Hydropower is essentially the process of capturing the energy of running water. Water is run through hydraulic turbines, producing electricity. Currently, hydropower accounts for around one sixth of all electricity generated in the world today. All hydropower processes are not created equal. There are different hydroelectricity systems, such as: reservoir; run-of-river; and, pumped storage. Hydropower operations also are present on different scales, including: small (mini and micro); medium; and, large.

Reservoir hydropower involves the storage of water in dams. This captured water is released and run through a turbine to generate electricity. The benefit of the reservoir system is the ability to immediately generate electricity to meet demand. The run-of-river system, also called diversion, involves diverting a part of a river and using the running water or flow to create electricity. The run-of-river system is not as flexible as the reservoir method, in that there is not as much opportunity to generate electricity upon demand.

A pumped storage hydropower system involves two reservoirs. When the need for electricity is low, water is pumped to a higher water storage area. Once electricity demand increases, the water stored in the higher area is released into the lower area - flowing through the turbine and generating electricity.

Environmental Benefits of Hydropower

One of the largest environmental benefits of hydropower is that there is no carbon dioxide produced during electricity generation. Hydropower does not require fossil fuels and does not emit greenhouse gases associated with the burning of fossil fuels. As such, in these terms, it is one of the most environmentally-friendly methods of electricity generation. Another environmental advantage of hydropower is that water is not polluted during the process and can be utilized for additional processes, such as crops or water supplies.

Hydropower is referred to as a renewable energy. That is, the water used to generate electricity is not depleted by the process. In other words, this means that the water can be used repeatedly and that depletion of the resource quantity does not occur.

A hydropower project is suggested to have a life of between fifty and one hundred years, and they can quite easily be updated to meet new technological developments. This is also an environmental benefit as there is no need to create additional impacts constructing new projects each time a scientific breakthrough occurs.

Despite being kinder to the environment than fossil fuel electricity generation, hydropower also has negative impacts upon the environment.

Negative Environmental Impacts of Hydropower

Some of the most common impacts upon the environment include:

• Changes in Ecosystem. The natural ecosystem is affected by both storage and river hydropower generation processes. That is, the unnatural flooding and flows of the water alters naturally occurring cycles. There is no denying that this impacts the natural flora and fauna that exists within the ecosystem.
• Flooding of the Social and Physical Environment. Hydropower requires vast quantities of water. The consequences of this are that large quantities are stored and released to generate the energy required. In some instances, entire towns and communities are flooded to create massive scale dams. This not only has negative impacts upon the physical environment, but also significant social impacts. Families can lose their ancestral homes and ancient communities can be torn apart.
• Environmental Impacts. Due to alterations in the physical environment as a result of flooding, significant amounts of natural vegetation begin to decompose. This in itself produces greenhouse gas emissions.
• Fish/Wildlife Impacts. A well-known impact is that of the effects upon fish migration and reproduction. Although, in some instances, runs are built to allow fish to continue their breeding cycle.

There are certainly both positives and negatives surrounding hydropower generation. It is true, on the one hand, that hydropower does not burn fossil fuel when generating power; however, on the other hand, there are additional environmental impacts that often result (such as to wildlife and natural ecosystem).