Best Site For A Dam

Question 1

Which rocks would be unsuitable for a dam?

Answer 1

Limestone would be unsuitable because it is as soft rock and could be eroded and so would not support the dam

Question 2

Why is is important for the rocks to be hard and strong?

Answer 2

Hard rocks ensure that no water will get through or erode the rock on the dam - dam is successful.

Question 3

Give an example of a suitable hard rock

Answer 3

Granite

Question 4

The dam reservoir should be

Answer 4

Deep and narrow as this ensures that as much water as possible can be stored without facing the effects of evaporation
As much water as possible is stored - little lost

Question 5

What areas are best to avoid and why?

Answer 5

Area with high evaporation rates because this means that as little as possible is lost and there is maximum storage

Question 6

How to reduce the amount of water lost

Answer 6

Engineers may try to reduce the amount of water lost through evaporation by putting solid foundations in place using hard rocks such as granite

Question 7

What width of cross section should be used and why?

Answer 7

Narrow cross section because this reduces the area from which water can be evaporated

Question 8

What size of valley should be used and why

Answer 8

A large deep valley as this will mean that less water is evaporated from the surface

Question 9

What way should the arch face and why

Answer 9

Upstream as this deflects the pressure of the water to the canyon walls

Question 10

Rocks under a dam and reservoir should be

Answer 10

Impermeable
Because this prevents water from seeping through and being lost and also does not get trapped inside porous/permeable rocks

Question 11

Accessibility

Answer 11

Important to ensure that construction workers and maintenance staff can access the dam easily - proximity to settlement is key

Question 12

Benefits of the area

Answer 12

Nearby market for water and/or electricity limits the prospect of water loss via evaporation than if water is being transported further away
Reduction in cost of infrastructure required to move the water and/or electricity

Question 13

Land

Answer 13

Authorities have to consider the value of the land that is to be flooded following the construction of a large dam.
If farmland, settlement or important landmarks are lost then these will require compensation
Historical sites such as Native American burial sites must be treated sensitively to ensure that valuable landmarks are preserved

Question 14

Geology

Answer 14

Important that the bedrock is solid due to the weight of the dam and reservoir - soft rock avoided
Impermeable/non porous rocks will prevent water loss through the ground

Question 15

Supply

Answer 15

Areas with reliable rainfall and adequate water are identified to ensure that reservoirs fill to appropriate levels

Question 16

Climate

Answer 16

Low temperature preferred
Hot locations avoided
Minimises risk of water loss through evaporation