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Results of VLAP Sampling from July 29, 2009

Total Phosphorus


Deep Spot
Epilimniom (top) Layer
(2 Meters)
Deep Spot
Metalimniom (Middle) Layer
(6 Meters)
Deep Spot
Hypolimniom (Bottom) Layer
(13 Meters)
Inlet 6.50
Outlet 12.0

 "Definition: Phosphorus is the most important water quality parameter measured in our lakes. It is the nutrient that limits the algae's ability to grow and reproduce. Phosphorus sources around a lake typically include septic systems, animal waste, lawn fertilizer, erosion from road and construction erosion, and natural wetlands." *

New Hampshire's Median Value = 12μg/L 

Clough Pond stratifies each summer into three distinct layers by temperature. Total Phosphorus readings are taken at the approximate midpoint of each layer.  

Total Phosphorus Ranges for 
New Hampshire Lakes and Ponds 
Total Phosphorus

1-10 Low (Good)
11-20 Average
21-40 High
>40 Excessive

μg/L = micrograms per liter

*Source: DES VLAP Chemical Parameter Explanations

Oxygen, Temperature, and Percent
Saturation Readings

(0C / 
Dissolved Oxygen

 0 25.3 / 77.5 8.09 98.3
1 25.0 / 77.0 8.05 97.3
2 24.5 / 76.1 8.15 98.4
3 23.7 / 74.7 8.30 98.3
4 22.5 / 72.5 8.22 97.2
5 18.1 / 64.6 12.01 102.0
6 14.3 / 57.7 13.62 N/A
7 10.7 / 51.3 12.68 112.2
8 8.2 / 46.8 4.31 36.7
9 7.4 / 45.3 3.79 31.5
10 6.7 / 44.1 2.31 18.7
11 6.3 / 43.3 0.22 1.8
12 6.1 / 43.0 0.21 1.7
13 6.0 / 42.8 0.22 1.8
 14 5.9 / 42.6  0.23 1.8
 15 5.9 / 42.6  0.23 1.8
 16 5.9 / 42.6  0.26 2.1
 175.9 /

"Definition: Dissolved oxygen or 'DO' refers to the volume of oxygen contained within the water. Much of the DO in lakes comes from the atmosphere, inflowing streams and photosynthesis. Fish and other aquatic life depend on DO to survive. Seasonal changes can affect DO concentrations throughout the year. Warmer temperatures during the summer speed up the rates of photosynthesis and decomposition. When plants and algae die and decompose, oxygen is consumed. This decreases the amount of oxygen, especially in the uncirculated hypolimnion (lower) water layer. In the winter, under ice cover, the DO content can also deplete due to lack of circulation from the atmosphere.

DO levels above 5.0mg/L are considered sufficient for most aquatic life, although some cold water fish species require higher DO levels" *

mg/L = milligrams per liter

*Source: DES VLAP Chemical Parameter Explanations 

pH Readings

(Depth in Meters)


Deep Spot (2) 6.69
Deep Spot (6) 6.91
Deep Spot (13) 6.19
Inlet 6.56
Outlet 6.79

"Definition: pH is measured on a logarithmic scale of 0 to 14. Lake pH is important to the survival and reproduction of fish and other aquatic life. A pH below 5.5 severely limits the growth and reproduction of fish." *

Clough Pond stratifies each summer into three distinct layers by temperature. pH readings are taken at the approximate midpoint of each layer.  

pH Category

<5 Acidified
5.0-5.4 Critical
5.5-6.4 Endangered
6.5-8.0 Satisfactory

*Source: DES VLAP Chemical Parameter Explanations  

Acid Neutralization Capacity

(Depth in Meters)

mg/L as CaCO3
Deep Spot (2) 6.3

"Definition: Buffering capacity or Acid Neutralizing Capacity (ANC) describes the ability of a solution to resist changes in pH by neutralizing the acidic input to the lake. Historically, the waters in NH have had low ANC because of the prevalence of granite bedrock. The relatively low ANC means that NH surface waters are vulnerable to the effects of acid precipitation." *

mg/l as CaCO3


<0 Acidified
0-2 Extremely Vulnerable
2.1-10 Moderately Vulnerable
10.1-25 Low Vulnerability
>25 Not Vulnerable

mg/L = milligrams per liter 

*Source: DES VLAP Chemical Parameter Explanations  


(Depth in Meters

Deep Spot (2) 0.64
Deep Spot (6) 1.79
Deep Spot (13) 3.56
Inlet 0.82
Outlet 1.93

"Definition: Turbidity in the water is caused by suspended matter (such as clay, silt, and algae) that cause light to be scattered and absorbed, not transmitted in straight lines through the water. High turbidity readings are often found in water adjacent to construction sites. Also, improper sampling techniques (such as hitting the bottom sediments or sampling streams with little flow) may also cause high turbidity readings. The Class B standard for a water quality violation is 10 NTUs over the lake background level." *

Clough Pond stratifies each summer into three distinct layers by temperature. Yurbidity readings are taken at the approximate midpoint of each layer.  

 Statistical Summary of Turbidity Values for NH Lakes and Ponds


<0.1 Minimum
22.0 Maximum
1.0 Median

NTUs = Nephelometric turbidity measurement

*Source: DES VLAP Chemical Parameter Explanations 


(Depth in Meters)

Deep Spot (2) 77.20
Deep Spot (6) 76.47
Deep Spot (13) 87.09
Inlet 77.09
Outlet 79.45

"Definition: Conductivity is the numerical expression of the ability of water to carry an electrical current. It is determined by the number of ionic particles present. The soft waters of NH have traditionally had low conductivity values. High conductivity may indicate pollution from such sources as road salting, septic systems, wastewater treatment plants, or urban/agricultural runoff." *

"Note: Specific categories of good and bad levels can not be constructed for conductivity, because variations in watershed geology can result in natural fluctuations in conductivity. However, values in NH lakes exceeding 100 uMhos/cm generally indicate human disturbance."

Clough Pond stratifies each summer into three distinct layers by temperature. Conductivity readings are taken at the approximate midpoint of each layer.  

μMhos/cm = micromhos per centimeter 

*Source: DES VLAP Chemical Parameter Explanations  


(Depth in Meters)


Deep Spot (2) Not tested
Inlet Not tested
Outlet Not tested

"Definition: The chloride ion (Cl-) is found naturally in some surface waters and groundwaters and in high concentrations in seawater. Research has shown that elevated chloride levels can be toxic to freshwater aquatic life. in order to protect freshwater aquatic life in NH, the state has adopted acute and chronic chloride criteria of 860 and 230 mg/L respectively. The chloride content in NH lakes is naturally low, generally less than 2 mg/L in surface waters located in remote areas away from habitation. Higher values are generally associated with salted highways and, to a lesser extent, with septic inputs." *

mg/L = milligrams per liter 

*Source: DES VLAP Chemical Parameter Explanations  


(Depth in Meters)

Deep Spot (6)

"Definition: VLAP uses the measure of chlorophyll-a, a pigment found in plants, as an indicator of the alga abundance. Because algae is a plant and contains chlorophyll-a, the concentration of chlorophyll-a found in the water gives us an estimation of the concentration of algae." *


0-5 Good
5.1-15 More than desirable
>15 Nuisance amounts

mg/m3 = milligrams per meter cubed

*Source: DES VLAP Chemical Parameter Explanations  

Water Clarity
(Secchi-Disk Transparency)


Deep Spot 5.6 (VS)
5.8 (NVS)

"Definition: The Secchi-Disk is a 20cm disk with alternating black and white quadrants used to measure water clarity (how far a person can see into the water). Transparency, a measure of water clarity, is affected by the amount of algae, color, and particulate matter with in the lake." *

 Water Clarity

<2 Poor
2-4.5 Good
>4.5 Exceptional

NVS = Non-viewscope reading 
VS = Viewscope reading