According to Matthew Reed nospam at zootal dot com nospam:
How deep can a "shallow" well go? I think you can suck water from about 32
feet, but I don't know if most pumps can do that, and I think the deeper it
is the less volume you can get.

A "pure suction" shallow well is limited to about 20-22 feet at the very
most. Once you start getting closer to 32', the efficiency goes WAY
down.

You can likely convert your Gould to a jet pump. While they're not
nearly as nice as a full submersible, they can get you down to 100'
or a trifle more.

On a related topic - my pump is a Gould JRS5, and I can only get about 55
psi out of it with everything turned off.

Presumably the switch is set to cut out at that point.

How much pressure should I be able
to get? Under load, say 3 impact sprinklers, I can only get about 30 psi.

That's fairly good.

Most impact sprinklers take quite a bit of water, and are seldom
adjustable (like 3gpm). In contrast, Orbit gearheads, as an example,
can be choked down to about 1 gpm apiece. I get ample throw off
four of these units. The impact sprinklers struggle a bit with 3,
and will sometimes get stuck if on the downside of the pressure
cycle.

[I've tried making new orifices for our impact sprinklers, and it
didn't work very well in my brief test.]
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.