Hi;
Water depth meter smart home system how do i ?
I want do a system that cuts off water and electricity when the water level reaches a certain level
What are the necessary materials?
how do I do the encoding ?
this is my school project I would appreciate if you help 
A float switch is probably the simplest way to sense a certain level. To see how others have done it, Google "arduino measure water level".
spyo:
Hi;Water depth meter smart home system how do i ?
I want do a system that cuts off water and electricity when the water level reaches a certain level
What are the necessary materials?
how do I do the encoding ?
this is my school project I would appreciate if you help
An Arduino, a float switch or switches (as suggested by @groundfungus), and a relay are the main materials. You need a PC and the Arduino IDE for writng the sketch. You should start by reading the notes about using the forum and also look at some of the tutorials.
Don't dive into doing the project. Have a bit of a play with the equipment first so that you understand what you are doing.
People on the Forum will help you overcome problems if it is obvious you have been trying, and you state your problem clearly and simply, but they will not do your project for you.
Define your project very carefully;
"Water level" is vague, water level in what, and what is the range of possible levels.
"Cuts of water and electricity" is vague, what water flow are you cutting off is it m3/s or ml/min are we talking about 9V and milliamps or High Voltage and hundreds of Amp, is it Alternating Current or Direct Current.
Why do you need to cut them off, what are the consequences if you don't cut them off.
What should your system do if there is a fault.
In washing machines they often use an air pressure sensor attached to a tube that dips into the water. As the depth of water increases, the water being pushed up the tube compresses the air. This works for water containers that are emptied regularly.
you can also use an ultrasonic sensor and look at the top of the water - caution not all ultrasonic sensors like long term exposure to humidity. Also look carefully at the min/max sensor distances and accuracy limits.
NOAA and others also use a tube and pump a small amount of air in the tube and measure the air pressure with a sensor and calculate the depth of water above the end of the tube - used for tide gauges by NOAA
How accurately do you need to measure the level, are there waves?
All these things matter and affect the design and choice of equipment.
It is fun to dive straight into coding but avoid the temptation.
Spend a lot of time defining the problem and thinking through a solutiontion.
Thank you for the answers
The aim of the project is to detect the water in the floods and disable the electrical system.
For this simple depth sensor will be used because it is a prototype the sensor needs to close the 10-amp or 16-amp fuse when it reaches the middle level
What are the materials I will use for this?
In case of flooding, the store message must be sent to the owner.
It sounds like this is in a basement.
The Arduino does not need to be in the basement, only the sensors, so your processor can run off the mains. You will need an opto-isolated relay rated for the voltage and current that you want to turn off.
If there is mobile coverage in the area where the Arduino is located you could use a GSM shield to send messages but there are cost associated with having a SIM. If a network connection is available you could get a shield for that and use it to send messages.
What sensors you use depend on the depth of water you want to trigger an alarm.
If you want to trigger just as things are getting damp some sort of conductive sensor might be best.
For deeper water float switches (cheap), or ultrasonic (more expensive) might be best. I would tend to rule out air pressure systems as they might fail if the basement tends to be dry normally.
It would probaly be a good idea to use two different types of sensor at different levels to ensure you always catch a flood.
Although the system should cut the power before entering the basement people should isolate the electricity manually.
You could just use a float switch connected to a latching relay that trips the power .( look at start/stop circuits)
You manually reset the relay when the waters gone and the electrical system is checked out as ok.
No Arduino needed - simple is reliable , you need to know the circuit will work . .
You can get “dialers” for alarm systems to call out on the phone line.