Introduction

The U.S. Geological Survey (USGS) operates and maintains a nationwide network of about 7,500 streamgages designed to provide and interpret long-term, accurate, and unbiased streamflow information to meet the multiple needs of many diverse national, regional, state, and local users. The National Streamflow Information Program (NSIP) was initiated in 2003 in response to Congressional and stakeholder concerns about (1) the decrease in the number of operating streamgages, including a disproportionate loss of streamgages with a long period of record; (2) the inability of the USGS to continue operating high-priority streamgages in an environment of reduced funding through partnerships; and (3) the increasing demand for streamflow information due to emerging resource-management issues and new data-delivery capabilities. The NSIP’s mission is to provide the streamflow information and understanding required to meet national, regional, state, and local needs.

Most of the existing streamgages are funded through partnerships with more than 850 other Federal, state, tribal, and local agencies. Currently, about 90 percent of the streamgages send data to the World Wide Web in near-real time (some information is transmitted within 15 minutes, whereas some lags by about 4 hours). The streamflow information collected at USGS streamgages is used for many purposes:

• In water-resource appraisals and allocations—to determine how much water is available and how it is being allocated;
• To provide streamflow information required by interstate agreements, compacts, and court decrees;
• For engineering design of reservoirs, bridges, roads, culverts, and treatment plants;
• For the operation of reservoirs, the operation of locks and dams for navigation purposes, and power production;
• To identify changes in streamflow resulting from changes in land use, water use, and climate;
• For streamflow forecasting, flood planning, and flood forecasting;
• To support water-quality programs by allowing determination of constituent loads and fluxes; and
• For characterizing and evaluating instream conditions for habitat assessments, instream-flow requirements, and recreation.