Drainage basin terminology

Groundwater store

Water that is stored (sometimes for extended periods) in the lower layer of the bedrock

Interception

The preventing of precipitation from reaching the soil (trees or sometimes buildings)

Surface water

Water stored on the surface

Channel storage

Water stored in the river channel

Soil water

Water stored between particles of soil

Through fall

Water that is initially intercepted by a tree but then continues to fall

Stem flow

Precipitation intercepted by a a tree which then flows along the branches/trunk of tree to ground

Overland flow/Surface runoff

Flows above the surface (on an impermeable surface)

Channel flow

Water that flows in the river channel

Infiltration

How water on the ground enters the soil

Percolation

Water moving down through the soil into permeable rock

Throughflow

Water moving horizontally through the soil

Groundwater flow

Movement of water underground

Evaporation

Heating of water to water vapour

Evapotranspiration

Combination of evaporation and transpiration

Transpiration

Water moving through a plant and evaporating from its leaves, stem, flowers etc.

Precipitation

any form of water (rain, sleet, snow) that falls from the atmosphere to the land or oceans

River discharge

Volume of water flowing through a river channel (measured in cumecs)

Baseflow

Is the portion of streamflow contributed by groundwater discharge

Recharge

The process of water moving downward to replenish the groundwater reservoir (typically originating from precipitation that has worked its way down)

Spring

A place where water moving underground finds an opening to the land surface and emerges

Water table

The ​upper level at which the ​pore spaces and fractures in the ground become saturated

Porosity

The capacity of a rock to hold water (in it’s poor it’s pore space)

Permeability

The ability to transmit water through a rock via joints and fissures

Infiltration capacity

The maximum rate at which rain can be absorbed by a soil in a given condition

Antecedent soil moisture

Pre-existing levels of soil moisture

Water balance equation

P = O + E + / - S

P = precipitation

O = total runoff (as a % of P)

E = evapotranspiration

S = storage (in solid and rock)

Annual hydrograph

A graph showing a rivers discharge levels over a year

Storm hydrograph

A visual representation of discharge against rainfall

River regime

The annual variation of a river

Stormflow

The water that arrives in the river via surface runoff or rapid throughflow through the soil

Base flow

A proportion of the streamflow that is not runoff; it is water from the ground, flowing into the channel over a long time and with a certain delay

1. River discharge (cumecs)

2. Rainfall (mm)

3. Time

4. Lag time

5. Peak rainfall

6. Rising limb

7. Peak discharge

8. Falling limb

Drainage density

Number of tributaries in a drainage basin