Watershed Management Bureau

  Biomonitoring Program

The Biomonitoring program performs routine chemical analyses of New Hampshire rivers and streams in conjunction with its biological monitoring efforts. Chemical monitoring provides complementary information for assessing the biological integrity and aquatic health of our waters.

Most water quality parameters are measured using a multi-probe data logger, automatically reading and storing information on temperature, conductivity, pH, dissolved oxygen, and total dissolved solids.  Additional tests, such as E. coli bacteria, nitrogen, phosphorus, and alkalinity are measured on a case by case basis and are dependent on historic and current land use surrounding the particular biomonitoring site. Other  matrices, such as sediment, may also be monitored if they are suspected of impairing the water quality or impacting the biota of the waterbody.

The objectives of each particular survey will dictate the analytical parameters chosen to support the biological monitoring efforts. Listed below are the chemical parameters that are routinely measured, with a brief explanation on their importance in assessing water quality.

Specific Conductance: Water contains various natural and human-introduced materials that have the ability to pass an electric current.  Conductivity is a measure of this ability.  It is used as an indicator of the presence of chlorides, nitrates, sulfates, and phosphate anions (ions that carry a negative charge) and sodium, magnesium, calcium, iron, and aluminum cations (ions that carry a positive charge).  High conductivity levels may indicate a potential problem from any of these materials.  Specific conductance relates these ion concentrations to the temperature of the water.

Dissolved oxygen: Maintaining suitable dissolved oxygen (DO) levels is crucial to the survival of many aquatic species.  Low levels of DO can stress organisms and interfere with growth and reproduction, and very low levels can result in fish kills.  The DO criteria for Class B waters in New Hampshire is a daily average of at least 75% of saturation with the minimum value being no less than 5.0 mg/L, unless it occurs due to natural conditions.

pH: In simple terms, pH measures the acidity of the water, on a scale of 0-14 (14 being the most basic). The pH value is essential in determining living conditions within an aquatic community.  Allowable pH standards for New Hampshire waters range from 6.5-8.0 and are deemed protective of aquatic life. Values falling outside these ranges are considered violations and are harmful to aquatic life, except where they are occurring naturally.

Alkalinity or Acid Neutralizing Capacity (ANC): This indicator is a measure of the river's ability to neutralize acid inputs from precipitation or discharges.  Rivers with low alkalinity are subject to great fluctuations in pH that disrupt aquatic life.