The Hydrologic Data Systems Branch (HDSB) develops, maintains, and provides user support for data collection systems and prepares data products for use both in NWS operations and by external users. HDSB provides access to historical data for use in calibration of hydrologic models and development of hydrometerologic techniques as well as ensuring the capture and provision of needed data not collected by other agencies. Within the HDSB the Hydrometerologic Design Studies Center (HDSC) prepares and publishes U.S. design standards and estimates on behalf of the Federal Government, for probable maximum precipitation and precipitation frequencies.