetlands is sustained by the discharge of ground water, particularly during periods of dry weather.

Groundwater systems are dynamic and adjust continually to short-term and long-term changes in climate, groundwater withdrawal, and land use. Water-level measurements from observation wells are the principal source of information about the hydrologic stresses acting on aquifers and how these stresses affect groundwater recharge, storage, and discharge. Long-term, systematic measurements of water levels provide essential data needed to evaluate changes in the resource over time, to develop groundwater models and forecast trends, and to design, implement, and monitor the effectiveness of groundwater management and protection programs.

The U.S. Geological Survey (USGS) has collected water-level data for more than a hundred years, and many State and other agencies have a long history of water-level monitoring. However, water-level monitoring in the United States is fragmented and largely subject to the vagaries of existing local projects. A stable, base network of water-level monitoring wells exists only in some locations. Moreover, agency planning and coordination vary greatly throughout the United States with regard to construction and operation of water-level observation networks and the sharing of collected data.

For many decades, periodic calls have been made for a nationwide program to obtain more systematic and comprehensive records of water levels in observation wells as a joint effort among USGS and State and local agencies. O. E. Meinzer described the characteristics of such a program over 65 years ago:

"The program should cover the water-bearing formations in all sections of the country; it should include beds with water-table conditions, deep artesian aquifers, and intermediate sources; moreover, it should include areas of heavy withdrawal by pumping or artesian flow, areas which are not affected by heavy withdrawal but in which the natural conditions of intake and discharge have been affected by deforestation or breaking up of prairie land, and, so far as possible, areas that still have primeval conditions. This nationwide program should furnish a reliable basis for periodic inventories of the groundwater resources, in order that adequate provision may be made for our future water supplies."

Careful planning and design are required to ensure the collection of high-quality water-level data over the period of time needed to compile a useful hydrologic record of water-level changes. A further challenge is to supplement the long-term monitoring wells as hydrologic conditions in aquifers evolve. A comprehensive monitoring program should consider aquifers substantially affected by groundwater pumping, areas of future groundwater development, surficial aquifers that serve as major areas of groundwater recharge, and links with water-quality and surface-water monitoring.

A commitment to long-term monitoring is needed to avoid data gaps resulting from an inadequate distribution of observation wells or periods of no measurements in a hydrologic record. Many agencies lack formalized written plans for the design and operation of ground-water-level networks, and many agencies have difficulty maintaining funding and program continuity necessary to ensure long-term collection of water-level data. Disruptions in the hydrologic record provided by water-level data collection and the gaps in data coverage can hinder the ability of water-resources managers to make sound resource-management decisions. Where water-level data are not available, hydrologic information needed to address critical groundwater problems may be impossible to obtain. Much recent effort has been made in the application of computer modeling techniques to forecast future groundwater levels. However, the successful application of even these advanced methods requires that sufficient water-level data are available.

More effort is needed to increase the amount of ground-water-level data stored in electronic databases, to increase the compatibility between databases, and to improve access to ground-water-level data on the Internet. Although some water-level databases can be accessed in this way, detailed and complete records of historical water-level data usually are limited or unavailable. In many agencies, large backlogs of historical ground-water-level data have not been entered into electronic databases, let alone made available on the Internet. Consequently, potentially useful data are residing in paper files where accessibility and utility are very limited.

Finally, to increase the collection and accessibility of water-level data, agencies need to examine ways to increase interagency coordination in constructing and maintaining observation-well networks, collecting water-level measurements, and sharing and disseminating data. Greater interagency cooperation will help ensure that data-collection efforts are sufficient to address issues relevant to the greatest variety of local, state, regional, and national water-resources issues.

U.S. Patents #5,503,363, #5,618,022, #5,871,200, #6,073,906 and

#6,338,466, Canada Patent #2,293,391,

Australian #748767

Plus 23 International Patents Pending.