Almost half of all the water that flows through the Colorado River each year is consumed by just two states: Arizona and California. For the Biden administration to stabilize the river, one of the two states will have to lose big.

While expensive solutions like new reservoirs and seawater desalination grab attention, California communities are quietly building up their capacity to clean stormwater and wastewater for reuse for irrigation, industry and, yes, drinking water too.

Abrupt weather extremes, changing climate and frequent natural hazards such as floods and droughts create challenges for our nation’s aging reservoir systems. Researchers are working to help mitigate these problems.

After months of tense negotiation, a half-dozen states have reached an agreement to drastically cut their water usage and stabilize the drought-stricken Colorado River — as long as California doesn’t blow up the deal. The plan would cut water use on the river by roughly a quarter, drying up farms and subdivisions across the Southwest.

In 2014, California legislators, focused on groundwater’s accelerating decline during a prolonged drought, passed the Sustainable Groundwater Management Act. New agencies find making sustainability plans is hard, but easier than persuading growers to accept them.

Hunnic peoples migrated westward across Eurasia, switched between farming and herding, and became violent raiders in response to severe drought in the Danube frontier provinces of the Roman empire.

Snowcapped mountains generate mountain water runoff and snowmelt, which flow down to streams, rivers, lakes, and oceans. Around a quarter of the world depends on these natural “water towers” to replenish downstream reservoirs and groundwater aquifers for urban water supplies, agricultural irrigation, and ecosystem support. Carbon mitigation strategies are needed to maintain snowpack throughout the Americas. 

Texas’ biggest single solution to providing enough water for its soaring population in the coming decades is using more surface water, including about two dozen new large reservoirs. But climate change has made damming rivers a riskier bet.

An emerging deal would cut water deliveries to Southern California — but fall far short of federal demands.