Water Flashcards
What are the two forms of energy that drive the hydrological cycle?
Gravitational potential energy.
Solar energy (changes in state and wind direction).
What % of total global water budget is stored in oceans and what is the average residency time?
97%
3600 years
What % of total global water budget is stored in the cryosphere and what is the average residency time?
1.9%
15000 years
What % of the world’s water is freshwater?
2.5%
What is the difference between green water and blue water?
Blue - amount of rainfall that enters lakes, rivers and groundwater
Green - amount of rainfall that is intercepted or taken up by vegetation and evapotranspired.
What is ablation?
Loss of water stored in ice through melting.
What are the 3 types of rainfall?
Orographic
Frontal
Convectional
Describe orographic rainfall.
Humid air forced to rise over mountains. Air cools, condenses, clouds, gravity, rain. Most rain falls on slopes facing wind direction. Rain shadow effect on other side.
Give an example of where there is a rain shadow effect.
Eastern side of the UK receives less than the West due to the Western hills causing orographic rainfall.
Describe frontal rainfall.
Warm humid air forced to rise at a low pressure system (warm or cold front). Air cools, condense and forms clouds.
Describe convectional rainfall.
Ground and lower atmosphere heated by solar energy causing rising thermals of air. Rise, cool and form cumulo-nimbus clouds followed by thunderstorms and intense heavy rainfall.
What is the water table?
The boundary between soil surface and where the ground becomes saturated with water.
What is interception?
Layer of vegetation intercepting water before it reaches the ground. Proceed to stem and drip flow to the ground.
What is infiltration?
The downwards movement of water through soil (entering topsoil).
What is percolation?
The downwards movement of water through permeable or porous rocks.
What is throughflow?
Lateral (ish - it has to be downhill) movement of water through the soil but above the water table.
What is base flow (or groundwater flow)?
Downwards or lateral movement of water below the water table that eventually seeps into a river channel.
What is channel flow?
The volume of water contained within a river channel (discharge).
What is surface runoff?
Rain falling onto the ground flows over the surface because there is no time to infiltrate, ground is frozen or saturated or on impermeable surfaces.
Which water stores are considered non-renewable?
Fossil water
Much of the cryosphere
What is a drainage basin?
An area of land drained by a river and its tributaries (river system).
What is a watershed?
A high ridge of land marking the edge of a drainage basin.
What is a confluence?
When two or more flowing bodies of water join together to form one channel. Basically a tributary joining the main river channel.
Identify 5 physical factors that influence drainage basins.
Climate
Vegetation
Soils
Geology
Relief
Identify 4 human actions that impact drainage basins.
Deforestation
Urbanisation
Reservoir creation
Abstraction of water.
How much of the Amazon rainforest has been lost?
17%
What amount of water did the Amazon release into the atmosphere?
20km3
What reduction in rainfall is expected in the Amazon by 2050?
21% reduction
What is a water budget?
A balance between precipitation, evaporation and runoff. It is a tool to access availability in an area over a specific period of time.
What is a water surplus?
Positive water balance (inputs>outputs).
What is a water deficit?
Negative water balance (inputs<outputs).
What do water balance graphs show?
Balance between inputs (precipitation) and outputs (potential evapotranspiration) of water across a year.
What occurs during soil moisture utilisation and when does it occur?
Potential evapotranspiration exceeds precipitation - dry season. Soil moisture is used by plants or lost by evapotranspiration.
What occurs during soil moisture recharge and when does it occur?
Precipitation exceeds potential evapotranspiration - beginning of wet season. Moisture in soil is replenished.
What is the term for when the soil moisture is saturated and water now begins to recharge groundwater stores in the water table?
Field capacity.
Describe the water budget throughout the year in a tropical northern hemisphere climate.
Brazil transpiration rates consistent throughout year due to consistent temperature. Highest rainfall in winter (Feb) moisture surplus until May. May-Nov rainfall much lower, deficit by oct.
Describe the water budget throughout the year in a temperate northern hemisphere climate.
Southern UK similar precipitation all year with slight dip in summer. High evapotranspiration summer very low evapotranspiration winter. Deficit in July and August.
What are on the axes of river regimes?
Discharge, months.
What are simple river regimes?
A river that experiences periodically high followed by low discharge.
What typically causes simple river regimes?
When inputs depend on glacial meltwater, snowmelt or monsoons.
Give an example of a simple river regime.
River Rhône in the alps (France Switzerland). Large peak at end of winter due to snowmelt.
What are complex river regimes?
Rivers cross several different reliefs and climatic zones (or even human factors), therefore experiencing the impacts of multiple different climate events.
Give an example of a complex river regime.
The Yukon river in Alaska and Canada. Tundra and mountain biomes. Snowmelt = massive peak May-June. Decreasing discharge during winter due to reduced, frozen precipitation. Subarctic climate causes differing precipitation in different ares. Human influences include HEP, farming and water abstraction. Considered complex due to 850km2 drainage basin with many different inputs that can vary.
Describe influences on the Nile’s complex river regime.
2 tributaries - White and Blue Nile. Blue Nile more pronounced flood season than White. Flood season June-Aug, dry season Oct-May. Precipitation decreases as Nile travels north, reducing discharge. Aswan high dam (Egypt) reduces peak in flooding season to increase discharge in dry season.
What is the lag time on a storm hydrograph?
Time interval between peak rainfall and peak discharge.
What terms are used to refer to the sections of the storm hydrograph where discharge is increasing and decreasing?
Rising and falling limb.
What are the two types of storm Hydrograph?
Flashy and low/flat.
What shape and size of drainage basin would create a flashy storm hydrograph?
Small and circular.
What is drainage density and how does it impact storm hydrographs?
The number of surface streams per Km2. High drainage density means water will reach the river faster, causing flashy storm hydrographs.
Give the UN definition of drought.
An extended period of time (relative) of deficient rainfall relative to the statistical multi-year average for a region.