Everything about Artificial Lake totally explained
A
reservoir is, most broadly, a place or hollow vessel where something (usually
liquid) is kept in
reserve, for later use. Most often, a reservoir refers to an
artificial lake, used to store
water for various uses. Reservoirs are created first by building a sturdy
dam, usually out of
cement,
earth,
rock, or a mixture. Once the dam is completed, a
stream is allowed to flow behind it and eventually fill it to capacity.
Construction
There are two basic types of reservoir: the commonly-seen dam across a
valley, or the less-common fully-bunded dam.
A fully
water tower bunded dam has a continuous human made
embankment around its entire perimeter, most commonly using a central clay core as the waterproof element. The core is held in place by earth or rock piled either side of it in suitable volumes to resist the outward forces exerted by the water. The clay is joined directly to the natural underlying material, which itself is usually clay in order for the dam to be water tight. The reservoir is filled by mechanical pumps that draw water from an adjacent water course such as a river.
If a water tight roof is added then this dam can then be used for storing treated water before it goes to the tap and is known as a "Service" reservoir.
The more common dam across a valley relies on naturally formed features to form the water tight elements. Generally,
surveyors have to find river valleys which are deep and narrow; the
valley sides can then act as natural walls. The best place along the valley for building a dam has to be determined according to where the dam can best be tied into the valley walls and floor to form a water tight seal. If necessary, humans have to be re-housed and/or historic sites have to be moved, for example the temples of
Abu Simbel before the construction of the
Aswan Dam, creating
Lake Nasser in the
Nile River,
Egypt.
First, the river must be redirected slightly so as to not disturb construction of the dam. Once that's done, building of the dam may commence. This may take anywhere from a few months to a few years, depending on its size and complexity. After the dam is complete, the river is allowed to begin filling the large area behind the dam.
Some reservoirs are entirely underground. In the United Kingdom
Thames Water has many underground reservoirs beneath
London built in the 1800s by the Victorians, most of which are lined with thick layers of brick. Honor Oak Service reservoir, which was completed in 1909, is the largest of this type in Europe. The roof is supported using large brick pillars and arches and the outside surface is used as a
golf course.
Operation
A raw water reservoir doesn't simply hold water until it's needed. It is the first part of the
water treatment process. The time the water is held for before it's released is known as the retention time, and is a design feature that allows larger particles and
silts to settle out as well as time for the biological treatment of algae and bacteria by plankton-like creatures that naturally live within the water.
Water is then released from the reservoir, generally by
gravity, to be cleaned for
drinking water. In the event that major
rain occurs, water can be released, decreasing the reservoir's water level.
Levels
The normal maximum level of a reservoir lake is called
full pool, while the minimum level it can function at is
dead pool. The water below this point is also called the dead pool, while the water in between is called the
conservation pool. Full pool may have different levels in summer and winter, or based on the local wet and dry seasons.
Once a reservoir reaches dead pool, it's below the level at which the dam can release it downstream. At this point, the streambed beyond the dam goes nearly or completely dry, and electricity production stops as well. This is also often the point at which intakes for
municipal water systems begin to suck air in, and must be extended into deeper water, where
stagnant water quality is much poorer. This can be done either permanently with longer pipes, or temporarily with large
hoses floated on small
barges, such as until a severe
drought or dam
repairs are over.
Hydroelectricity
A
hydroelectric power station consists of large
turbines at the base of a dam. Water from the reservoir behind the dam is channeled through pipes and delivered to the turbines, which in turn, spin a
generator to produce
electricity. Generally, reservoirs behind hydroelectric dams are built specifically for electrical power generation and are not used for drinking water or irrigation.
Controlling watercourses
Reservoirs can be used in a number of ways to control how water flows through downstream waterways.
Irrigation
Water in an
irrigation reservoir is released into networks of
canals mainly for use in
farmlands or secondary water systems. Water in an irrigation reservoir is
generally not used for drinking water, but in some cases is. As with all reservoirs, water can be released if the reservoir is too full.
Flood control
Commonly known as an "attenuation" or "balancing" reservoir, these are used to prevent
flooding to lower lying lands,
flood control reservoirs collect water at times of unseasonally high rainfall, then release it slowly over the course of the following weeks or months. See
transvasement.
Compensation
If a standard reservoir is built on a river which is used as a source of power, a compensation reservoir may also be built to guarantee a sufficient flow of water downstream during the working hours of the water-powered industries.
Canals
Where a natural watercourse's water isn't available to be diverted into a
canal, a reservoir may be built to guarantee the water level in the canal; for example, where a canal climbs to cross a range of hills through
locks.
Recreation
Reservoirs often provide for
recreational uses. Most reservoirs are built for a civic purpose, but still allow
fishing,
boating, and other activities. At most reservoirs, special rules apply for the safety of the public.
History
Dry climate and water scarcity in
India led to early development of water management techniques, including the building of a reservoir at
Girnar in 3000 BCE. An artificial in present-day
Madhya Pradesh province of India, constructed in the 11th century, covered 650 square meters.
List of reservoirs
Largest reservoir by region
List of reservoirs by area
The following are the world's ten largest reservoirs by surface area:
Lake Volta (8,482 km²; Ghana)
Smallwood Reservoir (6,527 km²; Canada)
Kuybyshev Reservoir (6,450 km²; Russia)
Lake Kariba (5,580 km²; Zimbabwe, Zambia)
Bukhtarma Reservoir (5,490 km²; Kazakhstan)
Bratsk Reservoir (5,426 km²; Russia)
Lake Nasser (5,248 km²; Egypt, Sudan)
Rybinsk Reservoir (4,580 km²; Russia)
Caniapiscau Reservoir (4,318 km²; Canada)
Lake Guri (4,250 km²; Venezuela)
List of reservoirs by volume
Lake Victoria (204 km3; Uganda)
Lake Kariba (180 km3; Zimbabwe, Zambia)
Bratsk Reservoir (169 km3; Russia)
Lake Nasser (157 km3; Egypt, Sudan)
Lake Volta (150 km3; Ghana)
Manicouagan Reservoir (142 km3; Canada)
Lake Guri (135 km3; Venezuela)
Williston Lake (74 km3; Canada)
Krasnoyarsk Reservoir (73 km3; Russia)
Zeya Reservoir (68 km 3; Russia)
Other uses
A water tank is also a reservoir, feeding into a local water system when demand is high, and refilling when it's low. Typically they're placed in a higher part of the area it serves, so the system is gravity-fed from it.
A reservoir may also refer to the water for a steam iron or humidifier, or collected from a dehumidifier or air conditioner (before being carried or pumped outside, respectively). The term is also used for perfumes and liquid air fresheners, as well as the paint bottle for airbrushes, or for any other spray or atomizer.
Further Information
Get more info on 'Artificial Lake'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://reservoir.totallyexplained.com">Reservoir Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
