This book summarizes the various methods which have been used to measure the water level as per different needs. It also explains that the science of hydrology is intimately related to the development of human society.Besides this concept of Arduino and various sensors, the concept of IoT and its various applications in the real world have been explained. This book also defines that IoT wireless protocols are rapidly developing therefore, the wide variety of applications that make machines, devices and communication more effective are developing in a rapid mode.