Hy, This is one of my favourite projects because it is easy to make and needs a very few things. Mind it that I have not Invented it. Just made it by the help of other websites. As the current from the electrodes flow to each other through water and earth is provided the transistor gets charged and turns the led or the buzzer or whatever you have attached. I hope you like it.

Step 1: Supplies

Transistor BC 547   (2)
Led                          (2)
LDR                         (2)
Jumper Wires
Resistors :- 1k, 470 KR
Buzzer                    (Optional)

Step 2: Building

Firstly attach BC 547 any side of breadboard as you see in the picture.

Step 3:

Now attach the 1k resistor from the middle leg of the transistor to the GND side.

Step 4:

Attach the jumper wires from the leg of the transistor to the GND side.

Step 5:

Attach the 470KR resistor one pin down one pin right from transistor leg which will be use to reduce the current of buzzer and led.

Step 6:

Now attach the buzzer positive at the resistors leg and negative at the transistors leg line.

Step 7:

Now attach to wires in the same line you placed the buzzer if you want to put led. If no then follow the next steps. In this step you just have to make two terminal as I did to use both led and buzzer.

Step 8:

Now the final step take a jar and stick the electrotodes at the upper level or at any level you want. And attach the other two ends at the bread boards at the middle of the transistors leg line. Now you are done power it and tattatattta. You have successfully made a water level indicator, you can place it in your tank at your homes when the water will touch the electrodotes the buzzer will beep and led will be lit if you have done the setting of led. You can modify it and make two circuits on this breadboard, both will be same but place the other twol wires at the middle level which will show that the water reached the middle level.

Step 9: MY VIEW

What I made ?
As I defined I have made a water level indicator which is based on the water tanks we have at our home when we forget the stop or close the motor the tank overflows. This project will show the level like the middle level and full tank. And we can easily close the motor.

How did you made it ?
I made it at my house. I got the idea from the book that was given to me by my Grandfather and I worked alone as I always want to make things only by myself. As I worked on the project my ides changed and I modified as I have written in the last step you can make two circuits the other will show that the water has reached te middle level.

Where I made it ?
I made it at my home. It is connected to my science fair and my finals wher I successfully presented it and got full marks, 10 marks.

What I learnt ?
As I am only 11 years old so we have not ever heard about transistor and now I know much about transistors, ohms and much more about every thing I have put in my circuit. If I needed to make it again I would definetely make it with many modification I have in my mind.