Pros and Cons of Building Dams

There are many advantages and disadvantages to using dams. Their main purpose is to collect runoff and release it to control floods, generate electricity, and to channel water into specific areas. The dams that are currently in use increase the amount of water that is available to us for use by about 30%. However, dams built upstream will reduce the flow of water downstream, often adversely affecting the people living down the river. Also, by capturing this water, we are disturbing nature's hydrologic cycle which has far reaching consequences both in the near and far future.
The advantages of dams are as follows. They are a major source of clean electricity, that is, electricity that is generated without the burning of fossil fuels that pollute our atmosphere. Not only are they sources of electricity, dams are efficient and effective sources with their massive hydro-turbines. By using dams to generate electricity, we reduce our dependence on coal. The main purpose of a dam is for flood control. Without them, it is likely that people living downstream could suffer severe flooding that often brings along property damage and loss of life. Dams also increase the amount of water available to farms and to irrigation, increasing the agricultural output and stimulating economic growth. They are indispensible in heavily agrarian societies.
There are also drawbacks to dams that must be considered as well. The building of a dam is not cheap by any means. To embark on a project such as a dam is a major financial investment. Also, as with any human made structure, it impedes nature's processes and species migration patterns. Some fish may find it difficult to follow their old routines with a giant dam in the way. Also, dams are known to increase water pollution due to the reduced flow of water. Dams are of course not perfect and could result in the flooding of large areas of croplands and forests.
Dams are a controversial environmental issue that is still hotly debated by experts worldwide. They have important economical and practical uses for us but may disrupt natural cycles and processes.