The Orlando Subdistrict office of the U.S. Geological Survey is responsible for the collection of hydrologic data and interpretive studies of hydrology in central and northeast Florida. This work is conducted in cooperation with water management districts (St. Johns River, South Florida, and Southwest Florida Water Management Districts), other Federal agencies, counties, and other municipalities. The geographic area covered by the Subdistrict extends from the Georgia border to Lake Okeechobee, and from the Atlantic coast to the mouth of the Withlacoochee. The Orlando Subdistrict area has the most varied surface-water and ground-water hydrology of any of the other subdistricts in Florida, and features karst topography, wetlands, sand hills, sinkhole lakes, tidal streams, salt water occurrence in coastal and inland ground waters and surface waters, first magnitude springs, submarine springs, flowing wells, streams that terminate in sinkholes, recharge areas, and discharge areas. Major streams in the Subdistrict area include the St. Johns River, the Kissimmee River, the Withlacoochee River, and tributaries to these rivers. Hydrologic data routinely collected include ground water levels, surface water levels in lakes and streams, stream discharge, water quality, and a limited number meteorological data (rainfall, evapotranspiration). Hydrologic investigations include areal studies (county and regional assessments), ground-water and surface-water modeling, water-quality studies, and investigations specific to identified hydrologic or water-quality problems or potential problems. The data collected and studies conducted by the office are used to better understand the hydrology of central and northeast Florida, and are used as a resource for water managers in decision-making.