Climate change can impact the hydrological cycle globally and locally

Climate change results in the intensification, acceleration or enhancement of the hydrological cycle

• Short term: Changes in atmospheric circulation (eg. the ENSO) cycles
• Long term: Climate change

Climate Change's Impact of the Hydrological Cycle

Inputs and outputs
Precipitation (Input)	● Warmer atmosphere holds more water vapour = more precipitation ● Rainfall is also likely to have a greater intensity ● High latitude areas more likely to have precipitation as rain rather than snow ● Some current dry areas may have less rainfall as heat waves intensify
EVT (Output)	● Warmer temperatures lead to higher rates of evaporation ● They also ↑ rates of vegetation growth, & ∴ transpiration
Stores and flows
Snow and glacier melt	● Periods of snowfall likely to ↓ in length ● Spring snowmelt will begin earlier ● Glaciers will ↓ in size and their snouts retreat due to less accumulation and more melting (disappearing faster than forming)
Reservoirs and lakes	● Storage amounts may ↓ w/ more evaporation ● Conversely, if precipitation ↑ then storage may ↑
Permafrost	● More thawing will release more groundwater as the thickness of permafrost ↓ ● Methane release will add to global carbon stores and ↑ rates of climate warming
Soil moisture	● Likely to be unchanged as changes to precipitation and evaporation rates cancel each other out
Runoff and streamflow	● Greater variability of flows • more floods and more periods of low flow

Future Uncertainties

• Although the world's population increase rate is slowing down, there is going to be 1 bn + more people to find water for by the middle of the century Climate change will occur over both short and long term periods, creating uncertainty regarding the security of water supplies:

• Variations in the amounts of water held by reservoirs during a year

• Impact of reduced water amounts on forested areas

• Lower reliability of monsoon rains

• ↑ glacier melting may impact mountain communities

• Lower amounts of snowfall may impact tourist activities skiing

• ↓ stores in aquifers will affect water supplies in dry areas

• Droughts and associated heat waves may ↑ the incidence of wild fires