This is a coverage of the boundaries and codes used for the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program Study-Unit investigations in the conterminous United States, excluding the High Plains Regional Ground-Water Study. The data set represents the areas studied during the first decade of the NAWQA Program, from 1991-2001 ("cycle 1").
|Title||National Water-Quality Assessment (NAWQA) Study-Unit Investigations in the conterminous United States 1991-2001|
|Authors||K.J. Hitt, N. Nakagaki|
|Publication Subtype||USGS Unnumbered Series|
|Record Source||USGS Publications Warehouse|