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