It’s all up to the Imperial Irrigation District. The fate of a seven-state plan to address dwindling Colorado River water supply now appears to rest squarely with the sprawling southeastern California water district. Its neighbor to the north, the Coachella Valley Water District, voted unanimously on Tuesday to approve interstate agreements that would conserve water for use by 40 million people and vast swaths of agricultural lands. IID has tied its approvals to a binding promise to receive $200 million in federal matching funds to restore the fast-dwindling Salton Sea, which lost critical Colorado River water imports a year ago.