County water officials said Thursday that financial challenges they face may force them to substantially raise rates for wholesale water next year, a move that would lead to higher water bills across much of the county. … While the authority has made water sale deals in recent years that have yielded $40 million, those have left fewer opportunities for potential additional deals to pursue. The Trump administration could try to cancel a $19.4 million grant the authority was awarded last spring by the U.S. Department of the Interior for an intake pipe at the Carlsbad desalination plant. And while demand can fluctuate, the largest variable appears to be how sharply March rains cut back on customers’ March irrigation usage. Drops in usage make the authority’s finances worse, not better.