Wednesday, March 28, 2012

Lecture 22

Affect of Climate Change on Water Systems

Changes in Water Resources
• Change in future water resources due to: socioeconomic change (change in water use)
• In general, climate change is expected to lead to higher temperatures. A warmer atmosphere can hold more water vapour, and as a result there should be more precipitation

Temperature Change
• Globally increasing (greenhouse effect)
• Some regional differences in absolute amount and seasonality (ex: more pronounced in summer)
• Expected Effects: increase in potential evaporation (ex: less runoff), change in actual evapotranspiration depends on additional factures (ex: vapour pressure, vegetation cover, available water), smaller proportion of precipitation as snow, earlier snowmelt, reduced freezing of lakes and rivers (and earlier ice breakup), increased melting of glaciers and permafrost

Regions at Risk
• High altitudes (mountains)
• Tropics: warm atmosphere leads to higher
• Large lakes and wetlands:
• Semiarid areas:
• Endorheic (Inland) basins: system in balance – all inflowing waters evaporate from final lake or wetland (in equlibirum with water in and water out)
• Deltas and costal areas: system in balance – freshwater inflow from the river basin prevents saltwater intrusion from ocean, possible strong impacts if freshwater inflow from upstream is reduced while sealevels rise, possible seawater intrusion into groundwater, changes in river flows will also alter water chemistry and sediment transport
• Highly modified systems: irrigation areas may require even more water withdrawals if climate gets drier or more erratic, evaporation from reservoirs will increase with rising temperatures

Global Hydrological Modela (use GCMs as input)

Climate and Phenology
• Phenology: repeated (seasonal) lifecycle phases (mating, flowering, migration)
• Greening in the north: the growing season is getting longer
• Global change: length of growing season
• Covariance: red (high), white (low)

Climate and Species Range
• Warmer species are invading and moving north
• Trees: elm and ash become beach maple
• Plants that now grow in the middle applachations will be in northern Michigan and Canada

Global Change and Biodiversity
• Hot topic!
• More diversity of plants, more chemicals (ex: chemical to cure cancer)
• Climate, nitrogen deposition, atmosphere CO2
• Two biggest: land use and climate
• Break down by region, not all the same

SUMMARY OF CLIMATE IMPACTS ON ECOSYSTEMS
• Plants
• Ecosystem states, food webs, niche
• Terrestrial forests (tropical, boreal, arctic)
• Costal ecosystems (marine, mangroves)
• Phenology (animals, plants)
• Species rage
• Biodiversity