Hydrology and Fluvial Geomorphology: The drainage basin system

Question 1

What is precipitation?

Answer 1

Water falling from sky as rain, hail, sleet or snow

Question 2

What is interception?

Answer 2

The capture and storage of precipitation by level, branches, etc of trees and vegetation such that it does not directly fall to the ground. The water may then be evaporated or absorbed by the plant or reach the ground as throughfall or stemflow

Question 3

What is surface storage?

Answer 3

Water that has not infiltrated the surface and is stored on the surface in the form of puddles lakes etc. Some is temporary but others are permanent

Question 4

What is soil moisture storage

Answer 4

Subsurface water in the soil and subsurface layers above the water table

Question 5

What is groundwater storage?

Answer 5

Percolated water that is held within the aquifers below the water table (phreatic water). Groundwater accounts for 97% of all freshwater on earth. Recycling timeframe 20,000 yrs

Question 6

What is channel storage?

Answer 6

All water stored in rivers, streams and other drainage channels

Question 7

What is stemflow?

Answer 7

The progression of intercepted precipitation down the stems and trunks of vegetation

Question 8

What is through fall?

Answer 8

Water that falls to the Earth’s surface from branches/leaves through gaps in the vegetation or that drops from leaves & twigs

Question 9

What is overland flow?

Answer 9

Movement of water across the surface of the ground or downslope as it can’t be absorbed into the ground; leads to the low of water on the surface direct to the channel

Question 10

What is hortonian overland flow?

Answer 10

Movement along the surface which occurs when rainfall exceeds the infiltration capacity of the soil. This can be due to intensity of rainfall/snow melt/antecedent moisture/impermeability of the surface/slopes

Question 11

What is saturated overland flow?

Answer 11

Water is not infiltrated on a slope due to the saturated nature of the soil, and flows across the surface. This most frequently occurs on the lower parts of slopes that have been saturated by water from above.

Question 12

What is infiltration?

Answer 12

The movement of water downwards into the soil from the surface

Question 13

What is percolation?

Answer 13

The downward movement of infiltrated water under gravity through the pores, joints etc. of the soil and underlying permeable rock

Question 14

What is throughflow?

Answer 14

the lateral downslope movement of water below the surface within soils after it has been infiltrated into the soil. Soil flows under gravity towards a stream channel or lake through percolines and pipes

Question 15

What is groundwater flow/base flow?

Answer 15

Water flows under gravity and hydrostatic pressure towards the river channel. Discharge into a stream from the groundwater store, especially sustaining flow between rainfall events. Relatively constant, but increase slightly following rain

Question 16

What is groundwater recharge

Answer 16

Water that has soaked into the ground and moved through pores and fractures in the soil and rock to the water table to fill up previously depleted groundwater stores. Recharge maintains the supply of water that flows through the ground water system to wells, streams and springs. Occurs when precipitation exceeds evapotranspiration and water percolates downwards to the aquifer

Question 17

What is a spring?

Answer 17

Flows of water where the water table intersects with the surface

Question 18

What is channel flow/stream flow

Answer 18

Movement of water in channels such as streams or rivers

Question 19

What is evapotranspiration?

Answer 19

Combination of moisture loss due to evaporation and transpiration from the stomata of vegetation

Question 20

What is evaporation?

Answer 20

Process by which a liquid is changed into a gas

Question 21

What is sublimation?

Answer 21

Process by which solid is changed into a gas

Question 22

What is transpiration?

Answer 22

The movement of water within plants and its loss as vapour through the stomata of the leaves to the atmosphere.

Question 23

What is river discharge?

Answer 23

Movement of water in channels such as streams and rivers.

Question 24

What is the water table?

Answer 24

Upper layer of phreatic zone. This varies seasonally depending on precipitation levels.

Question 25

What is the phreatic zone?

Answer 25

Permanently saturated zone within solid rocks and sediments

Question 26

What is the aeration zone

Answer 26

Zone that is seasonally wetted and seasonally dries out above the water table.

Question 27

What is an aquifer?

Answer 27

Rocks that contain significant quantities of water

Question 28

What is porosity?

Answer 28

The proportion of pore space to solid material and therefore the ability to hold water

Question 29

What is permeability?

Answer 29

Permeability is the rate and ease with which water may be transmitted within a rock or the rate with which it is able to pass through it via joints and fissures

Question 30

What is antecedent moisture?

Answer 30

Moisture in the soil that is retained after a period of rainfall

Question 31

What is the hydrological cycle?

Answer 31

Cycle of water between atmosphere, lithosphere & biosphere

Question 32

What is infiltration capacity?

Answer 32

Maximum rate at which rain can be absorbed by a soil in a given condition