Hydrology

Hortonian overland flow

surface run off on an impermeable man-made surface

Aquifers / groundwater

water that is stored underground, on top of a layer of impermeable rock

water table

a boundary below the grounds surface. The depth below which the ground is saturated

Aquiclude

impermeable layer e.g. clay , that supports a raised aquifer

Abstraction

the process of withdrawing freshwater from underground storage

Recharging

the process of adding freshwater to underground storge

Water budget

the balance between precipitation and potential evapotranspiration

Potential evapotranspiration

the amount of water that could go back into the atmosphere if there was an unlimited supply of soil moisture

Actual evaporation

the actual amount of water that leaves the drainage basin in the form of water vapour.

Equation for water budget?

S = P - Q - E

S = soil moisture

P = precipitation

Q = channel flow

E = Evapotranspiration

Lag time

Time between peak rainfall and peak discharge

What is a storm hydrograph?

a graph representing change in the discharge of a river during a storm.

Bankfull discharge

the maximum amount of discharge held by a river channel before it " bursts its banks"

Base flow

the sustained level of discharge in a river due to GW flow ( precipitation if not involved )

Storm flow

Flow due to precipitation

Long profile of a river

A way of observing a river system from its source to mouth

4 Types of erosion

Abrasion, Attrition, Hydraulic action, corrosion

Eddie

A swirling surface current

Bedload

the sustained level of discharge in a river due to GW flow ( precipitation if not involved )

Load

what and how much a river is carrying ( sediment )

Capacity

Total amount of load

competence

the maximise size particles the river is capable of transporting

4 types of transportation

Traction

Saltation

Suspension

Solution

Flocculation

clay particles coagulate together and behave like larger pieces of sediment/load. This happens due to charged ions in the sea water

Equation for Hydraulic Radius

Channel cross sectional area / wetted perimeter

Laminar Flow

No turbulence, no eddies: water flows as a simple sheet

turbulent flow

Irregular flow with random variations in pressure.

Thalweg

fastest current in a river, usually far from the banks and bed

tubulence

violent or unsteady, unpredictable movement of water and air

Helicoidal flow

the spinning, corkscrew motion of flowing water, usually the thalweg

How do V shaped valleys form?

Erosion in the upper course is vertical and creates land forms like V-shaped valleys

Interlocking spurs

" fingers " of land that protrude into a river valley, forcing the stream to flow around them.

Swirling abrasion

rocks that are stuck in depressions or potholes on the river bed get moved around in a spiral motion due to eddy currents, causing vertical erosion

Wavelength

The distance from the outside of one meander to the next

What is the distance between Pool to Pool

4-5 times width of the channel