#ColoradoRiver Basin is and will continue taking a beating from #ClimateChange #NCA4 #COriver #aridification #ActOnClimate

From KUNC.org (Luke Runyon):

The effects of climate change are not far off problems for future generations. They are existential problems for everyone alive today.

That’s one big takeaway from the U.S. federal government’s latest roundup of climate science, the National Climate Assessment, now in its fourth iteration…

In a chapter dedicated to climate change effects in the southwest, climate scientists say “with very high confidence” that warm temperatures are reducing the water content of mountain snowpack and the flows of rivers and streams that depend on snowmelt. The chapter’s landing page features a photo of low water levels at the nation’s largest reservoir, Lake Mead outside Las Vegas, Nevada, a near perfect symbol of the region’s ongoing water challenges.

Lake Mead December 2017. Photo credit: Greg Hobbs

Without coming up with new ways to manage water and cut greenhouse gas emissions, the report’s authors say existing gaps between water supplies and demands in the desert southwest will only continue to grow.

Much of the report confirms and reconfirms what scientists already know. Here are some of the biggest takeaways for the southwest, which the report defines as California, Nevada, Arizona, New Mexico, Colorado and Utah:

Figure 25.1: Temperatures increased across almost all of the Southwest region from 1901 to 2016, with the greatest increases in southern California and western Colorado.23 This map shows the difference between 1986–2016 average temperature and 1901–1960 average temperature.23 Source: adapted from Vose et al. 2017.23. Map credit: The National Climate Assessment 2018

1. “Water security in the United States is increasingly in jeopardy.”

That’s the sentence that greets readers of the report’s third chapter, dedicated to exploring how climate change will stress U.S. water infrastructure…

2. Shrinking snowpack likely to continue

Southern Rocky Mountain snowpack in Colorado, Wyoming and Utah supplies the vast majority of river flows in the Colorado River watershed. And it’s becoming increasingly scarce…

3. We know how to adapt. But can we do it fast enough?

Some parts of the southwest are already showing resilience in the face of a warming climate, the report says…

The severity of southwestern water shortages is largely up to us, as the report notes in its section on how confident climate scientists are in their findings: “The actual frequency and duration of water supply disruptions will depend on the preparation of water resource managers with drought and flood plans, the flexibility of water resource managers to implement or change those plans in response to altered circumstances, the availability of funding to make infrastructure more resilient, and the magnitude and frequency of climate extremes.”

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