Texas Water Resources: Civil Engineering and Uses of Dams

What Is a Dam?

A dam is a barrier that slows or stops the movement of water. Dams create reservoirs, which can serve many purposes. Along with acting as a flood suppression tool, they can also be used for drinking water, aquaculture, recreation, and irrigation. Some dams and reservoirs are used to generate electricity. The first known dam was built in Jordan around 3,000 B.C. and is known as the Jawa Dam.

  • Jawa Dam: The oldest known dam in the world was built in a desert, probably to provide needed water to the surrounding community during dry seasons.
  • What Is a Dam? Learn about why a community would want to build a dam and how dams are constructed.

What Are the Main Uses of a Dam?

  • Water Supply: Storing water in reservoirs can provide fresh water when needed in times of drought. Releasing water during a drought also can provide downstream ecosystems and wildlife with needed water during droughts.
    • Water Storage and Supply: California explains how it uses dams and reservoirs to help regulate the state's water supply.
  • Irrigation: Many places use water stored in reservoirs or behind dams to irrigate crops.
    • Burrinjuck Dam: Located in New South Wales, this Australian dam serves as a water storage device for the Murrumbidgee Irrigation Area.
  • Electrical Generation: Dams can produce hydropower, which is a clean type of power that does not add to air pollution or global warming. The United States is a large producer of hydroelectricity, but Canada is the largest producer in the world.
    • Hydropower Explained: The U.S. Energy Information Administration explains how hydropower is produced.
  • Flood Control: Historically, one primary reason for dam construction was to protect flood-prone areas. Flooding costs lives and damages property. Flood control dams either control the release of water downstream or divert the water.
  • Water Storage: The reservoirs created by dams provide water for a variety of uses, including agricultural and industrial purposes. Water storage allows excess water collected during rainy seasons to be stored for use in dry seasons or droughts.
    • Surface Storage: The Northern California Water Association developed surface water storage to protect the areas around Sacramento from flooding and to provide necessary water supplies for the region.
  • Mine Tailings: The United States is home to more than 1,300 mine tailings impoundments. These dams contain waste from mining operations.
    • Mount Polley Mine Disaster: This mine's tailings dam failed in 2014, and the result was 24 million cubic meters of waste from the mining operations flowing into surrounding rivers and lakes.
  • Debris Control: Dams can retain sediment and hazardous materials to keep them out of surrounding waterways.
    • Debris Dam Assessment: The Sierra Fund explains how debris dams were used during the period when the Sierra Nevada was actively mined and discusses the potential impact of these dams today.
  • Navigation: Dams, along with locks, stabilized the inland systems of rivers and allowed for year-round travel.
    • Bonneville Dam: Located in Portland, Oregon, the Bonneville Dam was built as a navigation dam.
  • Recreation: The reservoirs created by dams provide recreational spaces. Boating, swimming, fishing, sailing, and camping are all supported by the lakes created by damming local rivers.

Dam Terminology, Vocabulary, and Definitions

  • Abutment: The part of the dam constructed against the valley side of the embankment
  • Berm: A nearly horizontal bench or step found in the sloping face (either upstream or downstream facing) of a dam
  • Boil: Boils occur when water discharging below the surface of the ground disrupts the soil surface and forms a ring (resembling a miniature volcano) around the site of the disruption.
  • Breach: An opening in the dam that allows water to leave the reservoir. Controlled breaches are purpose-built openings; uncontrolled breaches are a byproduct of dam failure.
  • Centerline: The axis of the dam when viewed from a longitudinal perspective
  • Crest: The highest point of an embankment dam is known as the crest.
  • Conduit: The closed channel that moves water safely around, under, or through a dam is known as the conduit.
  • Control Section: The segment above the open channel spillway of a dam where reservoir water is discharged as part of the water movement system of the dam
  • Cross Section: A view of the dam, either drawn or modeled, created to allow the viewer to see the vertical elevation and the natural horizontal water flow pattern simultaneously is known as a cross-section.
  • Drain, Toe, or Foundation : A system of sand and gravel designed to collect water and move it to a safe outlet forms the foundation (also called the drain or toe) of a dam.
  • Drainage Area (Watershed) : The area where any water that falls on the surrounding land will flow into the dam; this is an essential component of the groundwater system.
  • Evacuation Map: The map that designates which areas downstream of a dam should be evacuated in case of a dam breach
  • Filter: Sand and gravel are layered in a drain, which allows seepage to drain away without eroding soil around the dam.
  • Foundation: Soil or natural rock foundations are typically used as the base of a dam.
  • Freeboard: The vertical distance between the reservoir's water level and the top of the dam
  • Hydroelectric Power : Some dams produce electricity, which is known as hydroelectric power.
  • Hydrograph: A graph that depicts the flow rate or flow depth at a particular breach point (either above or below the dam)
  • Hydrology: The overall science of water, including the distribution, circulation, use, and properties of it
  • Levee: Long, low embankments built along a river to protect the surrounding land from flooding
  • Outlet Works: The structure that provides for the normal water flow throughout the dam is referred to as the outlet works.
  • Migration: The creation of dams can interfere with the natural migration, or movement, of fish.
  • Reservoir: The body of water created when a dam slows or changes the natural flow of a river or stream
  • Riprap: Suitable materials (including blocks, cement bags, and layers of rock) are placed along an embankment to protect against erosion.
  • Seepage: Natural water movement through the abutments, embankments, or foundation of a dam
  • Slide: A mass of earth moving down a dam embankment or slope is known as a slide.
  • Slope: The angle of the side of the dam's embankment
  • Spillway: The structure that allows for the controlled movement and dissipation of excess water by conducting the water either around, over, or through the dam
  • Stilling Basin: The area purposefully built to allow the energy of fast-moving water to dissipate safely without causing erosion to the dam, embankments, or nearby land
  • Trash Rack : The device situated at the dam's intake that prevents debris from entering the intake.
  • Tributary: A tributary is an offshoot stream of a larger body of water.
  • Turbine: A machine that produces power when a wheel, usually fitted with vanes, is made to move by fast-flowing water
  • Watershed: A specific land area where all water on it or under it drains to the same place
  • Weir: A low dam built across a stream to raise the water level upstream

Texas Dams and Reservoirs

Hydropower Explained

Humans have long been using the force of flowing water to produce mechanical and electrical energy. Thousands of years ago, the power of water was used to turn paddle wheels that ground grain. Before electricity was available, grain and lumber mills in the United States were powered by hydropower. Hydropower was first used to generate electricity in the United States in 1880 in Grand Rapids, Michigan. Two years later, in 1882, the first hydroelectric power plant in the U.S. opened near Appleton, Wisconsin. Large dams on major rivers help to generate most of the hydroelectricity produced in the U.S., and most of these dams were built before 1980. Hydroelectricity is the largest renewable energy source the United States uses, representing about 7% of all electricity generated.

Hydroelectric power plants are typically located on a body of water. Swiftly moving water in a large river, like the Columbia River, has a powerful flow, as does water that falls from a high point, like Niagara Falls. That energy is captured when the water enters a pipe and then pushes against the blades of a turbine. The turbine spins, and this energy is captured by a generator to produce power. There are two different types of hydroelectric systems. Run-of-the-river systems use the force of the river's natural flow to spin the turbine, while reservoir systems rely on releasing water from a reservoir through a dam.

By: Jim Olenbush