The water cycle Flashcards
What are drainage basins?
open, local hydrological cycles - the area surrounding a river (where rain falls and enters that river) - river catchment
. boundary of drainage basin - watershed
. open systems (inputs and outputs)
what are the inputs of a drainage basin?
precipitation - all the way that water exits from the atmosphere
what are the storages of a drainage basin?
- interception - rain lands on vegetation or manmade structures - creates a significant store (wooded areas)
- only temporary (evaporate or throughfall) - vegetation storage - water taken up by plants
- surface storage - depression storage (puddles, lakes)
- soil storage - moisture in soil
- groundwater storage - stored in ground - water table (top of zone of saturation) - porous rocks (aquifers)
- channel storage - water held in stream or river
what are the flows of a drainage basin?
- infiltration - water soaking into soil - influenced (soil type, soil structure, how much water already in soil)
- overland flow - (runoff) flowing over land (water falls faster than infiltration)
- throughfall - dripping from one plant to another
- stem flow - running down stem or trunk of tree
- throughflow - moving slowly downhill through soil
- percolation - seeping down through soil - water table
- groundwater flow - slowly below the water table (permeable rock)
- baseflow - groundwater feeds into rivers through banks and beds
- interflow - downhill through permeable rock above water table
- channel flow - flowing in river or stream (rivers discharge)
what are the outputs of a drainage basin?
- Evapouration - turning into water vapour
- transpiration - evaporation in leaves
- evapotranspiration - process of evaporation and transpiration together
- river discharge / river flow
What is water balance?
worked out from inputs and outputs - affects how much water is stored in the basin
what seasonal patterns does the water balance in the Uk show?
. wet seasons - more rain than evapotranspiration (water surplus) - ground stores fill - more surface runoff - higher discharge - river levels rise
. drier seasons - rain is lower - ground stores depleted (water is used up) - some flows into river channel - not replaced by rain
. end of dry season - deficit of water - recharged next wet season
What is a hydrograph?
graphs of river discharge over time - volume of water changes over a period of time (certain point in river)
What is a flood hydrograph?
a hydrograph shows river discharge (volume of water that flows per second - cumecs) around the time of a storm event - short period of time
What does a hydrograph include?
- peak discharge - highest point on graph - river discharge at its greatest
- lag time - delay between peak rainfall and peak discharge - time for water to flow (short lag time increase peak discharge)
- rising limb - up to the peak discharge - increases as water flows into the river
- falling limb - after peak discharge - decreasing - less water flow into the river (shallow - water is flowing in fro stores - after rain stopped)
What is a flashy hydrograph?
a basin with rapid runoff and not much capacity to hold water - short lag time and high peak discharge
steep, roughly symmetrical rising and falling limbs
What affects the shape and runoff of a hydrograph?
- size of drainage - larger - catch more rain - higher peak discharge - smaller - shorter lag time (less distance to travel)
- shape of drainage basin - circular - more likely to have flashy - watershed roughly same distance - water reaches river at same time
- ground steepness - water flows quicker downhill (steep) - short lag time - less time to infiltrate
- rock and soil type - impermeable rock - don’t store or infiltrate water - increase surface runoff - peak discharge increases water (shorter period to reach river)
- seasonal changes of precipitation
What are the physical factors that affect the water cycle?
Storms and precipitation - intense storms (more rain & greater peak discharges)
- infiltration- may not be able to occur rapidly enough - increasing runoff
what are more physical factors that affect the water cycle?
Seasonal changes and vegetation -
size of inputs, flows and stores - varies with seasons
during winter - water can freeze - reduce flows - store of frozen water grows - as ice melts increase in water flow (can cause flashy floods)
- seasonal vegetation - intercepts slows movement to the river
. more vegetation - more water is lost through transpiration and evaporation - reducing runoff and peak discharge
What are the human factors that affect water cycle? - farming
Farming practices -
. ploughing breaks up surface so that more water can infiltrate - reducing the amount of runoff
. crops increase infiltration and interception compared to bare ground - evapotranspiration also increases - increase rainfall
. livestock - trample and compact soil - decreasing infiltration and increasing runoff
. irrigation increase runoff - groundwater or river levels can fall - taken for artificial watering
