Here is another project I’ve had on my to-do list for a while that I finally got around to. The Secchi disk is a tool that can be used to measure water clarity. It can be easily made yourself, so we made one out of corrugated plastic futureboard and black waterproof electrical tape and a length of old scrap aluminum rail:

The idea is to push it into the water until the disk just disappears and measure how deep it is. We added tape marks on the rail at 1m and 1.5m to assist in measuring depth.

Here is a picture of the disk at 1.0m:

And here is another at 1.5m:

The point at which it disappears appears to be about 1.8m (~5.9ft)

For comparison, here is page from Penn State University that describes water quality concerns for ponds. In particular, if you look at Table 1, they list the maximum turbidity for swimming as a Secchi depth of 3 feet, and a maximum turbidity for aesthetic ponds as a Secchi depth of 5 feet.

So my measurement of 5.9 feet does reasonably well. And I’ve noticed that the water is getting clearer and clearer the longer that the solar powered circulation pumps keep pumping the water slowly through the biofiltration sand zones, so now I will begin measuring it to see if it is still increasing over time.