I know that much of the city of Escondido has high water table (literally 10-15 feet below surface), that was a concern because the city council has been trying to put a big hotel downtown for the last 5 years, and there was a risk that the underground parking garage of the hotel could get flooded.
most of Temecula is 30 to 70 feet to groundwater.[/quote]
As I said in my post, E, your area,Escondidio, has some atypical situations. I was not including Temecula when I made my statement about San Diego County. It does make sense that the Temecula valley would act as a more typical aquifer as compared to the comparatively rugged and solid terrain of San Diego county. Shelter valley, on the way to Borrego from Julian, may be similar to Temecula.
The site you link covers mainly monitoring sites where a hydrologist expect to find high ground water. There are even some that report above grade water. This is because they are monitoring groundwater basins as in this picture: http://www.mwdh2o.com/mwdh2o/pages/yourwater/supply/groundwater/PDFs/SanDiegoCountyBasins/CentralSanDiegoCountyBasins.pdf
As you can see these aquifers geographically cover little of San Diego and less of a portion of the areas outside of water districts, where people will be drilling wells. The numbers I mention will pretty much stand to an in-depth study,outside of flat coastal areas and these runoff basins… in other words most of San Diego geographically.
One other thing to consider is that there is often a difference between the resting place of the static head of a particular well and where the usable amounts of water actually intersect with the drilled hole. When the static water comes to rest above the entrance point of the water in the fractured rock this is called an artesian well. This is the case of my well and many others. The static head on mine comes to within 40 feet of ground level but that is practically useless for water collection purposes. No functional well w/o going down where it gushes in pretty good. This happens because I live in a valley, in an area of several seasonal streams. It is not so typical to have such high static water levels at my elevation 2000′. My terminology might not all be exact but I think you can get the idea.
