GeoGraph - photograph every grid square

This graceful swan soared past us as we walked around the southern tip of Startopsend Reservoir. It landed a few yards further on. This reservoir along with its neighbours, Tringford, Marsworth and Wilstone Reservoirs is unusual in not storing water for consumption, but for release into the Grand Union Canal to maintain its water level, as the nearby SP9213 : Marsworth Top Lock marks the beginning of the Tring Summit Level - the highest point on the G.U.Canal and therefore the point from which water must be supplied. These man-made lakes provide welcome areas of water for many birds, as this area of the Chilterns is quite short on such features due to the chalk allowing most water to drain away. These are good lakes to observe Bewick Swans on their migration for example.