Submersible pump well problem

Starting about two months ago the underground sprinkler system started to malfunction. I have checked for water leaks in the system, ohm leaks at the control box and am now to this: water pressure at the house is fine, but I have not turned on all water taps at the same time. when the sprinkler system start up, the well pressure gauge shows 50#, after the system runs for 2/3 min. the pressure gauge starts to fall and shortly thereafter the water pressure/streams start to diminish, the gauge goes the 30, needle jumps and then goes to 20 , at that point I have just gurgles at each of the sprinkler heads. I am concerned the submersible pump is starting to fail.

 

It sounds to me like you're running out of water.