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70% of the Earth's surface is covered in water, why can't a hydroelectric power plant be set up on each and every river? Is it that its too expensive?

Why is electricity still a problem in countries that have abundant number of rivers? Why can't each and every river be associated with a hydro power plant through dams? What makes a river unsuitable?

My basic question is that Earth has got abundant amount of water. Then why is (hydro) electricity still scarce in some places? Is it that its too expensive?

My research shows that it might be expensive to set up but it is quite cheap in the long run compared to other power plants besides itself being low-maintenance.

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    $\begingroup$ Many rivers are used by ships. To be cost effective, you need a dam. Dam causes a flood plane. Loss of a lot of land. $\endgroup$ – StainlessSteelRat Nov 12 at 12:29
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    $\begingroup$ @StainlessSteelRat The ecological impacts are way too large, in some cases, dams generate more $CO_2$ than the conventional centrals thank to decaying organic materials behind the dams. $\endgroup$ – Sam Farjamirad Nov 12 at 15:13
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    $\begingroup$ @SamFarjamirad + toxins released into the water (methylmercury) poison fish and mammals. $\endgroup$ – StainlessSteelRat Nov 12 at 16:02
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    $\begingroup$ @SamFarjamirad not if the dams are mostly above the treeline... $\endgroup$ – Solar Mike Nov 12 at 16:06
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    $\begingroup$ There's always a reason why Your Pet Idea hasn't dominated the world, and it's vanishingly rare that the answer is Big Corporation Suppression. $\endgroup$ – RonJohn Nov 13 at 7:42
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Because most of the water is at the lowest point is can be, the ocean.

Second issue is that you need quite a bit of vertical drop for water power to be a viable power source.

There are DIY hydro power setups but they include diverting part of a stream through a pipe into a turbine down the hill, but those tend to only be enough to power a single household and they require a suitable geography.

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    $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – hazzey Nov 18 at 2:10
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There are two issues, harnessing and market. You need both to be viable.

A market, makes most of the 70% of the land mass covered by water unusable, because even if you could harness the power, it is impossible to get the power to consumers. There are no practical storage alternatives, either.

Ocean buoys do harness ocean currents to meet their individual power needs.

Wave power does exist, but this is on a small scale, mostly experimental, close to land.

Tidal power has great potential by either harnessing tides as they flow in and out or using dams to capture hide tide and harnessing outflow. But they have to overcome damage by mother-nature or deal with impact on marine animals / environment.

Many rivers are ruled out because there are used by ships/boats, which would require locks to allow passage or damming would create a flood plane, which would impact existing infrastructure (farm land, communities).

Other rivers are ruled out because of spawning fish. Fresh-water spawning fish, like salmon, can pass dams by fish ladders, but dam flood plane is impacted because fish need calm areas to spawn.

Countries with remote rivers (like Canada - 9% of land mass is fresh water - James Bay, Churchill Falls) have dammed them up and harnessed them. This creates large amounts of power, which is shipped via transmission lines to urban regions. They take up a lot of real estate, which impacts local communities, either having to relocate or impacting hunting / fishing / recreation territory.

Smaller rivers/lakes with a significant water head are harnessed as appropriate. Wikipedia list of generating facilities for Newfoundland and Labrador, Canada. Not all are on the island of Newfoundland (Churchill Falls), but the hydro-electric facilities (~38 facilities) are not enough to supply the power needs of ~400,000 people. This is supplemented by Diesel Turbine facility to meet peak power demand.

Micro-hydro exists. Any flow of water can potentially be harnessed. Water-wheels to grind wheat. There may be legislative hurdles to overcome. After all you are impacting a community resource.

Canada, despite it's large geographic area and considerable hydro-electric facilities, still supplements peak power requirements with atomic, wind, solar and diesel (for remote regions).

Pumped Storage is another alternative. Usually used to balance the grid load, pumped storage pumps water to a higher height during periods of low power usage to be delivered during peak power periods. A nuclear power plant is kept at optimum efficiency, so during non-peak times, extra power is available to pump water uphill. This makes sense because the extra Pumped Storage capacity is available in times when peak demand occurs (breakfast, lunch, supper).

To answer the question: Most significant hydro-electric resources are either harnessed or planned to be harnessed. There is a significant investment (money, resources) to harness these renewable resources, but the return on investment is worth the investment.


The Grand Canyon would make an ideal dam site (remote, formed by water, no population [people or herds]), except for two things: rainfall & desert. It does get some rain, but it is mainly dry because it is in a desert zone. If it had the water flow, it would dammed and harnessed.

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    $\begingroup$ Some places have valleys that are useless for much else other than water storage as they are very steep sided and only ock with little to no vegetation... $\endgroup$ – Solar Mike Nov 12 at 16:08
  • $\begingroup$ Are Newfoundland's hydro installation insufficient to provide for the province, or are other sources needed because they sell a large amount of the generated power? For example, I think Quebec is buying a lot of the power from Churchill falls, and the Maritime Link project was done to sell their energy to the Eastern grid as well (though I don't know if the Maritime Link was completed yet). $\endgroup$ – JMac Nov 12 at 22:14
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    $\begingroup$ Majority of upper Churchill power goes across Quebec to market. Some (up to 5%) is consumed within western Labrador. Coastal Labrador uses Diesel. Lower Churchill will supply Island needs and excess will be sold to Nova Scotia, with rights to access New Brunswick and eastern seaboard US markets when Upper Churchill contract ends (2041). That is what I understand of the plans. $\endgroup$ – StainlessSteelRat Nov 12 at 23:09
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    $\begingroup$ @RonJohn now you can have the fun using a map and working out the catchment area - a standard part of the task when analysing a hydro project. $\endgroup$ – Solar Mike Nov 13 at 15:58
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    $\begingroup$ @SolarMike you make an outrageous claim and then tell us to do our own research. That's the kind of tactic which conspiracy theorists employ. $\endgroup$ – RonJohn Nov 13 at 16:58
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Rivers in a flat landscape are often unsuitable because you need a height difference to make the turbine work. Let's say a 1 meter height difference is required. There are many areas where the river's gradient is so shallow that raising the river's level by 1 meter would inundate everything for miles around, so you'd need to build a dam to contain the river. There comes a point where the dam's more expensive to construct than the value of the electricity you can extract from this height difference.

There's also the cost to shipping: every lock slows down traffic, and is another expensive bit of engineering to build and maintain.

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    $\begingroup$ Correct - aggravated by the fact that such low gradients are typically seen in coastal deltas, which happen to be the most densely populated areas in the world. I.e. hydro doesn't work where it's needed most. $\endgroup$ – MSalters Nov 14 at 9:35
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In years past I would have been a fan of hydroelectric power but I have read1 about some of the downsides over the years. These include:

  • Major ecological problems including blocking fish migration. Putting in fish ladders or stairs doesn't really work well as the fish can't find them with all the din of the spillways and turbines.
  • Most silt up drastically reducing their reservoir capacity. I thinks 25 years or so is typical.
  • More people have been killed by hydroelectric dam failures than by nuclear accidents. See Major dam failures for example.

As a result, it seems, in North America there are many dam removal programs to bring the rivers back to their more natural state.


1I think Something New Under the Sun: An Environmental History of the Twentieth-Century World (The Global Century Series) Paperback – April 17, 2001 by J. R. McNeill was one.

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  • $\begingroup$ Where other answers focus on technicalities or economics, yours hits the nail on the head. The real question is: why would you want hydro energy in some places? In grade school we learned that hydro is great, infinite power at no emissions, but they avoided real-world issues like forced migration, fish, historical sites, erosion, water allocation, world bank loans and structural adjustment programs (SAP) . . . $\endgroup$ – Roland Nov 14 at 14:09
  • $\begingroup$ I don't think it's fair to hydroelectric comparing its safety to nuclear power. Nuclear is the safest form of power generation in terms of deaths/TWh. Hydroelectric is the least safe "green" energy source but its still safer than any fossil fuel. $\endgroup$ – EldritchWarlord Nov 14 at 16:00
  • $\begingroup$ The dams being removed are generally quite small: the largest I've found had 22 MW of generating capacity, and most have capacities in the single digits. $\endgroup$ – Mark Nov 15 at 1:39
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Water is a valuable resource, getting more valuable by the minute. Simply locations that can build hydro power are scarce. In addition to significant ecological impact damming also changes how rivers flow.

This is not a trivial thing. People who live in the basin you use as the hydro dam storage need to relocate. Worse people downstream may lose access to water, or atleast severly change their acess. This can cause problems with water tables etc. In addition people working in fishing and agriculture may be impacted. All of this is especially problematic if the river crosses a border. There are few places where this has caused tensions to rise to the level that may even trigger a war! (Not much of a hydro plant if your neighbour bombs it when your getting finished)

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Geography is one thing (change in height as mentioned above, finding suitable areas to store large volumes of water, canyons are usually suitable places for hydro instead of rivers that doesn't change over height so countries such as Denmark and the Netherlands are at a disadvantage while places like Switzerland & India have large rivers that are concentrated)so having a river that can continually provide a water flow that is substantial to keep a consistent pressure and not dry up all of a sudden is also important but damming it is a huge economic cost and investment as well. So plenty of things to consider. As well dams are more used during peak times when the load on the grid is high and water is then pumped back up when the load is low. Since dams can't hold a load for a long period of time.

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Hydroelectric power is (indirectly) solar and geothermal power: Heat causes evaporation, temperature gradients create flow of air and water vapor to higher elevations, clouds form, rain falls, and hydroelectric power simply harvests the gravitational potential energy originally imparted by heat to the raindrops.

Therefore, you can harvest hydroelectric power (a) anywhere it rains, and (b) anywhere between where it rains and a lower elevation so long as there is a continuous and preferred canal to supply the drainage from the high-rainfall areas.

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  • $\begingroup$ In theory, yes. In practice, very much no. For example, getting hydropower from the Caloosahatchee River would require a dam 200 km long to get just three meters of hydraulic head (less at high tide). $\endgroup$ – Mark Nov 15 at 2:07

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