With some beautiful weather this past weekend, a welcome respite from the recent rainy pattern, Lisa and I spent an afternoon kayaking the meandering Ipswich River. As you can see from the photo above, water levels were quite high. This bodes well for the health of the river this summer, as its history of low-flow issues have given it the dubious distinction of being among the “10 Most Endangered Rivers in America“.
Also evident in the picture above are the wonderful shadows, reflections, and patterns cast across the river on a sun-filled afternoon. At the time this particular photo was taken, we were taking a break along the bank, enjoying the scenery and a snack. It was then, in the clear shallow water by the shoreline, that we noticed the wonderful shadows being cast by water skimmers as they moved across the surface. Strangely incongruous with the size and shape of the skimmers themselves, these shadows are far larger than the skimmers and include circular shadows created by the points where the skimmers legs are touching the water. (Explanation: The dark shadow for each of the water strider’s legs is an example of refraction, an optical effect resulting from the depression in the surface of the water caused by each leg.)
I made this image (above) to help me remember a wonderful afternoon spent with Lisa, the Ipswich River, and its treasures.
For more information about the science behind water striders and their locomotion, check out this cool Water Strider Study out of MIT’s Fluid Dynamics Lab . In addition to some great information, it includes some beautiful images, like the one below generated by the movement of striders across water dyed with Thymol Blue.