The site covers about ten acres, centred on a deepwater 3 acre lake originally constructed in 1974 as an irrigation reservoir, but never used as such. Over the years it has naturalised to provide several distinct and bio diverse habitats.
The lake itself is 27ft deep, alkaline pH, crystal clear and filled only by rainfall, and thus is entirely protected from agricultural run off. It has the biological characteristics of the great lime stone loughs of Connemara and Sutherland, base rich but nutrient poor. The presence of three species of stone worts, the characteristic vegetation of the limestone loughs, attests to this. The fringe of dense Norfolk reed extending to over an acre adds even more to maintaining outstanding water quality, exemplified by the presence of the only extant colony of Native White Clawed Crayfish known to have survived in Cambridgeshire and Bedfordshire. The lake also supports a very diverse group of dragon flies, damsel flies and demoiselles, some extremely rare. There is a strong annual hatch of May fly.
The reed bed always hosts half a dozen pairs of nesting reed warblers. The males sing vociferously when you pass their territory, so doing the annual census is easy. The reeds also shelter dabchicks, coot, moorhen, great crested grebes, and diving ducks, and hunting kingfishers.
The nutrient deficient calcareous subsoil from the excavation forms a two acre plateau at the south end of the lake and the surrounding bank. It supports a rich chalk land flora that changes through the season, first colt’s foot yellow, then copious cowslips, daisies, a rich array of clovers and vetches, followed in high summer by teasels, wild carrot and ragwort, itself supporting a vigorous population of Cinnabar moths. A wide range of butterflies inhabits the wild meadow.
The site is flanked by a small chalk stream formed by springs arising at Bassingbourn Wellhead and Odsey, on the fringe of Royston and Therfield Heaths, some three and six miles away. Between the stream and the lake a dense scrub has developed which provides habitat for the increasingly rare Turtle Dove. The stream has some 15 ancient pollarded willows on its banks, providing rich habitats, second only to old oaks in the diversity of wildlife they support.
Otters travel up the stream frequently, at least weekly, and we have constructed an otter holt on the southern bank of the lake. Badgers, foxes, bats and voles abound.
The lake is frequently visited by Hobbies hunting dragon flies, exhibiting extraordinary aerial skills. Barn owls nest in the black barns just beyond the reserve and hunt over its grassland in the evenings.
Apart from its rich and diverse wildlife the reserve offers remarkable views, up to the heath lands to the south and the source of the Cam at Ashwell to the west. Not a single house can be seen. We built an enchanting summer hut on the eastern bank, cantilevered over the water below, with inspirational views. It doubles as observation hut, fishing hut and pic nic spot. The water is stocked once a year with a modest number of rainbow trout which thrive in its deep and transparent waters, gaining weight rapidly. We cull them using dry fly only, destined for the kitchen.