Water Resource Changes
Most of our current knowledge about local-scale precipitation changes in mid-latitude areas is derived from direct impacts of warmer temperatures on water availability and water quality that are evident now. These changes include shorter snow seasons, an earlier spike in spring runoff, a rise in sea levels and increased evaporation from oceans, soil, shallow groundwater and vegetation.
As these changes occur, the ramifications could be significant. A shorter snow season will reduce water supplies in large parts of the world that now rely on water from rivers that comes from the melting of mountain snow packs and glaciers. These vast tracks of frozen water store moisture during the winter and in the warming temperatures of the spring the water flows downstream to be used for irrigation and in the cities and towns in the area. Increased future warming will result in earlier run off in snow fed rivers and streams causing premature winter and spring flooding and in turn reducing the amount of water available in summer and early fall. Initially, glacier fed waterways will increase the flow of water by adding to the summer time flow. But as warming increases and the glaciers are decimated this source of moisture is in great jeopardy for future generations. In fact, mountain ranges in some parts of the western United States records show that just since 2002 warming temperatures have shifted the peak of spring runoff some one to four weeks earlier than before.
The warming climate will assuredly cause sea levels to rise due to a combination of the expansion of warmer water and the melting of glaciers and mountain tops. Many cities and towns on coastal land who rely on groundwater for human use will have find other resources as their traditional source will be contaminated with salt water ebbing into the underground water supply.
Above ground water quality is likely to be compromised by warmer temperatures because oxygen under warmer conditions will cause a decrease in the natural filter in lakes and streams; and warmer water will cause an increase in algae and bacteria. Water quality will be affected as water levels decrease in some areas because pollutants become more concentrated in reduced water volumes. Heavy rainfall will cause poor water quality by allowing a variety of pollutants-including pesticides, organic matter and heavy metals to enter the water supply.
While there are still many questions to be answered about future water resources and hazards of rising sea levels there can be no doubt that the future will be very different than it has been for thousands of years. Nor is there uncertainty about the occurrence of climate change and the huge challenges facing people everywhere. In spite of a rather pessimistic outlook, scientists are sure about a number of certainties and knowing ahead of time provides opportunities to find solutions. According to the experts there are several points on imminent climate change that scientists do agree on:
- Earlier snow melt will affect the amount and timing of flowing water in mountainous and high-latitude regions;
- Sea levels will continue to rise;
- North America and northern Eurasia will see more precipitation with greater amounts of runoff;
- The incidences of heavy deluges of rainfall will increase most likely where there is already an increase in precipitation, and;
- Subtropical areas will deal with continuing water unavailability.
It is necessary to plan now for adapting to the climate and water changes we know will occur while continuing to research the unknown effects of worsening scenarios. There is sufficient evidence to support that some areas of the globe where it is already very hot will suffer more than other regions. These areas tend to be heavily populated and have limited water resources to begin with. Reductions in influx of water will hit some regions hard while others will risk danger from increased flooding due to the warming effect of the climate.
The tropics which tend to be heavily populated, as in some parts of Asia, will be faced with a double dilemma – as sea levels rise, so will the amount of precipitation during the monsoon season. Heavy rainfall over low lying areas will put the population at greater risk of damaging floods and rushing waters and the destruction it wreaks to homes, infrastructure and human safety. It is possible to mitigate the damage by replanning land use and ensuring that infrastructures are built to withstand the deluge.
Sub-tropical regions it is predicted will dry out. In many places in the world including much of the western U.S., the Mediterranean basin and parts of Asia, water is already a declining resource. This will further be affected by population growth and the water requirements needed to sustain the population. Under these circumstances, it will be a tremendous challenge to meet international agreements for improving access to safe drinking water and sanitation. Without the run off in these regions there will be more pressure on water resources and further altering of aquatic ecosystems.
