NHDES Lake Trophic Surveys from 1975 - 2010

This program was initially established in 1975 in order to identify the trophic state of NH lakes and ponds, as required by Section 314(a) of PL 92-500 (the Federal Water Pollution Control Act Amendments of 1972). The purpose of the program is to determine lake trophic class and monitor physical, chemical and biological water quality parameters. Each year, 40 different lakes and ponds are surveyed, once in the summer and once in the winter. The surveys are comprehensive physical, chemical and biological surveys, including electronic depth soundings, macrophyte identifications and abundance ratings, shoreline bacteria sampling and at the deep spot a temperature/dissolved oxygen/percent saturation profile, Secchi disk transparency reading, samples for chlorophyll, Ca, Mg Na, and K in the upper water layer, phytoplankton and zooplankton net hauls for identification and counts and discrete water samples at two or three depths for pH, acid neutralization capacity, apparent color, conductivity, TP, Total Kjeldahl nitrogen, nitrite+nitrate nitrogen, chloride, and sulfate. The surveys are designed to assess current baseline conditions and compliance with water quality criteria, identify the lake’s trophic status, determine acid rain impacts and the existence of exotic aquatic plants and provide information for gross long-term trend analyses. See NH_STATION_REPORT for geographic and lake information