Soil moisture and river regime Flashcards
(17 cards)
soil moisture budget is…
the change in the amount of water stored in the soil throughout the year
soil moisture budget is closely linked to..
water balance
main factors involved in the soil moisture budget
precipitation and potential evapotranspiration
what is potential evapotranspiration and how does it link to temperature
is the amount of evapotranspiration that could occur if there was sufficient water available in the system.
linked to temperature: higher temperature, the greater amount of water available
why are there higher levels of evapotranspiration in the summer
as it is warmer the air can hold more water (has a higher dew point). and there are more plants= more transpiration
what is water surplus
where precipitation exceeds evapotranspiration- lots of surface run off
what is river discharge
is how much water is in the river at any given time
how to calculate river discharge
cross sectional area of water (metres squared) x speed (m/s) = cumecs (metres cubed/ second)
what affects the level of river discharge
the speed and velocity of water
- if there is a higher volume of water then the discharge will be larger
- if it is faster there will be more discharge per second
physical factors that affect storm hydrographs (6)
high drainage density= flashy hydrographs
if the basin is already saturated (lag time reduced)
impermeable ground
thick vegetation (subdues hydrograph)
amount and intensity of precipitation
size of drainage basin
human factors that affect storm hydrographs (6)
deforestation (reduces interception- flashy hydrograph)
afforestation
agriculture
urban areas impermeable surfaces
soft engineering flood management strategies (subdued hydrograph)
water abstraction - reduces base flow
(factors that influence the water cycle- deforestation, agricultural soil drainage, water abstraction). example of deforestation
tropical south America rainforests
explain the impact that deforestation has on the water cycle
deforestation can cause decreased rainfall via atmospheric feedbacks
if this decrease in rainfall doesn’t occur then discharge will be significantly increased
what happens during agricultural soil drainage
subsurface drainage removes excess water from the soil profile
how does agricultural soil drainage impact the water cycle
artificially increases the speed of throughflow in the soil
can lead to nitrate loss- eutrophication
when is water abstracted
when demand exceeds amount available
how does water abstraction affect the water cycle
sinking water tables can make rivers less reliable- as they are maintained in summer by water tables
groundwater also helps sustain surface reservoirs of water that can sustain ecosystems
