The attorney general of Montana has filed a friend-of-the-court brief in a case that could affect some Iowa water rights. The suit was filed by North and South Dakota, over management of the Missouri River. Years of drought have lowered the water so much, the fishing and boating industries upriver and the big hydro-power dams are demanding to keep their share of it — while downriver states like Iowa want more water released from those dams so the river’s high enough for farming and barge shipping. The Montana attorney general says under the Flood Control Act of 1944 the US Army Corps of Engineers cannot give priority to downstream users. He says the law requires the corps to accommodate all uses — including the needs of upstream states for recreation, fishing and wildlife. A federal judge in Minnesota who’s hearing at least half a dozen lawsuits will hear that and other pre-trial issues and then tell the states what he’s decided before they bring their final cases to trial.