The Ythan catchment area lies between the catchments of the rivers Don, Deveron and Ugie and being mainly spring fed it is regarded as a spate river.
There are three main tributaries of the River Ythan:
The river’s catchment area covers approximately 690 km2 (266 sq miles). Most of this is used for agriculture, with approximately 5 percent of scrub, heath, woodland and urban areas.
The river rises at the Wells of Ythan to the east of Huntly in Aberdeenshire and flows 40 miles to enter the North Sea at Newburgh. From its source the river flows northeast to Auchterless before turning sharply to the southeast to flow past the villages of Fyvie, Methlick and the town of Ellon to its estuary at Kirkton of Logie Buchan. The estuary is 4 miles long and enters the North Sea approximately 15 miles north of Aberdeen.
The North Ugie Water rises in the upland area near New Pitsligo, and the South Ugie Water's source is to the west Bucklay Castle near Maud in Aberdeenshire. Both flow southwesterly through arable farmland and meet at Millbank to form the Ugie. The river then flows for 5 miles to enter the North Sea at Peterhead. Being a spate river, the levels and fishing depend on local rainfall and agricultural drainage.
The Deveron has a separate page, so have a look at the Deveron information there too.