Rivers at work and play

Southern Sierra spring snowmelt has begun 

The high hopes and great expectations for El Niño to inundate California with rain and snow have not materialized. 2016 will be recorded as an average water year - still a huge improvement over the last 4 years, and especially over the last 2 years.

Snowmelt in the high Sierra means waterfalls, including everybody's well-known favorites in Yosemite Valley which feed the Merced River. Visitors to Devil's Postpile National Monument - accessible from the east side of the Sierra - will be familiar with the appropriately named Rainbow Falls on the upper San Joaquin River. 

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Photo: Bill Gracey

At Hetch Hetchy, Tueeulala Falls - described by John Muir as "the most graceful fall I have ever seen" - normally reaches its peak in early May. Wapama Falls, the endpoint of many day hikes around the reservoir, is not quite as tall as Tueeulala but carries more water and runs longer. Standing under Wapama and looking up is a marvelous experience, but the entire waterfall can only be seen by those privileged to enjoy a boat ride on San Francisco's Reservoir (a privilege we were granted once many years ago - long before we filed a lawsuit against the city).  

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Inset shows the lower portion of the Wapama Falls which can be seen from the trail. The entirety of Wapama Falls will not be appreciated until Hetch Hetchy Valley is restored. Photo: Tim Connor

 

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Photo: Yosemite National Park - click image to see the flow

Rancheria Falls is a 13 mile round trip from the Hetch Hetchy trailhead - a longer day hike than most visitors want to undertake. When Hetch Hetchy Valley is restored, the hike to Rancheria will be shorter, cooler and certainly more popular.

Further downstream the Sierra rivers go to work. San Francisco's hydropower plants are operating at levels well above last year and recent averages. 

 

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San Francisco's three hydropower plants will all be operational when Hetch Hetchy Valley is restored. There will be some loss of generation, but much less than the power lost when four dams on the Klamath River are removed.

The situation at the major terminal storage reservoirs on southern Sierra streams varies. See Figure 1. Flows on the Stanislaus and Merced Rivers (in spite of the Merced's spectacular displays in Yosemite Valley) will be insufficient to fill their associated terminal reservoirs. Don Pedro Reservoir on the Tuolumne will come close to filling, but note that some of the runoff will be stored upstream in Hetch Hetchy and Cherry Reservoirs, and some will be used for other purposes before the end of July. 

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Photo: Dept. of Water Resource

The much smaller Millerton Reservoir on the San Joaquin will certainly fill. Flows into Millerton are already being diverted into canals for recharging depleted groundwater basins. This is good news and smart management for San Joaquin Valley farmers. 

Most of the flow on these four rivers will eventually be delivered to San Joaquin Valley farmers. San Francisco is the only major urban water system which derives its water from these rivers, and it is a relatively small amount. 

For salmon, it is a different story. In 2016, as in most years, very little water is left in the lower San Joaquin River. Both the State Water Board and the Federal Energy Regulatory Commission are in the process of considering how much of the natural flow of these rivers should be required to remain instream to benefit fish and wildlife.

 

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In context, restoring Hetch Hetchy Valley represents only a tiny piece of the water management challenges in California. But restoration is critical for making Yosemite whole once again and renewing the integrity of America's National Park System as we approach the NPS centennial this coming August.