Final answer:
Hydropower has a major disadvantage in terms of limited scalability and environmental impacts.
Step-by-step explanation:
A major disadvantage of hydropower relative to other power types is its limited scalability and the associated environmental impacts.
While hydroelectric power is a simple and low-tech form of renewable energy, it is not easy to expand beyond its current level of usage. The construction of dams for hydropower can lead to habitat destruction, forced displacement of people, and obstruction of fish migration. Additionally, the decomposing plant material in the reservoirs can increase water acidity and cause erosion to the hydroelectric turbines, leading to long-term problems.