A way to measure how much water each person in a community uses each day. This is typically calculated in aggregate for communities, counties, or states, or nationally, by dividing the total volume of water used in a month, divided by the total population and the number of days in that month. Major discrepancies exist in how different entities calculate GPCD, which population numbers they use, and the source of those numbers (full-time resident, transient, census, state demographers), making it difficult to compare numbers across state lines or across communities. The indicators report uses GPCD numbers from the USGS National Water Use Science Project, part of the National Water Census.