Department of Water Resources
A daily compilation of significant news articles and comment
May 8, 2009
3. Watersheds –
Peter Moyle, John Durand and William Bennett: Change needed for better Delta ecosystem
The
By Peter Moyle, John Durand and William Bennett
The authors are ecologists affiliated with the Center for Watershed Sciences,
The Sacramento-San Joaquin Delta is changing, and the pace of change is accelerating. While the ecosystem still contains an abundance of fish, invertebrates and plants, many are undesirable species that were not around a few decades ago. In the near future, we can expect to see even more dramatic change. We can either fight it at great expense – and lose – or figure out how to make change work in our favor.
Most big decisions for the Delta today are made in reaction to lawsuits, levee breaks and droughts, often to prevent change. We think it is possible to break this cycle of reactive management by understanding the Delta's history.
Understanding the past makes possible reasonable predictions of the future, allowing a more proactive approach to managing the Delta and its ecosystem.
The Delta began as a vast freshwater tidal wetland, intimately connected to its inflowing rivers and their floodplains, as well as to saltier parts of the San Francisco Estuary downstream. Starting in the mid-19th century, the Delta was altered by blocking off floodplains with levees, creating Delta islands through diking and draining marshlands, and diverting water upstream.
Then, dozens of dams were built for irrigation and urban water supply. At the same time, myriad non- native species invaded the region. The native fish were left to survive in barren rock-lined channels and tiny bits of floodplain and marsh habitat.
Given the extent of the transformation, it is a miracle that only two native fish species were driven to extinction, with most species remaining fairly common until recently.
The present crisis has its origins in the big water projects that diverted more and more water from the rivers, culminating in the completion of Oroville Dam in 1967. Although voters rejected a peripheral canal in 1982 – in part from fear of a "water grab" – more and more water moved south. The diked channels of the Delta were increasingly treated as canals to convey water to Valley agriculture and to
In response, estuary-dependent fishes such as Delta smelt, longfin smelt and striped bass declined, while freshwater lake species such as largemouth bass, bluegill and catfish increased. This shift would have gone by virtually unnoticed were it not for the state and federal endangered species acts.
Only when Delta smelt, green sturgeon, winter and spring chinook salmon and longfin smelt reached critically low numbers and became listed as threatened or endangered did management of the Delta ecosystem begin to change. However, initial responses to the crisis were feeble.
They involved mainly minor changes in timing and amount of water diversions and allocations, followed by more studies and lots of hand-wringing. The fish continued to decline. Finally in 2007 and 2008, Judge Oliver Wanger issued decisions stating that protective actions for smelt and salmon were insufficient, ordering reduced exports from the giant pumps in the south Delta.
Meanwhile, sea level continues to rise and farmed islands continue to sink, indicating that the Delta ecosystem is headed for another transformation. Two recent reports by UC Davis scientists and the Public Policy Institute of California indicate that major changes will come from levee failures on the most deeply subsided Delta islands, especially from inevitable earthquakes.
Much of the western and central Delta will shift from fields of alfalfa, grass and corn to expanses of open water, 15 to 30 feet deep. Most likely, the water will be too salty for export.
This inevitable increase in open water will probably be good for some fishes now in decline, such as Delta smelt, longfin smelt and striped bass,and bad for some non-native species, such as largemouth bass and sunfish. Regardless, the new Delta will be unlike anything that existed previously.
There are a variety of ways to deal with these changes including creating a more "natural" pattern of water flow through the Delta, reconstructing large expanses of variable tidal marsh habitat in both fresh and brackish water, re-creating floodplains and deliberately flooding some islands before levees collapse. Given the increased difficulty of channeling water exports through the Delta, a peripheral canal that conveys some
Creating a Delta that is better for desirable fish and for most Californians is not simple. The choice is whether to take action now or wait to respond to a "disaster," as we humans like to call sudden change. The UC Davis/PPIC studies indicate that a reasoned response will be cheaper than a reactionary one. It is also more likely to result in a Delta that will be better for fish and humans alike. #
http://www.sacbee.com/opinion/story/1843878.html
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
DWR’s California Water News is distributed to California Department of Water Resources management and staff, for information purposes, by the DWR Public Affairs Office. For reader’s services, including new subscriptions, temporary cancellations and address changes, please use the online page: http://listhost2.water.ca.gov/mailman/listinfo/water_news . DWR operates and maintains the State Water Project, provides dam safety and flood control and inspection services, assists local water districts in water management and water conservation planning, and plans for future statewide water needs. Inclusion of materials is not to be construed as an endorsement of any programs, projects, or viewpoints by the Department or the State of
No comments:
Post a Comment