Water-quality comparison of the Gulf Coast aquifer system at various scales in Texas from National Water-Quality Assessment groundwater studies, 2013–15

One of the objectives of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Project is to assess groundwater quality in aquifers that are important sources of drinking water such as the coastal lowlands aquifer system, which is often referred to in Texas as the “Gulf Coast aquifer system.” The Gulf Coast aquifer system extends from Louisiana to Mexico and is a source of groundwater for several cities including Houston, Tex. The NAWQA groundwater studies in Texas in 2013–15 that assessed the Gulf Coast aquifer system included Principal Aquifer Surveys (PAS), Major Aquifer Studies (MAS), and Land Use Studies (LUS). These three study types are based on sampling networks of wells distributed in an area of interest. The PAS networks typically consist of public-supply wells that are relatively deep, the MAS networks typically consist of domestic-supply wells that are intermediate in depth, and the LUS networks typically consist of monitoring wells that are relatively shallow.