A telemetry system of water depth monitoring is required to have bidirectional communication to obtain an effective and efficient measurement system. It should be run at any meaningful time requested by user so that the collected data become more crucial and eventually generate an energy and memory saving modem. This work proposed the scheme to be applied in a campus lake with flooding and drainage warning systems to avoid the common natural disaster in raining and dry seasons, respectively. The system based on Arduino board and Ultrasonic sensor equipped by Wi-Fi modem to communicate with user’s phone who able to start a measurement and monitored the water depth through a website. The result showed that in the laboratory test, the alert was successfully sent to user’s phone whenever the depth rose past the threshold value. In the field test, the measurement of the lake’s water depth had been effectively monitored via website throughout 12 hours using 6000 mAh battery lasted for 72 times of data transmission.