Paper 1: Core Geography
Physical core
Topic 1: Hydrology and Fluvial Geomorphology
1.1 The Drainage Basin System
Hydrological Cycle -> cycle of water between air, land, sea
Drainage Basin -> Area of land that drains water by river and it’s tributaries, land where any precipitation
will drain into
Drainage basin = Open System allows movement of energy and matter across boundaries:
• 1 main input: Precipitation
• 2 outputs: Evapotranspiration and overland flow
• 3rd output: Leakage -> Occur from deeper subsurface to other basins
Water Storage in cycle:
• Interception storage (vegetation)
• Surface Storage
• Soil moisture storage
• Groundwater storage
• Channel storage
Human Modifications (example)
Large scale changes of channel flow and storage
Irrigation (supply water) and land drainage
Large scale abstraction of groundwater and surface water for domestic/industrial use
Urbanization -> converting land into concrete surface
Watershed – Catchment area of drainage basin
Drainage Density
Total length of all streams in drainage basin divided by total area of drainage basin
Measures how well/poorly water is drained by stream channels
More streams, better drained (steeper rising limb and peak flow)
Stream Ordering
Numbering streams part of drainage basin network
1st order streams – numerous
Higher order streams - fewer
Bifurcation Ratio
Ratio of num of stream segments of one order to number of
next higher order
BR low, less than 2.5 means it’s complex (branched)
BR high, large num of 1st order streams joining main channel (higher risk of flood)
Example:
Stream order 1 = 27
Physical core
Topic 1: Hydrology and Fluvial Geomorphology
1.1 The Drainage Basin System
Hydrological Cycle -> cycle of water between air, land, sea
Drainage Basin -> Area of land that drains water by river and it’s tributaries, land where any precipitation
will drain into
Drainage basin = Open System allows movement of energy and matter across boundaries:
• 1 main input: Precipitation
• 2 outputs: Evapotranspiration and overland flow
• 3rd output: Leakage -> Occur from deeper subsurface to other basins
Water Storage in cycle:
• Interception storage (vegetation)
• Surface Storage
• Soil moisture storage
• Groundwater storage
• Channel storage
Human Modifications (example)
Large scale changes of channel flow and storage
Irrigation (supply water) and land drainage
Large scale abstraction of groundwater and surface water for domestic/industrial use
Urbanization -> converting land into concrete surface
Watershed – Catchment area of drainage basin
Drainage Density
Total length of all streams in drainage basin divided by total area of drainage basin
Measures how well/poorly water is drained by stream channels
More streams, better drained (steeper rising limb and peak flow)
Stream Ordering
Numbering streams part of drainage basin network
1st order streams – numerous
Higher order streams - fewer
Bifurcation Ratio
Ratio of num of stream segments of one order to number of
next higher order
BR low, less than 2.5 means it’s complex (branched)
BR high, large num of 1st order streams joining main channel (higher risk of flood)
Example:
Stream order 1 = 27
