Neighbor is draining his pool and flooding our yard!?

Once again, the renters in the house behind us are draining their above ground pool. Our backyard is flooded, as is the neighbor next to us. We've worked hard to establish the flowers and shrubs in our yard -- do we have any legal recourse if this kills our plants and gr? We talked to other tenants when this happened in the past, but it seems that every year there's a new tenant. Is there any way to get the landlord to take the pool down?