Lau Shui Heung Reservoir was not built to be beautiful, though it became so. Construction began in 1966 and finished in 1968, as part of the engineering programme that created the much larger Plover Cove Reservoir nearby. While Plover Cove was the primary storage facility — one of Hong Kong's most ambitious water supply projects, impounding an entire marine bay — Lau Shui Heung served a different role: collecting runoff from the northwestern slopes of the Pat Sin Leng range and channeling it through a conveyance tunnel to supply the larger reservoir. The main dam is a concrete gravity structure 24 meters high and 54.9 meters long; a secondary earth dam stands 7.3 meters high. Small by any measure — the reservoir covers just 3.5 hectares with a storage capacity of 170,000 cubic meters — it was designed as a component in a system, not as a destination. It also serves as an irrigation reservoir for nearby farmland, feeding the Kwan Tei River and ultimately the Ng Tung River beyond.

The engineering purpose never explained why the place was so good to look at. Set inside a valley within Pat Sin Leng Country Park, Lau Shui Heung is enclosed by wooded ridges and ringed by rows of Melaleuca trees — a genus of paperbark known for its white, peeling bark and the reflective quality it gives to standing water. The reservoir sits deep enough that its color shifts to green, a consequence of both depth and the filtering of light through the surrounding canopy. On still mornings, the surface becomes genuinely mirror-like, reflecting clouds, ridges, and sky with a clarity that has made it a popular subject for photographers and a draw for hikers who come for the views along the Lau Shui Heung Country Trail. The trail passes directly through the reservoir area, making it accessible without special access. The fish below — including Channa asiatica, a small snakehead species uncommon in Hong Kong — move through a substrate of sand and rock that the reservoir's depth and clarity make visible.

The 2018 dry season was worse than usual. A winter with below-average rainfall, combined with irrigation demand from surrounding farmland and, authorities suspected, groundwater drainage from the nearby Lung Shan Tunnel construction project, left the reservoir severely depleted by April. Cracks appeared at the bottom. The Water Supplies Department confirmed the situation and attributed it primarily to drought and irrigation draw. What made the case puzzling was that Hok Tau Reservoir — a nearby irrigation pond of similar size — did not dry up. The comparison suggested something specific had happened at Lau Shui Heung, not just a regional drought effect. Then the rains came. In early June, Tropical Storm Ewiniar brought outer rainbands across northern Hong Kong. Nearly 100 millimeters fell in three days — more than the previous two months combined. In the northern New Territories, more than 200 millimeters fell in a single 24-hour period. The cracked lakebed filled. The mirror was restored.

Pat Sin Leng Country Park, which surrounds the reservoir, takes its name from the ridge that defines its skyline — Pat Sin Leng translates roughly as 'Eight Immortals Ridge,' a reference to the eight peaks that compose it. The park covers rugged terrain in the northeastern New Territories, between Tai Po and the mainland border, and is less visited than more accessible parks closer to the urban core. That relative quiet is part of Lau Shui Heung's appeal. The Lau Shui Heung Country Trail connects the reservoir to broader trail networks in the area, linking to routes through Fung Yuen and beyond. The woodlands are mature and diverse, the valleys secluded. Barbecuing at the reservoir has become a local tradition — the combination of accessible flat ground, scenic water, and shade making it a natural gathering place for families who make the journey from Fanling and Sheung Shui to the south.

Hong Kong's water supply story is one of constant engineering against scarcity. The city receives substantial annual rainfall but lacks the land area and natural storage to hold it; reservoirs are essential, and they are numerous — more than a dozen serve different parts of the territory. Lau Shui Heung is among the smallest, but its function in the Plover Cove system illustrates how interdependent these structures are. When one dries, the chain is disrupted. When the rains return, as they did in June 2018, the whole system resets. The 'mirror of the sky' is a nickname earned by appearance, but it also describes something true about the reservoir's relationship to the weather: what you see on that surface is a direct reflection of what the clouds have recently given or withheld.