Hydrological Cycles (Hydrosphere)

Question 1

• What is the hydrological cycle of a ‘drainage basin’?

Answer 1

• INPUT:
  ➞ The main input within a drainage basin
  ↳ is precipitation (e.g. rain, snow, etc) 💧❄
  ➜ with the amount & duration having an impact on the level of water in the system ⏳
  ➜ rain clouds are fed by evaporation from water sources including the seas/oceans 🌊
• STORAGE:
  ➞ Water
  ↳ then makes its way into a number of stores within the drainage basin 🏺
  ➜ on the surface, water is stored in rivers and lakes 🌊
  (water can also be stored on the surface within vegetation, which intercepts precipitation 🌳)

➞ Water
↳ is also stored below the surface as groundwater 🚰
➜ the permeability of the soil & rock in the area will determine how much water can be stored as groundwater

TRANSFERS:
➞ Water
↳ is transferred on the surface of the basin 🏞️
➜ This is occurs in 2 ways as SURFACE RUN-OFF 💧
* where water flows (across the surface)
* & (via river channels) within the drainage basin

➞ Throughflow & groundwater flow
↳ refer to the movement below the surface 🔽
➜ and are characterized by slow movement of water.

OUTPUT:
➞ Outputs
↳ are the means by which water exits the drainage basin (e.g. discharged back to seas/oceans)
➜ Water can be lost directly from the channel or water stores through the process of evaporation and evapotranspiration.

Question 2

• What is the influence of DEFORESTATION on the hydrological cycle in a drainage basin?

Answer 2

1.) * DEFORESTATION:
➞ Deforestation
↳ results in increased runoff 🌊

➞ However,
↳ this may be matched by increased afforestation (planting trees on previously non-forest land) 🌳
➔ areas of mature woodland are able to reduce the impact of precipitation 🌧️

➞ But,
↳ when areas cleared
➔ even moorland and grassy areas are less effective in delaying rapid run-off and discharge

➞ Soil erosion
↳ may also increase with the loose soil being carried to the river
➔ reducing channel capacity and resulting in less water being required before flooding takes place 🌊

➞ Plant roots (especially trees)
↳ reduce throughflow by taking up water from the soil.

Question 3

• What is the influence of AGRICULTURE & IRRIGATION on the hydrological cycle in a drainage basin?

Answer 3

2.) * AGRICULTURE & IRRIGATION:
➞ Overgrazing & ploughing
↳ leaves areas with less vegetation
➔ resulting in a similar outcome to deforestation 🪵

➞ When you take water from a river or the ground (using a well) ⛲️
↳ you may reduce river discharge
➔ water will also be more exposed to evaporation from open canals, ditches and channels

➞ Irrigation
↳ has an impact on the hydrological cycle
➔ since it alters flow & storage.

Question 4

• What is the influence of MINING & INDUSTRIAL ACTIVITIES on the hydrological cycle in a drainage basin?

Answer 4

3.) * MINING & INDUSTRIAL ACTIVITIES:
➞ Opencast mining/quarrying
↳ often results in the displacement of courses & rivers

➞ Silting-up
↳ of lakes, reservoirs & rivers
➜ reduces their storage capacity & increases run-off & discharge.

➞ Opencast quarrying
↳ reduces vegetation cover & increases evaporation

Question 5

• What is the influence of CLIMATE CHANGE on the hydrological cycle in a drainage basin?

Answer 5

4.) * CLIMATE CHANGE:
➞ This can cause
↳ an alteration in river discharge

➞ Some climatologists
↳ suggest that there will be an increase of rainfall
➜ with more storms in some areas & increased flooding.

Question 5

• What is the influence of FLOOD MANAGEMENT on the hydrological cycle in a drainage basin?

Answer 5

5.) * FLOOD MANAGEMENT:
➞ These types of projects,
↳ (e.g. the construction of dams)
➜ alter discharge levels.

➞ Although,
↳ such projects are intended to reduce the likelihood & impact of flooding
➜ they alter river regimes too!

Question 6

• What is the influence of URBANISTATION on the hydrological cycle in a drainage basin?

Answer 6

6.) * URBANISAION:
➞ Urbanisation
↳ results in:
* houses 🏘️
* factories 🏭
* roads 🛣️
(covering the land)
➜ means that infiltration levels decrease & surface runoff increases.

➞ When roads are constructed
↳ there is an increase in the impermeable surface area
➜ which means there is a reduction in the amount of water that returns to ground & soil.

Question 7

• What is the impact of LAND USE on the interpretations of hydrographs?

Answer 7

1.) LAND USE:
➞ Urban areas 🌆
↳ are often covered in materials where water cannot infiltrate (impermeable) - (such as tarmac)
➜ This will have the same effect as in a river surrounded by impermeable rock or soil:
the water will travel overland,
* reducing lag time
* increasing peak discharge

➞ As water doesn’t infiltrate easy in urban areas,
↳ humans often build ‘storm drains’ that run directly into a river:
* reducing lag time
* increasing (river’s) peak discharge

➞ Forested areas🌳
↳ are covered in trees which intercept the falling precipitation (some of which will be stored and absorbed)
* increasing lag time
* reducing discharge

Question 8

• What is the impact of DRAINAGE DENSITY on the interpretations of hydrographs?

Answer 8

2.) DRAINAGE DENSITY:
➞ Basins that have many streams (high drainage density) drain more quickly 🌊
* shorter lag time
* steep falling limb

➞ This is due to the high drainage density
↳ which allows more water to drain out of them more quickly
➜ however, there is an increased risk of flooding.

Question 9

• What is the impact of PRECIPITATION & TEMPERATURE on the interpretations of hydrographs?

Answer 9

3.) PRECIPITATION & TEMPERATURE:
➞ Heavy storms ⛈️
↳ result in more water entering the drainage basins which results in higher discharge
➜ while the type of precipitation can also have an impact.

➞ The lag time is likely to be greater if the precipitation is snow rather than rain ❄️
↳ This is because snow takes time to melt before the water enters the river channel
➜ when there is rapid melting of snow, the peak discharge could be high.

➞ When precipitation is prolonged 🗓️
↳ then the land and soil will become waterlogged & saturated
➜ and once maximum saturation has been reached, then the drainage into the river will be fast.