The reservoirs are a 106.5-hectare (263-acre) biological Site of Special Scientific Interest[2][3] managed by the Herts and Middlesex Wildlife Trust.

Species include the Pipistrelle bat, which despite measuring just 4 cm in length and weighing approximately 5 grams, can consume around 3000 insects every night.

Other species include the Daubenton's bat which skims across the water's surface to prey on caddis flies.

[10] The reservoirs are popular with anglers and most famous for holding British record sized specimen fish like wels catfish to 60 lb, with a former British record wels catfish of 43 lb 8oz caught by Richard Bray at Wilstone reservoir in 1970.

[14][13] The current (to 2017) British record Perch was caught at Wilstone Reservoir by Ken Brown on 18 Sept 2012 weighing 6 lb 3oz.