Water Availability

The hydrologic cycle is defined as the movement of water between land surface, oceans and atmosphere. Water that is in the atmosphere is soon sent back to the land surface and oceans in the form of precipitation. When the water reaches the land surface, it will either become streamflow, or be absorbed into the soil where it may or may not be plants, or it will filter through to the groundwater. Eventually, water will make its way back into atmosphere via the process of evaporation from surface waters, or through transpiration from plants. This perpetual cycle is powered by solar energy. If there is an increase in net solar radiation or temperature, the process will be sped up.

Because of the intricate exchanges between the hydrologic cycle and global circulation patterns, a boost of energy to the hydrologic cycle won’t necessarily result in increased precipitation in all geographic regions. Future changes that the precipitation patterns might endure can not easily be predicted. Similarly, predicting regional streamflow changes and changes in groundwater recharge caused by climate change are also very difficult to predict. This is due in part to the general uncertainty in regional predictions concerning how precipitation trends may change.

Changes in precipitation patterns, temperature, and snowmelt can all have significant impacts on the availability of water. The net impact on the water supply will depend primarily on changes in precipitation such as the total amount, seasonal timing and form. Higher temperatures will decrease water supplies by way of evaporation. In general, areas which see a sufficient increase in precipitation may find that net water supplies may not be affected at all, or in some cases even increase. In areas where precipitation remains the same or decreases, it is expected that water supplies will diminish. In those areas that see a decrease of water, the demand for water will likely rise. This may have a substantial impact on agriculture, as it is the largest water consuming industry. Other municipal as well as industrial outfits that are dependent on the water supply may have their operations compromised due to a dwindling supply and cost inflating demand.

Upward trends in temperature can affect the amount of snowfall, as well as the duration of time that it lasts on the ground. This in turn can affect the timing of streamflow. Recent studies have shown drastic declination of many glaciers. It is expected that glaciers will continue their trend of retreating, and several small glaciers may vanish altogether. It is expected that peak streamflow may very well shift from late spring to early spring or late winter. Changes in streamflow can have serious impacts on water and food management and irrigation. If water supplies are in fact reduced, off-stream water users like irrigated agriculture as well as in-stream users such as fisheries, hydropower, and reaction and navigation could potentially be most affected by the shortage.