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Lake Lacawac - Lake Ariel, PA

Lake, River, or Waterfall
Michael Gadomski

Fifty-two-acre Lake Lacawac, the heart of the sanctuary, has been called “the southernmost unpolluted glacial lake in North America.”

Beginning in the 1950s, researchers from the Academy of Natural Sciences in Philadelphia found this lake invaluable as a field laboratory. Shaped like a half-moon, this “ice scour” lake has two distinct habitats—an organically rich bog to the west and north and sand and rock to the east and south. The latter habitat was formed by continual wave action from prevailing northwest winds and supports only a few plants. The bog, on the other hand, is rich in plants.

Thirty-five crustacean species and thirty species of aquatic plants including eight rare plants have been identified in the lake. On the south side of the sanctuary, a series of rocky ledges dropping 250 feet to the shores of Lake Wallenpaupack support twenty-one species of ferns and numerous mosses and lichens, as well as a mature forest.

Lake Lacawac was listed as a National Natural Landmark in 1968.


In 1955, Dr. Ruth Patrick, then head of the limnology department at The Academy of Natural Sciences in Philadelphia, visited the pristine glacial lake at Lacawac and recognized its research potential. Shortly thereafter, she began studying diatoms in the lake and influenced her colleagues to work at Lacawac.

One of those colleagues was Dr. Clyde Goulden, who began studying Lake Lacawac in the early 1960s and continued to work on the lake through 1995. Research efforts began at the lake, but scientists were also interested in the surrounding woodlands and during the 1960s a small but growing number of scientific publications came from field work at Lacawac.

In the early days of research, Lacawac's existing buildings did not lend themselves to laboratory work. Hence, in the late 1960s , the academy set up a trailer near the Lodge to provide laboratory space for researchers. That trailer was removed in 2014 and was replaced by a environmental laboratory adjacent to the Coulter Visitor Center. The new laboratory was funding through a grant from the National Science Foundation in cooperation with Miami University, Oxford OH.

While the Academy of Natural Science was a major user of Lacawac through the 1970s, it was unable to maintain a well-funded research presence. In 1986, Dr. Goulden invited Dr. Craig Williamson, a faculty member at Lehigh University, to visit Lacawac. Dr. Williamson recognized the tremendous potential of Lacawac as a venue of research and education in aquatic ecology.

A new element entered the picture in 1988, the emergence of Lehigh University as major user. Their Earth and Environmental Sciences Department brought to the region a group of field biologists as teachers and researchers. With help from the Mellon and Dodge Foundations, a dynamic program known as the Pocono Comparative Lakes Program (PCLP) was instituted, doing serious research in three area lakes, and recruiting small groups of highly motivated students for training in research methods. Again, with Mellon and Dodge assistance, mini-grants lured researchers from other institutions to the PCLP program. Programs at Lacawac over the years have changed the lives of many people, opening their eyes and their minds to scientific professional responsibilities enhanced and influenced by their experience at Lacawac. Some of the classes and conferences demonstrate that a critical mass of human numbers exists which vastly intensifies the intellectual ferment and productivity of a group.

Pet Friendly Notes

Pets welcome

Recreational Opportunities

Seasonal guided paddles, hiking and educational programs about healthy lakes and other various water quality topics.

Lake Lacawac is a place for reflection and hiking and communing with nature.


Optional $10 donation

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