Water level measuring

Hi,
I’m a hydrologist and need to find a way to measure the maximum water level from over 200 water level meters.

Currently, after a rain event we have to go out and take readings at each of those stations. As you can imagine, that’s a big PITA.

I want to be able to establish a wireless communication network and pass on those readings to a remote data logger or similar.

The wireless network is not the issue. I can develop that. But taking the readings is.

I will try to describe the existing method of measuring the water levels. Imagine a long, square and hollow tube. Inside that tube is a removable sleeve with small cups attached which fill with water as the river rises. The water enters through a small hole in that tube, rises up and fills each cup until maximum water level has reached, and the level falls again. At this point, we go out, open a door that enables access to the sleeve with the attached cups, we slide out the sleeve and measure up to what level the water filled the cups. This gives us the maximum water level reached in that river.

Simple enough, but doing this across potentially hundreds of such devices, is really not awfully motivating.

Any ideas of what sort of sensors I could use and how to set them up inside to obtain the maximum water level? The size of the tube is about 120 mm x 120 mm. I can take out the inner sleeve to provide more room inside.

I”ve seen one solution that uses a differential pressure sensor where one end is attached to the bottom of the tank ( from the outside) and the other end is just a short tube for atmospheric pressure measurement. This is apparently the best solution for a water tank. This isn’t so good for a ‘tank’ that gets submerged and thereby submerges the pressure sensor equipment box.

Suggested solutions?