power supply for the device used to detect the water level

I am trying to build a device which will be used to detect the water level in any house-whole tanker. this product is for commercial used proposed. here am using arduino uno, sonar sensor and wifi module and a cloud based system. so can u suggest me the way for power supply management for this particular device

Just go for a solar panel + 1 NiMH cell + stepup. What sonar module do you use?

ultrasonic sensor

I think it is enough to measure once every 10 minutes or so. The measurement will take (much) less than 1 second. If you use sleep properly you should have average power consumption in order of microamps. If done properly you may use non-rechargeable batteries (2 or 3 AA/C cells). They will be depleted by self-discharge, not by your device supply current.

Borish: ultrasonic sensor

yes, but which one? if it's not waterproof, you will get problems within a year of operation - it will simply rott away.

For power supply, simple. Just plug it into the nearest mains outlet.