Hydrology Flashcards
Name 8 physical influences on hydrography and drainage basins
- Geology - permeable, impermeable, porous
- Temperature
- Soil
- Drainage density
- Tides and storms
- Size, shape and relief of basin
- Precipitation - intensity, duration, amount
- Vegetation
Good Toes Send Dads To Spain Parle Vouz
Large drainage basins catch more precipitation so have a _______ peak discharge compared to smaller basins.
Higher
Smaller basins generally have _____ lag times as water doesn’t have as far to travel.
Shorter
Drainage basins that are more circular in shape lead to ______ lag times and a ______ peak discharge than those that are long and thin because water has a ______ distance to travel to reach the river.
Shorter
Higher
Shorter
How does precipitation affect drainage basins
Heavy storms = more water entering drainage basin = higher discharge
Snow = higher lag time than rain. Because snow takes time to melt before water enters river channel.
How does geology affect drainage basins
Permeable - Allowing water to low through = slower surface runoff
Impermeable - Not allowing water to flow through = faster surface runoff
Porous - Allowing water to soak through and be stored within/ allowing water to run along bedding planes. = slower surface runoff
How does drainage intensity affect a drainage basin
Basins that have many streams drain quicker and have shorter lag times, increase risk of flooding
How does temperature affect a drainage basin
Low temp = water stored as snow or ice, reducing runoff
Higher temp = melting and runoff increase and increase evaporation/ evapotranspiration
How does soil affect a drainage basin
Larger pore spaces in sandy soils = greater water storage and reduces flooding.
Clay soil = doesn’t have as much storage space and rain will have faster discharge, increasing risk of flooding
How does vegetation affect a drainage basin
Vegetation intercepts rain and slows movement of water into river, increasing lag time
Water also lost due to evaporation and transpiration, reducing peak discharge
How do tides and storms affect a drainage basin
High tides prevent water from entering the sea, increasing risk of flooding. When tidal water and flooding water meet this results in a surge of water ‘banking up’.
Base flow
Groundwater flow that feeds into rivers through river banks and beds
Channel flow
Water flowing in a river, aka river discharge
Condensation
Water heats up and cools down back to water
Evaporation
When liquid water is transformed into water vapour
Evapotranspiration
Mix between evaporation and transpiration
Groundwater
Water stored within rocks, rock pores and joints
Groundwater flow
Water flowing slowly below the water table through permeable rock
Infiltration
Water soaks up and moves through soil
Interception
When raindrops are prevented from directly reaching soil surface
Percolation
As water moves through and seeps down the soil it may continue to move deeper into the rocks and settle to the water table
Runoff/ overland row
The total of all the water that flows over the surface of river basin
Stem flow
Water running down a plant stem or tree trunk
Throughfall
Water dripping from one leaf or plant to another
Throughflow
Water that continues to move downhill through soil and ground which may emerge into river, lakes or streams
Transpiration
Water is lost from plant through minute pores in leaves.
Peak rainfall
The hour of greatest rainfall
Park discharge
Time of maximum discharge by river
Lag time
Period of time between peak rainfall and peak discharge
Falling limb
Period of time when rivers discharge is falling
Normal flow
Base flow of the river
Rising limb
Period of rising river discharge following period of rainfall
What is a confluence
Where two rivers meet
What is a watershed
Area of high land between two drainage basins
Inputs into a drainage system
Precipitation (rain or snow)
Outputs in a drainage basin
Transpiration
Evapotranspiration
River carrying water to sea
Transfers in a drainage basin
Stemflow Infiltration Percolation Surface runoff Throughflow Groundwater flow
Storage in a drainage basin
Interception by vegetation
Surface storage
Soil moisture storage
Groundwater storage
Name six human factors affecting storm hydrographs
- Urbanisation
- Deforestation and afforestation
- Agriculture and irrigation
- Mining and industrial development
- Climate change
- Floor management and river basin projects
How does urbanisation affect hydrographs
Urbanised areas = increase in use of impermeable building materials e.g. - asphalt
Infiltration levels decrease and surface runoff increases as houses and buildings take up all land = short lag time and increase in peak discharge
How does deforestation affect hydrographs
Increases runoff
Soil erosion may increase and loose soil is carried to river reducing channel capacity
How can climate change affect hydrographs
Increase in rainfall with more storms and increased in flooding
How does mining affect hydrographs
Displaces water courses. Lakes increase in silt and this reduces storage capacity and increases runoff and discharge
How does irrigation affect hydrographs
When water is taken from the ground this reduces discharge - alters flow and storage
How does flood management and river basin projects affect hydrographs
Alter discharge levels, alter river regimes
