Urban Rainfall Monitoring

Commercial Microwave links for Urban Rainfall
Monitoring (CoMMon)

The problem of accurate measurements of rainfall has important implications in meteorology, hydrology, agriculture, environmental policies and aquatic sciences. In urban water management, precipitation is extremely important for the design and operation of urban drainage infrastructure (i.e., sewers, rainwater retention tanks, combined sewer overflow tanks, etc.).

To capture relevant rainfall-runoff processes accurate and precise information is needed on appropriate spatial and temporal scales. As an example, for urban catchments on the order of 100 ha or smaller, a resolution of 1-5min and 0.5-2km is recommended. Standard national or regional rain measurement networks based on gauges or radar cannot provide this information. Recently, Microwave Links (MLs) have been suggested as a promising tool for precipitation monitoring, which could solve the problems associated with radar rainfall uncertainity and sparse rain gauges.

A ML consists of a transmitter and a receiver with associated recording equipment. Its radio signal is attenuated by rainfall and can be used to continuously estimate (path-integrated) rainfall intensities along a path near the surface in real-time. While most studies focus on research-MLs with specifically tuned frequencies, standard MLs from existing commercial telecommunication networks hold great promise for urban water management. They have a high spatial density, especially in urban areas and provide gratuitous information on precipitation. However, despite generally promising results, challenges remain regarding the optimal pre-processing of link signals and the derivation of rain rates from specific link attenuation data in real-time.

At Eawag, the Urban Water Catchments group (UWC) is currently studying how the application of commercial MLs could better protect receiving waters and minimize urban flooding.