Its head waters are a network of drainage ditches west of the A41 near Bushy that feed into Aldenham reservoir. The outlet of the reservoir then flows north into the lake in Haberdasher Askes School grounds known as Tykes Water Lake. It then proceeded north to make a confluence with a secondary stream, also called Tykes Water , near Kendal Hall Farm. 
The secondary Tykes Water also known as Borehamwood Brook on some maps rises to the south of Borehamwood near Yavneh College and runs north through the town where it has been dammed to produce ornamental lakes in Aberford Park. It then runs north through open country .
A minor tributary collects water from farm land north of Borehamwood and also joins near Kendal Hall Farm.
Kitwells Brook joins the main stream just north of Radlett and drains land to the east in the direction of Shenley.
In popular culture
Tykes Water Bridge in Aldenham Country Park features in the open credits to the Peter Cushing and Christopher Lee film, Dracula A.D. 1972, and is used in several episodes of the Diana Rigg and Linda Thorson seasons of The Avengers .
- "Tykes Water Lake, Hertsmere - area information, map, walks and more". OS GetOutside. Retrieved 2019-03-16.
- "Tykes Water and Beyond" (PDF). Hertfordshire County Council. 2015.
- Elstree & Borehamwood Museum Friends Newsletter September 2018 : Issue Number 18 (2018). "Our History Walk Through The Northern 'Wood's" (PDF).