The River Tees flows eastward through northern England from its source in the Pennines mountains to the North Sea. It serves as a key water source for homes and industry, and several reservoirs help regulate water supply and control flooding. The lower course grows more urban as it passes through towns and the major port of Teesside. Flood defenses including walls and embankments have been constructed along the river, and the Tees Barrage was built to improve water quality and reduce flooding risk in the lower stretches.