The proposed water level sensors, presented a suitable per-formance for measurement of variations on water level, with anadequate sensitivity, based on changes on the optical power. Thetwo proposed sensors can be used for in situ applications of waterlevel monitoring. However, the sensor S025 presented better signalperformance than S050.The advantages of employing such sensors, in structural healthmonitoring systems, to monitor groundwater levels, are the sim-plicity of the measurement system and a suitable sensitivity, addedto the low manufacturing, interrogation and maintenance costs.