Broadly speaking climate change will cause:
- Increased variability in climate with more "severe weather events". Hence, increased heavy rainfall, more flooding and longer droughts.
- Loss of snow and ice.
- Higher temperatures in the atmosphere and sea.
This will affect water quality, supply and demand. This post summarises a few general statements made in the UN report to business and provides an overview of what might happen, but not much in the way of detail.
This rather cheery picture shows how supplies of freshwater may change by the end of the century (it's from the IPCC...)
These changes will probably cause:
Supply
1. Water shortages due to changes in rainfall and hence the water table. Drier in the subtropics and mid-latitudes which are already poor.
2. Glaciers and snowcaps reduced. One-sixth of population live in river basins fed by glaciers and snow melt. Notably China, India, Pakistan and western USA.
3. Damaged ecosystems due to temp increases, changes in rainfall and longer droughts. Ecosystems filter water and buffer against floods, but not when they deteriorate.
4. Flooding, extreme weather and sea-level rise will mess with existing water infrastructure (treatment and distribution). e.g. The future climate is likely to be more variable with floods followed by drought. Capacity to store large volumes during flood to carry through a drought may not exist. E.g. sea level rise could compromise water treatement.
5. Non-consumptive activities may be affected by drought, flood or extreme events. E.g.
Tourism that depends on snow or water;
Freight by river (e.g. Rhine in Europe, Mississippi in US);
Freshwater fisheries.
Quality
1. Extreme rainfall and floods increase erosion and contaminate water. Also wash soil based pollutants and toxins into fresh water.
2. Sea level rise can contaminate coastal surface and groundwater supplies (rivers, deltas and aquifers)
3. Increased algal and bacterial blooms due to higher temperatures.
4. Greater health risks e.g. flooding mobilises pathogens and contaminants.
Demand
1. Prolonged dry spells and drought increase irrigation demand. e.g. estimate is 40% increase in land needing irrigation by 2080.
2. Higher temps mean farm animals need more to drink.
3. More cooling water needed in industrial applications due to higher atmospheric and water temps.
Disasters
1. There's likely to be flooding and inundation of coastal areas, flood plains etc. due to sea level rise and heavier rainfall in certain places.
