Spreck Rosekrans is an Economic Analyst at EDF.

It is hard to really enjoy these balmy January days if you are thinking about the drought and how much water will be available for California’s rivers, cities and farms this year (and perhaps beyond). It is looking like 2009 will the third dry year in a row. But is it California’s worst drought in modern history as asserted by USA Today?

It depends on how you define the terms “drought” and “modern history”. If 2009 continues to be dry, 2007-2009 is likely to be the second driest three year period in the past 40 years – slightly wetter than 1990-1992. If we are luckier and we get some decent storms in the next two months, 2007-2009 will be wetter than several other three year periods.

But we are asking our water supplies to go further than we did in 1990. Our population has since increased by a third, much of it in the southern California inland deserts where water use is high. And we have decided to dedicate more water to the environment. We have increased water flows from the Delta into San Francisco Bay and along the Trinity River, both of which support endangered fish, lessening the amount that would otherwise be available for our farms and cities.

As a result, after dry years in 2007 and 2008, we began 2009 (water years begin October 1), with barely 4 million acre-feet of total supply stored in the principal CVP and SWP reservoirs (Clair Engle, Shasta, Oroville, Folsom and San Luis). As shown below, we have managed to retain slightly higher storage levels during other two-year dry periods, however, even when river flows were lower than they were in 2007 and 2008.

It is clear we are overextended and that some long-term changes need to be made. Some would build more dams (though no water agencies have volunteered to pay for them). Others would reduce environmental flows.

At EDF, we remain unconvinced about the cost-effectiveness of new dams until specific proposals are put forward for fair analysis and we steadfastly oppose reducing environmental flows. We believe the path to a sustainable future lies in providing economic incentives to increase efficiency in our cities and on our farms. We may end up with less low-value high water use crops in the Central Valley and less water guzzling landscapes in our arid suburbs, but we will have healthy rivers, thriving agriculture and reliable water supplies in all our cities.