Hydrological cycle

Question 1

The beginning of the hydrological cycle - origins of clouds

input

Answer 1

Sun’s energy heats oceans/lakes/rivers and areas of surface water, and causes the water vapour to be evaporated and lifted into the atmosphere, where it cools and condenses to form clouds = CONDENSATION

Clouds are moved through ADVECTION, where they lose precipitation over land/ over water, through rain, sleet or snow

Question 2

As precipitation falls, it can reach the ocean in a number of ways: (5)

Answer 2

1. Rain falling directly on water, will flow in rivers or lakes, making its way back to the ocean = STREAMFLOW
2. Rain falling on land, will flow over land towards a river, contributing to SURFACE RUN OFF
3. It can fall on land and infiltrate into the soil, passing through the surface soil layer, travelling towards a river channel in a process known as THROUGH FLOW
4. It can percolate down in to the soil layer, to the rock layer at the bottom where it moves as GROUNDWATER FLOW towards a river channel
5. Water can be stored in a loch, lake, or river, where it can be EVAPORATED directly from the body of water

Question 3

Water can be intercepted before it reaches the ground through:

Answer 3

1. Interception by TREES, where the trees and plants may absorb the water and use/store it in roots
2. Trees/plants may hold the water on their surface, where it can be evaporated or absorbed into the leaves and exhaled from the leaves when its warm, so the water is lost through EVAPOTRANSPIRATION, back into the atmosphere

Question 4

Snow’s part in hydrological cycle

Answer 4

Snow that falls on hills takes longer to reach the ocean, as it may be STORED in glaciers or in sheet ice until the temp warms and it melts and flows into a stream

Sometimes sun is strong enough it can evaporate moisture from the snow = SUBLIMATION

Question 5

Human impact on the hydrological cycle

Answer 5

Deforestation
Urbanisation
Mining
Dams and reservoirs
Irrigation

Question 6

Human impact on the hydrological cycle

Deforestation

Answer 6

• cutting down trees increases surface run off, which could lead to flooding
• there’s a decrease in interception (the capture of water by plants and leaves) which increases the amount of water reaching the ground
• decreases evapotranspiration (when water is evaporated from leaves), which leads to decreased cloud formation as there’s less water being evaporated

Question 7

Human impact on the hydrological cycle

Urbanisation

Answer 7

• Natural surfaces are removed and covered with tarmac, which is an impermeable layer meaning water can’t infiltrate into the ground. Instead, water is channelled into drains which speeds up overland flow as the water is artificially managed, and so water reaches the river much faster
• Evaporation from tarmac increases, as there’s no percolation into the ground, meaning there’s more cloud formation
• This means less water reaches the groundwater storage so the water table is reduced

Question 8

Human impact on the hydrological cycle

Mining

Answer 8

• Reduced vegetation leads to increased surface run off, higher evaporation and cloud formation, which alters rainfall patterns
• The silting of lakes, rivers, reservoirs etc. leads to reduced storage capacity as the bodies of water are clogged with sediment
• Power stations (particularly coal) use high amounts of water for cooling processes, reducing groundwater storage levels + water vapour is artificially released, increasing number of clouds and influencing local rainfall patterns

Question 9

Human impact on the hydrological cycle

Dams and reservoirs

Answer 9

• Due to large surface areas of water, evaporation is increased. Water turns into gas and as the moist air rises, it cools and condenses to form clouds, which increases clouds and rainfall in areas - local climate is affected
• Water storage is increased and due to the artificial placement of dams/reservoirs = stream flow is decreased

Question 10

Human impact on the hydrological cycle

Irrigation

Answer 10

• Field drains are used to speed up through flow rates on land in to rivers - the drains have tiny holes whereby water seeps through the soil much faster than usual as the soil is drained to be used in agriculture
• This decreases through flow and more water is infiltrated into the ground. This means there’s more water in storage within the ground and plants, and so less water reaches the river