Storage of water is common to all human for domestic and industrial utilization. Today, water tanks are the conventional and a major component in water storage systems as they have the capacity to hold large volume of water over a long period of time. They come in different shapes and sizes. However inadequate monitoring of water level in this storage facility may lead to either shortage of water supply when needed or its wastage during lifting process. Hence, there is need for proper monitoring of water level in a storage facility. This need motivates this work, which is the development of water level monitoring system that based on sonar technology. Materials employed in the development include ultrasonic sensor module, ATmega-328P microcontroller, 16MHz crystal oscillator, 12V dc water pump among others. The developed system monitors the water level and activates the pump as appropriate based on the input the ultrasonic sensor gives to the microcontroller which occupies the centre of the system. The developed system has potential of mitigating the attendant problems that usually arise from wastage or shortage of water supply with respect to water storage facility. Keywords—SONAR, water storage, monitoring system