Impound More Water

The total quantity of water in the earth system, in all physical states and in all locations, is fixed (with the exception of water vapor emitted by the combustion of hydrocarbons, which is relatively trivial). The vast majority of this water exists as saltwater in the globe’s oceans. Most of the remainder exists as freshwater in glaciers, snow fields, land and sea ice, aquifers, lakes, rivers and streams or as brackish water at the interfaces between fresh water sources and the oceans.

Accessible freshwater resources provide water for residential, commercial, institutional and industrial consumption and for agricultural irrigation. These resources are replaced by precipitation, although that replacement is not always contemporaneous or complete. The result can be excessive precipitation and flooding, or insufficient precipitation and drought. These situations can be adapted to with the construction of additional water impoundments, such as artificial lakes and reservoirs.

Many areas on the globe are exposed to very large variations in precipitation on a seasonal basis, such as the monsoon, hurricane and typhoon seasons in many nations, the impacts of El Nino and La Nina events and the snow melt at the end of winter. In many cases, failure to impound the large quantities of water made available during these events result in both flooding during the events and inadequate water supplies between the events. These situations are exacerbated by increasing population, which puts additional pressure on resources and also increases the percentage of impervious surfaces, which increase and accelerate runoff.

In coastal regions which rely on aquifers for significant portions of their freshwater supplies, land subsidence has become a growing issue which has aggravated the effects of rising sea levels. This has been an issue along the US East Coast, specifically around Norfolk, Virginia and Miami, Florida. It is also an issue on the US Gulf Coast, specifically in the Mississippi Delta around New Orleans, Louisiana. Some areas have installed reinjection pumps to move surface water into the aquifers to restore capacity and avoid or minimize subsidence.

California has experienced rapid population growth over the past 50 years, However, it has not built a new reservoir during that period. This has resulted in significant pressure on water resources during normal years and rationing during periods of drought, which are frequent since much of California is desert. Then, in recent years, there has been greater than average rainfall and snowfall, much of which has flowed unused to the sea rather than being stored for use in the inevitable periods of drought. Water rationing has begun to impact California agriculture, causing large orchards and farms to be abandoned.

It is clearly time to move from a sole focus on climate change mitigation to a broader focus which includes significant adaptation efforts. Water should be a high priority focus of these adaptation efforts, with regard to both increasing impoundment for future use and more effectively channeling water which cannot be impounded.