2010 water quality monitoring activities -medicine lake -twin lake
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2010 Water Quality Monitoring Activities -Medicine Lake -Twin Lake. Keith Pilgrim Barr Engineering March 17, 2011. brain huser is great. 2010 Lake Water Quality Study for Medicine Lake. Long Term Monitoring Program. Detect Long Term Trends in Lake Water Quality… Land use changes - PowerPoint PPT PresentationTRANSCRIPT
2010 Water Quality Monitoring Activities
-Medicine Lake-Twin Lake
Keith PilgrimBarr EngineeringMarch 17, 2011
brain huser is great
2010 Lake Water Quality Study for Medicine Lake
Long Term Monitoring Program Detect Long Term Trends in
Lake Water Quality… Land use changes BMP implementation In-lake activities Other, e.g. climate
What is Monitored Phosphorus Chlorophyll a Clarity (by Secchi disk) Basic lake characteristics Zooplankton Phytoplankton Aquatic plants
Medicine Lake
Medicine Lake (map)
Class: Level 1Size: 886 acMax Depth: 49 ftAverage Depth: 16 ftLittoral Area: 33% of total
Watershed:11,600 acLand use: commercial and residentialWater
Quality Monitoring Locations
Medicine LakeHistoric Data: Summer Averages
91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 100
10
20
30
40
50
60
70
80 Main Basin Total Phosphorus
Year
Tota
l Pho
spho
rus
(ug/
L)
Medicine LakeHistoric Data: Summer Averages
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 20100
10
20
30
40
50
60
70Main Basin Chlorophyll a
Year
Chl
orop
hyll
a (u
g/L)
Medicine LakeHistoric Data: Summer Averages
90 92 94 96 98 00 02 04 06 08 100.0
0.5
1.0
1.5
2.0
2.5
3.0Main Basin Clarity
Year
Secc
hi D
isc
(m)
Medicine Lake2010 Data Compared to State Standards
April May June July August September October0
102030405060708090
100110120 0
1
2
3
4
5
6
7
8
Main BasinC
once
ntra
tions
(µg/
L)
Secc
hi D
epth
(m)
Secchi Disc State Standard of > 1.4 m
SD
0102030405060708090
100110120 0
1
2
3
4
5
6
7
8
Main BasinC
once
ntra
tions
(µg/
L)
Secc
hi D
epth
(m)
Total Phosphorus State Standard of < 40 µg/L
Secchi Disc State Standard of > 1.4 m
SD
TP
April May June July August September October0
102030405060708090
100110120 0
1
2
3
4
5
6
7
8
Main BasinC
once
ntra
tions
(µg/
L)
Secc
hi D
epth
(m)
Chlorophyll a State Standard of <14 µg/L
Total Phosphorus State Standard of < 40 µg/L
Secchi Disc State Standard of > 1.4 m
SD
TPChl a
Medicine Lake2010 Data Compared to BCWMC Standards
April May June July August September October0
102030405060708090
100110120 0
1
2
3
4
5
6
7
8
Main BasinC
once
ntra
tions
(µg/
L)
Secc
hi D
epth
(m)
Chlorophyll a Goal of <10 µg/L
Total Phosphorus Goal of < 38 µg/L
Secchi Disc Goal of > 2.2 m
Chlorophyll a Goal of <10 µg/L
Total Phosphorus Goal of < 38 µg/L
SD
TP
Chl a
April May June July August September October0
102030405060708090
100110120 0
1
2
3
4
5
6
7
8
Main BasinC
once
ntra
tions
(µg/
L)
Secc
hi D
epth
(m)
Secchi Disc Goal of > 2.2 m
SD
April May June July August September October0
102030405060708090
100110120 0
1
2
3
4
5
6
7
8
Main BasinC
once
ntra
tions
(µg/
L)
Secc
hi D
epth
(m)
Total Phosphorus Goal of < 38 µg/L
Secchi Disc Goal of > 2.2 m
Total Phosphorus Goal of < 38 µg/L
SD
TP
Aquatic PlantsSpecies: 20+Tolerance: ModerateCoverage: Growth to 10 ftDensity: Low to mediumInvasives: Eurasian watermillfoil, curlyleaf pondweed
Potential Lake Changes with TMDL Implementation
Increased lake clarity Reduced blue-green algae
populations Increased aquatic plant coverage Increased dissolved oxygen
throughout the lake water column
If improved lake clarity, aquatic plant coverage, and dissolved oxygen, then improved habitat for aquatic life
Recommendations
Continued implementation of TMDL, BCWMC, and Plymouth Creek projects
Continued lake monitoring Document and track activities and
projects in the watershed that reduce phosphorus loading to Medicine Lake
Twin Lake Internal Phosphorus Loading Special
Investigation
Purpose of Study
Identify reasons for recent increases in
nutrients and algae in Twin Lake
Pertinent Twin Lake Characteristics
Surface area: 21 acres (small) Maximum depth: 54 feet (quite deep) Average depth: 25.7 Sheltered (protected from wind) Small, largely undeveloped watershed Connected to Sweeney Lake Strongly stratified Largely self contained, changes in water
quality and biota due to internal (non-watershed) processes.
Very low dissolved oxygen Nearly permanently low at depths below 16
feet Very high rate of phosphorus loading from
lake sediments (internal loading) during the summer and winter
Phytoplankton population now dominated by blue-green algae (cyanobacteria)
Pertinent Chemical and Biological Characteristics
Lake sediments are permanently oxygen depleted
Nearly all phosphorus deposited on sediment is re-released (nutrient cycling)
Spring mixing=phosphorus transport to lake surface
Fall mixing=phosphorus transport to lake surface
Phytoplankton levels may be influenced by: Zooplankton abundance Blue green algae upward mobility
What Is Affecting the Water Quality of Twin Lake?
Why Has Phosphorus Increased in Recent Years…
The lake is warmer, oxygen is lower for more of the lake
Management Options for Internal Load Control
Hypolimnetic withdrawl
Sediment phosphorus inactivation
Requires water inputs to replace water removed from lake bottom, several other drawbacks
Relatively inexpensive, can be effective on a long term basis for lakes with small watersheds
Management Options for Internal Load Control
Biomanipulation
Barley straw
Aeration
Innovative and natural way to control algae, appears to be occurring in Twin Lake already to some degree.Most often used for small lakes and ponds, can prevent algal growth in some cases, requires annual treatment.Can increase oxygen in lake water, however, may not stop internal loading and may transport phosphorus to the lake surface for algal growth
Management Options for Internal Load Control
Dredging Can reduce internal loading, primary drawback is high cost