Water-level measurements from observation wells are the principal source of information about the effects of hydrologic stresses on ground-water systems. Long-term water-level data are required to address the effects of aquifer development and to compile a hydrologic record of water-level monitoring, uses of long-term water-level data, and improvements in the collection and accessibility of water-level data.
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USGS Numbered Series
Ground-water-level monitoring and the importance of long-term water-level data