Geo P2 Lesson 11: Dams and Resevoirs

Dam

- A barrier placed across a river to block the flow of water

Locks

- A structure that allows boats to navigate around the dam on a river

Disadvantages - Expensive

- Building a dam can be very expensive

Advantage - Water Storage

- Dams act as reservoirs in place where rain is seasonal - In times of high precipitation, water is stored in reservoir - This water can be used in the dry season when river flow is low

Multipurpose Scheme

- Dams are often built not to just provide renewable energy, but also to prevent flooding and create a store of water

Disadvantages - Dam Failure

- Dams can cause serious flooding downstream if structural failure occurs

Changes to Hydrology Upstream of Dam

- Evaporation is higher in reservoir because it has a higher surface area than the river, leading to water loss - Aswan Dam loses 30% of water from this - Siltation (sedimentation) of the reservoir occurs when the river flow stops, depositing mud in reservoir, decreasing water storage capacity - Shallow water also evaporates more easily

Disadvantages - Evaporation of Stored Water

- Evaporation is higher in reservoir because it has a higher surface area than the river, leading to water loss - Can be reduced by covering reservoir surface with plastic balls

Disadvantages of Dams and Reservoirs

- Expensive - Flooding - Evaporation of Stored Water - Siltation (Sedimentation) - Production of Concrete Creates Greenhouse Gases - Dam Failure

HEP

- Hydroelectric Power - Electricity generated by the force of falling water

Disadvantages - Production of Concrete Creates Greenhouse Gases

- Producing concrete from limestone releases large amounts of Carbon Dioxide

Changes to Hydrology Downstream of Dam

- Reduced flooding because dam controls water flow - Reduced sediment in water can affect levees, deltas, and floodplains downstream - Lower water temp. because water released from reservoir is often from the bottom and can affect the ecosystem - Less oxygen in water, because water released from the bottom of reservoir contains less oxygen

Disadvantages - Flooding

- Reservoir created by dam can flood nearby settlements and agricultural land

Advantage - Recreation Purposes

- Reservoirs good for tourism (fishing and boating)

Disadvantages - Siltation (Sedimentation)

- Sediment slowly fills up in the reservoir - This decreases water storage capacity - Shallow water evaporates more easily

Resevoir

- The artificial store (lake) that develops behind a dam wall

Advantages of Dams and Reservoirs

- Water storage - Flood control - Hydroelectric power - Recreation purposes

Advantage - Hydroelectric Power

- Water stored in the dam can be used to generate hydroelectric power

Advantage - Flood Control

- When floodwaters from upstream reach a dam, water is held back and released in a controlled manner = This regulates flooding downstream