1.1 The drainage basin system Flashcards
Define the hydrological cycle
- Describes how the water move through the biosphere, atmosphere and lithosphere
- The cycle is a closed system because water cannot be created, destroyed, it gets recycled all the time
Define drainage basin
- An area the river water takes in from precipitation - It is part of the water cycle
- A drainage basin is an open system meaning it has inputs and outputs
Define watershed
an area or ridge of land that separates waters flowing to different rivers, basins, or seas
Define drainage density
- Total length of all the streams and rivers in a drainage basin divided by the total area of the drainage basin.
- It is a measure of how well a watershed is drained by stream channels.
How can the drainage basin system be divided?
- Inputs
- Outputs
- Stores
- Flows
Inputs of a drainage basin system
- Precipitation
- Solar energy for evaporation
Define evapotranspiration
The process by which water vapour escapes from the leaves and enters the atmosphere
Define potential evapotranspiration
The amount of evaporation that would occur if a sufficient water source were available.
Stores of a drainage basin system
- Vegetation
- Surface (ponds, puddles)
- Soil
- Ground water
- Water channels
Flows of a drainage basin system
The different ways that water can move from point A to B in a drainage basin
Define interception and what type of interception are there?
- Interception: refers to water that is caught or stored by vegetation
- Interception loss - water that is retained by plant surfaces and which is later evaporated away or absorbed by plant
- Throughfall - water that either falls through gaps in the vegetation or drops from leaves, twigs or stems
- Stemflow - water that trickles along twigs and branches and down to the main trunk
Define inflitration and inflitration capacity
- The process by which water soaks into or is absorbed by the soil
- Infiltration capacity - maximum rate at which rain can be absorbed by a soil
Define percolation
The movement of water moving downwards from soil into the bedrocks
Define overland flow (surface runoff)
Water that flows over the land’s surface because the bankful discharge has been exceeded
Define groundwater
- Refers to subsurface water
- Depends on the porosity of the rock, water can move fast/slow
Define baseflow
Refers to part of a river’s discharge that is provided by groundwater seeping into the bed of the river
Define recharge
Refers to the filling of water in pores where the water has dried up or extracted by human
Define water tables
The layer that separates unsaturated and saturated soil
Define springs
A spring is any natural situation where water flows from an aquifer (rocks that contain water) to the earth’s surface
Define coniferous and deciduous
- coniferous: trees that have needle-like leaves
- deciduous: broad flat leaves
Define throughflow
Refers to the water flowing through the soil in natural pipes and percolines. Usually horizontal
Define river regime
- annual variation in the flow of a river
- influenced by:
- the amount of precipitation
- the rocks - porosity and permeability
- morphology of drainage basin
Define recurrence interval
The regularity of a flood of a given of a given size
Small floods may be expected to occur regularly. Larger floods occur less often
Define porosity
a measure of how much of a rocks volume is open space (pores).
Define permeability
a measure of the ease with which water can move through a porous rock
