(trial court properly found that Walck entitled to damages for lost crop production caused by Kerbs, and properly measured those damages based on FSA county-wide average even though Walck's historical hay and pasture crop production was 68.5 percent of county-wide average; Kerbs violated state water law by installing outlet pipe in ditch so as to change means of conveyance of water without permission from the state and because Walck injured by such change in diversion point).