Impacts of Isolated Conveyance on Delta Agriculture: Update

I have been too busy to follow much of anything for a few days, but a concern has been raised to me that the $200 million agriculture loss from isolated conveyance reported in the post below and a newspaper article is an exagerration because it reflects a heavy pumping scenario, not what is actually proposed in the current BDCP.  This is a good point, and I agree that a "would" should have been a "could" or presented as a range and I take responsibility for that slip.  It will be corrected in presentations later this week, similar to what is written below. 

If forced to use a single number, I am using an estimated impact of agricultural revenue losses of $50 million.  How is it supported?  The models that have been developed for the report estimate annual losses ranging from $27m under current south Delta salinity standards (0.7 EC) to $64m under proposed  (1.0 EC) salinity standards currently under consideration by the SWRCB (I note that these numbers are revised modeling results with lower numbers than I was provided to include in the 1st draft).  In addition, the footprint of the tunnel conveyance is 8,000 acres which will be primarily farmland in a zone that currently averages $2,075 per acre.  Assuming some of it takes out non-farmland, a reasonable estimate is another $8m to $16m from the footprint.  That gives you a reasonable estimate of revenue losses of isolated conveyance to Delta agriculture (assuming it is operated as proposed in the draft BDCP) of $35m to $80m.  Thus, I am comfortable using $50m as a discussion number, and have rewritten the summary of this results as:

"If operated as proposed in the draft BDCP, isolated conveyance would decrease Delta agricultural production by about $50 million, and would have a negative impact on tourism development and the rural quality of life.  If a large isolated conveyance were operated to maximize water supplies, south Delta salinity could triple and agricultural production losses could increase to $200 million.  The higher scenario illustrates the risk of a large capacity conveyance to the Delta since there will be financial and political pressure to increase exports to high levels."

I also emphasize that it is a draft, results continue to be refined, but that the impacts are in fact very consistent with those Prof. Howitt estimated in 2007; $70m loss, up to $200m in high scenarios. Not much difference in this number, but the adjectives we use and our overall view of the situation is very different.

I don't intend to post every little update and revision to this report as it progresses through drafts, but felt this clarification was needed now given a concern that has been raised.

Update:  There was a typo in the original post, the upper level of salinity loss is $64m but was originally reported as $54m.