(1.3.2 A) factors affecting discharge

Define discharge (rivers).

The amount of water flowing through a river channel.

Define annual regimes (rivers).

The way in which a river’s discharge varies throughout the year.

How does hot, dry weather affect discharge and annual regimes?

(physical, climate)

Hot weather → faster evaporation → increased output → decreased river discharge

Dry weather → little precipitation → decreased input → low discharge

however

dry weather → harden land → less permeable → increased surface run-off for any rain that does reach land

How does freezing temperatures affect discharge and annual regimes?

(physical, climate)

freezing temp → hard ground → lack of infiltration → any rain will go through surface run-off → increasing discharge

How does snowfall affect discharge and annual regimes?

(physical, climate)

snowfall accumulates → no water reaching river → eventual melting → surge of water flowing → possible quick saturation → surface run-off → increased discharge

How does prolonged rainfall affect discharge and annual regimes?

(physical, climate)

consistent input → increased discharge

+

soil saturation → surface run-off increased → quicker increase in discharge

How does deciduous woodland affect discharge and annual regimes?

(physical, vegetation)

leaves only shed in the winter → no interception in winter → water to river quicker in winter than summer

+

no interception loss in winter → more water reaching river → higher discharge

How do steep slopes affect discharge and annual regimes?

(physical, geology)

steep slopes → difficult for water to infiltrate → promote surface run-off → quick-flow process → river discharge increase quickly

How does loam soil affect discharge and annual regimes?

(physical, geology)

sand, silt, clay → increased permeability → more infiltration of water into the ground → reduced surface run-off → reduced rate of increase of discharge

How do impermeable rocks affect discharge and annual regimes?

(physical, geology)

impermeable rocks under soil → less percolation → less groundwater → increased soil saturation → surface run off chance → quick-flow process → quick increase of discharge.

How do urban areas affect discharge and annual regimes?

(human)

reduced soil area → reduced infiltration → increased surface run-off → faster river discharge increase

urban areas are designed to focus water towards rivers (gutters, drains, sloping roofs), increasing discharge quickly

How do fields of crops affect discharge and annual regimes?

(human)

crops absorb precipitation + intercept rainfall + roots aid infiltration → water takes longer to reach river

after harvest, crops are gone → water reaches rivers quicker → increased discharge

How do man-made dams affect discharge and annual regimes?

(human)

Reduced flow → reduced + controlled discharge → breaking = flooding

How do diversion channels affect discharge and annual regimes?

(human)

directs water out of main river and into tributary → reduced discharge in river