Because the quantitative ratios among water inputs from different sources in the network vary with time , we evaluated the hourly and annually dynamics of iodine concentration in tap water. The hourly dynamics were measured in 2 Israeli cities: Holon (the central district) and Rehovot (the central-south district). The tap water samples were collected from the very same faucet in June 2021 during 24 hours with a 4-hour interval (Fig. ). The CI95% range was 0.22-0.70 and 5.95-7.42 µg I L -1 with median values of 0.39 and 6.48 µg I L -1 in Holon and Rehovot, respectively. The mean values between the two cities were found to be significantly different (p<0.0001). The concentration dynamics may be characterized by CV values that were 12% and 56% for Holon and Rehovot, respectively, which were close to the same parameter measured for Mg . Rehovot is known as a city supplied almost entirely by DSW (more than 80%) which explains a low iodine content in the tap water.