SALIDA — Normally, a smiling “Grinch” appears in the snow on 14,235-foot Mount Shavano around the June solstice, signaling to locals the arrival of the big water that boosts their fortunes along the Arkansas River, America’s most rafted waterway. This year, however, the Grinch is already gone. And climate change, combined with increasing tourist demands, is forcing adjustments in Colorado’s $193 million river recreation industry from installation of defibrillators to turning up artificial flows. Peak flows on the Arkansas River apparently happened May 18, more than a month earlier than usual.