Survey of Reservoir Greenhouse gas Emissions
file:///P:/PDF_Harvest/ScienceInventory/ScienceInventoiyHarvest/600.
Survey of Reservoir Greenhouse gas
Emissions
Lake Redstone Water Quality Survey
Jake Beaulieu
25 July, 2022
1. Background
Between 2020 and 2023 the US Environmental Protection Agency (USEPA) will survey water quality and
greenhouse gas (GHG) emissions from 108 reservoirs distributed across the United States (Figure 1). The
objective of the research is to estimate the magnitude of GHG emissions from US reservoirs.
All reservoirs included in this study were previously sampled by the USEPA during the 2017 National Lakes
Assessment (2017 NLA). Data from the 2017 NLA can be found at the EPA website (https://www.epa.gov/national-
aquatic-resource-surveys/data-national-aquatic-resource-surveys). Data for Lake Redstone can be found under
SITE J D NLA17_WI-10010.
Afield sensor is used to measure chlorophyll a, dissolved oxygen, pH, specific conductivity, water temperature,
and turbidity near the water surface at a minimum of 10-20 locations within each reservoir. Water samples are
collected from the deepest site for analysis of nutrients and chlorophyll a.
This preliminary report presents water quality results for Lake Redstone. These data will be included in a formal
peer-reviewed publication to be submitted for publication in 2024.
Ecoregions
Coastal Plains
Northern Appalachians
Northern Plains
Southern Appalachians
Southern Plains
Temperate Plains
Upper Midwest
Western Mountains
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Figure 1, Location of the 108 Reservoirs Included in Study.
2. Lake Redstone Survey Design
i 'X Nls/M sensor sites
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The Lake Redstone survey design included 14 sampling sites that were sampled on 2021-06-01. Water chemistry
samples were collected from a 7.9m deep site nearby the dam (Figure 2). Click on any of the sites to see the site
id, water temperature, pH, turbidity, and dissolved oxygen at the water surface.
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Survey of Reservoir Greenhouse gas Emissions
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Figure 2. Location of the 15 sampling sites in Lake Redstone.
3. Lake Disturbance and Trophic Status
Lakes are often classified according to their trophic state. There are four trophic state categories that reflect
nutrient availability and plant growth within a lake. A eutrophic lake has high nutrients and high algal and/or
macrophyte plant growth. An oligotrophic lake has low nutrient concentrations and low plant growth. Mesotrophic
lakes fall somewhere in between eutrophic and oligotrophic lakes and hypereutrophic lakes have very high
nutrients and plant growth. Lake trophic state is typically determined by a wide variety of natural factors that
control nutrient supply climate, and basin morphometry. A metric commonly used for defining trophic state is the
concentration of chlorophyll a, an indicator of algae abundance, in the water column. Chlorophyll a concentration
was 12 ug/L during the sampling, indicating the lake was eutrophic.
Trophic State Classification
Analyte
Oligotrophic
Mesotrophic
Eutrophic
Hypereutrophic
chlorophyll a (ug/L)
<=2
>2 and <=7
>7 and <=30
>30
In addition to classifying lakes by trophic status, lakes can be classified by degree of disturbance relative to
undisturbed lakes (i.e. reference lakes) within the ecoregion. Degree of disturbance can be based on a wide
variety of metrics, but here we use nutrients (total phosphorus (tp), total nitrogen (tn)), suspended sediment
(turbidity), chlorophyll a, and dissolved oxygen (do). Lake disturbance values range from least to most disturbed.
Chemical Condition Indicators Measured at Water Chemistry Site
Threshold Values Observed Values
parameter
units
least disturbed
moderately disturbed
most disturbed
concentration
status
do
mg/l
>5
>3 t
i<5
<3
9
least disturbed
turbidity
NTU
<2.13
>2.13 t
i <2.89
>2.89
0.00
least disturbed
tp
ug/l
<28
>28 {
L <41
>41
35
moderately disturbed
tn
ug/l
<722
>722 f
5c <920
>920
400
least disturbed
chlorophyll a
ug/l
<6.7
>6.7 f
*<9.6
>9.6
12.3
most disturbed
4. Within-lake Spatial Patterns
A field sensor was used to measure water temperature, pH, dissolved oxygen, and turbidity near the water surface
at all sampling sites. Data are reported in figures and tables below. Hover the cursor over any point in the figures
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to reveal the sitelD corresponding to the adjacent data table. Alternatively, click on any row in the data table to
reveal the location of the sampling site on the map.
Water temperature, pH, turbidity, and dissolved oxygen were greatest near the river inflow. This pattern is
sometimes observed when the tributary is the primary nutrient source to the water surface. Elevated nutrients near
the tributary can stimulate algal growth, leading to elevated dissolved oxygen, algal turbidity, and pH. Elevated
water temperature can further stimulate algae growth.
water
sitelD temp
2 22.05
3 20.03
4 19.7
5 20.55
16 18.69
17 19.45
18 19.02
19 18.65
20 18.66
21 18.6
22 19.74
23 18.77
24 18.12
25 18.97
sitelD pH
2 9.38
3 8.93
4 8.79
5 9.01
16 8.45
17 8.56
18 8.57
19 8.51
20 8.64
21 8.42
22 8.45
23 8.52
24 8.51
25 8.49
Turbidity
sitelD (NTU)
2 10.2
Water
Temp.
(°C)
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Turbidity
sitelD (NTU)
3 2.7
4 1.9
5 2.6
16 0
17 0
18 0
19 0.6
20 0.4
21 0.4
22 0
23 0.6
24 0.7
25 0.4
DO
sitelD (mg/L)
2 22.54
3 14.13
4 12.47
5 15.24
16 9.09
17 10.15
18 9.55
19 10.17
20 10.84
21 9.72
22 9.22
23 10.53
24 9.6
25 10.2
5. Depth Profiles
Dissolved oxygen is one of the most important environmental factors affecting aquatic life. The biological demand
for oxygen is often greatest near the sediment where the decomposition of organic matter consumes oxygen
through aerobic respiration. Near the surface of lakes, photosynthesis by phytoplankton produces oxygen, often
leading to a general pattern of decreasing oxygen availability with increasing depth. This pattern can be
exacerbated by thermal stratification. Thermal stratification occurs when lake surface waters are warmed by the
sun, causing the water to become less dense and float on top of the deeper, cooler lake water. Since the deeper
layer of water cannot exchange gases with the atmosphere, the dissolved oxygen content of the deep water
cannot be replenished from the atmosphere. As a result, the deep water can become progressively depleted of
oxygen as it is consumed by biological activity, sometimes causing dissolved oxygen to become sufficiently scarce
to stress oxygen sensitive organisms including some fish and insects.
The deepest sampling location in Lake Redstone was 7.9 m deep, in relatively shallow lakes like Lake Redstone,
wind induced mixing of the water column is often sufficient to prevent thermal stratification. Lake Redstone had
only minor thermal stratification, yet dissolved oxygen was nearly depleted near the lake bottom, indicating strong
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biological oxygen demand in lake sediment.
Lake Redstone Depth Profiles
10
15
Temperature (°C)
20
25
30
o-
Q.
O 4
6-
2.5
5.0
7.5
Dissolved Oxygen (mg L 1)
10.0
1. Jake Beaulieu, United States Environmental Protection Agency, Office of Research and Development,
Beaulieu.Jake@epa.gov (mailto:Beaulieu.Jake@epa.gov)«J
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