Hydrosphere

Question 1

Describe the Global Hydrological Cycle (8) [DIAGRAM]

Answer 1

DRAW DIAGRAM

• Water evaporates from the ocean into the atmosphere
• This water condenses to form clouds
• Wind carries the clouds inland by advection
• The cloud droplets become heavy and fall as precipitation
• The precipitation reaches land and runs off the surface to the ocean if the land is impermeable
• If the land is permeable, the water droplets infiltrate the soil and move towards the ocean as soil through-flow
• The water could also percolate into the rock below the soil and move as groundwater flow towards the ocean
• Some run off os soil through-flow may be absorbed by trees and transpired back into the atmosphere

Question 2

How have humans had an effect on the Global Hydrological Cycle? (10)

Answer 2

Mining has an impact on cycle

• Mining reduces vegetation cover, resulting in more surface run off
• Reduced vegetation cover also results in lower evapo-transpiration, altering rainfall patterns

Urbanisation has an impact on cycle

• More impermeable surfaces increases surface run off, raising river levels
• Impermeable surfaces also decrease amount of groundwater storage, reducing the water table
• Urbanisation requires takes water to use in cities, reducing water in rivers due to reservoirs being built

Deforestation has an impact on cycle

• Cutting down trees increases surface run off
• It also decreases evapo-transpiration, and alters cloud formations
• There will be more extreme river flows as water is not intercepted by vegetation

Irrigation has an impact on cycle

• It can increase evaporation by placing water in surface stores
• It involves taking water from a river which can reduce the rivers flow
• The crops that irrigation is used for will absorb water as they grow, which increases evapo-transpiration

Question 3

Describe the movement of water within a drainage basin, referring to inputs, storages, transfers and outputs (8)

Answer 3

Each drainage basin is a system with inputs, storages, transfers and outputs.

• Inputs are where water enters the system

• Water can enter the system as precipitation

• Storages are places where water is held in the system

• Water can be held on lakes on the surface or in soil and rocks in the ground

• Tranfers are processes by which water moves through the system

• The water can move as surface run off, or as through-flow underground

• Outputs are where water leaves the system

• The water can leave the system by entering the sea through rivers or by being evaporated into the atmosphere

Question 4

How does erosion change from the upper course to the lower course of a river? (5)

Answer 4

The Upper Course

• Areas with steep gradients will have an increased velocity and so the potential for erosion is higher
• The river can transport larger pieces of rock in the upper course so can erode the sides of the river by abrasion
• Hydraulic action occurs so will wear away the river bed by the force of water acting on it

The Middle Course

• The main areas of erosion will occur on the outside bends of the river through hydraulic action and abrasion

The Lower Course

• Erosion at this point is minimal but may be found in meanders

Question 5

Describe the formation of a meander (8) [DIAGRAM]

Answer 5

• Meanders begin where riffles and pools develop across the bed of a river
• A riffle is a shallow area of the river where there is less speed, so more deposition
• A pool is a deep area of the river where there is more speed, so more erosion
• The flow of the river is deflected away from the slow moving riffle towards the fast moving pool, swinging the current from side to side
• As the river swings in this motion, lateral erosion occurs, creating a river cliff on alternating banks
• As these banks increase in size more water is deflected here, so there is less water flowing across the riffles
• As the energy of the water in the riffles decrease, the river deposits here and creates a point bar
• This process keeps going, and creates a clearly defined meander in the river

Question 6

Describe the formation of an ox-bow lake (6) [DIAGRAM]

Answer 6

• At lateral erosion continues to occur, the river’s meander becomes more sinuous
• lateral erosion at the outer banks narrows the neck of the meander
• During a time of extra river energy, like a flood, the river cuts through this neck of the meander and forms a new channel
• After the flood the river may continue to flow through this channel
• As the river flows along this channel, it deposits at the sides due to slow flow, and eventually these deposits seal off the old meander
• The old meander now becomes an ox-bow lake

Question 7

Describe the formation of a waterfall (6) [DIAGRAM]

Answer 7

• The river flows over bands of softer and harder rocks
• The softer rock is eroded more quickly
• The river undercuts the harder rock leaving an overhang
• The river forms a plunge pool below the waterfall
• As the overhanging rock is unsupported, it falls into the plunge pool
• The waterfall is moved upstream, and this process continues to cut back a gorge into the hillside

Question 8

Describe and explain the changing river levels in a typical hydrograph (6)/(6) [DIAGRAM]

Answer 8

Rising Limb

- Short Lag time

• The drainage basin may be small, so water takes less time to reach the river
• The slopes of the basin may be steep, so water gets to the river more quickly
• If rock is impermeable in the basin, water flows as run off and not through soil
• If the stream density is high in the basin then more water can flow into the river through tributaries
• If there is little vegetation, water is not intercepted

OR

- Long lag time

• The drainage basin may be large, so water takes more time to reach the river
• The slopes of the basin may be gentle, so water gets to the river slowly
• If rock is permeable in the basin, water flows through flow and not as run off
• If the stream density is low in the basin then there is less water that can flow into the river through tributaries
• If there is lots of vegetation, water is intercepted

Falling Limb

• Less steep than the rising limb as water is still reaching the river as soil though flow or groundwater flow

Question 9

What are the 7 characteristics of a river can you comment on?

Answer 9

• Width
• Straightness
• Discharge (Tributaries)
• Stage
• Tidal
• Artificial or natural
• Landforms