Hydrological Cycle

Question 1

What are drainage basins?

Answer 1

Local open systems

Question 2

What is the global hydrological system?

Answer 2

A closed system - there are no input or outputs

Question 3

4 facts about drainage basin hydrological cycles?

Answer 3

1. a river’s drainage basin is the area surrounding the river where the rain falling on the land flows into that river. Also known as the river’s catchment
2. the boundary of a drainage basin is the watershed - any precipitation falling beyond the watershed enters a different drainage basin
3. drainage basins are open systems with inputs and outputs
4. water comes into the system as precipitation and leaves via evaporation, transpiration and river discharge

Question 4

Inputs - precipitation - define?

Answer 4

includes all the ways moisture comes out of the atmosphere

mainly rain, but also snow, hail, dew and frost

Question 5

storage - water coming into the system - types? (5)

Answer 5

interception
vegetation storage
surface storage
groundwater storage
channel storage

Question 6

explain interception

Answer 6

when some precipitation lands on vegetation or other structures, like buildings and concrete or tarmac surfaces, before it reaches the soil
creates a significant store of water in wooded areas
storage is only temporary as the collected water evaporates quickly

Question 7

explain vegetation storage

Answer 7

water thats been taken up by plants

is all water contained in plants at any one time

Question 8

explain surface storage

Answer 8

includes water in puddles (depression storage), ponds and lakes

Question 9

explain groundwater storage

Answer 9

water stored in the ground, either in soil (soil moisture) or in rocks
water table is the top of the surface of the zone of saturation - zone of soil or rock where all the pores in the soil or rock are full of water
porous rocks (lots of holes in them) that hold water are called aquifers

Question 10

explain channel storage

Answer 10

water held in a river or stream channel

Question 11

types of flows and processes (10)

Answer 11

surface runoff
throughfall
stemflow
throughflow
infiltration
percolation
groundwater flow
baseflow
interflow
channel flow

Question 12

explain surface runoff/overland flow

Answer 12

water flowing over the land
can flow over whole surface or in little channels
common in arid areas where torrential rain falls on hard baked land

Question 13

explain throughfall

Answer 13

water dripping from one leaf (or another plant) to another

Question 14

explain stemflow

Answer 14

water running down a plant stem or a tree trunk

Question 15

explain throughflow

Answer 15

water moving slowly downhill through the soil

faster through ‘pipes’ - things like cracks in the soil, or animal burrows

Question 16

explain infiltration

Answer 16

water soaking into the soil
infiltration rates are influenced by soil type, soil structure and how much water is already in the soil
in a heavy storm, water can’t infiltrate fast enough, so it flows over the surface

Question 17

explain percolation

Answer 17

water seeping down through soil into the water table

Question 18

explain groundwater flow

Answer 18

water flowing slowly below the water table through permeable rock
water flows slowly through most rocks, but rocks that are highly permeable with lots of joints (gaps water cannot get through) can have faster groundwater flow, e.g limestone

Question 19

explain baseflow

Answer 19

groundwater flow that feeds into rivers through river banks and river beds

Question 20

explain interflow

Answer 20

water flowing downhill through permeable rock above the water table

Question 21

explain channel flow

Answer 21

water flowing in the river or stream itself

also known as river’s discharge

Question 22

outputs - water leaving system

4 types?

Answer 22

evaporation
transpiration
evapotranspiration
river discharge/river flow

Question 23

explain evaporation

Answer 23

water turning into water vapour - liquid to gas

Question 24

explain transpiration

Answer 24

evaporation from plant leaves
plants and their trees take up water through their roots and transport it to their leaves where it evaporates into the atmosphere

Question 25

explain evapotranspiration

Answer 25

process of evaporation and transpiration together

Question 26

what is potential evapotranspiration

Answer 26

amount of water that could be lost by evapotranspiration

Question 27

what is actual evapotranspiration

Answer 27

what actually happens
e.g in desert PET is high (as heat increases amount of evap) but actual transpiration is low (as not much moisture in first place)

Question 28

what is the water balance

Answer 28

shows balance between inputs and outputs

affects how much water is stored in the basin

Question 29

what is the water balance in the UK

Answer 29

1. in wet seasons, precipitation exceeds evapotranspiration. this creates water surplus. ground stores fill with water so theres more surface runoff and higher discharge, so river levels rise.
2. in drier seasons precipitation is lower than evapotranspiration. ground stores are depleted as some water is used(e.g by plants/humans) and some flows into the river channel, but isn’t replaced by precipitation
3. so, at the end of a dry season theres a deficit (shortage) of water in the ground. ground stores are recharged in the next wet season (i.e autumn)