where does the river thames start

The River Thames starts in Gloucestershire, England. The traditional and official source is called Thames Head, located near Kemble in the Cotswolds, about 3 miles southwest of the town of Cirencester. This source is marked by a stone in a field at about 356 feet (108.5 meters) above sea level. However, the exact source can shift due to groundwater levels, and the River Churn, a tributary rising near Seven Springs, also claims to be the ultimate source with a higher elevation at about 700 feet (213 meters) above sea level. In very dry conditions, the start of the river can move downstream to places like Somerford Keynes. Thus, the official origin is Thames Head, but there is some debate and variability in the precise point where the river begins.