From a distance, the reservoir appears topped by a flotilla of rubber duckies. On closer inspection, the water’s surface is packed with thousands of free-floating, 13-inch plastic balls, clustered to form an undulating cover. Developed by the Israeli startup Neotop (formerly known as Top-It-Up), the mass of balls serves as a floating cooling tower, reducing surface temperatures, algae and evaporation up to 95 percent. It’s one of many potential water-saving solutions to come out of Israel’s high-tech dream factory. This could make a difference in California. With the state’s reservoirs at historic lows — the two biggest, Shasta Lake and...
