Water Supply and Use
Drought and Climate Change
Drought is a period of dryness. A "megadrought" is an extended, severe period of drought. The southwestern United States has been in a megadrought since the year 2000. A significant factor in this megadrought is climate change. Increased temperatures have increased the rate of surface water evaporation to the point where rainfall alone does not replenish it. Water levels in major reservoirs, such as Lake Mead, have fallen dramatically. Current projections indicate that the megadrought may last to the end of the century.
Thus, drought mitigation must involve climate change mitigation, which is hampered by politics and personal attitudes, among other obstacles. A crucial additional component of drought mitigation is better water resource management. The WWP proposes a workable, sustainable plan for water relocation from the Northwest to the Southwest.
California Supply and Use Charts
The California Natural Resources Agency, Department of Water Resources has compiled data on water supply and use in the state from 1998 to 2020. Their findings may be seen here.
The chart shows that the main sources of water supply are Instream Environmentals, ground water, and reuse water, supplemented by local projects. The main areas of use are Irrigated Agriculture and Wild & Scenic River.
Water Management Alternatives
Conservation
Water conservation includes such steps as restrictions on use, rainwater and graywater harvesting, and treating and recycling waste water. Many of these steps are aimed at residential water use, which consumes a relatively small portion of the total use. Agriculture consumes a much greater portion, but agricultural water conservation is a complex matter.
Conservation is a viable short-term solution for the Southwest, but is ultimately unsustainable.
Desalination
Desalination is the conversion of sea water to fresh water. Methods include distillation (i.e., heating the water so it evaporates, and cooling it so it condenses) and filtering (passing the water through a filter that removes mineral contents, often via reverse osmosis).
Desalination plants along the coastline can provide fresh water, but the Southwest would need dozens of them to satisfy its current needs. Desalination infrastructure costs are over $500 billion, plus very costly annual operating expenses. Desalination plants consume a tremendous amount of energy while introducing visual and environmental pollution to the region.
For example, the Carlsbad desalination plant near San Diego took 10 years of planning and permitting and six years to build. It is ten miles long overland, and its average discharge rate is 153 acre-feet (50M gallons) of water per day.
1 Terms
Terms used in hydrology and water management.
1.1 Acre-foot
In the United States, the volume of a large water source is often measured in acre-feet (AF). This unit equals the amount of water that would fill one acre (an area of about 209 ft x 209 ft) to a depth of one foot.
One cubic foot of water contains about 7.5 gallons. One acre-foot is 43,560 cubic feet, and contains approximately 325,853 gallons.
MAF = million acre feet. One MAF is approximately 326 billion gallons.
In the metric system, similar water volumes are usually expressed in cubic meters (m³) or
1.2 Discharge rate
A river's discharge rate, also known as streamflow, is the volume of water that flows through a given point over a specific time period. It is commonly measured in units of cubic feet per second (ft³/s or CFS) or cubic meters per second (m³/s or CMS).
The average discharge rate of the Columbia River is 273,000 CFS, or 7,504 CMS, which is equivalent to roughly 2 million gallons per second.
1.3 Drainage area
A river's drainage area, also called a drainage basin, is the total area of land where the river, its tributaries, and its streams flow into the river's mouth or into an ocean or lake.
1.5 Watershed
A watershed, also called a drainage divide, is an area of land that separates different drainage areas, thereby forming a geographic boundary for the drainage area. Often it is a mountain or ridge.