I have the same needs and will, therefore, follow this with great interest.
There is also this thread. As I understand that setup, it uses ultrasonic waves to report the water level. The sensor connects to a wifi module and a custom SmartThings DTH is used to report the data in ST.
I have purchased the hardware, but I haven’t had the courage to start the project. All the instructions presuppose a certain level of programming skills, which I don’t have.