Irrigators in central Idaho river basins are likely to experience water supply shortages, following a winter of lackluster snowfall that's left many reservoirs far from filled.  That's from Ron Abramovich, the Idaho Natural Resource Conservation Service's water supply specialist. He predicts that water supply shortages are likely for farmers and ranchers in the Magic, Salmon Falls, Big Lost, and Little Lost River basins.  Only marginally adequate water supplies are expected for the Boise, Snake River and Oakley basins.  It was cold in April, so Abramovich says the snow melted more slowly than usual.  As a result, high elevation snowpack remains.  That's the good news.  The bad news is, snowpacks are below their seasonal peaks, so there is not a lot of snow up there to sustain stream flows, Abramovich says.