Nutrient Criteria for New Hampshire’s

EstuariesBackground Information

Phil TrowbridgeNH DES / NHEP

September 30, 2005

Existing “Nutrient Criteria” for NH

• Dissolved oxygen: 5 mg/L (instantaneous)75% sat (24 hr average)RSA 485-A:8

• Nutrients: “Class B waters shall contain no phosphorus or nitrogen in such concentrations that would impair any existing or designated uses, unless naturally occurring.”

Admin Rule: Env-Ws 1703.14

• Chlorophyll-a: 20 ug/L (>10% of samples)DES-WMB Policy # 009

Goal for the Nutrient Criteria Process

• To improve these criteria and/or add other criteria so that DES can accurately assess cultural eutrophication in NH’s estuaries.

Regulatory Implications

• Assessments: Criteria will be used to determine violations of water quality standards (“impairments”).

• TMDLs: For most impairments, a Total Maximum Daily Load study will be done.

• Regulations: Results of TMDLs become discharge limits in point source NPDES permits and other sources.

• This process has already begun using the existing criteria.

2004 Dissolved Oxygen or Chlorophyll-a Impairments in 2004

Nutrients in NH’s Estuaries

• Long-Term Water Quality Trends in Great Bay

• Current Conditions from 2004 Probabilistic Survey

• NH nutrient concentrations relative to other systems in the Northeast

Seasonal Mean Dissolved Inorganic Nitrogen at Low Tide at Adams Point

0

0.1

0.2

0.3

0.4

0.5

1970 1975 1980 1985 1990 1995 2000 2005

Year

DIN

(m

g/L

) Winter

Spring

Summer

Fall

Seasonal Mean Orthophosphate at Low Tide at Adams Point

0

0.01

0.02

0.03

0.04

0.05

0.06

1970 1975 1980 1985 1990 1995 2000 2005

Year

PO

4 (m

g/L

)

Winter

Spring

Summer

Fall

Seasonal Mean Chlorophyll-aat Low Tide at Adams Point

02468

101214

1970 1975 1980 1985 1990 1995 2000 2005

Year

Ch

la (

ug

/L)

Winter

Spring

Summer

Fall

Current Conditions in NH’s estuaries

Nutrient and Eutrophication Parameters from NCA 2004

Parameter N Median RangeTN (mg/L) 35 0.36 (0.0161-1.14)TP (mg/L) 40 0.07 (0.025-0.248)SiO2 (mg/L) 41 0.62 (0.166-5.639)Kd (1/m) 17 -1.31 (-5.753- -0.366)TN:TP ratio 34 5.89 (2.875-16.09)

* Samples taken during summer season

Nitrogen in Northeast Estuaries

Average Total Nitrogen in Estuarine Waters (2003) Source: NCA and LISS

0

0.2

0.4

0.6

0.8

1

1.2

1.4

ME NH MA RI LIS NJ DE

TN

(m

g/L

)

Phosphorus in Northeast Estuaries

Ave Total Phosphorus in Estuarine Waters (2003)Source: NCA and LISS

0

0.02

0.04

0.06

0.08

0.1

0.12

ME NH MA RI LIS NJ DE

TP

(m

g/L

)

Summary

• New Hampshire’s existing nutrient criteria are minimal and not specific to estuarine environments.

• Impairments for DO and chlorophyll-a criteria already exist.

• Winter DIN concentrations have increased in Great Bay.

• Average TN and TP concentrations are similar to RI and Long Island Sound.