Great Hill Pond, Portland - 2023

Transect Data | Water Data

   Great Hill Pond is a 76-acre artificial lake in Portland, CT, fed by Rattlesnake Brook. There is a 10-foot dike at the south end of the pond where water is released into Great Hill Pond Brook and flows directly to the Connecticut River. Public access is via a carry-in boat launch with minimal parking. On average the pond is 5.5 feet deep with a maximum of 9 feet in a small area to the south.

   Since our initial survey in 2006, aquatic vegetation has become more abundant with coverage of nearly the entire pond. The OAIS survey team documented a diverse plant community of 22 different aquatic plant species. There were also three wetland plant species documented along the shoreline. Of the 22 aquatic plant species found, two species are invasive, fanwort (Cabomba caroliniana) and curlyleaf pondweed (Potamogeton crispus). Fanwort was present in our 2006 survey, while curlyleaf pondweed has appeared in the years since. Both invasive species cover large areas of the pond and are considered a nuisance. Of the shoreline species documented, cattail is native while phragmites and purple loosestrife are invasive.

   In 2023, 20 native aquatic plant species were documented. Comparatively, there were 16 native aquatic plant species found in 2006. Of the native species found in 2023, eelgrass is dominant and can be found throughout much of the pond. The coves to the north and northeast of the pond are dominated by floating species: watershield (Brasenia schreberi), white water lily (Nymphea odorata), and yellow water lily (Nuphar variegata).

   Small pondweed was found in 2006 and Berchtold’s pondweed was found in 2023. Small pondweed (Potamogeton pusillus) and Berchtold’s pondweed (Potagmogeton berchtoldii) are often confused species. It is possible that Berchtold’s pondweed was misidentified as small pondweed in 2006.

   There are six new native aquatic plant species from 2006 to 2023: slender naiad (Najas flexilis), bur-reed (Sparganium species), great duckweed (Spirodela polyrhiza), low watermilfoil (Myriophyllum humile), primrose-willow (Ludwigia species), and quillwort (Isoetes species). There are 2 species that were found in 2006 but not in 2023: spotted pondweed (Potamogeton pulcher) and white water crowfoot (Ranunculus longirostris). Charaphyte, a plant like algae, was found in both 2006 and 2023, however it is not illustrated on the 2023 map.