Sensors

It's a complex world out there. At water resources management we believe that to understand the processes that govern our lives (rainfall, temperature, wind, flooding, etc.) one needs to understand the complex spatial variability and impact of those processes. To do so, one central sensor, no matter how accurate, is inferior to collections of sensors. In the research that we do, we focus on distributed measurements: measuring one process at more locations at the same time to understand the spatial variability and impact.

To do this, we either employ state of the art sensor systems, or when those don't exist, we build our own sensors.

Distributed Temperature Sensing

Our group pioneered the use of optical distributed temperature sensors (DTS) systems in environmental sensing. DTS allows the instantaneous measurement of temperature along an optical fibre: every second, every meter, for kilometers of cable. We have used DTS for, among others:

• finding illicit connections in sewer systems;
• measuring heat fluxes in 2D around small streams;
• finding and measuring sources of upwelling groundwater in polder systems;
• measuring heat fluxes into and out of the top layer of the soil to derive soil moisture content;
• measuring evaporation fluxes according to the Bowen ratio.

Building our own

When current state of the art does not supply us with sensors for our need, or when those sensors are to costly to use in a distributed fashion, we design our own. Prime example of this is the work done in the TAHMO project where a $200 weather station for the african market is developed. Other examples include:

• using a wii-mote for water level measurements;
• using an accelerometer to gauge wave movement;
• measuring stream discharge by producing air bubbles at the bottom of a stream cross-section.