Category: Technology

Venal Pool

Daytime high temperatures in the first half of June in Middlebury are historically in the 70s F, but so far this year half of the days in June have been in the 80s F. Historically in June, Burlington gets 2.5 inches of rain by the 20th, but so far has gotten only 0.4 inches (last year they got 3.8 inches by now). So maybe I should not have been so surprised on Friday to find that our vernal pool was completely dry. Ned and I visited to collect data from the loggers and install a new version of the DIY water depth and water temperature logger. The new logger might not have much work to do for a while.

Figure 1. This clearing in the woods was a vernal pool a couple of weeks ago. Click to embiggen.

Ultra depth sounding

Six weeks ago I installed version 3 of a water depth data logger in the vernal pool we are monitoring. I liked that logger more than the earlier versions because the parts cost $35 instead of $50. After posting about it I noticed that many Arduino hobbyists measure distance with an ultrasonic rangefinder instead of the laser rangefinder I had used, so I ordered a few HC-SR04p rangefinders.

The top of a peanut butter jar with an ultrasonic rangefinder (HC-SR04p, top), a temperature, humidity, and pressure sensor (BME280, left), and the cable for a water temperature sensor (DS18B20, right). The ultrasonic sensor sends a sound from one side (left) and senses the reflected sound on the other side (right).

Visit 3, Version 3

On May 3 we made the official third visit to the vernal pool we are monitoring. During this visit we are supposed to collect the frog call recorder and do the final surveys for amphibian eggs and aquatic invertebrates. At the second visit we failed to find any fairy shrimp, so I was looking forward to adding them to my crustacean life list. I was also looking forward to collecting the microSD card from the data logger we had installed on April 17 and examining two more weeks worth of data. And at the last minute I decided to bring a 24 foot-long pole and get some “aerial” photos from above the pool. By the time we left the pool to hike back to the road, I was dismayed at my lack of success at most of these goals.

Ned brought his waders and I didn’t, but somehow I was the one wading out to install the new version of the data logger. Photo by Ned, May 3, 2020.

Vernal pool data logging

Vernal pools are little ponds which have no permanent stream entering or exiting. They fill with snowmelt, rain, and groundwater, but in droughty years they often dry out before summer’s end. These characteristics prevent fish from living in vernal pools (fish can’t get to them and fish couldn’t escape when they dry out). This allows animals with little defense against hungry fish to prosper in vernal pools, especially if they can also survive when the pool dries out.

Ned is installing the data logger on a wooden post in about 20 inches of water. There is still some ice at the edge of the pool. March 28, 2020.