(ROR) is a type of hydroelectric
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
generation whereby a considerably smaller water storage called pondage
Pondage usually refers to the comparably small water storage behind the weir of a run-of-the-river hydroelectric power plant. It is considerably less storage than the reservoirs of large dams and conventional hydroelectric stations which can store water for long periods such as a dry season or year...
or none is used to supply a power station. Run-of-the-river power plants are classified as with or without pondage. A plant without pondage has no storage and is, therefore, subjected to seasonal river flows and serves as a peaking power plant
Peaking power plants, also known as peaker plants, and occasionally just "peakers," are power plants that generally run only when there is a high demand, known as peak demand, for electricity.-Peak hours:...
while a plant with pondage can regulate water flow and serve either as a peaking or base load power plant
Baseload is the minimum amount of power that a utility or distribution company must make available to its customers, or the amount of power required to meet minimum demands based on reasonable expectations of customer requirements...
Run-of-the-river hydroelectricity is ideal for streams or rivers with a minimum dry weather flow or those regulated by a much larger dam and reservoir upstream. A dam, smaller than that used for traditional hydro, is required to ensure that there is enough water to enter the "penstock
A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. It is a term that has been inherited from the technology of wooden watermills....
" pipes that lead to the lower-elevation turbines. Projects with pondage, as opposed to those without pondage, can store water for peak load demand or continuously for base load, especially during wet seasons. In general, projects divert some or most of a river’s flow (up to 95% of mean annual discharge) through a pipe and/or tunnel leading to electricity-generating turbines, then return the water back to the river downstream.
ROR projects are dramatically different in design and appearance from conventional hydroelectric projects. Traditional hydro dams store enormous quantities of water in reservoirs, necessitating the flooding of large tracts of land. In contrast, most run-of-river projects do not require a large impoundment of water, which is a key reason why such projects are often referred to as environmentally-friendly, or "green power."
The use of the term "run-of-the-river" for power projects varies around the world and is dependent on different definitions. Some may consider a project ROR if power is produced with no storage while a limited storage is considered by others. Developers may mislabel a project ROR to sooth public image about its environmental or social effects. The Bureau of Indian Standards
The Bureau of Indian Standards is the national Standards Body of India working under the aegis of Ministry of Consumer Affairs, Food & Public Distribution, Government of India. It is established by the Bureau of Indian Standards Act, 1986 which came into effect on 23 December 1986...
describes run-of-the-river hydroelectricity as:
A power station utilizing the run of the river flows for generation of power with sufficient pondage for supplying water for meeting diurnal or weekly fluctuations of demand. In such stations, the normal course of the river is not materially altered.
Many of the larger ROR projects have been designed to a scale and generating capacity rivaling some traditional hydro dams. For example, one ROR project currently proposed in British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
(BC) Canada—one of the world’s new epicentres of run-of-river development—has been designed to generate 1027 megawatts capacity.
When developed with care to footprint size and location, ROR hydro projects can create sustainable energy minimizing impacts to the surrounding environment and nearby communities. Advantages include:
Cleaner power, fewer greenhouse gases
Like all hydro-electric power, run-of-the-river hydro harnesses the natural energy of water and gravity, eliminating the need to burn coal or natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
to generate the electricity needed by consumers and industry.
Substantial flooding of the upper part of the river is not required for smaller-scale run-of-river projects as a large reservoir is not required. As a result, people living at or near the river don't need to be relocated and natural habitats and productive farmlands are not wiped out.
Run-of-the-River power is considered an “unfirm” source of power: a run-of-the-river project has little or no capacity for energy storage and hence can't co-ordinate the output of electricity generation to match consumer demand. It thus generates much more power during times when seasonal river flows are high (i.e, spring freshet), and much less during drier summer months.
Availability of sites
The potential power at a site is a result of the head and flow of water. By damming a river, the head is available to generate power at the face of the dam. Where a dam may create a reservoir hundreds of kilometers long to form the head at the face of the dam, in run of the river the head is usually delivered by a canal, pipe or tunnel constructed upstream of the power house. Due to the cost of upstream construction, a steep drop in the river is desirable. At the Three Gorges Dam
The Three Gorges Dam is a hydroelectric dam that spans the Yangtze River by the town of Sandouping, located in the Yiling District of Yichang, in Hubei province, China...
in China a reservoir has been raised 110 meters over a distance of 660 kilometers. A location with a gradual drop is not suitable for run of the river.
While small, well-sited ROR projects can be developed with minimal environmental impacts, many modern run-of-river projects are larger, with much more significant environmental concerns. For example, Plutonic Power Corp.’s Bute Inlet Hydroelectric Project in BC will see three clusters of run-of-river projects with 17 river diversions; as proposed, this run-of-river project will divert over 90 kilometres of streams and rivers into tunnels and pipelines, requiring 443 km of new transmission line, 267 km of permanent roads, and 142 bridges, to be built in wilderness areas.
British Columbia’s mountainous terrain and wealth of big rivers have made it a global testing ground for run-of-river technology. As of March 2010, there were 628 applications pending for new water licences solely for the purposes of power generation – representing more than 750 potential points of river diversion.
Many of the impacts of this technology are still not understood or well-considered, including the following:
- Diverting large amounts of river water reduces river flows, affecting water velocity and depth, minimizing habitat quality for fish and aquatic organisms; reduced flows can lead to excessively warm water for salmon and other fish in summer. As planned, the Bute Inlet project in BC could divert 95 percent of the mean annual flow in at least three of the rivers.
- New access roads and transmission lines can cause extensive habitat fragmentation for many species, making inevitable the introduction of invasive species and increases in undesirable human activities, like illegal hunting.
- Cumulative impacts—the sum of impacts caused not only by the project, but by roads, transmission lines and all other nearby developments—are difficult to measure. Cumulative impacts are an especially important consideration in areas where projects are clustered in high densities close to sources of electricity demand: for example, of the 628 pending water license applications for hydropower development in British Columbia, roughly one third are located in the southwestern quarter of the province, where human population density and associated environmental impacts are highest.
- Water licenses issued by the BC Ministry of Environment, enabling developers to legally divert rivers, have not included clauses that specify changing water entitlements in response to altered conditions; this fact means that conflicts will arise over the water needed to sustain aquatic life and generate power when river flow becomes more variable or decreases in the future. However, it should also be noted that under section 101 of the BC Water Act, regulations regarding a water licenses can be changed by the government at any time, including the amount of water that a power plant is required to release to protect aquatic life .
- Chief Joseph Dam
The Chief Joseph Dam is a concrete gravity dam on the Columbia River, upriver from Bridgeport, Washington, USA. The dam was authorized as Foster Creek Dam and Powerhouse for power generation and irrigation by the River and Harbor Act of 1946...
, 2,620 MW
- Beauharnois Hydroelectric Power Station
The Beauharnois Hydroelectric Power Station is a run-of-the-river hydroelectric power station along the Saint Lawrence Seaway on the Saint Lawrence River, in Quebec, Canada. The station was built in three phases, and comprises 38 turbines, capable of generating up to of electrical power...
, 1,903 MW
- Satluj Jal Vldyut Nigam Ltd, Satluj River
The Sutlej River is the longest of the five rivers that flow through the historic crossroad region of Punjab in northern India and Pakistan. It is located north of the Vindhya Range, south of the Hindu Kush segment of the Himalayas, and east of the Central Sulaiman Range in Pakistan.The Sutlej...
, Shimla, India, 1,500 MW
- Ghazi-Barotha Hydropower Project on River Indus in Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
, 1,450 MW
- La Grande-1 generating station
The La Grande-1 is a hydroelectric power station on the La Grande River that is part of Hydro-Québec's James Bay Project. The station can generate 1,436 MW and was commissioned in 1994–1995...
, 1,436 MW
- Bute Inlet Hydroelectric Project, British Columbia, Canada, 1,026 MW
- Baglihar Hydroelectric Power Project
Baglihar Dam , also known as Baglihar Hydroelectric Power Project, is a run-of-the-river power project on the Chenab River in the southern Doda district of the Indian state of Jammu and Kashmir. This project was conceived in 1992, approved in 1996 and construction began in 1999. The project is...
on Chenab River
The Chenab River چنRiver' آب) is a major river of Jammu and Kashmir and the Punjab in Pakistan. It forms in the upper Himalayas in the Lahaul and Spiti district of Himachal Pradesh, India, and flows through the Jammu region of Jammu and Kashmir into the plains of the Punjab, Pakistan...
in India, 900 MW
- Carillon Generating Station
The Carillon Generating Station is a hydroelectric power station on the Ottawa River near Carillon, Quebec, Canada. Built between 1959 and 1964, it is managed and operated by Hydro-Québec. It is a run-of-river generating station with an installed capacity of 752 MW, a head of , and a reservoir of...
, Quebec, Canada, 752 MW
- East Toba/Montrose Hydro Project, British Columbia, Canada, 196 MW
- Forrest Kerr Hydro Project, British Columbia, Canada, 195 MW
- Upper Toba Valley, British Columbia, Canada, 123 MW
- Environmental concerns with electricity generation
The environmental impact of electricity generation is significant because modern society uses large amounts of electrical power. This power is normally generated at power plants that convert some other kind of energy into electrical power...
- Environmental impacts of dams
The environmental impact of reservoirs is coming under ever increasing scrutiny as the world demand for water and energy increases and the number and size of reservoirs increases....
Hydropower, hydraulic power, hydrokinetic power or water power is power that is derived from the force or energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as...
- Microhydro systems
Microhydro Systems are structures used to generate around 2 to 100 kW of hydroelectric power using the natural flow of water.Microhydro systems are very flexible and can be deployed in a number of different environments. They are dependent on how much water flow the source has and the...
- Pumped-storage hydroelectricity
Pumped-storage hydroelectricity is a type of hydroelectric power generation used by some power plants for load balancing. The method stores energy in the form of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost off-peak electric power is used to run the pumps...
- Small hydro
Small hydro is the development of hydroelectric power on a scale serving a small community or industrial plant. The definition of a small hydro project varies but a generating capacity of up to 10 megawatts is generally accepted as the upper limit of what can be termed small hydro. This may be...