Spatial and Temporal Change Flashcards
What is the water budget?
The balance between inputs and outputs in a system - affects how much water is stored in a system
What is water surplus?
When precipitation > evaporation. Occurs in wet seasons and allows for groundwater to recharge
What is water deficit?
When precipitation < evaporation. Occurs in dry seasons and groundwater stores may be depleted
What is the water balance formula?
Precipitation = evaporation + transpiration + river flow +/- storage
What is the river regime?
The variability in river discharge throughout the year
What influences the river regime?
Precipitation, evapotranspiration, drainage basin characteristics and land use, geology, tributaries
What is utilisation?
Plants using water stores
What is the recharging period?
Groundwater stores refilling after a water deficit
What is river discharge measured in?
Cumecs (cubic meters per second)
What are the characteristics of a flashy hydrograph?
Short lag time, steep rising limb, falling limb falls slower than rising limb due to throughflow and groundwater flow reaching river
What are the characteristics of a subdued hydrograph?
Long lag time, gradual rising limb
What is lag time?
Peak discharge - peak precipitation
What physical factors affect hydrographs and discharge
Shape and size of drainage basin
Relief/gradient
Intensity of precipitation
Soil/rock type
Vegetation cover
Antecedent conditions
What human factors affect hydrographs and discharge?
Deforestation
Agriculture
River flood management
Water abstraction
Urbanisation
How do storm events affect the water cycle?
Can cause flash floods as intense rainstorms mean there is more surface runoff and thus more flooding
How do seasonal changes affect the water cycle?
Wet seasons - groundwater stores full so more surface runoff
Dry seasons - groundwater stores depleted so less surface runoff
What are the effects of localised deforestation on the water cycle?
Lower evapotranspiration, less interception
More surface runoff due to less interception increasing river discharge and risk of flooding
What are the effects of extensive deforestation on the water cycle?
Most of the water leaves the area in channel flow rather than being recycled in the atmosphere by evapotranspiration. A reduction in water vapour decreases precipitation and causes river levels to fall
What are the effects of soil drainage as a farming practice on the water cycle?
Farmers use a system of plastic tubes to drain water from soils when the water table is high. These tubes can artificially increase throughflow which can lead to flooding and the dry surface layer can become prone to wind erosion. Can also cause eutrophication as the tubes may carry fertiliser to the river.
What are the effects of water abstraction on the water cycle?
Water abstraction removes water from a groundwater source. It can lead to rivers drying up, sinking water tables, damage to wetland ecosystems, intrusion of salt water can contaminate groundwater sources, can impact underground infrastructure.
Example - overexploitation of aquifers during the early 19th and 20th centuries caused the water table in South England to drop as low as 88 meters below sea level. The rising groundwater now poses a threat to building foundations and the London Underground
