Wetlands are often very productive ecosystems, which can flourish due to water availability, nutrient cycling, and the sun’s energy. They provide critical habitat for a wide variety of plant and animal species, including the larval stages of many ocean fish. Wetlands also deliver a wide range of important services, including water supply, water purification, carbon sequestration, coastal protection, and outdoor recreation (see Chapter 1). Globally, many such regions are under severe environmental stress, mainly from agriculture and urban developments, pollution, and rising sea level. However, there is an increasing recognition of the importance of these habitats, and mitigation and restoration activities have begun in a few regions. A key element in wetland conservation, management, and restoration involves hydrological monitoring as the entire ecosystem depends on its water supply. Heretofore, hydrological monitoring of wetlands is mostly conducted by stage (water level) measurements at gauging stations, which provides good temporal resolution but suffers from poor spatial resolution, as stage gauging stations are typically distributed several or even tens of kilometers from one another.