Answer: Unfortunately, dogs seem to be drawn to water for drinking and swimming and will leap into a pond, if need be, to get to it. If you think they are simply thirsty, perhaps you could provide them with another source of good clean fresh water to use instead.
You might want to look into taking time to show them one acceptable path to reach it and train them to use just that, so they will stop stomping on everything else, or you might try using one of the repellent sprays on the market, or perhaps you will need to resort to a fence (invisible or otherwise) to keep them out.
If the dogs do not belong to you, you might try discussing the problem and the cost of the damage they cause as well as the dog's safety with their owners. (In most areas there is a leash law.)
Using thorny plants might help and laying thorny branches on the soil surface might discourage them, but the thorns will hinder you, too, when you maintain the pond.
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