low maynard reservoir low maynard reservoir low maynard reservoir is located in walthamstow in the london borough of waltham forest. the storage reservoir is part of the lee valley reservoir chain and supplies drinking water to london. low maynard reservoirlooking north from ferry lanelow maynard reservoirlocationlondon borough of waltham forestcoordinates51.58848°n 0.049782°w﻿ / 51.58848; -0.049782typereservoirbasin countriesunited kingdommax. depth3.0 m (9.8 ft)water volume0.15 gl (0.033×10^9 imp gal) history the reservoir was constructed in the mid 19th century by the east london waterworks company on former marshland. it is now owned and managed by thames water. ecology the reservoir is part of the walthamstow reservoirs site of special scientific interest, and it supports a large concentration of breeding wildfowl. the fringes of the reservoir contain species of plants uncommon in greater london, including: caltha palustris marsh-marigold schoenaoplectus lacustris common club-rush typha angustifolia lesser bulrush carex x subgracilis the 'graceful' sedge recreation access to the water, which is by permit only, is popular with birdwatchers, walkers and anglers.