Economist: MICHAEL VEENSTRA’S 60-berth marina at Goolwa has room for only 30 boats: half the moorings are now on dry land. Over the past 18 months, the water level has dropped and its salt content has risen. Goolwa faces the mouth of the Murray River. Yet drought, climate change and more than 100 years of irrigation have left the Murray in one of its worst crises. The Murray and its main tributary, the Darling, are Australia’s longest river-system and the lifeblood of its crop farms. It …