Horn Pond is classified as "Potentially Non-supporting" under the New Hampshire Department of Environmental Services' revised water quality standards for oligotrophic lakes. The Horn Pond watershed covers 1,139 acres (461 ha) that is primarily forested (70%). Only 6% of the watershed is developed, with 34% buildable area. The shoreline of Horn Pond is composed primarily of low density houses and camps (51%) and undeveloped shoreline (44%). 70% of the structures along the shoreline are within 50 feet (15 m) of the water's edge.[citation needed]
Horn Pond water quality monitoring has been collected since 1982. During this period, 11 years of secchi disk transparency data, 7 years of total phosphorus (TP) data, 2 years of chlorophyll-a (Chl-a) data, and 5 years of dissolved oxygen (DO) data has been collected. From this data, the median TP concentration is 8.0 parts per billion (ppb) and the mean transparency is 6.6 m (21.7 ft).[citation needed]
The Horn Pond Association has been recently redeveloped and aims to protect and improve the water quality of Horn Pond.[2]