CHOCORUA LAKE Water Quality Monitoring: 2017 Summary and Recommendations NH LAKES LAY MONITORING PROGRAM By: Robert Craycraft & Jeffrey Schloss Center for Freshwater Biology University of New Hampshire To obtain additional information on the NH Lakes Lay Monitoring Program (NH LLMP) contact the Director (Jeff Schloss) at 603-862-3848 or Coordinator (Bob Craycraft) at 603-862-3696. This page intentionally left blank PREFACE This report contains the findings of a water quality survey of Chocorua Lake, Tamworth, New Hampshire, conducted in the summer of 2017 by the University of New Hampshire Center For Freshwater Biology (CFB) in conjunction with the Chocorua Lake Conservancy. The report is written with the concerned lake resident in mind and contains an executive summary of the 2017 results as well as more detailed "Introduction" and "Discussion" sections. Graphic display of data is included, in addition to listings of data in appendices, to aid visual perspective. A simplified and stand-alone three page, Chocorua Lake “sampling highlight” report was also produced for distribution among interested residents and officials. i ACKNOWLEDGMENTS 2017 was the thirty-sixth year the Chocorua Lake Conservancy (formerly the Chocorua Lake Association) participated in the New Hampshire Lakes Lay Monitoring Program (LLMP). The volunteer monitors who collected and analyzed water quality Table 1: Chocorua Lake samples are highlighted in Table 1 while Dwight Volunteer Monitors Baldwin again acted as the liaison to the Universi- (2017) ty of New Hampshire Center for Freshwater Monitor Name Biology (CFB). The CFB congratulates the volun- teer monitors on the quality of their work, and the Barbara Baldwin Dwight Baldwin time and effort put forth. We look forward to con- Katharine Baldwin tinuing our partnership with our existing Chocorua Tim Baldwin Lake volunteers and invite other interested resi- Lawson Hackman dents to join the Chocorua Lake water quality moni- toring effort in 2018 and expand upon the current database. Funding for the Chocorua Lake water quality monitoring program was provided by the Chocorua Lake Conservancy. The New Hampshire Lakes Lay Monitoring Program is a not-for- profit citizen based research program coordinated by Robert Craycraft and di- rected by Jeff Schloss, Associate Director of the UNH CFB. Members of the CFB-LLMP summer field team included Sabina Perkins, Erich Berghahn, Lucy Spence, Abby Foley, and Taylor Hickox, while Athena Ryan, Kaylee Verrington, and Alexander Amann provided additional assistance in the fall analyzing, com- piling and organizing the water quality data. The LLMP acknowledges the University of New Hampshire Cooperative Extension for major funding and furnishing office and storage space while the College of Life Sciences and Agriculture provided laboratory facilities and addi- tional storage space. The LLMP would like to thank the Caswell Family Foundation for their continued generosity in providing long-term support for undergraduate assistantships. Participating groups in the LLMP include: Acton-Wakefield Watershed Alliance, Green Mountain Conservation Group, North River Lake Monitors, the associations of Baboosic Lake, Bow Lake Camp Owners, Chocorua Lake, Conway Lake Conservation, Crystal Lake, Goose Pond, Governors Island, Great East Lake, Lake Kanasatka Watershed, Tuftonboro Islanders, Lovell Lake, Mendums Pond, Merrymeeting Lake, Milton Three Ponds Lake Lay Monitoring, Mirror Lake (Tuftonboro), Moultonborough Bay, Lake Winnipesaukee Watershed, Na- ticook Lake, Newfound Lake Region, Nippo Lake, Silver Lake (Madison), Squam Lakes, Sunset Lake, Swains Lake, Lake Wentworth and the towns of Alton, Amherst, Enfield, Gilford, Laconia, Madison, Meredith, Merrimack, Milton, Moultonborough, New Durham, Strafford, Tuftonboro and Wolfeboro. Major collaborators with the UNH CFB in 2017 included the New Hamp- shire Lakes Association, New Hampshire Department of Environmental Ser- vices, Dartmouth Hitchcock Medical Center and EPA New England. ii Chocorua Lake 2017 Executive Summary Volunteer water quality data were collected at the deep Chocorua Lake sampling station between April 25 and October 13, 2017. Generally speaking, the 2017 Chocorua Lake seasonal water transparency was high and averaged 14.4 feet (4.4 meters), the amount of microscopic plant “algal” growth (green- ness) was moderate, and the phosphorus (nutrient) concentrations were general- ly low and reflected the conditions typical of an unproductive New Hampshire Lake (Table 2). The following section reviews the 2017 Chocorua Lake water quality data and when applicable incorporates historical data into the discus- sion. Refer to Appendix D for a complete listing of the 2017 Chocorua Lake water quality data and refer to Appendix E for a description of the box and whisker plots that are included in the report. Table 2: 2017 Chocorua Lake Seasonal Average Water Quality Readings and Water Quali- ty Classification Criteria used by the New Hampshire Lakes Lay Monitoring Program. Oligotrophic Mesotrophic Eutrophic Chocorua Lake Chocorua Lake Parameter “Excellent” “Fair” “Poor” Composite Average (range) Classification Water Clarity (meters) > 4.0 2.5 - 4.0 < 2.5 4.4 meters (range: 3.3 – 5.5) Oligotrophic Chlorophyll a < 3.3 3.3 – 5.0 > 5.0 4.3 ppb (range: 1.1 – 16.9) Mesotrophic (ppb) Total Phosphorus (ppb) < 8.0 8.0 – 12.0 > 12.0 5.4 ppb (range: 3.3 – 9.7) Oligotrophic The Massachusetts Department of Cyanobacteria Public Health considers dangerous The New Hampshire Department of Environmental services posts (cell counts, microcys- microcystin (MC) levels to be 14 warnings at State beaches when cyanobacteria cell numbers ex- tin concentration & parts per billion (ppb) lake water, ceed 70,000 cells per milliliter lake water. Water safety) and/or 70,000 cyanobacteria cells per milliliter lake water. * Total phosphorus and chlorophyll a data were collected in the surface waters (epilimnion). # The water clarity classification criteria are based on standards devised by Forsburg and Ryding (1980) while the chlorophyll a and total phosphorus criteria are based on the New Hampshire Department of Environmental Services aquatic life nutrient criteria. 1) Water Clarity (measured as Secchi Disk transparency) – The 2017 sea- sonal average water transparency of 14.4 feet (4.4 meters) is characteristic of an unproductive New Hampshire lake. Secchi Disk transparency measurements varied seasonally with three out of ten readings falling below 13.2 feet (4.0 me- ters) that is considered the boundary between an unproductive and moderately productive New Hampshire lake. The shallower water clarity measurements were documented in July and early August and generally corresponded to ele- vated chlorophyll a and dissolved color concentrations (Appendix A). The 2017 median Secchi Disk transparency measurement, documented at Site 1 South, is one of the lower annual median water clarity values documented since volunteer water quality monitoring was initiated in 1982 (Appendix B and C). However, the 2017 median water clarity values remained within the range of iii historical measurements documented since 1982; no new water transparency minimum or maximum values were recorded in 2017 (Appendix B). A regression analysis of the long-term Chocorua Lake Secchi Disk transparency data indi- cates a trend of gradually decreasing water transparency between 1982 and 2017 (Appendix C). 2) Microscopic plant abundance “greenness” (measured as chlorophyll a) – The 2017 seasonal average Chocorua Lake chlorophyll a concentration of 4.3 parts per billion (ppb) was above the concentration of 3.3 ppb that is considered the boundary between an unproductive and moderately productive New Hamp- shire lake (Table 2). The 2017 median Chocorua Lake chlorophyll a concentration was higher (i.e. more algal greeness) than the 2016 median chlorophyll a concentration but remained within the range of historical median values documented since 1982 (Appendix B and C). On the other hand, the July 26, 2017 chlorophyll a concen- trations measured 16.9 ppb and set a new single day maximum for Chocorua Lake (Appendix B). A regression analysis of the long-term Chocorua Lake chlorophyll a data indicates a trend of decreasing chlorophyll a concentrations between 1982 and 2017 (Appendix C) while further analyses were undertaken to examine the trends over shorter periods of time. Chlorophyll a data were analyzed over the span of 1982 through 1999 that represents the period prior to the “Berms and Swales” project along the Route 16 travel corridor. A regression analysis per- formed on the 1982 and 1999, pre-best management practice (BMP) period, indi- cates a trend of increasing chlorophyll a concentrations (Appendix C). A second regression analysis was performed on the chlorophyll a data collected between 2000 and 2017 that is representative of the post-BMP construction period. The post-BMP regression analysis indicates trend of decreasing chlorophyll a concen- trations following the construction of BMPs (Appendix C). While there are many factors that can affect water quality from year to year, the decreasing chloro- phyll a concentrations documented over the past 18 years tend to suggest the BMPs are helping attenuate the nutrient phosphorus before it enters Chocorua Lake. 3) Background (dissolved) water color: often perceived as a “tea” color in our more highly stained lakes – The 2017 seasonal average Chocorua Lake dis- Table 3. Dissolved Color Clas- solved color concentration of 35.6 chloroplat- sification