Water-quality data for the USGS National Water-Quality Assessment (NAWQA) has moved and is now available via the Water Quality Portal, a website that also serves data collected by over 400 state, federal, tribal, and local agencies.
Downloading NAWQA data on the Water Quality Portal:
The Portal offers several standard selection filters, to download the data you want. You can retrieve NAWQA-only samples by applying the appropriate ProjectID filter. Type National Water Quality Assessment Program into the ProjectID text field (see image below) to find the NAWQA Project ID in the picklist, then select it to add it as a filter.
If you have any questions about how to use the Water Quality Portal please submit your questions to the Water Quality Portal Team.