"More evidence that high exports are bad for the Bay-Delta system
Last week, two scientists writing for the U.S. Geological Survey published a paper that adds to the growing body of scientific concern about the effects of exports on the Bay-Delta Estuary. The paper, by James E. Cloern and Alan D. Jassby, is Drivers of Change in Estuarine-Coastal Ecosystems: Discoveries from Four Decades of Study in San Francisco Bay.
It is worth remembering how much of the Bay-Delta Estuary lies outside the Delta (which has a specified boundary at Chipps Island just west of Antioch): Cities and habitat in Suisun Bay, San Pablo Bay, Central Bay, and South San Francisco Bay all depend to varying degrees on outflows from the Delta, as do ocean-specific species beyond the Golden Gate. The map on page 4 of the paper illustrates why outflow from the Delta into the rest of the estuary cannot be considered "wasted."
Cloern and Jassby explore the impacts of reduced amounts and altered timing of freshwater flow beginning in 1956. Flows in the San Francisco Bay-Delta watershed are heavily managed for reservoir operations, interbasin diversion, and irrigation consumption. The authors note that "Flow management of the . . . watershed is so pronounced that a median 39% of its unimpaired runoff is consumed upstream or diverted from the estuary . . . ." One result is that annual exports sometimes exceed 50% of inflow.
The authors distinguish between upstream effects and Delta effects - uses and diversions that occur once flows reach the Delta. Looking at the period from 1956-2003, they note that "The Delta effect . . . increased over time, at the expense of outflow to San Francisco Bay. The trend in Delta effect is due to a trend in water exports from the Delta . . . as opposed to within-Delta depletion that contributes a median of only 19% of the Delta effect and has no long-term time trend." Exports increased from approximately 5% to 30% of Delta inflow, leveling off in the 1990s following the Bay-Delta Accord to set monthly quotas for export.
The effects of high exports are varied and dramatic.
read more...... http://campaign.r20.constantcontact...sarFz1DjtQVJeecs7V9bOZa_HzkaO9cAvS4qMlzza1Q==
www.restorethedelta.org
Last week, two scientists writing for the U.S. Geological Survey published a paper that adds to the growing body of scientific concern about the effects of exports on the Bay-Delta Estuary. The paper, by James E. Cloern and Alan D. Jassby, is Drivers of Change in Estuarine-Coastal Ecosystems: Discoveries from Four Decades of Study in San Francisco Bay.
It is worth remembering how much of the Bay-Delta Estuary lies outside the Delta (which has a specified boundary at Chipps Island just west of Antioch): Cities and habitat in Suisun Bay, San Pablo Bay, Central Bay, and South San Francisco Bay all depend to varying degrees on outflows from the Delta, as do ocean-specific species beyond the Golden Gate. The map on page 4 of the paper illustrates why outflow from the Delta into the rest of the estuary cannot be considered "wasted."
Cloern and Jassby explore the impacts of reduced amounts and altered timing of freshwater flow beginning in 1956. Flows in the San Francisco Bay-Delta watershed are heavily managed for reservoir operations, interbasin diversion, and irrigation consumption. The authors note that "Flow management of the . . . watershed is so pronounced that a median 39% of its unimpaired runoff is consumed upstream or diverted from the estuary . . . ." One result is that annual exports sometimes exceed 50% of inflow.
The authors distinguish between upstream effects and Delta effects - uses and diversions that occur once flows reach the Delta. Looking at the period from 1956-2003, they note that "The Delta effect . . . increased over time, at the expense of outflow to San Francisco Bay. The trend in Delta effect is due to a trend in water exports from the Delta . . . as opposed to within-Delta depletion that contributes a median of only 19% of the Delta effect and has no long-term time trend." Exports increased from approximately 5% to 30% of Delta inflow, leveling off in the 1990s following the Bay-Delta Accord to set monthly quotas for export.
The effects of high exports are varied and dramatic.
read more...... http://campaign.r20.constantcontact...sarFz1DjtQVJeecs7V9bOZa_HzkaO9cAvS4qMlzza1Q==
www.restorethedelta.org