Water and Climate Change Flashcards
Non-climatic factors affecting water resources
- Pollutant emissions
- Land-use change
- Reservoir management
- Water and wastewater management
- Agriculture
- Lifestyle
- Food consumption (ingluding type of diet)
- technology
- Economy policy
- Population changes
- Society’s view about the water
Water and Climate change
- Climate change is an important driver of change in the world’s water resources and adds additional stress through its effects on other externalities.
- Collecting water is expected to become increasingly burdensome (pesado )with global warming. More regions will experience water shortages, as rainfall becomes erratic, glaciers melt and seas rise.
- People living within 60 miles of a shoreline — a full third of the world’s population — will be hit especially hard.
- Climate change is predicted to have a whole range of impacts on water resources.
Climate Change and the Hydrologic Cycle
Hydrologic cycle as the key external driver of the water cycle is accelerating due to climate change. Projected increases in global temperatures are associated with changes in the hydrologic cycle, including increased atmospheric water vapour, changes in precipitation
patterns (frequency and intensity), as well as changes in groundwater and soil moisture.
Projected climatic changes to the hydrologic cycle
- More intense storms with more flooding and extreme winds.
- more evapotranspiration. Drier vegetation and soils. More frequent and severe droughts. Increased wildfires and area burned.
- Sea level rise. More coastal erosion. Saltwater intrusion into coastal freshwater aquifers.
- Glaciers are reduced or eliminated. Increased high elevation erosion.
- More rain and less snow. Snow melts sooner in spring.
- Ealier spring runoff. Larger flood peaks. Less summer stream flow. Smaller headwater stream network.
Precipitation (including extreme events) and water vapour
- Over the 20th century, mean precipitation has mostly increased over land in high northern latitudes over the period 1901 to 2005, while decreases have dominated from 10°S to 30°N since the 1970s.
- Widespread (extendido) increases in heavy precipitation events have been observed, particularly in midlatitude regions and even where total precipitation has decreased.
- Globally, soil moisture has decreased. Droughts have become more intense and longer, especially in the tropics and subtropics.
- There is observational evidence that intense tropical cyclone activity has increased is some regions (e.g., North Atlantic since about 1970). There is no clear trend in the frequency of tropical cyclones.
Snow and land ice
- Snow cover has decreased in most regions, especially in spring and summer.
- Considerable mass loss has occurred on the majority of glaciers and ice caps worldwide.
Trends and projections of key hydrologic variables
**Precipitation: **trend is unclear. General increases in precipitation over land from 30°N to 85°N. Notable decreases from 10°S to 30°N. Projections for 21: Increase in total precipitation (about 2%/°C). High latitude areas generally projected to increases. Many low to mid-lattitude areas projected to decrease. Changes at the regional scale vary.
Atmospheric water vapor content: increasing in lower atmosphere in specific humidy; little change in relative humidity. Projections: increasing
Intensity of precipitations: disproportionate increase in volume of precipitation in heavy or extreme precipitations events. Projections: increasing about 7%
Droughts: as measured by the Pamer Drought Severity Index, increased in the 20th Century, although some areas became wetter. Projection: Increasing in many areas, particularly lower latitudes. Decreasing in many high latitude areas. Patterns are complex.
Tropical cyclones: increases in intensity, particularly in North Pacific, Indian Ocean, and Southwest Pacific. Projections: Increase in intensity. Changes in frequency and track are uncertain.
**Glaciers and snow cover: **decrease in mass of glaciers, but not in all regions. Decrease in snow cover in regions in the northern Hemisphere. Earlier peak runoff from glacier and snowell. Project: conitued decrease in glacial mass and snow cover.
Sea level increaed about 0.2 meters over the 20th century. A rise equivalent to 0.3 meters per century was recorded since the early 1990s, but it is not clear if this is an acceleration of long term sea level rise. Project: IPCC projects 0.2 to 0.6 meters by 2100, but upper and could be much higher.
Impact on Water resources: Changes in the hydrologic cycle will have both direct and indirect effects on:
- the magnitude and timing of runoff
- groundwater recharge
- water quality
- frequency and intensity of extreme events (droughts and floods).
Runoff and river discharge
Total annual river runoff globally is projected to increase, although there is considerable
variability across regions with significant decrease in mid‐latitudes and some parts of the dry
tropics and significant increase in high latitudes and wet tropics.
Groundwater Recharge
Groundwater recharge, when averaged globally,
increases less than total runoff.
By 2050 there may be significantly less recharge
(up to 70% less) in north‐eastern Brazil, western
southern Africa and along the southern rim of
the Mediterranean Sea and Australia.
Water quality. Potential effects have been noted:
- Increased water temperatures would impact biochemical processes in lakes and reservoirs, as well as the capacities of rivers to breakdown organic wastes.
- Increased precipitation intensity would, on the one hand, increase dilution, but would, on the other, potentially increase nutrients, pathogens and toxins transported to downstream water bodies.
- Longer periods of low flows would reduce the dilution capacity, reduced dissolved oxygen, increase algal blooms, and magnify the impact of water pollution, effecting human health, ecosystems, and water supplies.
- Sea level rise could increase saltwater intrusion in estuaries and coastal aquifers, and may also interfere with storm water drainage and sewage disposal.
Floods and Droughts
Globally, the number of great inland flood catastrophes during from 1996–2005 is twice as
large, per decade, as between 1950 and 1980. This has been associated with an increasing
frequency of heavy precipitation events.
Since the 1970s, droughts have also become more common, especially in the tropics and subtropics.
Rainfall in Australia
- Droughts conditions persisted in the south-east from around 1996 to 2010.
- Research has shown that some aspects of this drought are consistent with global warming.
Queensland
- Less water for cities, industries, agriculture, and natural ecosystems.
- Less frost damage to crops, higher wheat yields but lower wheat quality, increased pest and disease risk.
- 20% increase in intensity of a 1‐in‐100‐year rainstorm could, for example, inundate 7000 properties in the Nerang catchment in southern Queensland.
South Australia
- Farming of land at the drier fringe likely to be increasingly marginal if rainfall declines substantially.
- Grape quality in the Barossa Valley likely to decline due to higher temperatures.
- Potential doubling in the number of days over 35ºC in Adelaide by 2070
