Final answer:
The true statement regarding hydropower is that it accounts for more than a quarter of all renewable energy use. While hydropower does not directly produce greenhouse gases, there are indirect emissions and environmental impacts associated with dam construction and operation, including effects on wildlife and habitats.
Step-by-step explanation:
Of the statements provided regarding hydropower and its environmental impact, the true statement is that hydropower accounts for more than a quarter of all renewable energy use. This is because hydropower is considered a clean and renewable source of energy, and though it can have serious environmental impacts, such as obstructing fish migration and affecting aquatic habitats, it does not directly produce greenhouse gases.
Hydropower includes the construction and use of dams to generate electricity by converting the potential energy of stored water into kinetic energy, which is then used to rotate turbines. However, the statement that the use of dams for hydropower produces no greenhouse gases is misleading because there are indeed indirect emissions associated with dam construction and, in some cases, reservoirs may release methane, a powerful greenhouse gas.
While hydroelectric facilities are an important part of our renewable energy portfolio, they must be developed responsibly to mitigate potential ecological disruptions. Small run-of-the-river projects are often considered environmentally preferable as they can have fewer impacts than large-scale dam projects. These smaller projects use the natural flow of the river and do not impound significant amounts of water, reducing some of the negative effects associated with larger dams.