IB Geography Topic A.1.2 River Discharge and Streamflow Revision Notes (SL/HL)

IB Geography Topic A.1.2 River Discharge and Streamflow Revision Notes (SL/HL) | RevisionDojo

Written by official IB examiners

Factors Influencing River Flow

Imagine standing by a river, watching the water rush past.
Have you ever wondered why some rivers flow steadily while others surge unpredictably?

Note

Understanding the factors that influence river flow is essential for predicting floods, managing water resources, and studying river ecosystems.

1. River Discharge: The Volume of Water Flowing in a River

Definition

River Discharge

River discharge is the volume of water passing a specific point in a river per unit of time, usually measured in cubic meters per second (cumecs).

Example

During a storm, rainwater quickly enters the river, increasing its discharge.
In contrast, snowfall may not affect discharge until it melts.

2. Soil Saturation

Infiltration Capacity: When soil is already saturated, additional rainfall leads to overland flow, increasing river discharge.
Dry vs. Wet Conditions: Dry soils absorb more water initially, reducing immediate runoff, while saturated soils contribute to higher discharge.

Common Mistake

Note

Don’t assume that dry soil always reduces discharge.
If rainfall is intense, even dry soil can become saturated quickly, leading to runoff.

3. Geology

Permeable Rocks: Rocks like sandstone allow water to infiltrate, reducing surface runoff and lowering discharge.
Impermeable Rocks: Rocks like granite prevent infiltration, increasing runoff and discharge.

Example

In areas with limestone bedrock, water infiltrates easily, reducing surface runoff.
In contrast, regions with clay soils experience higher runoff and discharge.

Channel Characteristics: How the River’s Shape Affects Flow

The physical characteristics of a river channel play a crucial role in determining how efficiently water flows.

1. Width, Depth, and Velocity

Wider and Deeper Channels: These can accommodate more water, increasing discharge.
Velocity: Faster-flowing water increases discharge. Velocity is influenced by the channel’s gradient and roughness.

Example

A steep, narrow mountain stream may have a lower discharge than a wide, deep river in a floodplain, even if the velocity is higher.

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IB Geography A.1.2 River Discharge and Streamflow Notes

Factors Influencing River Flow

1. River Discharge: The Volume of Water Flowing in a River

2. Soil Saturation

3. Geology

Channel Characteristics: How the River’s Shape Affects Flow

1. Width, Depth, and Velocity

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Duis aute irure dolor in reprehenderit

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Factors Influencing River Flow

1. River Discharge: The Volume of Water Flowing in a River

2. Soil Saturation

3. Geology

Channel Characteristics: How the River’s Shape Affects Flow

1. Width, Depth, and Velocity

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Duis aute irure dolor in reprehenderit

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1 Changing Population3 subtopics

2 Global Climate - Vulnerability and Resilience3 subtopics

3 Global Resource Consumption and Security3 subtopics

4 Power, Places and Networks (HL only)3 subtopics

5 Human Development and Diversity (HL only)3 subtopics

6 Global Risks and Resilience (HL only)3 subtopics

Option A Freshwater - Drainage Basins4 subtopics

Option B Oceans and Coastal Margins4 subtopics

Option C Extreme Environments4 subtopics

Option D Geophysical Hazards4 subtopics

Option E Leisure, Tourism and Sport4 subtopics

Option F The Geography of Food and Health4 subtopics

Option G Urban Environments5 subtopics

IB Geography A.1.2 River Discharge and Streamflow Notes

Factors Influencing River Flow

1. River Discharge: The Volume of Water Flowing in a River

2. Soil Saturation

3. Geology

Channel Characteristics: How the River’s Shape Affects Flow

1. Width, Depth, and Velocity

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Factors Influencing River Flow

1. River Discharge: The Volume of Water Flowing in a River

2. Soil Saturation

3. Geology

Channel Characteristics: How the River’s Shape Affects Flow

1. Width, Depth, and Velocity

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

1 Changing Population3 subtopics

2 Global Climate - Vulnerability and Resilience3 subtopics

3 Global Resource Consumption and Security3 subtopics

4 Power, Places and Networks (HL only)3 subtopics

5 Human Development and Diversity (HL only)3 subtopics

6 Global Risks and Resilience (HL only)3 subtopics

Option A Freshwater - Drainage Basins4 subtopics

Option B Oceans and Coastal Margins4 subtopics

Option C Extreme Environments4 subtopics

Option D Geophysical Hazards4 subtopics

Option E Leisure, Tourism and Sport4 subtopics

Option F The Geography of Food and Health4 subtopics

Option G Urban Environments5 subtopics