The water cycle Flashcards
(22 cards)
What are the 4 global stored of water ?
-Hydrosphere
-Lithosphere
-Cryosphere
-Atmosphere
Explain Oceanic water
-Oceans contain 97% of Earths water
-Covers 72% of Earths surface
-Salts allow it to stay liquid below 0°
-pH is falling due to increased atmospheric carbon
Explain what the lithosphere is
-water stored in the crust/upper mantle
-Surface water is water in lakes, ponds and wetlands.
-Groundwater collects underground in the pore spaces of rock, comes to surface to create wetlands.
-Biological water is water stored in all biomass, if vegetation is destroyed water is lost to atmosphere
Explain what the cryosphere is
-The portions of Earths surface where water is frozen
-Sea ice (don’t raise sea level)
-Ice sheets e.g. greenland contain more than 99% of the freshwater ice
-Ice caps are fount in mountainous areas and are dome shaped
-Alpine glaciers are thick ice in deep valleys or upland hollows
-Permafrost is ground that remains under 0° for at least 2 years
Explain the atmosphere as a water store
-Atmospheric water absorbs, respects and scatters solar radiation keeping the temp at one that can support life.
-Amount of water that can be held by air depends on temp (cold air can’t hold as much)
-A small increase in water vapour leads to an increase in atmospheric temps. Leads to positive feedback (increase temp, increase water vapour levels, enhance warming)
-Clouds are visible masses of water
Explain the different types of rainfall
-Relief (when moist air is forced to rise over a physical barrier)
-Convectional (warm air rises and then cools to condense into cumulonimbus clouds)
-Frontal (when warm moist air meets cold dense air. warm air forced to rise above cold air, as it cools it condenses to clouds)
Explain cloud formation
-Water vapour condenses when cool
-Particles within the air (pollen,dust) allow water to condense onto it
-Water droplets grow into cloud and is large enough gravity causes them to fall due to weight
Explain cryospheric processes
-Processes affecting total mass of ice
-Contains 1.8% of all water on earth but 70% of all fresh water
-Accumulation of more snow and ice can build them or higher temps take away (ablation)
-Earth goes through glacial periods where there’s lots of ice
-Over the past 740,000 years there have been 8 glacial periods
What is a drainage basin ?
An area of land drained by a river and its tributaries.
Each drainage basin is separated by a watershed
How do stores and flows vary within a drainage basin ?
-Amount of vegetation
-Type of vegetation
-Antecedent conditions
-Rock type
-Steepness of slope
-Shape of drainage basin
-Climate
Define a Hydrograph
Record of river discharge over a period of time
Define a storm Hydrograph
Shows the change in discharge caused by a period of rainfall
Define a river regime
The variability in a rivers discharge throughout the course of a year in response to precipitation, temperature, evapotranspiration and drainage basin characteristics.
Key features of a flood hydrograph
-Discharge (cumec)
-Time
-Precipitation (mm)
-Peak rainfall
-Rising limb
-Falling limb
-Peak discharge
-Lag time
-Stormflow
-Baseflow
Explain the sequence of events of a flood hydrograph
-Heavy rainfall lands into drainage basin
-As water enter the river through overland flow and through flow, the discharge increases (shown by the rising limb)
-Discharge then increases until peak discharge
-When the majority of water has passed through the system, discharge decreases shown by the falling limb
-As the additional water from the rainfall leaves the river system, the river begins to return to its normal base flow
-River returns to bas flow as water is removed Bia evapotranspiration or moved to the sea
Features of a subdued hydrograph
-Gently sloping
-Long lag time
-Low peak discharge
What causes a subdued hydrograph ?
-Permeable rock
-Lots of vegetation
-Gently sloped drainage basin
-Large drainage basin
-Forest in the summer
-Precipitation as snow
-Elongated river basin
Features of a flashy hydrograph
-Steep
-Short lag time
-High peak discharge
What causes a flashy hydrograph ?
-Steep-sided river basin
-Urbanisation
-Deforestation
-Rounded drainage basin
-Impermeable rock
-Small drainage basin
-Intense rainfall
-Forest in the winter
-Previous long dry spell
What are natural changes to the water cycle ?
-Seasonal changes
(Less precipitation, more evapotranspiration in summer, reduced flows in winter as frozen)
-Storm events
(Floods and replenishment of some water stores. Unlikely to be long-term change)
-Droughts
(Major stores are depleted, flows decrease, can be long term change with climate change enhancing)
-Cryospheric processes
(Glaciers store a lot of freshwater, melting of all means 60m sea-level rise)
-El nino/nina
(Every 2-7 years there is a predictable increase (Nino) or decrease (Nina) in global temps)
What are human impacts that cause changes to the water cycle ?
-Farming practices
(Ploughing breaks up surfaces increasing infiltration, Crops increase interception and evapotranspiration, animals compact the soil so less infiltration and more runoff, irrigation removes water from local rivers decreasing flows)
-Land use change
(Deforestation decreases interception and evapotranspiration, construction does the same and increases runoff)
-Water abstraction
(Reduces vol of water in surface stores (lakes), increases dry seasons, Human abstraction from aquifers to meet water demands is greater than the inputs to aquifers leading to a decline in global long-term water stores)
What is the water balance/budget ?
The balance between inputs and outputs
P=Q+E+/-S
