The environmental consultants, Forrest Bell Environmental Associates, will be making a presentation for the public on the status of the Merrymeeting Watershed including Merrymeeting Lake and all rivers and streams merging with the Merrymeeting River between the Merrymeeting Lake and Lake Winnipesaukee. This meeting will address recurrent blooms of cyanobacteria seen in both New Durham and Alton and the sources of phosphorus, a nutrient, which is causing this problem. While Merrymeeting Lake enjoys some of the most pristine water in the State, the lake may become vulnerable, in the future, due to shoreline erosion and failing septic systems. The recent effect of logging on Merrymeeting Lake streams will also be covered.
The Merrymeeting River has been damaged by the discharge of many pounds of phosphorus, nitrogen and suspended solids from the Powder Mill State Fish Hatchery. The impact from the hatchery can be felt all the way to Lake Winnipesaukee. Efforts to minimize the discharge of nutrients from the hatchery must be instituted soon. Progress is being made both in terms of an interim facility to treat waste water, reducing phosphorus in the fish food, and raising some of the fish off-site. A permanent long-term solution requires establishing safe levels of phosphorus in the River. Recently the Water Quality Goals Committee met and set the maximum phosphorus concentrations everywhere in the Merrymeeting River at 10ug/L monthly average each month of the year. This is an ambitious goal which will require a permanent state-of-the-art hatchery waste water treatment facility.
Other problems arise in the Alton span of the Merrymeeting River particularly via Coffin Brook and Mill Pond. Using GIS-based Land use models the areas of high phosphorus stormwater runoff have been identified. While some sources of this phosphorus are occurring naturally, e.g. water leaving peat bogs, in many instances stormwater runoff is being influenced by fertilizer use, agricultural practices, culverts and roadside erosion, plowing practices and residential stormwater runoff. Each of these problems can be addressed and, once remediated, will greatly reduce the availability of phosphorus in waterbodies.
Another potential problem will appear after the hatchery discharge is discontinued. Several of our impounded waterways, i.e. Marsh and Jones Ponds for certain and possibly Mill Pond, develop a state of oxygen depletion near the sediment during the summer. When this happens, internal loading can occur. Internal loading refers to the ability of the sediment to release bound phosphorus back into the water and this could continue to cause elevated phosphorus concentrations until this storage site (the sediment) is depleted, which may take decades. Approaches to resolve these problems will be discussed.
However, it is how we develop the remaining land in the future which can have the greatest long-term impact. If all the remaining land available for residential housing in the watershed is built-out the number of new buildings will exceed the current number of buildings by over 200%. Should this new construction be allowed to proceed unabated the consequences for the Merrymeeting River and Lake Winnipesaukee are profound.