Initially the Kilkeel and Annalong rivers were diverted and transported to Knockbracken near Carryduff on the outskirts of Belfast, this reservoir had a storage capacity of 100 Million gallons.
Building of the actual dam didn't begin until 1923 when a dam was built across the Kilkeel River which flowed in the Happy Valley. This work continued for the next ten years, a narrow gauge railway was built from Annalong on the coast which transported men and materials to the work site.
A temporary village which became known as Watertown was constructed to house the workforce, it had a police station with a policeman called Lawless. Many problems were encountered such as silt and gravel and gigantic boulders, but all were eventually overcome and the project was completed in 1933.
In 1949 it was decided to drive a tunnel through Slieve Binian to carry water to the Silent Valley, this was considered a better option to building another dam the tunnel measured 7 feet x 8 feet (2.1 metres x 2.4 metres) and is nearly 2 1/4 miles (3.6 kilometers) long.
Demand continued to grow and was met by building another dam close to Ben Crom mountain this dam became known as The Ben Crom Dam, it is 230 yds (210M) across and 155 ft (42.25M) high, it took 186 men only three years to build the dam which was completed in 1957, this was a concrete dam while the Silent Valley dam was rock and earth.
Collectively the dams in the Mourne
Mountains supply approximately 400,000 people with some 30,000,000 gallons
of water daily.
Spare a thought for the men who built this wall, walking from their homes to the heart of the Mountains in all weather each morning and home again in the evening. The annual Mourne Wall Walk takes place in the summer and attracts walkers for far and wide.
Today the valley is no longer silent, it attracts around 50,000 visitors a year who come to enjoy the majestic grandeur of the Mourne Mountains. The wildlife has returned in the spring birds can be seen busying themselves with nest building in preparation for a new generation.
The the Valley is administered by Northern Ireland Water who has provided a number of visitor facilities at the valley including a restaurant, information centre, conference centre and education centre - all housed in two old colonial style bungalows and enjoying delightful views over the parkland.
For more information please see their website.