Hydrology and Fluvial Geomorphology Key Terms

Question 1

Hydrological Cycle

Answer 1

The circulation of water through the atmosphere and across the Earth’s surface

Question 2

Global Hydrological Cycle

Answer 2

The distribution of water as it moves either as a liquid, solid or vapour between the ocean, atmosphere and the land

Question 3

Local Hydrological Cycle

Answer 3

The movement and distribution of water in a drainage basin

Question 4

Porosity

Answer 4

The ability of rocks to store water

Question 5

Precipitation

Answer 5

The fallout of water drops or frozen particles from the atmosphere
Precipitation intensity and type makes a big difference

Question 6

Interception

Answer 6

Water that is caught / intercepted by vegetation
Water is stored temporarily until it is transpired or gravity moves it downwards by throughfall or stemflow
Interception rates can differ depending on the season (in winter there are less leaves so less water is intercepted)`

Question 7

Throughfall

Answer 7

When water falls directly through the air to the ground
It is much faster than stemflow

Question 8

Stemflow

Answer 8

The flow of water down the trunk or stem of a plant
The process that directs precipitation down plant branches and stems

Question 9

Interception Loss

Answer 9

Evaporation from the surface of the leaf

Question 10

Surface Storage

Answer 10

The part of precipitation retained at the ground surface
Includes temporary things such as puddles as well as larger things such as ponds and lakes

Question 11

Infiltration

Answer 11

When surface water soaks down from the surface into the soil
The ground absorbs the water and prevents it from flowing into rivers (as surface runoff) which could cause flooding

Question 12

Factors affecting Infiltration

Answer 12

Rainfall intensity and duration
Vegetation cover
Antecedent soil moisture
Evaporation rate
Slope angle
Degree of urban development
Soil composition / permeability

Question 13

Soil Type affecting Infiltration

Answer 13

Clay has low levels of infiltration as it has limited pores which water can enter so it flood quickly
Loam and Sand are much more porous so they can hold more water so it doesn’t flood as easily or quickly

Question 14

Overland Flow / Surface Runoff

Answer 14

The movement of water over the land due to gravity or a downslope to a body of water
It occurs when precipitation exceeds the infiltration capacity of the soil
They are very fast lateral flows
It is a key factor in causing flash flooding

Question 15

Hortonian Overland Flow

Answer 15

Soil is not saturated but precipitation rate exceeds infiltration rate

Question 16

Saturated Excess

Answer 16

Soil is already saturated and no more infiltration can occur

Question 17

Throughflow

Answer 17

The movement of water laterally and downhill through the upper layers (more shallow and aerated) of the soil
The water travels through percolines which are natural gaps in the soil
It is faster and shallower

Question 18

Groundwater Flow

Answer 18

Throughflow that occurs in the bottom section of the soil
It is slower and deeper

Question 19

Groundwater Storage

Answer 19

Water stored in pores and spaces of underlying permeable and porous rocks
The phreatic zone concerns the layers of rock which are saturated.
This is dynamic and shifts over seasons and decades.

Question 20

Baseflow

Answer 20

The portion of river’s discharge that comes from groundwater and throughflow only

Question 21

Evapotranspiration

Answer 21

Evapotranspiration is the sum of evaporation and transpiration
It is an output
Both are affected by similar factors

Question 22

Factors affecting Evapotranspiration

Answer 22

Temperature
Humidity
Wind speed
Light intensity
Vegetation type

Question 23

Aquiclude

Answer 23

Stops percolation

Question 24

Springs

Answer 24

The emergence of throughflow occurs at the surface due to impermeable layers of rock
The shallow underground throughflow force to the surface and becomes surface runoff
Leaves rocks as surface runoff

Question 25

River Discharge

Answer 25

The volume of water moving in a river.
At its lowest point, a river will discharge into an ocean or sea
This is an output

Question 26

Trellised Drainage Pattern

Answer 26

Trellised pattern develops in areas of alternating, weak and resistant bedrock

Question 27

Rectangular Drainage Pattern

Answer 27

Rectangular pattern develops on highly jointed bedrock

Question 28

Dendritic Drainage Pattern

Answer 28

Dendritic pattern develops on relatively uniform bedrock

Question 29

Radial Drainage Pattern

Answer 29

Radial pattern develops on isolated volcanic cones or domes

Question 30

Discharge

Answer 30

The movement of water in channels such as streams and rivers

Question 31

Water Balance / Budget

Answer 31

When inputs and outputs are balanced, the system is said to be in a state of dynamic equilibrium

Question 32

Soil Moisture Deficit

Answer 32

The degree to which soil moisture falls below field capacity.
In temperate areas, during late winter and early spring, soil moisture deficit is very low, due to high levels of precipitation and limited evapotranspiration

Question 33

Soil Moisture Recharge

Answer 33

It occurs when precipitation exceeds potential evapotranspiration - there is some refilling of water in the dried-up pores of the soil

Question 34

Soil Moisture Surplus

Answer 34

It is the period when soil is saturated and water cannot enter, and so flows over the surface

Question 35

Soil Moisture Utilisation

Answer 35

It is the process by which water is drawn to the surface through capillary action

Question 36

Percolation

Answer 36

When water moves slowly downwards from the soil into the bedrock

Question 37

Aquifers

Answer 37

They are permeable rocks, such as sandstone and limestone, that contain significant quantities of water
The water in aquifers moves slowly so they act as natural regulators in Hydrological Cycle by absorbing rainfall that would otherwise enter streams and cause flooding
They also maintain stream flow during dry periods

Question 38

River Regime Graph

Answer 38

Annual variation in the discharge of a river

Question 39

Storm Hydrograph

Answer 39

Shows how the discharge of a river varies over a short period of time

Question 40

Water Table

Answer 40

The uppermost layer of the phreatic zone is the water table
It separates the water-saturated ground and the unsaturated ground