It is normal to relate reservoirs only to those which supply drinking water, but indeed there is another type of reservoirs - irrigation reservoirs.  Of all the 8 irrigation reservoirs in Hong Kong, seven are located in the New Territories. Tsing Tam Irrigation Reservoir is one of them. Providing farmers with irrigation water supply, Tsing Tam Upper and Lower Irrigation Reservoirs are located in the valley behind Tsing Tam Village, Yuen Long, and can be reached by following the flat forest track after getting off at Lui Kung Tin bus station on Route Twisk. After passing through the sitting-out area where accessible toilets are available, the route continues with three uphill sections that are surrounded by increasingly luxuriant trees giving some welcome shade. The forest track itself, usually carpeted with fallen leaves and embellished with white flowers of Tung-oil trees between April and May, is a masterpiece by nature, and the views it offers from afar are equally magnificent - from there you can see Kai Kung Leng, Tai To Yan, Kwun Yam Shan, the stretches of farmland and wetlands on Yuen Long Plain, and Tin Shui Wai New Town behind the mountain. Wheelchair users are advised to enlist help from people nearby to slow the wheelchairs down before beginning the brief yet steep descent in the second half of the route. Not far away is the dam between the upper and lower reservoirs, where the views on each side contrast sharply with each other - on the left is the upper reservoir surrounded by hills and woodlands; on the right is the lower reservoir hidden under the canopy of leaves. The road continues as far as Ho Pui Tsuen, but given the considerable distance and the steep slopes, it is best to take the return trip at the end of the dam.

Points to note:
1) Traffic along the road from bus station at Lui Kung Tin Tsuen to Shek Kong Barbecue Area site no. 3 is busy on Sundays and Public Holidays.
2) There are no ramp and crossing place at Lui Kung Tin Tsuen station. Watch out for cars when crossing Route Twisk.
3) The elevation on section to Tsing Tam Upper Irrigation Reservoir is around 1:4 (~13 degree).
4) Return at Tsing Tam Upper Irrigation Reservoir.
5) Extended reading and experience sharing: Oasistrek/ Trailwatch /Wheel Power Challenge (in Chinese)

Oasistrek https://www.oasistrek.com/bf_tsing_tam_reservoir.php

Trailwatch: https://www.trailwatch.hk/en/?t=activities&rid=10194417