The U.S. has more than 87,000 dams greater than six feet high (and two million overall). While many dams continue to provide benefits such as flood control, irrigation, and water supply, for other dams the cost of maintenance or the negative effects on communities, fish, and tribes justifies their removal.
Dam owners and regulators decide whether to remove a dam by weighing many factors including: the cost of removal and the ability to replace any lost power generation against avoided long-term maintenance; safety concerns; benefits to endangered fish populations; increased recreational and commercial fishing; and restoration of cultural values of nearby tribes.
By 2020, roughly 70% of dams will be more than 50 years old, inviting us to reconsider the value to the public of long-term investments in this infrastructure.
Answer:
Water
Explanation:
Water is essential to human life. Hence, human settlements tend to crop up near water sources such as rivers. This is particularly evidence in Africa, which has many quite dry regions.
Indian ocean
Atlantic ocean
pacific ocean
Earth is a large spherical landmass, which is divided into three major layers, known as crust, mantle, and core. The innermost layer of the Earth is the core.
<h3>What is the core?</h3><h3 />
- The core of the Earth is the innermost layer, present beneath the mantle and crust.
- The core is entirely made up of iron and nickel. The core of the Earth is also called NIFE, which symbolizes the elements present in the core, Iron (Fe) and Nickel (Ni).
- Core has a radius of approximately 1220 kilometers and is responsible for the generation of the magnetic field.
- Core also consists of the earliest history of the planet and is extremely hot, such that the temperature is close to the Sun's temperature.
Thus, the correct answer is Option D.
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