River Lathkill flowing over the tufa dam at Lathkill Lodge

Originally posted for the Guesswhere UK group.

The River Lathkill in full flood, surging through the tufa dam at Lathkill Lodge, Lathkill Dale, in the White Peak, Derbyshire.

Uprising, carbonate-rich groundwater flowing into the river bed in certain places causes deposition and accumulations of calcareous tufa (a harder and more extensive version of a furred-up kettle), blocking the stream and enabling plants to colonise the river bed. Normally the water flows very slowly here and is sometimes completely dry in the summer.

At high flow times, the river surges through the tufa dam, finding its way through a network of shallow channels, as in the picture.