Pond layouts with contours showing depth (black indicates 0 m depth and lightest colour indicates maximum depth); inlets are located on the left and hatching indicates vegetation. (a) Regular basin pond, maximum depth 1·5 m. (b) Curvilinear basin pond, maximum depth 1·5 m. (c) Pond with island, maximum depth 1·5 m. (d) Wetland, maximum depth 0·6 m