Drainage Basin Characteristics- Inputs, Outputs, Stores, Flows

Question 1

Stemflow

Answer 1

water which trickles along twigs and branches and finally falls down the main trunk

Question 2

Precipitation

Answer 2

Conversion and transfer of moisture in the atmosphere to the land via rainfall, hail, dew and snow.

Question 3

Interception loss

Answer 3

water that is retained by plant surfaces and is later evaporated away or absorbed by the plant. Interception loss varies with different types of vegetation.
Less from grasses (shoots have smaller surfaces) than from woodland trees such as beeches. For agricultural crops (cereal). In the winter coniferous trees intercept more than deciduous in winter (lose their leaves in autumn and winter and therefore have a lower SA)

Question 4

Aquifers

Answer 4

rocks which contain significant quantities of water and are permeable providing a reservoir for water. Natural Regulator in hydrological cycle as water moves very slowly and absorbs water which would otherwise reach streams quickly. Also maintain stream flow in dry periods.

Question 5

Field Capacity

Answer 5

Amount of water held in the soil after excess water drains away-saturation or near saturation.

Question 6

Channel storage

Answer 6

all water that is stored in rivers, streams and other drainage channels. Some are seasonal and may disapear underground naturally (in areas with carboniferous limestone) or in urban areas where they are culverted

Question 7

Throughflow

Answer 7

the lateral movement of inflitrated water in soil. The water moves parallel to the surface (horizontally) down the slope to the river channel along percolines (defined lines of seepage).

Question 8

Soil Moisture Budget

Answer 8

the annual balance between precipitation, evapotranspiration, and runoff i.e. annual balance between the inputs and outputs. It is calculated from the formula:
P = E + R +/- S
(Where P is precipitation, E is evapotranspiration, R is runoff and S represents changes in storage over a period of time, usually one year)

Question 9

Aeration Zone

Answer 9

zone which is seasonally wetted and seasonally dries out.

Question 10

Drainage Basin Definition

Answer 10

An area of land drained by a river and its tributaries. Is an open system as it allows for the movement of matter and energy across its boundaries

Question 11

Groundwater

Answer 11

subsurface water stored in rocks. Accounts for over 96% of all freshwater on earth.

Question 12

Interception and its 3 main components

Answer 12

when water is caught and stored by vegetation. The 3 main components are Interception loss, Throughfall, and Stemflow.

Question 13

Water Table

Answer 13

Water table is an underground boundary. It marks the point below which the soil or rocks are permanently saturated with water.

Question 14

Surface Runoff

Answer 14

water that flows over the lands surface when :
- precipitation exceeds infiltration rate
- the soil is saturated

Question 15

Saturation

Answer 15

refers to a soil’s water content when practically all pore spaces are filled with water. If precipitation continues on a saturated soil, it will result in surface runoff, water percolation down to the water table & groundwater stores being recharged. If soil is poorly drained and/or compacted so that water is unable to drain away, it can lead to the soil becoming waterlogged.

Question 16

Inflitration Capacity

Answer 16

The maximum rate at which water can be absorbed by the soil. Is influenced by
- Duration of Rainfall (decreases with time) ie; 0-4mm/hr on clays, 3-12mm/hr on sands
- Vegetation-(increases inflitration as the speed at which water reaches the surface is reduced) IE; bare soils w/rainsplash impact = 10mm/hr, vegetation cover= 50-100mm/hr
-Antecendent soil moisture
-soil porosity
-raindrop size
-slope angle

Question 17

Variations in Seasonal Soil Moisture Budget

Answer 17

Soil Moisture Deficit- SM falls below field capacity. Temperate areas- late Winter/ early Spring SM is low as a result of high levels of precipitation and limited EVT.
SM Recharge- precipitation exceeds evapotranspiration
SM surplus- soil is saturated and water cannot enter resulting in surface runoff
SM utilization- water is drawn up to the surface by capillary action ( the process of a liquid flowing in narrow spaces without the assistance of, or even in opposition to, external forces like gravity.)

Question 18

Below Ground

Answer 18

Infiltration
Percolation
Throughflow
Baseflow

Question 19

Surface Water

Answer 19

Temporary or permanent stores of water. Temporary- small puddles and turloughs (seasonal lakes in the west of ireland)
Permanent stores- marshes, swamps, lakes

Question 20

Channel Flow

Answer 20

movement of water in channels such as rivers

Question 21

Soil Moisture

Answer 21

subsurface water in the soil and subsurface layers above the water table.
Water can be
-absorbed
-held
-transmitted downwards towards the water table
-transmitted upwards towards the soil surface and the atmosphere.

Question 22

Groundwater Recharge

Answer 22

Infiltration
Seepage- through banks and beds of surface water
Groundwater leekage inflow-from adjacent rocks and aquifers
artificial recharge- irrigation and reservoirs

Question 23

Pheratic Zone

Answer 23

lays below the water table and is the permanently saturated zone within rocks and sediments.

Question 24

Throughfall

Answer 24

when water falls through gaps in vegetation or when it drops from leaves or twigs

Question 25

Input of Drainage Basin system

Answer 25

The addition of water to the drainage basin through precipiation or leekage.

Question 26

available soil water

Answer 26

is the amount of water that can be stored in the soil and is available for growing crops. This is valuable to users, such as farmers, who can use it to identify when irrigation might be required, and how much.

Question 27

EVT accounts for how much precipitation loss?

Answer 27

100% in arid areas 75% in humid areas

Question 28

Groundwater Recharge

Answer 28

refilling of water pores in dry areas or hwere water has been extracted by humans

Question 29

Stores

Answer 29

Interception Soil Water Surface Water Groundwater Channel Store

Question 30

Baseflow

Answer 30

Water which has percolated into the bedrock and then moves laterally down slope to seep into the bed of the river. Constant flow though may increase slightly after a wet period.

Question 31

Factors affecting precipitation and its effects on the drainage basin system,

Answer 31

FACTORS AFFECTING PRECIPITATION - temporal variability - climates of different countries (polar and temperate climates snow-melt is a significant input. FACTORS AFFECTING LOCAL DRAINAGE SYSTEM -The amount of precipiation - the type of precipitation -intensity of precipitation (mm/hr) -geographical distribution of precipitation

Question 32

Water Table

Answer 32

an underground boundary. It marks the point below which the soil or rocks are permanently saturated with water. Varries seasonally - Temperate zones- higher in the winter after increased levels of precipitaion

Question 33

Above ground flows

Answer 33

Throughfall Stemflow Surface Runoff

Question 34

Evapotranspiration

Answer 34

the combined loss of evaporation ( process of transforming liquid water from the earths surface into water vapour) and transpiration (the loss of water through vegetation and to the atmosphere)

Question 35

losses of groundwater

Answer 35

EVT- in low-lying areas where water table is close to surface Natural Discharge- seepage Groundwater outflow- into adjacent aquifers Artifical Abstraction- Saudi Arabia- groundawter reserve in 2010 was 42% less than in 1985

Question 36

Percolation

Answer 36

Water moves slowly downwards from the soil into the bedrock

Question 37

Wilting point

Answer 37

Range of moisture content in which permanent wilting of plants occurs.

Question 38

Potential Evapotranspiration PEVT

Answer 38

evapotranspiration that would occur if there was an unlimited water supply for vegetation use in the soil. For example, Egypt has 250mm of EVT due to low rainfall but PEVT is 2000mm

Question 39

Outputs

Answer 39

Evapotranspiration