Gold Ridge Resource Conservation District

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Untangling the Complexities of California’s Proposition 3 Water Bond

ON NOVEMBER 6, California voters will decide the fate of Proposition 3 (the Water Supply and Water Quality Act of 2018), which authorizes the sale of $8.9 billion in new general obligation bonds for water-related infrastructure and environmental projects. This includes funds – most of which would be distributed through grants – for various projects related to water supply, watershed health, flood management, groundwater, facility upgrades and fish and wildlife habitat.

Many are confused about the bond, and numerous organizations have taken positions supporting or opposing it. We at the Pacific Institute, a California-based think-tank focused on water, are taking no formal position on Proposition 3, opting instead to offer the voting public some insights into its complexities.

For context, California has authorized approximately $60 billion (in 2018 dollars) in water-related bonds since 1960. If passed, Prop. 3 would be the fourth-largest water bond in California history. Further, the combination of Prop. 68 (approved by voters in June 2018) and Prop. 3 would make 2018 the second-highest funding year for water-related bonds in the state’s history. The largest authorization was in 1960, when California voters approved construction of the State Water Project.

Continue here.

Source:  Heather Cooley, Sonali Abraham, Sarah Diringer and Cora Kammeyer, Water Deeply, October 29, 2018

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Geomorphology of a river: what happens when you install a dam or a weir and how the sediment transport changes

River Geomorphology Video created by Little River Research and Design, with funding from the Missouri Department of Natural Resources. http://serc.carleton.edu/details/file…

As the clip opens you see shallow flow with uniform bedmaterial transport throughout. A small low head wier or dam is installed. This produces deep subcritical flow above the dam and critical flow over it. Below the dam we see supercritical flow.

The deeper, low velocity flow above the dam cannot move the coarse bedload (Q = VA, and since A is greatly increased and Q is unchanged above the dam, V is greatly decreased) and we see deposition occur until depth is shallow enough (and A small enough) that the increase in V moved bedload again. Deposition occurs to the top of the dam.

When the dam is installed, we see a classic disruption in sediment transport continuity. Coarse transport essentially ceases through the dam until deposition builds a higher streambed. Sediment is blown out below the dam (often scoured to bedrock in the real world) This is the well known “hungry water” effect seen below dams.

At low-water crossings in the Missouri Ozarks, many of which are essentially low dams, we often see this condition, manifested as a wide, sediment-filled channel with low banks upstream of the bridge. This contrasts with a deep, scoured channel below, sometimes with high, unstable banks.

At the end of the demonstration, the downstream gate is lowered and a hydraulic jump appears which is then drowned as stage increases. The depositional dune and slipface then move past the dam. The gate is then raised somewhat, allowing a jump to reform and sediment is blown out below the dam.