North West Water Supply Scheme
Tymon Mellor: In the summer of 1963, with severe water restrictions of only four hours every fourth day in urban Hong Kong, the Colonial Government was searching for new water supplies that could be expeditiously developed. A number of schemes had been explored and these were presented to the Executive Council in October, 1963. In addition to the Plover Cover Scheme, they recommended the North Western Scheme, the Tung Chung Bay Flood Pumping Scheme and Silvermine Bay Flood Pumping Scheme along with the development of seawater desalination. Exco agreed to commission Binnie and Partners to investigate the three new storage and supply options[i].
On the 7th October, 1963 Binnie and Partners was engaged to undertake a rapid feasibility study of the North Western Scheme and the two flood pumping schemes. They presented their initial findings one month later in early November, 1963 and then in an Interim Report in February 1964.
Flood Pumping Schemes
The flood pumping schemes were a strategy to increase the catchment areas of the existing Shek Pik Reservoir. The initial plan was to build a dam to establish a small reservoir but allowing a nominal flow to pass to support existing water demand and pump the excess flood water back into the Shek Pik Reservoir.
With a review of the design, it became apparent that the Tung Chung scheme could be staged to initially provide a temporary solution for the 1964 wet season and ultimately with a long-term solution providing an additional 7 million gallons a day. The temporary solution was to build a small dam and install a pipeline up the hill to deliver water into Shek Pik Reservoir using a series of electric pumps. The permanent solution was to excavate a tunnel from Shek Pik to pick up water from three mountain streams.
Both solutions required the construction of an access road from Chung Sha to Tung Chung. Thus, in January 1964 the scheme was announced and work commenced on construction of the road and excavation of the tunnels. The tunnels were commissioned in April 1966 and the road was completed and formally opened by the Governor, Sir David Trench in September 1966.
As for the Silvermine Bay scheme, the study concluded that only a limited water yield could be achieved and was insufficient for the large local demand for water. The scheme was not developed.
North West Water Supply Scheme
The North West Water Supply Scheme was a series of new reservoirs capturing the water from the as yet un-tapped catchments in the north west. The scheme comprised of:
- Construction of a bund creating a shallow reservoir north of Ping Shan, adjacent to Deep Bay with the water being pumped back to the Tai Lam Chung Catchwater initially yielding 5-10 million gallons a day, but by raising the height of the bund it increased it to 30-40 million gallons a day;
- Construction of the Fanling Dam forming a reservoir in the Fan Kam Road Valley, between Shek Kong and Fanling, with a capacity of 6,000 million gallons;
- Construction of a reservoir at Nim Wan to capture the water from Castle Peak Catchment providing a possible yield of 50-55 million gallons a day.
Nim Wan Reservoir
A number of sites were identified in the area but only two reservoirs were identified at the preferred location. With a high earth embankment, each site could form a reservoir of 4,500 to 5,000 million gallons. However, both of the sites along with the connecting tunnels were within the military firing range. Just to arrange a site visit and a survey had to be carefully coordinated with the authorities as the facility was in use three days a week.
If the project was to proceed, initial access would be from the sea with a new road constructed around the coast. However, it would be necessary to temporary limit military operations where construction was ongoing and in the long term cease firing within the vicinity of the new water works structures.
Deep Bay Reservoir
The Deep Bay scheme was a more complex arrangement, converting an area of mud flats and fish ponds into a shallow reservoir retained by a 6m embankment. Flood waters would be pumped from an intake structure at Yuen Long along with local intakes into the reservoir. The retained water would then be pumped out and transferred to the Tai Lam Chung reservoir catchwater.
The scheme would have impacted about 200 families living in wooden huts above the fish ponds. There was also a War Department Defence Signals Bureau (DSB) listening station, comprising of “two chocked up vehicles” that would need to be relocated.
The new reservoir would require the construction of a north dam, 58m high across the valley with two secondary dams to the south of 30m and 11m high. The recently constructed military road and water supply pipeline would need to be relocated around the site. The catchment area for the reservoir would be enlarged with catchwaters around the adjacent hillsides. Construction of the reservoir would have impacted around 1000 residents.
All of the schemes had their technical challenges, and none could be implemented quickly. However, the biggest constraint for all the proposals was their impact on the military. The Fanling scheme would impact the Fan Kam Road, a key military road used for the movement of troops and equipment, while the Nim Wan scheme was within the military firing range, and the Deep Bay scheme impacted the DSB listening post.
In the end, all the schemes were dropped in favour of Lower Shing Mun Reservoir, extraction of water from the Indus river, and the Plover Cover Scheme, along with the new water supply from Shenzhen and the East River Scheme. With these new resources water restrictions were eased and meeting the additional demand from the growing population.
[i] HKRS 724-11-7 North West Water Supply Scheme
This article was first posted on 19th November 2022.
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