The fill valves hang over the rims of the tanks but the mustangs can flip them out of the water, as seen in this video, wasting a critical resource.
They are now held in place by wood blocks that were attached to the rims with carriage bolts and wing nuts.
In case you did not know, the eleventh commandment on the high desert is “Thou shalt not put thy well to the test.” You don’t buy land in this area with visions of high-tech irrigation systems and lush green lawns!