Power-up ardruino whith a flooding sensor

First of all, I am a beginer with arduiuno and my question is probably very stupid but I try-it anyway.
I have a sistem composed with: A moto-rotary valve, arduino and a flooding sensor.
When water is detected, arduino closes the rotary valve and sends me alert on the phone.
It is possible to power-up arduino only when flooding sensor detects water with some kind of relay?,
I am trying to reduce power consumption and power arduino, valve and sensor with batteries.

mwcrc:
First of all, I am a beginer with arduiuno and my question is probably very stupid but I try-it anyway.
I have a sistem composed with: A moto-rotary valve, arduino and a flooding sensor.
When water is detected, arduino closes the rotary valve and sends me alert on the phone.
It is possible to power-up arduino only when flooding sensor detects water with some kind of relay?,
I am trying to reduce power consumption and power arduino, valve and sensor with batteries.

That is what "float switches" are used for.

Paul

You can put the Arduino to sleep for periods and drastically reduce power consumption - another option, google “ Arduino sleep”