Need advise to deal with silt / boulder granule in bore well that has stopped the pump

It has been close to 3 years since I have been using a Grundfos 2HP pump which is 550 ft below the ground in my home bore well. It was all fine, till it stopped working a few days back. No electric or water level issues have been found. On taking the pump out we were shocked to see silt and boulder granules that have made their way into the mesh and damaged the pump. The motor appears to be ok.

Now the service guy is fixing the pump at a higher price, however he does not guarantee against recurrence of the problem. I would like to know if there is better way of dealing with this than letting the silt / granule enter into pump and go bad again.

Thanks in advance for your expert advise!