interception and throughfall Flashcards
What are types of hydrologic losses?
- interception
- wetland storage
- evaporation and transpiration
- infiltration and soil water/groundwater storage
- lake and reservoir storage
what is interception loss?
proportion of precipitation that may be intercepted by a vegetation canopy and lost to the atmosphere via evaporation without reaching the ground
what is gross precipitation?
measured above the canopy or in a clearing
what is throughfall?
precipitation reaching the ground directly or via canopy drip
what is stemflow?
water reaching the ground by flowing along tree trunks and plant stems
what is total interception loss?
sum of all canopy interception and losses
what is net precipitation?
gross precipitation minus total interception loss
what is release throughfall?
precipitation that is intercepted and then released via 1-2 mechanisms (canopy drip or splash throughfall)
why is interception hard to measure directly?
- spatial variation (vegetation density and type, wind…)
- temporal variation (after interception capacity is achieved, less interception)
what is the hierarchy of canopy storage by vegetation type?
tropical forests -> conifers -> grasses -> deciduous trees
what are the three kinds of interception measurements?
- above and below canopy
- plastic sheets
- cantilever effect (measuring the bend of branches)
how to measure stemflow?
collecting stem flow on the stem of the tree and leading the water to a bucket
how to measure throughfall?
open tube that goes through an opening in the forest
from largest to smallest, vegetation type’s annual interception
conifers -> broadleaves -> tropical forests -> eucalyptus -> soybeans -> corn -> wheat
during short-duration events, almost all incoming rainfall can be intercepted by vegetation. True or false?
in most cases, statement is true -> more time for water to be distributed amongst trees and branches
high winds lead to more interception of snow and rain by plants. True or false?
depends. with snow, high winds causes snow to stick onto vegetation and make bridges between leaves and branches.
interception by plants is limited when a rain event occurs shorter after another one ended. True or false
often true, if canopy storage is full after one event, it will be full before the second one making interception difficult
what are the factors influencing interception?
- precipitation intensity
- precipitation duration
- precipitation frequency
- wind speed
- precipitation type
how does wind speed influence interception?
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
how does the precipitation type influence interception?
- 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
how does precipitation intensity influence interception?
- 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
how does precipitation frequency influence interception?
long delays between consecutive events allows wet vegetation to dry out and canopy storage to become available before the next storm
what is depression storage?
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
what is retention storage?
storage is held for a long period of time and depleted by evaporation (ex. farmers keeping water to reuse)
what is detention storage?
short-term storage depleted by flow away from the storage location (ex. farmers using spring rainfall)
define storage in wetlands
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
what are the three criteria for wetlands? (1 of 3 must be met)
- at least periodically, the land supports predominantly hydrophytes
- the substrate is predominantly undrained hydric soil
- the substrate is saturated with water or covered by shallow water at some time during the growing season of the year
what is the major hydrological benefit of wetlands?
they trap excess water in their depressions, leading to less runoff and less intense flooding
what is hydric soil?
soils that are saturated, flooded or ponded long enough during the growing season to develop oxygen-free conditions in the upper6 inches
what is hydrophytic vegetation?
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