From the Chicago Tribune:

As beaches officially open this weekend, health officials are using cutting-edge computer systems, frequent water testing and even specially trained dogs to monitor water quality and keep Lake Michigan safe for swimming.

Communities across the country traditionally have relied on testing water samples to determine if there are dangerous levels of bacteria. The tests can take up to 24 hours to process, however, forcing officials to decide whether to ban swimming based on day-old data.

But new technology is beginning to slash that lag time, allowing health officials to analyze results more quickly and accurately.