Drainage Basins

Question 1

What is a drainage basin

Answer 1

A river’s drainage basin is the area surrounding the river where the rain falling on the land flows into that river. This area is also called the river’s catch
Drainage basins are open systems with inputs and outputs.

Question 2

Drainage Basin

Answer 2

The boundary of a drainage basin is the watershed - any precipitation falling beyond the watershed enters a different drainage basin.
Water comes into the system as precipitation and leaves via evaporation, transpiration and river discharge

Question 3

Inputs of Drainage basins

Answer 3

Precipitation includes all the ways moisture comes out of the atmosphere. Precipitation is mainly rain, but it also includes other types like snow, hail, dew and frost.

Question 4

Storage of Drainage basin

Answer 4

Interception is when some precipitation lands on vegetation or other structures, like buildings and concrete or tarmac surfaces, before it reaches the soil. Interception creates a significant store of water in wooded areas. Interception storage is only temporary because the collected water may evaporate quickly, or fall from the leaves as throughfal

Question 5

Vegetation storage

Answer 5

Vegetation storage is water that’s been taken up by plants. It’s all the water contained in plants at any one time.

Question 6

Surface storage

Answer 6

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

Question 7

Soil storage

Answer 7

Includes moisture in the soil.

Question 8

Groundwater storage

Answer 8

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

Question 9

Channel storage

Answer 9

Is so obvious that it’s often overlooked- it’s the water held in a river or stream channel

Question 10

Flows of Drainage basins

Answer 10

Infiltration is water soaking into the soil. Infiltration rates are influenced by soil type, soil structure and how much water’s already in the soil.

Question 11

Surface runoff

Answer 11

Is water flowing over the land. It can flow over the whole surface or in little channels. It happens because rain is falling on the ground faster than infiltration can occur.

Question 12

Throughfall

Answer 12

Is water dripping from one leaf (or other plant part) to another.

Question 13

Percolation

Answer 13

Is water seeping down through soil into the water table

Question 14

Stemflow

Answer 14

is water running down a plant stem or a tree trunk

Question 15

Throughflow

Answer 15

Is water moving slowly downhill through the soil. Throughflow is faster through “pipes” - things like cracks in the soil or animal burrows.

Question 16

Groundwater flow

Answer 16

Is 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 that water can get through) can have faster groundwater flow, e.g. limestone.

Question 17

Channel flow

Answer 17

Is the water flowing in the river or stream itself. This is also called the river’s discharge.

Question 18

Outputs of Drainage Basins

Answer 18

Evaporation
Transpiration is evaporation from within leaves -plants and trees take up water through their roots and transport it to their leaves, where it evaporates into the atmosphere.
River discharge, or river flow, is another output

Question 19

Evapotranspiration

Answer 19

Is the process of evaporation and transpiration together.

Question 20

Water Balance

Answer 20

Water balance is worked out from inputs (precipitation) and outputs (channel discharge and evapotranspiration). The water balance affects how much water is stored in the basin.

Question 21

The general water balance in the UK shows seasonal patterns: Wet seasons

Answer 21

In wet seasons, precipitation exceeds evapotranspiration. This creates a water surplus. The ground stores fill with water so there’s more surface runoff and higher discharge, so river levels rise.