Completed in 1892, the Searsville Dam sits astride San Francisquito Creek, which connects watershed in the mountains above Silicon Valley to the San Francisco Bay. Sedimentation has “reduced the reservoir to 10 percent of its original capacity“. At this rate, the reservoir will completely fill in 15 years, and then, sediment would wash over the dam, through the creek, and into the bay. This old dam and silted-up reservoir pose both a threat and an opportunity for the Bay Area: sediment washing down the creek returns an age-old flood threat to downstream communities like Palo Alto and Menlo Park; one reservoir of sediment is a potential source of mud needed to help save the South Bay from sea-level rise.
Sediment washing over a completely filled dam could clog the creek and lead to flooding. Floods aren’t new to the alluvial Santa Clara Valley. Resting on up to 1,500 feet of sediment, the valley floor is broad and flat because of past floods deposited sediment across the valley. The Bay Area was thinly settled when the dam was built in 1892. Since then, Silicon Valley homes and offices have been built next to the creek, limiting flood control options.
In addition to flood risk from the creek, the Bay Area has a long shoreline that is at risk from rising seas. “Back in June 2016, Bay Area voters approved Measure AA to raise $500 million to pay for wetlands restoration, flood control and wildlife projects around San Francisco Bay.” But to protect the Bay Area, the structures will need more mud than is available, per the Scientific American post.
Searsville Dam holds “approximately 2.7 million cubic yards of sediment that has built up behind the dam since its construction in 1892“. This sediment is a potential source of mud for the Bay.
Finally, Searsville Dam filling with sediment illustrates that a dam has a limited lifetime. The Bay Area is planning to build another dam. As we do this, we should consider the life-cycle costs of new dams as well as existing dams.
Continue reading Stanford’s Searsville Dam
This summer we visited the island of Kauai in Hawaii, where we enjoyed Kauai‘s high cliffs, deep valleys, and water. For six million years, “high annual rainfall has eroded deep valleys in the central mountains, carving out canyons with many scenic waterfalls.”
Above is a sunrise from our condo, where the rising sun paints the beach and trees with a red glow.
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Completed in 1966, the Glen Canyon Dam holds back the Colorado River to flood Glen Canyon, forming Lake Powell just upstream from Horseshoe Bend. Looking at the height of white bathtub ring, the water level doesn’t look down much, but a park ranger told me that the reservoir had risen to 55% full after the past wet winter.
Lake Powell loses water to evaporation and leakage; I wondered if the water loss is significant. Running the numbers, Lake Powell loses enough water to supply over half (57%) the people in the San Francisco Bay Area with water — every year. After weathering years of drought, the water loss from Lake Powell is very significant.
Continue reading Glen Canyon Dam
After the heavy rains that ended California’s five-year drought, our state’s wildflowers have made a comeback. Enjoying last year’s superbloom at Death Valley, we visited the Carrizo Plain National Monument, a premier place for California wildflowers. Shown above, coreopsis and fiddleheads bloom above Soda Lake, an alkaline lake ringed by salt. Reflected in Soda Lake, the Temblor Range is painted with swaths of wildflowers. I can see an impressionist painter splashing bold strokes of color on the canvas.
When rain falls, the water dissolves salts from the soil and usually flows to the ocean, already salty from past rain. Like Death Valley, Carrizo Plain has no outlet for rainwater, so water collects in the lowest spots and evaporates, leaving behind salts. Invasive plants struggle with this salty environment, while native plants that evolved here flourish without invasive competition. Consequently, Carrizo Plain has vast fields of California native plants and their spring blooms.
Continue reading Wildflowers of Carrizo Plain
After the storms of January and February, the San Francisco Bay Area is drying out and getting ready for spring. Our first iris bloomed in late March. It’s a Douglas iris, iris douglasiana, a California native plant. Hardy, drought-tolerant, and disease-free, these irises are stars for a California garden, with beautiful flowers in the spring and green leaves year-round. They’re easy to divide and move to new places in our yard.
California’s reservoirs are full, and the mountain snowpack is very large, so there’s lots of water to distribute to farms and urban users. Future challenges will be whether the water conservation forced by the drought will persist and dealing with groundwater overdrafts.
Continue reading Los Altos Weather – Spring is in the Air
The American Southwest has always been parched, so water supplies become overextended as farms and cities grow. John Fleck’s Water is for Fighting Over examines legal and political fights and settlements for water from the Colorado River.
From this experience we can find lessons learned and paths to share water.
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Northern California and my home town of Los Altos received more rain than normal in January and February 2017, as the atmospheric river continued to flow here. After five years of drought, California’s surface water and snow pack are above normal.
In early March, bee’s bliss sage (salvia ‘Bee’s Bliss’) begins to bloom, attracting bees. Bee’s bliss sage is a California native plant that is drought tolerant and likes full sun.
Continue reading Los Altos Weather – Soggy February