interception and throughfall

Question 1

What are types of hydrologic losses?

Answer 1

• interception
• wetland storage
• evaporation and transpiration
• infiltration and soil water/groundwater storage
• lake and reservoir storage

Question 2

what is interception loss?

Answer 2

proportion of precipitation that may be intercepted by a vegetation canopy and lost to the atmosphere via evaporation without reaching the ground

Question 3

what is gross precipitation?

Answer 3

measured above the canopy or in a clearing

Question 4

what is throughfall?

Answer 4

precipitation reaching the ground directly or via canopy drip

Question 5

what is stemflow?

Answer 5

water reaching the ground by flowing along tree trunks and plant stems

Question 6

what is total interception loss?

Answer 6

sum of all canopy interception and losses

Question 7

what is net precipitation?

Answer 7

gross precipitation minus total interception loss

Question 8

what is release throughfall?

Answer 8

precipitation that is intercepted and then released via 1-2 mechanisms (canopy drip or splash throughfall)

Question 9

why is interception hard to measure directly?

Answer 9

• spatial variation (vegetation density and type, wind…)
• temporal variation (after interception capacity is achieved, less interception)

Question 10

what is the hierarchy of canopy storage by vegetation type?

Answer 10

tropical forests -> conifers -> grasses -> deciduous trees

Question 11

what are the three kinds of interception measurements?

Answer 11

• above and below canopy
• plastic sheets
• cantilever effect (measuring the bend of branches)

Question 12

how to measure stemflow?

Answer 12

collecting stem flow on the stem of the tree and leading the water to a bucket

Question 13

how to measure throughfall?

Answer 13

open tube that goes through an opening in the forest

Question 14

from largest to smallest, vegetation type’s annual interception

Answer 14

conifers -> broadleaves -> tropical forests -> eucalyptus -> soybeans -> corn -> wheat

Question 15

during short-duration events, almost all incoming rainfall can be intercepted by vegetation. True or false?

Answer 15

in most cases, statement is true -> more time for water to be distributed amongst trees and branches

Question 16

high winds lead to more interception of snow and rain by plants. True or false?

Answer 16

depends. with snow, high winds causes snow to stick onto vegetation and make bridges between leaves and branches.

Question 17

interception by plants is limited when a rain event occurs shorter after another one ended. True or false

Answer 17

often true, if canopy storage is full after one event, it will be full before the second one making interception difficult

Question 18

what are the factors influencing interception?

Answer 18

• precipitation intensity
• precipitation duration
• precipitation frequency
• wind speed
• precipitation type

Question 19

how does wind speed influence interception?

Answer 19

it can promote interception loss by evaporation but it can also increase interception by blowing water into the interior of plants and plastering wet snow against trees and shrubs

Question 20

how does the precipitation type influence interception?

Answer 20

• at temperatures around 0 degrees, rain can freeze to plants
• snow is more easily blown off or away from plants
• wet snow sticks more easily to plants and some snowflakes can bridge gaps between leaves

Question 21

how does precipitation intensity influence interception?

Answer 21

• high intensity rainfall events: water can be delivered too quickly to accomodate
• low-intensity rain events: larger proportion of precipitation will be intercepted, as new storage capacity is continuously created by ongoing drippage and stemflow

Question 22

how does precipitation frequency influence interception?

Answer 22

long delays between consecutive events allows wet vegetation to dry out and canopy storage to become available before the next storm

Question 23

what is depression storage?

Answer 23

gross precipitation or throughfall retained in puddles, stock ponds, ditches and other depressions on the ground surface. Either evaporates or contributes to soil moisture or subsurface flow later on

Question 24

what is retention storage?

Answer 24

storage is held for a long period of time and depleted by evaporation (ex. farmers keeping water to reuse)

Question 25

what is detention storage?

Answer 25

short-term storage depleted by flow away from the storage location (ex. farmers using spring rainfall)

Question 26

define storage in wetlands

Answer 26

transitional systems between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water

Question 27

what are the three criteria for wetlands? (1 of 3 must be met)

Answer 27

1. at least periodically, the land supports predominantly hydrophytes
2. the substrate is predominantly undrained hydric soil
3. the substrate is saturated with water or covered by shallow water at some time during the growing season of the year

Question 28

what is the major hydrological benefit of wetlands?

Answer 28

they trap excess water in their depressions, leading to less runoff and less intense flooding

Question 29

what is hydric soil?

Answer 29

soils that are saturated, flooded or ponded long enough during the growing season to develop oxygen-free conditions in the upper6 inches

Question 30

what is hydrophytic vegetation?

Answer 30

plants typically adapted to wetlands and aquatic habitats; plants which grow in water or on a substrate that is at least periodically deficient in oxygen due to excessive water content