Holne Bridge in Summer

We've had a lovely day here in South Devon, much against all the forecasts. I decided to go to the medieval Holne Bridge on Dartmoor. It's still the main thoroughfare through the southern part of the moor but being a single carriageway, it can cause delays and confusion. 

The water's very low at the moment and a there's a trail of foam coming down. I'd like to think it's caused by organic breakdown and not pollution.