Unsaturated Zone

what happens after rain

evapotranspiration, surface runoff, infiltration, storage on surface

canopy interception

is the process where precipitation is caught and held by tree canopies, preventing some of it from reaching the ground. This can affect the amount of water that enters the soil.

saturation excess

overland flow

when soil saturated, water flows across the land surface.

infiltration excess

overland flow

water infiltrates into the soil until the infiltration capacity is reached

excess water overflows the land surface

unsaturated zone

the upper portion of the soil profile

most plant available water

below unsaturated zone

water fully occupier all porous space

soil

fraction of sand, silt, and clay

porosity

proportion of porous medium volume made of void space

sand is least and clay is most

hydraulic conductivity

rate water drains through porous medium

capillarity

the ability of water to flow in narrow spaces against the force of gravity, influenced by surface tension and adhesion.

filed capacity

total amount of water can be held by medium without drainage to subsurface

groundwater

in aquifers unconfined or confined

water flows downhill

aquitard

unconfined sitting onto of confining aquifer

restrict flow and confine underlying unit

well

open over the entire depth of borehole, intended for water supply

piezometers

screened over discrete interval

measuring device

what controls hydraulic conductivity

pore size (large pores → high K)

conductivity of large pores (more connected → high k)

grain size/fractures (more fractures/large size → high k)