By Jay Lund and William Fleenor
Where does water exported from the Delta come from? And where does the salt in Delta exports come from?
Water and salt exported from the Delta comes from several sources:
- Sacramento River (largest high-quality source) (Sac)
- San Joaquin River discharge (usually modest flow, but much saltier from agricultural drainage) (SJR)
- smaller eastside streams (Mokelumne River, etc.; usually small, but good quality) (East)
- Delta drainage water and precipitation (lower quality) (Delta)
- Ocean water (salty, mixed in by tidal action, if above sources are inadequate) (Martinez).
Here are some answers in two plots, routinely produced by the California Department of Water Resources (DWR), showing estimates of the mix of these sources in southern Delta water exports. These are for State Water Project (SWP) exports so far in 2016. (The tidally-averaged estimates are made using DWR’s DSM2 model.)
Where does your water come from?
For 2016, so far, most of the water exported by the SWP from the southern Delta is actually Sacramento River (Sac) water which has been hydraulically dragged through the Delta. The San Joaquin River (SJR) contributes some, and the Eastern streams (East) a bit as well. “Delta” (Delta) water is also present, as is ocean water (Martinez) just a little in January.
Where does your salt come from?
The salinity in SWP exports varies with both the quantity and quality of each water source. In January, the little bit of salty ocean (Martinez) water is a disproportionate contributor of salt to urban and agricultural diversions in the southern Delta. The fairly low Delta water quality is also seen, disproportionate from its more modest quantity of diversion. The Sacramento River, which is 60-80% of the water diverted, only contributes a third of the salt. Note also the extra salinity of the lower San Joaquin River.
Note also that the field data on salinity at the SWP diversion is a bit higher that what the model estimates. So there is some model error in this case, probably mostly from errors in the ocean boundary conditions and estimated in-Delta consumptive use.
What does a wet year look like?
2011 was the most recent wet year, with the last quarter of 2011 shown in the figures below. The mix of sources was very different. The Sacramento River remained the dominant source, with much more from the San Joaquin River (with better-than-usual water quality), less Delta water, and some eastern streamflow.
Salinity was much better, until the end of the year when a bit of ocean (Martinez) water intruded. The San Joaquin River contributed to salinity disproportionately as well. The model fit the field data much better.
The Delta is a complex and changing place. Its waters also change in quality and quantity with the tides, seasons, and years.
The authors are with the Center for Watershed Sciences, University of California – Davis.
California Department of Water Resources, Delta water fingerprinting archive, 2005-2016, This is a rich and thought-provoking set of field observations and modeling results.
Fleenor, W., E. Hanak, J. Lund, and J. Mount, “Delta Hydrodynamics and Water Quality with Future Conditions,” Appendix C to Comparing Futures for the Sacramento-San Joaquin Delta, Public Policy Institute of California, San Francisco, CA, July 2008.
Medellin-Azuara, J., E. Hanak, R.E. Howitt, Fleenor, W.E., and J.R. Lund, “Agricultural Losses from Salinity in California’s Sacramento-San Joaquin Delta,” San Francisco Estuary and Watershed Science, Vol. 12, No. 1, 2014.
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Do you know someone that can model using the DWR’s DSM2 model?
Reduce SALT by installing tidally controlled louvers between 10 of the 12 Benicia bridge support, a shipping lock, and leaving one section open for fish and small water craft. The DSM2 model will give us results as to how much salt will be kept out of the Delta and SWP. Help return the Delta back 100 years to a fresher water body that support more life.
There have been proposals to build such barriers since the 1920s. The most recent study I ever say was published in 1978 by the Army Corps to build a sill at Caquinez strait to hold back the denser salt water. The early 1920s studies found that it was cheaper to use reservoir operations to provide a “hydraulic barrier” than to build a physical barrier. Imagine what a pure physical barrier approach would do to fish migration.
Então se transforma em necessário gretar para projetos mas ambiciosos, como a compra de equipamentos
profissionais de mixagem e também reprodução ao vivo. http://lpmvoice.com