Water Storage: The Pros and Cons of Dams & Reservoirs

Water Goes With the Flow

When you turn on a garden hose, it doesn’t take long for the water to come out. This is because water is fluid and mobile – it likes to move! Water isn’t fond of staying in one place. Even if it seems to be motionless, there is a lot going on behind the scenes that you can’t see. Some of the surface water is evaporating into the air; some of the water at the very bottom is seeping into the ground below. And, even the water you do see is constantly moving ever so slightly.

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How and Why We Store Water

As difficult as it is to prevent water from moving, it’s a top priority in the United States for several reasons. One of the most important reasons is flood prevention. Flooding is a natural, cyclical process that carries nutrient-rich sediments over large areas, which is beneficial to human agriculture and natural ecosystems.

These floodplains not only border beautiful waterways, but also provide a water supply and very fertile soils. These factors have drawn people to riverbanks for hundreds of years, and while flooding can be beneficial, it often destroys homes and livelihoods as well.

To prevent flooding, dikes and levees have been constructed. These are raised mounds of earth along riverbanks that hold water behind them. Dikes and levees are usually made of natural materials and build upon the ground that is already present, and the size of the mound depends on the water body behind it.

But, while dikes and levees are meant to prevent flooding, they may, in fact, add fuel to the fire. The flooding of New Orleans by Hurricane Katrina in 2005 was a result of failed levees – the water had built up so much behind the levees that once they broke, that accumulated water caused a catastrophic flooding event.

Water is also stored behind dams, which are obstructions placed along a waterway to stop the flow of water. This creates a reservoir, or a place where water is stored and prevents the water from continuing downstream. There are several benefits to damming waterways, such as flood prevention and providing a source of water for human consumption and agricultural irrigation.

Dam reservoirs also generate hydroelectric power, which is energy generated from the water turning turbine blades as it passes through the dam. Water that is stored in a reservoir can provide a steady, predictable amount of electricity that not only is inexpensive, but also doesn’t produce emissions like coal and gas do.

Though not a priority for building a water-holding structure, creating water reservoirs does provide new recreational opportunities. Lakes that are created behind dams, dikes and levees are often popular areas for fishing, boating and swimming.