GC: n

CT: A reservoir is an artificial lake where water is stored. Most reservoirs are formed by constructing dams across rivers. A reservoir can also be formed from a natural lake whose outlet has been dammed to control the water level. The dam controls the amount of water that flows out of the reservoir.
Service reservoirs are entirely manmade and do not rely on damming a river or lake. These reservoirs, sometimes called cisterns, hold clean water. Cisterns can be dug in underground caverns or elevated high above ground in a water tower.

S: NatGeo – http://education.nationalgeographic.co.uk/education/encyclopedia/reservoir/?ar_a=1 (last access: 13 February 2015)

N: 1. 1680s, “a place where something tends to collect,” originally figurative, from French réservoir “storehouse,” from Old French reserver “to reserve” (see reserve (n.)). Specific meaning “artificial basin to collect and store a large body of water” is from 1705.

2. A construction, partially or wholly man-made, for storage and/or regulation and control of water.
Term and definition standardized by ISO.

3. People build reservoirs because the amount of water in a river varies over time. During very rainy times or when mountain snow is melting, the water in a river rises and sometimes overflows its banks. By limiting the amount of water allowed to continue downriver, reservoirs help control flooding.
During droughts, or extended dry periods, the water level in a river may be very low. Under these conditions, more water is released from the reservoir so farmers can water their crops and homes and businesses can function normally.
Reservoirs serve other purposes. They are used for boating, fishing, and other forms of recreation. Some of the dams that create reservoirs are used to generate electricity.

4. Collocations: (reservoir) where water is stored.

• Adj.: natural | artificial, man-made | underground.
• Prep.: in a/the reservoir.

S: 1. Etymonline – http://www.etymonline.com/index.php?allowed_in_frame=0&search=reservoir&searchmode=none (last access: 13 February 2015). 2. TERMIUM PLUS (last access: 13 February 2015). 3. http://education.nationalgeographic.co.uk/education/encyclopedia/reservoir/?ar_a=1 (last access: 13 February 2015). 4. OCD – http://oxforddictionary.so8848.com/search?word=reservoir (last access: 20 May 2015).

SYN:
S:

CR: dam, elevated tank, hydraulic energy, hydroelectric power, lentic waters, swamp, weir.