In California, water is a public trust resource. It belongs to all of us, not just those who own the infrastructure to impound it and divert it to fields and cities. The state is legally obligated to balance its various beneficial uses, including protecting fish and wildlife species and the associated jobs, recreation and other uses.
This isn’t an easy task in a state where water rights total five times the amount of precipitation that falls on the state.
From an environmental standpoint, the system is obviously out of balance. Before the Tuolumne River was dammed and diverted, an estimated 130,000 salmon spawned in its waters. Last year, fewer than 500 of the iconic fish returned.
And it’s not just about salmon. The entire ecosystem is facing collapse. Healthy salmon populations transport tremendous amounts of nutrients from the ocean to upland habitats where they fuel an entire food web, from hawks and eagles to aquatic insects that feast on dead carcasses and in turn provide food for the next generation of salmon.
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Of more than 100 species that depend on salmon, humans are at the top of the list. The beautiful thing is that with a healthy salmon fishery, we can harvest half the fish and they will still return in the same abundance the following year. What other animal provides such a gift?
Only 20 percent of the Tuolumne’s natural flow now reaches its confluence with the San Joaquin. Of the diverted water, 80 percent is used for agriculture and 20 percent is put to urban use. Considering that approximately 10 percent of the Tuolumne’s natural yield recharges groundwater, agriculture uses 60 percent of the watershed’s entire flow.
A 2010 report released by the State Water Resources Control Board determined 60 percent of natural (unimpaired) flow from the lower San Joaquin River and its three main tributaries would be necessary to fully protect fish species. The current Bay Delta Water Quality Control Plan proposes just 40 percent, with the flexibility to increase or decrease it 10 percent, depending on whether biological goals are met. This adaptive management approach acknowledges that non-flow measures could help revive native fish populations.
While environmental groups believe a higher starting point would achieve greater results, we agree that a combination of flow and non-flow measures is a fair approach. If the Turlock and Modesto irrigation districts can achieve established goals (yet to be determined) by improving habitat, controlling exotic predators and implementing other measures, they should receive credit for their successes.
We also support the adoption of biological objectives that can be achieved reasonably by the districts. Measures should focus on conditions influenced by the operations of Don Pedro and La Grange dams, such as spawning success, juvenile fish survival and the out-migration of young salmon. The districts should not be held accountable for conditions outside their control, such as salmon killed by the Delta pumps and poor ocean conditions.
As The Bee has pointed out on many occasions, we need a comprehensive approach to address the dramatic decline in salmon, steelhead and other river-dependent species.
For those who believe low river flows are not a major part of the problem, consider: Following the record 1982-83 water year, the Tuolumne’s salmon population boomed. Juveniles were flushed downstream, and after growing in the ocean for 2½ years, almost 40,000 salmon returned to spawn in 1985. Similarly, during the extremely wet 1997-98 water year, so much water flowed down the Tuolumne that it spilled over Don Pedro Dam. Then, in 2000, nearly 18,000 fish returned to spawn. Graphs of salmon abundance and flow clearly show the two are closely related.
It also has been claimed that predation from non-native fish, such as bass, is the main cause of salmon mortality. Predation certainly is a problem, but consider this before placing your bets on predator control alone: Bass evolved in ecosystems featuring slow-moving, warm water, similar to what current river management has created. Salmon and steelhead, on the other hand, have adapted to fast-moving, cold Sierra streams. Until we address the extreme habitat shift humans have created, non-natives will continue to outcompete native fish.
Higher flows and cool water support a greater concentration of dissolved oxygen, dilute contaminants and provide faster-moving, turbid water that improves the ability of juvenile salmon to evade the bass. Higher flows also inundate flood plains, which serve as critical rearing habitat for juvenile salmon.
The explosion of water hyacinth is another example of a non-native species thriving in the Tuolumne’s altered ecosystem. Higher flows are effective in flushing the invasive weed that has choked the Tuolumne in recent years.
We hope we can get to a place where all parties work together to meet the co-equal goals of supporting our economy and reviving our waterways. Through water use efficiency, we can achieve a balance that works for everyone. In the Bay Area, water use from the Tuolumne decreased 30 percent over the past 10 years. We know we can do it!
Peter Drekmeier is the Tuolumne River Trust policy director. He wrote this for The Modesto Bee.