Why is California's central valley ideal for fruit and nut agriculture?

We needed to find out an answer for this question before we acquired some agricultural land. I mean, you see farms and orchards all over california, from coastal areas to very interior regions. I guess you could always farm something wherever there is (good) water. But, what exactly makes CA the largest supplier of stone fruit and nuts? Well, this is what we discovered.

California has two most productive growing areas for fruits and nuts: Sacramento Valley and San Joaquin Valley. Together they make up Central Valley. 

Q. Why is Central Valley the most productive agricultural region?

A. The right soil and the right prevailing climate (much like mediterranean):

• Loam soils -- nutrient rich, retain moisture, still allow excess water to drain away
• Mild, wet winters -- provide trees with stress-free rest, help them gain strength
• Warm, dry springs -- promote blooms and bee activity, resulting in higher fruit set
• Hot, dry summers -- offer crop disease protection

And, of course, abundant water supply! Central Valley is supported by two major river systems, viz., the Sacramento river and the San Joaquin river along with many of their tributaries. In addition, San Joaquin valley is fed by Don Pedro Reservoir which collects snow-melt water from The Sierras.