Does homeowner's insurance cover in ground pool damage due to drought?

Homeowners insurance specifically excludes damage caused by earthquake and movement of earth or soil unless you purchase a separate endorsement for it. The damage has to be the result of a covered cause like fire, lightning, windstorm, weight of ice and snow, vehicle collision, etc. If it is not a covered cause the policy does not provide coverage.

Answer

If drought or ground or soil movement (shrinkage, expansion, etc) is not listed on your policy as a covered peril, then it's probably not covered.

It would likely be considered an owners occasional maintenance issue.