The Spokane River will soon have its flow back.Tuesday morning, Avista Utilities increased the water allowed to pour from its dam in Post Falls. The water will slowly but surely meander west to once again fill portions of the riverbed that went dry this summer and last.In the coming days, the water will make its return to the route it’s known for centuries, moistening as much as 2 miles of riverbed that nonprofit Spokane Riverkeeper estimate wen…