Audio fileAs swimmers head for Nebraska lakes to cool off this summer, health officials warn: Make sure the spot you choose is safe. Recent health alerts at Maple Creek Recreation Area Lake in Colfax County, Maskenthine Reservoir in Stanton County and Rockford Lake in Gage County have been lifted but Nebraska health officials said harmful algal blooms can develop quickly during the summer. David Schumacher, surface water monitoring section supervisor for the Nebraska Department of Water, Energy and Environment, explained what water looks like with an algal bloom. He urged people to avoid affected water and keep pets away because contaminated water can be fatal to dogs. Although Nebraska tests dozens of public lakes each week during the summer, Schumacher acknowledged harmful algal blooms can develop between sampling days.