Factors Affecting Changes In The Water Cycle

Question 1

Natural changes over time affecting water cycles include?

Answer 1

1. Storm Events

2. Seasonal Changes

Question 2

Human changes over time affecting water cycles include?

Answer 2

1. Farming practices
2. Land use change
   (Including urbanisation + deforestation)
3. Water Abstraction

Question 3

Describe Storm Events as a Natural Change which Affects The Water Cycle

Answer 3

• Storm Events lead to increase in channel flow and Overland flow
• depending on the drainage basin, flood events may occur
• As air temperatures rise, there is an increase in Evaporation and an increase in the amount of water vapour held in the Atmosphere. This leads to intense rainstorms, where there is less infiltration, more Overland flow and more flooding due to the rainfall
• when water vapour condenses into rainfall, it releases heat energy and this drives a stronger intensity of the storm

Question 4

Describe Seasonal Changes as a Natural Change which Affects The Water Cycle

Answer 4

• in wet seasons, (e.g autumn, winter), precipitation exceeds evapotranspiration, which leads to a water Surplus. Groundwater stores are full and so more Overland flow results in higher discharge in rivers
• in drier seasons (summer, spring), evapotranspiration exceeds precipitation. Groundwater stores are depleted and water used by humans and plants are not replaced, which leads to a water deficit. Also soil water = drier soils encourage infiltration, but hard-baked soils encourage Overland flow. Storms more frequent in summer, but less rainfall. Also vegetation grows.
• in mountainous regions, increased Overland flow and runoff occur due to ice melting in warmer conditions. This means countries to south of Himalayas, may face flooding but will use the extra water for agricultural and domestic use

Question 5

Describe Farming Practices as a Human Change which Affects The Water Cycle

Answer 5

• particularly in hotter climates, farming has a significant effect on the water cycle.
• irrigation (watering crops w/ water from rivers + pipes rather than rainfall) of plants = lower channel levels in rivers and groundwater levels

Question 6

Describe Land Use Changes as a Human Change which Affects The Water Cycle

Answer 6

Land use changes that impact the water cycle the most is:
• Urbanisation
- the replacement of vegetated ground with impermeable concrete and tarmac. In urbanised environments, water cannot infiltrate the soil which increases Overland flow and makes flooding more likely. Soil water and groundwater stores are reduced
- also cities create Drainage systems to quickly transport water away from urban areas (these increase flooding as river levels receive water from the drainage system too quickly in a large amount)
• Deforestation
- the removal of trees, leading to Overland flow and soil erosion. This reduces soil water stores.
- Evapotranspiration is reduced as there is minimal vegetation cover with fewer leaves and roots
- less interception due to reduced canopy
- Overland flow and throughflow increase due to lack of vegetation to slow down these processes
- increased river discharge and risk of local flooding

Question 7

Describe Water Abstraction as a Human Change which Affects The Water Cycle

Answer 7

The extraction of water from rivers or groundwater aquifers. Water that is abstracted for irrigation, industry and domestic purposes have significant impacts on the local water cycle.

• growth of global population increases water demand
• where precipitation is low, groundwater is an alternative water supply
• supply of water in porous rocks underground is known as an aquifer
• excessive extraction of aquifers is unsustainable and can lead to groundwater stores being depleted
• aquifers can also become contaminated by inflowing saltwater if the water table drops below sea level. Abstraction can result In low flow conditions in rivers, which can have harmful impacts on ecosystems