Blackadder Water is a river in Berwickshire in the Scottish Borders area of Scotland, forming part of the River Tweed system. It reached 2.84m at Mouthbridge, which was its highest level ever recorded on Tuesday 22 October 2002 at 2:45pm.

Whiteadder Water is a river in East Lothian and Berwickshire, Scotland. It also flows for a very short distance through Northumberland before joining the River Tweed. In common with the headwaters of the Biel Water it rises on the low hillside of Clints Dod in the Lammermuir Hills, just ESE of Whitecastle Hillfort and 3 km (1.9 mi) south-east of the village of Garvald.