Small scale hydro power: Impacts on nature and people
21 May 2012 | Fact sheet
Are you planning to fund, build or manage a hydro power project? Have you considered the environmental, social and economic issues this can raise? Are you prepared to manage these issues?
Pacific Energy Projects: Impacts on nature and people
TYPICAL HYDRO POWER PROJECTS
Hydroelectric power uses water that has a height differential (head) to move a turbine, converting the kinetic energy to electricity, and releasing it at an outlet (spillway). In the Pacific, both reliable water supply and elevation are typically found on volcanic islands. As the scale and nature of hydro power projects can vary dramatically, so can their impacts – for example modifying an existing dam can have negligible impacts. Water management by a hydro power project falls into two categories:
Storage – the water flow is controlled, typically using a dam, to provide a consistent supply of water and electricity. This approach permanently floods the area behind the dam, modifies natural cycles of high and low flows, and restricts sediment movements and migrating species.
Run-of river – the natural flow is diverted, but with negligible time delay or storage facilities. A weir, small dam, canal, penstock and other structures may be used to direct the water to a turbine, under pressure and then is released.
HYDRO POWER PROJECT DEVELOPMENT
The best time to build positive outcomes and avoid negative impacts is during development and design, and this is especially true for hydro power projects. These tend to have long lead times, requiring many years of rainfall and river flow data for the design, but are hard to change once built.
In addition to the social aspects that are typical of energy projects, hydro power projects can impact on the catchment and distribution routes, and may have secondary impacts such as promoting irrigation.
Overall, a hydro power scheme adapts the natural variability of a river and its availability to species, and gives this power to people. This requires careful and ongoing thought as consequences can be far-reaching. Hydro power projects should consider the catchment affected, which requires an understanding of the environment and any patterns of change, sometimes over a wide area. Bigger storage and more heavily manipulated water flows usually have bigger impacts while run-of-river schemes can avoid or reduce most of these effects, and are therefore much lower impact.
Hydro power provides continuous renewable energy, avoiding the need for diesel or batteries. Even small systems however will need concrete and clearing for construction, will divert water, and will need an electricity network as the system itself must be near a river. If a dam is required, changes to stream flow can affect ecosystems, sediment movements and flooding patterns. Hydro power may require protection of upstream catchment, which can be positive for the environment.
The technology for hydro power is well developed, with information available on designing, building and maintaining various systems. The power is continuous, not intermittent like other sources, and its reliability is particularly useful for productive activities. Hydro power can raise issues of ownership and access rights for both water and land, and should be considered against current and future demands such as agriculture, drinking water supplies, fishing and ecosystem health. These interactions, together with the environmental impacts, can complicate decisions.
Large catchments may be suitable for multiple hydro power systems, especially pico or nano hydro (a few kW or less). Installing multiple systems on a river can add up to catchment level impacts, particularly during droughts or heavy rainfall (like cyclones). Access roads, poles and wires for distribution all contribute to the impacts of hydro power projects. The influence of the project may create secondary impacts, through access and influencing land use.
Further information on additional resources can be found on the PDF available for download.