1.1. The drainage basin system Flashcards
Outputs in the drainage basin system
Evaporation, evapotranspiration and river discharge.
Stores in the drainage basin system
Interception, soil water, surface water, ground water, and channel storage.
Flows in the drainage basin system
- Above ground – throughfall, stemflow, overland flow, and channel flow.
- Below ground – infiltration, percolation, throughflow, groundwater, and baseflow.
Underground water in the drainage basin system
Water tables, ground water, recharge, and springs.
Drainage Basin
The area drained by a river and its tributaries.
Watershed
A ridge, like that formed by a chain of mountains, which sends water to two different rivers on either side.
Precipitation
The main input into the drainage basin system. It is the conversion and transfer of moisture in the atmosphere to the land. It includes rainfall, snow, frost, hail and dew.
Hydrological cycle
The movement of water between air, land and sea.
Interception
Precipitation that is collected and stored by vegetation.
Throughfall
Water that either falls through gaps in the vegetation or which drops from leaves, twigs or stems.
Stemflow
Water that trickles along twigs and branches and finally down the main trunk.
Interception less
Water that is retained by plant surfaces and which is later evaporated away or absorbed by the plant.
Evaporation
The transformation of liquid water from the Earth’s surface into a gas (water vapour).
Transpiration
Water loss from vegetation to the atmosphere.
Evapotranspiration
The combined loss of water to the atmosphere through transpiration and evaporation.
Potential Evapotranspiration
The amount of evaporation that would occur if a sufficient water source were available.
Actual Evapotranspiration
The quantity of water that is actually removed from a surface due to the processes of evaporation and transpiration.
Antecedent Precipitation
The water in the soil that is retained after a period of rainfall.
Surface Runoff
The water flowing over the surface of the land.
Throughflow
The lateral (sideways) transfer of water through the soil layer.
Groundwater flow
The lateral transfer of water through bedrock.
Channel Runoff
The flow of water in streams, rivers and other channels.
Groundwater Storage
The water that is stored between the cracks and pore spaces in the underlying rock layers.
Soil Storage
The water contained between soil particles.
Surface Storage
Where water lies above the ground on the Earth’s surface such as in lakes, rivers, ponds, puddles.
Percolation
The downward movement of water through the soil and the underlying bedrock.
Zone of Saturation (Phreatic Zone)
The area in an aquifer, below the water table, in which relatively all pores and fractures are saturated with water.
Aquifer
Rocks that store large quantities of groundwater
- saturated zone beneath the water table.
Recharge
The process by which water moves downward from surface water to groundwater.
Factors affecting parts of the hydrological cycle
1) Duration of rainfall
2) Vegetation Cover
3) Antecedent soil moisture
4) Raindrop Size
5) Soil Porosity
6) Slope Angle
Duration of rainfall (Factors affecting parts of the hydrological cycle)
Longer duration of rainfall:
- Surface run off increases
- Infiltration decrease
Vegetation Cover (Factors affecting parts of the hydrological cycle)
In a forest:
- Surface run off is fairly low throughout, but does increase slowly
- Decreases slowly over time in a rain shower
On bare earth:
- Surface run off increases rapidly at the start of a rain shower and stays constantly high throughout
- Infiltration decreases rapidly in a rain shower and stays low
Antecedent soil moisture (Factors affecting parts of the hydrological cycle)
If the soil is saturated with moisture:
- Surface run off increases
- Infiltration is lower
Raindrop Size (Factors affecting parts of the hydrological cycle)
Bigger Raindrop size:
- Surface runoff increases
- Infiltration decreases
Soil Porosity (Factors affecting parts of the hydrological cycle)
High Porosity:
- Surface run off decreases
- Infiltration increases
Slope Angle (Factors affecting parts of the hydrological cycle)
Steeper slopes:
- Surface run off increases
- Infiltration decreases
