IGCSE Geography / River environments

River regimes and what controls them revision notes

Edexcel International GCSE Geography (4GE1), chapter 1: River environments, specification point 1.1c, 1.S5. Free lesson.

Watch the video lesson · IGCSE Geography past papers

A river regime is the pattern of a river’s discharge over a year. Understanding how to calculate and describe discharge helps you explain how physical and human factors make river flow rise and fall.

How to calculate discharge

Discharge is the volume of water passing one point in a river each second. It depends on the area of the river channel filled with water and how fast the water moves. Cross-sectional area is the area of a slice across the water. Velocity is the speed of the water. Discharge is measured in cubic metres per second, written as m³/s or cumecs.

What a river regime shows

A river regime is the pattern of a river’s discharge over a year, showing how its flow rises and falls from season to season. It is read from monthly data covering a whole year. Keep your description focused on discharge, not water quality or flood damage. In the made-up river, winter is the wettest season and summer is the driest. Discharge follows the rainfall pattern, with one peak: it is highest in January and lowest in August. The rainfall has picked up again by August, but discharge has not yet risen. To describe a regime, state when discharge is highest, when it is…

How physical factors change discharge

Physical factors are natural causes. For each one, explain the process and finish by saying what happens to discharge. Precipitation: wet seasons bring high discharge and dry seasons bring low discharge. Snow can remain on the ground for months before reaching the river. Temperature: below-freezing conditions store water as snow and ice, so discharge is low. Spring snowmelt can create a peak. Summer heat increases evaporation, so less water reaches the river. Vegetation: trees in leaf intercept, or catch, rain. Their roots also take up water, so discharge is lower during the…

How human factors change discharge

Human activities can change how much water runs into a river or is taken out of it. The effect on the regime depends on when the change happens. Land use: tarmac in towns cannot soak up rain, and cleared forest catches less rain. More water runs off into rivers, making wet-season peaks higher. Water abstraction means taking water from a river or the ground for farms, homes and industry. It lowers discharge, especially in dry months when demand is highest. A dam creates a reservoir, the lake behind it. The reservoir fills in the wet season and releases water in the dry season,…

Sort the factors and explain their effects

The first three factors are physical and the last three are human. Check which type the question asks about. For a regime question, every explanation should end with how river flow changes. Physical: precipitation, temperature and vegetation. Human: land use, water abstraction and dams. For a temperature explanation, connect winter snow storage to spring melting, then state the change in discharge.