Here is a tested Arduino project that uses 3 sensor probes as water level indicator with 3 leds and one LCD display + a simple controller that turns on a motor when the water has reached the desired ...

Using the motor starters available in the market, a Hindustan Shipyard Limited (HSL) employee has come out with an automated starter to save overflowing water and the electricity used for it.

Author Ejaz ur Rehman describes a an extremely simple water-level maintainer that keeps the water level between two predefined levels using an LM311.