Global warming is expected to increase average global temperatures by several degrees and have detrimental effects on water. According to the Intergovernmental Panel on Climate Change (IPCC, 2007, www. epa.gov), water will be affected by global warming in several ways.
- Warming of ambient temperatures will speed evaporation globally. This will cause increased precipitation and changes in the seasonal timing of precipitation and snow/ice melt.
- Global warming will negatively effect snowpacks, groundwater, lake, and river systems, and water quality.
- There will be increased human competition for water due to negative effects on water quality and supplies.
As global warming will speed evaporation, precipitation will increase. However, it is hard to judge where increased precipitation will take place and when. Some regions will experience more rain and snow than they have historically, while other regions will experience more drought. The natural rhythm of seasonal precipitation will change, pushing forward seasonal rains and melts in some areas, and prolonging dry spells in other areas. Rivers will flood more frequently and at different times, desert areas may get more flash floods, and coastal wetlands may also sustain greater water levels, which could eliminate this sensitive and important ecology altogether.
As global warming increases global temperatures, glaciers and snowpacks will continue to melt at a more rapid pace. Glaciers will continue to break off and disappear. Snowpacks will melt faster and earlier in the season, or not form as densely. The lack of snowpacks in some regions will negatively affect streamflow and water supplies. Declines in snow melt will cause drought in streamflow-dependent regions. Increased glacier melts will raise water levels of some river systems.
Groundwater systems will also be affected by climate change. In some areas, groundwater levels will rise, while in others it will fall. All areas, from deserts to inland plains to coastal areas will have effects on water due to global warming. Groundwater, as the water in rivers, lakes, and streams is affected by streamflow. Where precipitation and streamflow is increased, groundwater will be increased and vice versa. This will cause more flooding and droughts, depending on the region.
Climate Change will cause crises in water quality. More runoff due to heavy rains and floods will carry more harmful chemicals, such as pesticides and fertilizers into water supplies, and increase acid rains. Warmer water temperatures will encourage the flourishing of waterborne diseases. Global warming will also most probably increase the salinity of fresh water as oceanic evaporation accelerates. Soil erosion from heavy rains and floods due to global warming will also have effects on water, dumping more particulate and heavy metals into water supplies. Disappearance of wetlands and bogs will eliminate their beneficial water-filtering role, which will have further negative effects on water quality.
Changing supplies and water quality will increase human competition for plentiful and clean water for use as drinking water and in agriculture.