Assessing the degree to which groundwater and surface water are under stress as a result of natural (drought) and man-made (water withdrawals, changes in landuse, etc.) causes requires long-term monitoring. The Maryland Geological Survey partners with the U.S. Geological Survey to maintain a State-wide network of observation wells and surface-water gages. Water level- and stream-flow-data are stored in the USGS's National Water Information System, and are used frequently by both water managers and scientists in evaluating the State's water supply. Additional information regarding the network can be found on the USGS website.