Is it safe to swim in the lake?

Essentially all New Hampshire lakes are safe for swimming.

It is unsafe to swim wherever untreated sewage or human feces are present. The procedure for testing for the presence of human feces is the Escherichia coli (E. coli) test. E. coli is a bacteria that is found in the intestinal tract of all healthy warm-blooded animals including humans. It itself is not a pathogen (disease-causing bacteria) but is used as an indicator organism. High numbers of E. coli suggest that human feces may be present, and, if feces are present, then disease-causing bacteria may also be present.

New Hampshire does not allow sewage, even treated sewage, to be discharged to lakes. Essentially the only sources of human feces to lakes are failed septic systems and dirty diapers or washings from the human body. Elevated E. coli bacteria counts may occur at swimming beaches during crowded conditions if there is not sufficient water circulation. It is also possible to have bacterial counts exceed the swimming standards during or immediately after a rain event, particularly where urban or agricultural runoff enters a lake. Ducks, beaver, sea gulls or other warm-blooded animals can also be a source of E. coli. These occurrences of elevated bacterial counts are generally short lived since E. coli does not survive long outside a warm-blooded animal.

Although all New Hampshire lakes are generally safe for swimming, there are no guarantees. People swim at their own risk.

Can I drink the lake water?

No surface waters, regardless of purity, should be used as a drinking water source by an individual homeowner. Without adequate treatment there can be no guarantee concerning the safety of the water. Surface waters used for public water supplies are chlorinated as a minimum treatment and most are also filtered. This is true even where boating and swimming are prohibited and the watershed is undeveloped.

Is it safe to eat the fish?

New Hampshire, along with the majority of other states and all northeastern states, has a fish consumption advisory because of mercury which accumulates in fish. In New Hampshire the advisory is a general, statewide advisory that applies to all species of fish and to all inland surface waters. It does not prohibit the eating of fish - in fact people are encouraged to include fish as part of a healthy diet because they are high in protein and low in saturated fat and cholesterol compared to meat or poultry - but advises people (especially pregnant or nursing woman and children under 7 years of age) to restrict the amount of freshwater fish eaten and the size of fish consumed (the larger, older fish tend to have the higher mercury concentrations). Warmwater fish such as largemouth bass, smallmouth bass, pickerel and yellow perch also tend to have higher mercury levels. For some inland waterbodies, it is recommended for all individuals to avoid consumption. For more details about the fish consumption advisory, click here.

Are there restrictions regarding the use of the lake?

Jet skis are banned from all waterbodies under 75 acres. Some waterbodies are closed to all motors and others have restrictions on the type, size or speed of motors or the time of operation. Restrictions on boating on New Hampshire lakes are regulated by the Division of Safety Services, Department of Safety. Fishing restrictions are regulated by the NH Fish and Game Department.

Many public water suppliers also restrict boating, fishing and swimming or some combination of all three in all or parts of the waterbody. Contact the local water supply entity for information on restrictions.

Which lakes have non-native (exotic) plants?

Variable-leaf milfoil (Myriophyllum heterophyllum) is the major nuisance non-native plant in New Hampshire. Fanwort (Cabomba caroliniana) is also present in three lakes in the southeastern part of the state. At this time Eurasian milfoil (Myriophyllum spicatum) and water chestnut (Trapa natans), two other exotic aquatic plants in New Hampshire, are not found in lakes. The former is found only in the Connecticut River and the latter only in the Nashua River.

It is against the law in New Hampshire to transport exotic plants. Make sure all plant fragments are removed from your boat, motor and trailer before entering or leaving a waterbody.

For more information on exotic plant species, including a listing of waterbodies with exotic plants, click here.

Does tea-colored water in a lake mean it is polluted?

No. The color of water in a lake is not related to bacterial pollution or unsanitary conditions. It is caused primarily by decaying organic matter such as leaves, bark, humus and aquatic plants. Metals such as iron and manganese that occur naturally in the soils of the watershed and lake sediments may also contribute to a lake's color.