2016 research and monitoring report€¦ · ment releases an annual report summarizing the water...

2016 Research and Monitoring Report

2016 Research and Monitoring Report

Written by

Kelly Dooley

Collaborative Input by

Yvette Christianson, Craig Dawson, and Eric Fieldseth

Senior Field Staff

Kailey Cermak and Jill Sweet

Field Staff

Cameron Blake, Rachel Fleck, Mulugetta Fratkin, Johanna Grimsly, Marci Lapointe, and Andy Swanson

Cover Photo Credit:

Brianna Prahl

August 2017

15320 Minnetonka Boulevard || Minnetonka, MN 55345

952-641-4535 || www.minnehahahcreek.org/data-center

http://www.minnehahahcreek.org

iii

PREFACE

The Minnehaha Creek Watershed District (MCWD) was established in 1967, and is responsible for managing and protecting the water resources of the Minnehaha Creek watershed drainage basin. The drainage basin extends for 177 square miles draining into the Minnehaha Creek and ultimately into the Mississippi River. The watershed district encompasses 11 subwatersheds which drains 12 creeks, 129 lakes, and thousands of wetlands throughout two counties, 27 cities, and two townships. The monitoring program, which assessed the water quality in many of the lakes and streams was managed by consultants until 2004, when program management was brought in-house.

Since 2004, the monitoring program has grown, and continued to evolve with the monitoring and research efforts over the years. The Research and Monitoring Department (R/M), as it is known today, is comprised of the monitoring/analysis program and the aquatic invasive species (AIS) management program. The depart-ment releases an annual report summarizing the water quality findings for the prior year. The report has varied in size, depth and audience focus over the years. In the past decade, the annual reports have been published on the District’s website.

Starting in 2016, the District initiated a strategic planning process to re-prioritize, re-organize, and stream-line work. By the end of 2016, a new vision, mission, guiding principles and goals for the District were ap-proved. In February 2017, the Board of Managers approved the new purpose/focus for majority of the pro-grams.

Research and Monitoring program serves as the scientific base for the implementation of the District’s mis-sion, by collecting and analyzing data across the watershed’s natural resources. This information is used pri-marily to inform District planning and implementation, and secondarily to inform and educate members of the public. The program has the four following areas of focus: diagnose issues/stressors at a project-specific scale, maintain long-term data sets and assess trends across the watershed at select representative stations (i.e., anchor stations), conduct performance monitoring to assess project efficacy at priority project sites, and broadly characterize ecosystem health using the E-Grade system to support planning and public communications.

Assessing and managing the impact of aquatic invasive species is an additional expertise in the Research and Monitoring program. The efforts to understand and manage AIS provides a more holistic view of the water-shed’s ecological health. Activities focused on AIS include: managing AIS with high ecological impact, early detection monitoring and rapid response, promoting research, and supporting AIS prevention efforts led by District partners.

Throughout 2017, the District is in the process of implementing the new focus. Research and Monitoring staff have adjusted the 2017 monitoring plan, increased analytic capabilities, begun to integrate data into the planning process, and begun to redesign the annual report. Integrating the data with identified driver and stressors, and recommending strategies to improve the land and water resources will be the focus for the R/M program in 2018.

As mentioned, the redesign of the annual report is still in development phase; therefore, the 2016 report is an executive summary with supplemental tables and graphs.

iv

TABLE OF CONTENTS

Figures and Tables ........................................................................................................ v

Acronyms ..................................................................................................................... vi

Executive Summary ..................................................................................................... 1

Six Smaller Subwatersheds ........................................................................................... 2

Six Mile Creek Subwatershed ....................................................................................... 3

Painter Creek Subwatershed ......................................................................................... 4

Long Lake Creek Subwatershed .................................................................................... 4

Lake Minnetonka Subwaterhshed ................................................................................. 5

Minnehaha Creek Subwatershed ................................................................................... 6

Standards ....................................................................................................................... 9

Nutrient Impairments .................................................................................................... 10

Aquatic Invasive Species (AIS) Management ................................................................. 10

References ................................................................................................................... 12

Appendix A: 2016 Trends ............................................................................................. 13

v

FIGURES AND TABLES

FIGURES

1. Annual precipitation totals compared to historical average ............................................. 1

2. Comparing the monthly precipitation totals in 2014 to 2016 at MSP Airport .................. 1

3. Phosphorus loading into Lake Minnetonka from the 9 major streams ............................ 3

4. Dividing Lake Minnetonka into 3 groups is the predicted zebra mussel growth

based on food factors ....................................................................................................... 6

5. Phosphorus loading into Minnehaha Creek ...................................................................... 7

6. Statistical comparison of total phosphorus before and after the 1st and

2nd Minnehaha Creek re-meanders. .................................................................................. 8

7. Statistical comparison of sediment concentrations before and after the 1st and


8. Statistical comparison of chloride concentrations before and after the 1st and


9. Map of Minnehaha Creek Watershed District and the known impairments .................... 11

TABLES

1. Statistically significant trends for the anchor stream stations in the Six Mile Creek Subwatershed ................................................................................................................... 3

2. Statistically significant trends for the anchor stream stations in the Minnehaha Creek Subwatershed ................................................................................................................... 7

3. North Central Hardwood Forest Ecoregion Eutrophication Standards ............................ 9

4. North Central Hardwood Forest Ecoregion Chloride Standards ...................................... 9

5. North Central Hardwood Forest Ecoregion Standards for Streams ................................. 9

6. The list of lakes most likely to be evaluated in 2020 by MPCA for potential nutrient impairments ........................................................................................................ 10

7. The list of impaired lakes that have met the eutrophication standards for two or more years ........................................................................................................................ 10

vi

ACRONYMS

303 (d) List Minnesota Pollution Control Agency’s List of Impaired Waters under the Clean Water Act

CAMP Citizen Assisted Monitoring Program

CFS Cubic feet per seconds

CFU/100 mL Colony forming units per 100 milliliters

DO Dissolved oxygen

CHLA Chlorophyll-a

CLP Curly-leaf Pondweed

Cl Chloride

EPA Environmental Protection Agency

EWM Eurasian Watermilfoil

GPS Global Positioning System

lbs Pounds

LMCD Lake Minnetonka Conservation District

MCES Metropolitan Council Environmental Services

MCWD Minnehaha Creek Watershed District

mg/L (ppm) Milligrams per liter, parts per million

µg/L (ppb) Micrograms per liter, parts per billion

µS/cm Micro Siemens per centimeter

MnDNR Minnesota Department of Natural Resources

MPCA Minnesota Pollution Control Agency

MPRB Minneapolis Park and Recreation Board

MSP Minneapolis – St Paul International Airport

NCHF North Central Hardwood Forest (Ecoregion)

NOAA National Oceanic and Atmospheric Administration

OHW Ordinary high water (level)

OP Ortho-phosphate

NWS National Weather Service

SECC Secchi depth

TMDL Total Maximum Daily Load

TN Total nitrogen

TP Total phosphorus

TRPD Three Rivers Park District

TSI Trophic Status Index

TSS Total suspended solid

1

EXECUTIVE SUMMARY

The Minnehaha Creek Watershed District (MCWD) monitors lakes and streams within its watershed bound-aries on a seasonal basis for water quality indicators linked to recreational, aesthetic, and biological condi-tions. There are eleven major subwatersheds within the Minnehaha Creek watershed. The majority of lake trends were computed from 2001-2016, and the majority of stream trends were computed from 2005-2016 (Appendix A). Summarized are the notable findings that occurred during 2016.

2016 was the wettest year on record for MCWD. The District has been experiencing above average precipitation since 2012 (Figure 1). The total precipitation in 2016 was 40.43”, which was about 4.5” more of precipitation than the past two years. With all the precipitation, the District experienced little to no flooding in 2016. Why is that? It depends on the quantity of precipitation and when the precipitation falls.

In 2014, the District experienced record flooding due to a spike of precipitation in April, and then again in June. In 2016, the precipitation was spread out over the year (Figure 2).

View of Minnehaha Creek from Grays Bay Dam in October 2016

Figure 1 (Top). Annual precipitation totals compared to

historical average.

Figure 2 (Bottom). Comparing the monthly precipitation

totals in 2014 to 2016 at Minneapolis-St. Paul (MSP)

Airport.

In 2016, the Grays Bay Dam was open 264 days (almost ¾ the year), which is 49 more days than in 2015,

and 65 more days than in 2014.

2

Dutch Lake Subwatershed

Dutch Lake outlet drains into Lake Minnetonka: Jennings Bay. There were two statistically significant trends in the data at the Dutch Lake outlet stream station (CR 110) - phosphorus and total suspended solids (i.e., sediment) concentrations. Over the past 12 years, phosphorus and sediment concentrations have been de-creasing over time.

Langdon Lake Subwatershed

Langdon Lake outlet drains into Lake Minnetonka: Cooks Bay. There were two statistically significant trends in the data at the Langdon Lake outlet stream station (CR 110) - stream discharge and phosphorus concentra-tions. Over the past 12 years, the volume of water flowing (stream discharge) through the Langdon Lake out-let has been increasing, but the phosphorus concentrations have been decreasing.

Increased precipitation is a factor for the increase in stream discharge at Langdon Lake’s outlet. More precipi-tation keeps the stream flowing year-round, where 10 years ago the stream would run dry by August. Beaver impoundments also have been actively removed by residents in the recent years, which would naturally hold back water in the area.

Lake Virginia Subwatershed

Lake Minnewashta is the District’s second largest lake at 677 acres and has a maximum depth of 21 m. Lake Minnewashta drains into Lake Virginia, which then drains into Lake Minnetonka: Smithtown Bay. The only statistically significant trend in the data at Lake Minnewashta was with water clarity. Over the past 16 years, clarity has been decreasing over time. The change in clarity is small, about 0.05 m/year; therefore, the Dis-trict will continue to monitor clarity through volunteers on Lake Minnewashta. (Note: Zebra mussels have been found in the lake, but to the District’s knowledge, the zebra mussel population remains low.)

Schutz Lake Subwatershed

Schutz Lake is the only lake in this subwatershed. Currently, Schutz Lake is not impaired, but it continues to fluctuate between meeting and not meeting the eutrophication standards set by the MPCA. In 2016, Schutz Lake only met the clarity and phosphorus standards. Clarity, chlorophyll-a, and phosphorus concentrations are worsening over time, yet the change is not statistically significant.

The complete E-Grade report will be available in 2018, which could highlight issues within the subwatershed. In efforts to prevent the lake from becoming impaired, MCWD is working with the City of Victoria to identify what sources are the largest contributors of phosphorus to the lake.

Six Smaller Subwatersheds

Key

Map Color Subwatershed Name

Blue Langdon Lake

Orange Dutch Lake

Yellow Gleason Lake

Pink Christmas Lake

Green Lake Virginia

Purple Schutz Lake

3

Six Mile Creek Subwatershed

Six Mile Creek Subwatershed is the largest upper subwatershed that drains into Lake Minnetonka. Six Mile Creek drains a series of lakes and wetlands into Lake Minneton-ka: Halsted Bay. Six Mile Creek is the 2nd largest transporter of phosphorus to Lake Minnetonka (Figure 3).

One of the most notable sources of phos-phorus is from the Six Mile Marsh, a wet-land complex between HWY 7 and Lake Minnetonka: Halsted Bay. Data and modeling indicate that the marsh is a source of soluble phosphorus, which can lead to the algae blooms in Halsted Bay. Reducing phosphorus exports from the wetland complex will be one step towards improving water quality in Halsted Bay.

Another notable result is that out of the 20 lakes within this subwatershed, only two lakes

have statistically significant trends. Turbid Lake has a statistically significant trend in declining water quality. Phosphorus and chlorophyll-a have been increasing in concentration over the past 16 years. Lake Zumbra has a significant trend indicating improvement in clarity and chlorophyll-a concentrations.

There are three anchor stream stations the District monitors to assess long term trends. The anchor stations in the Six Mile Subwatershed are: East Auburn Lake inlet (HWY 5), Lundsten Lake North outlet (Carver Park), and Mud Lake outlet (Highland Rd).

East Auburn Lake inlet has a significant trend with stream discharge: the volume of water passing through the East Auburn Lake inlet has increased over the past 12 years. Increased precipitation is a factor for the in-crease in stream discharge at East Auburn Lake’s inlet. A secondary factor is development. The area upstream of the East Auburn Lake inlet has been under development during the last decade.

There were also significant trends in phosphorus and sediment concentrations at all three anchor stations (Table 1). Phosphorus and sediment concentrations have been decreasing over the past 12 years indicating improvements in water quality at these stations along Six Mile Creek.

Station TP

TSS East Auburn Lake Inlet Imp Imp Lundsten Lake N Outlet Imp Imp

Mud Lake Outlet Imp Imp

Table 1. Statistically significant trends for anchor stream stations in Six Mile Creek Subwatershed

(Imp = Improvements in water quality).

Figure 3. Phosphorus loading

(pounds) into Lake Minnetonka

from the 9 major streams.

4

Painter Creek Subwatershed

Painter Creek Subwatershed is the 2nd largest subwatershed that drains into Lake Minnetonka, but transports the most phosphorus to the Lake (Table 1). There is an anchor stream station located at West Branch Rd, upstream of the inlet into Lake Minnetonka: Jennings Bay. The 10-year average at the anchor station is about 2500 lbs of phosphorus. Statistical analysis of the data at the West Branch Rd stream station indicates a significant trend in

phosphorus concentrations. Over the past 12 years, phosphorus concentrations have increased at this anchor stream station.

In 2014, the year with record flooding, phosphorus loading almost tripled the anchor station’s 10-year aver-age. In 2016, the wettest year on record, about 3500 lbs of phosphorus was transported into Lake Minneton-ka: Jennings Bay. The Painter Creek Subwatershed has altered wetlands and channels that discharge phos-phorus during precipitation events. Timing and quantity of the precipitation determines the phosphorus load.

Moving upstream in Painter Creek, MCWD conducted initial diagnostics of the water quality at the outlet of Painter Marsh. Analysis of the data indicates the marsh is exporting phosphorus. Further diagnostics are needed to determine the major sources of nutrient loads in this Subwatershed.

Long Lake Creek Subwatershed

Long Lake Creek is the 3rd largest subwatershed draining into Lake Minnetonka, and is the 3rd largest transporter of phosphorus to the Lake (Table 1).

The northwestern portion of the subwatershed is drained by the School Lake Tributary, which flows through a series of lakes. Two of three lakes along this tributary have nutrient impairments. The northeastern portion of the subwater-shed is drained by the Holy Name Tributary. Holy Name Lake is the headwaters of the tributary, and is im-paired for nutrients. Dickey Lake, currently non-impaired, is only exceeding the phosphorus standard. Both tributaries, as well as Dickey Lake, discharge into Long Lake, which is nutrient-impaired.

The majority of lakes cycle phosphorus from the sediments to be used by algae and plants at the surface wa-ters. However, when lakes receive excessive loads of phosphorus from upstream waterbodies and storm-water runoff, they becomes overwhelmed by external and internal sources of phosphorus. Frequent precipi-tation events flush the upstream altered wetlands and lakes which then discharge phosphorus into down-stream waterbodies, negatively impacting lakes such as Long and Tanager.

Most of the lakes in this subwatershed act as treatment basins, especially Long Lake and Tanager Lake,

5

holding back phosphorus from impacting downstream resources. Ironically, Long Lake has a significant trend in improving water clarity, but the amount of improvement over time is so small that it does not result in observable changes to the lake. To make effective water quality changes in the Long Lake Subwatershed, MCWD is attempting to diagnose specific phosphorus sources up stream of Long Lake in 2017.

Lake Minnetonka Subwatershed

Lake Minnetonka Subwatershed is named for its namesake, Lake Minnetonka. The Lake covers 43% of the acreage of the sub-watershed, which is the largest subwater-shed in the District. The nine subwater-sheds addressed earlier in this report all drain into Lake Minnetonka. Painter Creek, Six Mile Creek and Long Lake Creek transport the most phosphorus into Lake Minnetonka (Table 1). It is no surprise that their receiving waters still remain impaired

for nutrients - Jennings Bay, Halsted Bays and Tanager Lake. These bays and Peavey Lake were initially im-paired from the legacy phosphorus deposited during the days of wastewater treatment plants (WWTP) adja-cent to the Lake, which were decommissioned beginning in the 1970s. These bays act as treatment basins, holding back nutrient-rich water, essentially protecting the majority of the Lake.

Lake Minnetonka could be divided into three groups from west to east, with water quality tending to im-prove as it flows towards Grays Bay Dam (Figure 4). Grays, Crystal, and Wayzata bays have significant trends of improving clarity. Lafayette Bay and Lower Lake South have significant trends of improving clarity and chlorophyll-a concentrations. Spring Park Bay has significant trends of improving clarity and phosphorus con-centrations. Carsons and St. Albans bays have significant trends indicating improvements in all three water quality parameters.

Peavey Lake has the only significant degrading trend indicating clarity and phosphorus concentrations are getting worse. Zebra mussel research is indicating the lake is changing by their presence, primarily by im-proving water clarity and reductions in chlorophyll-a concentrations.

Blue-green algal blooms occur in Long Lake in late summer-early winter. Late fall – winter blue-green algal blooms are often harmful or toxic.

Right: Harmful Algal Bloom (HABs) flowing through the Long Lake outlet in November 2016

Note: The discharge from the Grays Bay Dam is converted into runoff, which translates into the volume of water drained 6 from the upper watershed.

Minnehaha Creek Subwatershed

Minnehaha Creek resides within the Minnehaha Creek Subwatershed, and is the only receiving water for the drainage from the ten upper subwatersheds. The headwaters to the Creek is managed by an adjustable control structure to reduce flooding on Lake Minnetonka and Min-nehaha Creek.

Baseflow conditions, when the dam is closed, are low to stagnant pools that are scattered across the reaches, though the Creek can be flashy and maintain flow

from runoff even when the dam is closed. Minnehaha Creek is vulnerable to any pollutant the upper subwa-tershed discharges, as well as by the pollutants from the Creek’s surrounding uplands. The Minneapolis Chain of Lakes also drain into the Creek. Currently, Minnehaha Creek is impaired for chloride, dissolved oxygen, fe-cal coliform (i.e., E. coli) and is unable to consistently support macroinvertebrates and fish communities.

During wet years, like 2016, Minnehaha Creek is flowing almost year-round. In 2016, the Creek received just under 12 inches of runoff from the upper subwatersheds, which is above the 10-year average of 9.30 inches. Similar to Painter Creek, precipitation flushes the altered wetlands adjacent to Minnehaha Creek, erodes the Creek’s banks, and generates stormwater runoff. The Creek received between 8-10 inches of run-off from the surrounding uplands in 2016, which is above the 10-year average of 6.80 inches.

With the precipitation dispersed throughout the year, Minnehaha Creek did not receive a spike of nutrients like in 2014 (Figure 5).

There were several statistically significant trends throughout this subwatershed. Along Minnehaha Creek, phosphorus concentrations have significantly improved over the past 12 years at all the anchor stream sta-tions. There are handful of anchor stations along Minnehaha Creek that have had statistically significant im-provements in sediment concentrations (i.e., total suspended solids (TSS)) over the past 12 years, and one station, I-494 access ramp, with degrading trend (Table 2).

Figure 4. Dividing Lake Minnetonka into three

groups is the predicted zebra mussel growth

based on food factors.

7

Chain of Lakes:

Minneapolis Parks and Recreation Board staff monitor and manage the Chain of Lakes within the Minnehaha Creek Subwatershed. Since the lakes reside within MCWD boundaries, MCWD staff also report on Chain of Lakes health. There were several statistically significant trends throughout the Chain of Lakes when analyzing the data from 2001-2016.

Cedar and Powderhorn lakes have statistically significant trends indicating degrading water clarity. In 1996, Cedar Lake had an alum treatment; however, the dosing method in 1996 resulted in less alum applied than how lakes are dosed now. The effect of the alum has diminished over time, hence the degrading water clarity in the lake. Improvements to the watershed have continued as redevelopment occurs.

Lake Harriet has a statistically significant trend indicating phosphorus concentrations have increased over the past 16 years. The increase in phosphorus concentrations over time is so small that it does not result in observable changes to the lake. Harriet Lake had a mini-alum treatment in 2001. The treatment was meant to address the algae in the littoral zone, but inadvertently and partially addressed internal loading of phosphorus. The phospho-rus is not being “locked-up” by the alum for as long of a period of time as it would had if the lake had re-ceived a full dose of alum in an intentional whole-lake treatment.

Lake of the Isles and Lake Nokomis have statistically significant trends of improving chlorophyll-a and phosphorus concentrations. Although the improvement in Lake of the Isles is great, the Lake has highly variable water quality. The past few years, spring concentrations of chlorophyll-a and phosphorus have been low, but by August, the concentrations increase leading to poor water clarity in the Lake. The improvements in Lake Nokomis’s water quality are most likely due to projects conducted within the past decade by MCWD and the MPRB to improve the watershed and the lake itself (e.g., Lake Nokomis Biomanipulation project).

Station Year Range TP

TSS

Grays Bay Dam 2005-2016 Imp Imp

I-494 2005-2016 Imp Deg

Aquila Ave 2005-2016 Imp

Excelsior Blvd 2005-2016 Imp Imp

W 56th St. 2005-2016 Imp Imp

21st/MH Pkwy 2007-2016 Imp Imp

Hiawatha Ave 2005-2016 Imp

Table 2. Statistically significant trends for

anchor stream stations in Minnehaha Creek

Subwatershed (Imp = Improvements and

Deg = Degrading in water quality).

Figure 5. Phosphorus loading (pounds) into Minnehaha Creek.

8

Project Effectiveness - Minnehaha Creek Re-meanders:

The Excelsior Blvd stream station is downstream of both Minnehaha Creek re-meander projects: Methodist Hospital and Minnehaha Greenway. The Minnehaha Greenway project also incorporated stormwater treatment ponds. Data range from 1999-2016. The period after the first re-meander is from 2010-2012 (Methodist - white circle). The period after the second re-meander is from 2010-2016 (Greenway - green circle).

Data was compared before and after both re-meanders projects, and the notable results are:

Total and soluble phosphorus concentrations have significantly decreased (Figure 6*). Even though Minnehaha Creek received record precipitation and record levels of phosphorus in 2014 and 2016, there was still a 30% reduction in phosphorus concentrations at the Excelsior Blvd stream station.

Sediment concentrations decreased, but were not significant (Figure 7).

Chloride concentrations were significantly different and higher compared to concentrations before both re-meanders. The differences in chloride concentration most likely has to do with precipitation and salt application during the period examined (Figure 8).

Figures 6 -8. Statistical comparison of total phosphorus, sediment and chloride concentrations before and after the 1st

and 2nd Minnehaha Creek re-meanders. *Only Total Phosphorus concentrations are shown in Figure 6.

Fig. 8

Fig. 6

Fig. 7

9

Standards

Minnehaha Creek Watershed District (MCWD) resides within the North Central Hardwood Forest Ecoregion (NCHF). This is the transitional area in central Minnesota where the southeastern agricultural area meets the northeastern forested area. Much of this area has been developed for residential, recreational, urban and agricultural land use. The MPCA has established standards specific to the NCHF ecoregion for both lakes and streams. At this time, there are no NCHF eutrophication standards for wetlands.

Lake eutrophication standards are used for assessing the recreational use of lakes in Minnesota (Table 3). If a lake fails to meet two or more of the standards over two consecutive years, then the MPCA evaluates listing the lake as impaired for nutrient/eutrophication biological indicators. Table 4 lists the criteria for lakes and streams to be evaluated for chloride impairment. Table 5 lists the stream standards for eutrophiocation, dissolved oxygen, total suspended solid (TSS) and E. coli.

Table 3. North Central Hardwood Forest Ecoregion Eutrophication Standards for Lakes

Eutrophication Standards

(June-Sept Means) North Central Hardwood

Forest Ecoregion

Units Shallow Lakes* Lake Hiawatha Lake Nokomis Deep Lakes

Secchi Depth (SECC) m ≥ 1.0 ≥ 1.4 ≥ 1.4 ≥ 1.4

Chlorophyll-a (CHLA) µg/L ≤ 20 ≤ 14 ≤ 20 ≤ 14

Total Phosphorus (TP) µg/L ≤ 60 ≤ 50 ≤ 50 ≤ 40

*Shallow lakes are defined as a having a maximum depth less than 15’ and a littoral zone greater than 80% of the lake sur-

face area

Table 4. North Central Hardwood Forest Ecoregion Chloride Standard

North Central Hardwood

Forest Ecoregion

Chloride Standard

Chronic = 230 mg/L Acute = 860 mg/L

Lakes Impaired: 2 or more

exceedances in 3 years Impaired: 1 or more exceedances of

the max standard

Streams Impaired: Over a 4-day average Impaired: Over a 1-hour duration

Table 5. North Central Hardwood Forest Ecoregion Standards for Streams

North Central

Hardwood Forest

Ecoregion

TP* CHLA* DO TSS

E. coli

Units µg/L µg/L mg/L mg/L Chronic = 126 cfu/100 mL Acute = 1,260 cfu/100 mL

April - Sept ≤ 30 Impaired: Geometric mean of not less than 5

samples within an calendar month

Impaired: Not more than 10% of all samples taken during any

calendar month individually exceed

June - Sept ≤ 100 ≤ 18 ≥ 5

* MCWD currently does not collect data for assessment of the two stressors - Diel DO flux and Biochemical Oxygen Demand (BOD)

10

Nutrient Impairments

Currently there are 28 lakes with nutrient impairments , and for all other impairments (i.e., chloride, mercury, E. coli , etc.) within MCWD refer to the 2017 Watershed Management Plan (Figure 9). Table 6 lists the lakes most likely to be evaluated in 2020 by the MPCA for potential impairment, and table 7 lists the impaired lakes that have met the eutrophication standards for 2 or more years.

The 2016 summer means are available by request. Lake Nokomis is the only lake listed in Table 7 that has sig-nificant trends indicating improvement. The rest of the lakes listed in Table 7, except Holy Name, are showing signs of improvements, but not statistically significant. Holy Name has insufficient years of data to run trends.

Aquatic Invasive Species (AIS) Management

In 2016, zebra mussel populations continued to be monitored on Lake

Minnetonka and Christmas Lake. The monitoring on Lake Minnetonka is part

of a long-term zebra mussel study assessing how zebra mussels are affecting

water quality.

Early detection monitoring was conducted weekly by checking zebra mussel

sampler plates and sampling vegetation at public accesses. Monitoring at

Lake Minnewashta led to the discovery of zebra mussels in August 2016.

Upon discovery, a rapid response effort was initiated. Copper product

EarthTec-QZ treatment occurred from August - September, over a 29-acre

bay of Lake Minnewashta. Post-treatment monitoring, indicated 100%

mortality of zebra mussel in the treatment area. Update: On June 2017, post

treatment survey in Lake Minnewashta found one zebra mussel within the treatment area. This zebra mussel

was removed, and subsequent monitoring has occurred. No additional zebra mussels have been found.

Also, in 2016, 15 aquatic plant and 37 score-the-shore surveys were completed as part of the E-Grade assess-

ments in the Six Mile Creek, Schutz Lake and Minnehaha Creek subwatersheds (Reports available in

2018). MCWD also partnered with the University of Minnesota on a zebra mussel veliger control study, and

with Montana State University and University of Minnesota on hybrid watermilfoil research. The Six Mile

Creek Carp Assessment, conducted by the University of Minnesota, concluded its third and final year (See

website for report).

Table 7. The list of impaired lakes that have met the eutrophication standards for 2 or more years

Subwatershed Lake

Lake Virginia Tamarack Lake

Long Lake Creek Holy Name Lake

Minnehaha Creek Lake Hiawatha*

Lake Nokomis

Six Mile Creek Stone Lake

*Only met the standards in 2016

Table 6. The list of lakes most likely to be evaluated in 2020 by MPCA for potential nutrient impairment

Subwatershed Lake

Lake Minnetonka Lake Minnetonka: Priests Bay

Minnehaha Creek Pamela Lake*

Powderhorn Lake

Painter Creek Thies Lake

Six Mile Creek Lundsten Lake South

Church Lake

*Chloride impairment evaluation as well Note: To evaluated for listing and/or delisting the MPCA needs at least 8 paired total phosphorus, chlorophyll-a, and Secchi measurements (June to September) over a minimum of 2 years for the most recent 10 years.

11

Figure 9

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12

REFERENCES

Emmons and Olivier Resources, Inc. 2003. Minnehaha Creek Watershed District’s Hydrologic Hydraulic and Pollutant Loading Study Report.

MacIssac, H.J., 1996. Potential Abiotic and Biotic Impacts of Zebra Mussels on the Inland Waters of North America. American Zoology 36:287-299.

McCollor and Heiskary. 1993. Selected Water Quality Characteristics of Minimally Impacted Streams from Minnesota’s Seven Ecoregions. Minnesota Pollution Control Agency Water Quality Division.

Minneapolis Parks and Recreation Board (MPRB). 2016. Email Correspondence with Rachael Crabb.

Minneapolis Parks and Recreation Board (MPRB). 2017. Email Correspondence with Rachael Crabb and Rob Brown.

Minnehaha Creek Watershed District (MCWD). 2017. Comprehensive Water Resources Management Plan: 2017-2027.

Minnesota Pollution Control Agency (MPCA). 2014. Guidance Manual for Assessing the Quality of Minnesota Surface Waters for the Determination of Impairment, 305(b) Report and 303 (d) List.

Minnesota Pollution Control Agency (MPCA). 2014. 2014 Proposed Impaired Waters List (wq-iwl-47). https://www.pca.state.mn.us/water/minnesotas-impaired-waters-list.

Shaw, B., C. Mechenich, and L. Klessig. 2004. Understanding Lake Data. University of Wisconsin: Extension. Pp 3-4.

Wenck Associates, Inc. 2013. Minnehaha Creek Watershed District: Six Mile Creek Diagnostic Study.

13

Appendix A: 2016 Trends

14

Statistical Analysis - 2016 Trends:

Prior to computing statistical long-term trends, staff analyzed the lake and stream data for normality.

Environmental data is often non-normal; therefore, a non-parametric trend test is recommended for use to

compute trends. Using R-studio statistical software, trends were computed using the Mann-Kendall test on

yield and flow-corrected concentrations of total phosphorus (TP) and total suspended solids (TSS) for stream

stations with at least eight years of consecutive data. Trends for lakes were also computed using Mann-

Kendall test on Secchi disk depth measurements (SD), surface chlorophyll-a (CHLA), and surface total phos-

phorus concentrations (TP). Statistical analysis was computed on lakes with at least eight years of consecu-

tive data. The threshold used determine a significant trends was an alpha of less than or equal to 0.05. The

following tables in this appendix are grouped by subwatershed, and list the station, the year range of analy-

sis, and the parameters analyzed. Also listed in the tables are the p-values, slope of change, statistically sig-

nificant results, and the status of the trend (i.e., improving or degrading).

Statistically

15

Station Station Type Year Range Parameter p-value Slope

Statistically Significant

(alpha ≤ 0.05)

Status

Christmas Lake Subwatershed

LCH01 Christmas Lake 2001-2016

SD 0.37 0.077

CHLA 0.56 0.062

TP 0.53 -0.039

Dutch Lake Subwatershed

LDU01 Dutch Lake 2001-2016

SD 0.53 0.011

CHLA 0.34 -0.705

TP 0.86 0.275

CDU01 Dutch Lake Creek Outlet 2005-2016

Yield 0.37 0.021

TP 0.003 -6315 Yes Improving

TSS 0.006 -2493 Yes Improving

Gleason Lake Subwatershed

LMO02 Mooney Lake 2006-2016

SD 0.75 -0.009

CHLA 0.25 -3.125

TP 0.35 -2.028

LGL01 Gleason Lake 2001-2016

SD 0.30 0.02

CHLA 0.50 -1.084

TP 0.26 -2.1

Lake Virginia Subwatershed

LMW01 Lake Minnewashta 2001-2016

SD 0.04 -0.057 Yes Degrading

CHLA 0.06 0.418

TP 0.42 0.204

LJOE01 Lake St. Joe 2004-2016

SD 0.16 -0.027

CHLA 0.76 -0.113

TP 0.64 -0.133

LLV01 Lake Virginia 2001-2016

SD 0.72 -0.008

CHLA 0.14 1.128

TP 0.34 0.429

Langdon Lake Subwatershed

LLA01 Langdon Lake 2001-2016

SD 0.18 0.027

CHLA 0.08 -2.485

TP 0.39 -1.473

CLA01 Langdon Lake Creek

Outlet 2005-2016

Yield 0.03 0.038 Yes Increasing

TP 1.19E-05 -6103 Yes Improving

TSS 0.84 -115

Schutz Lake Subwatershed

LSC01 Schutz Lake 2002-2016

SD 0.34 -0.026

CHLA 0.12 0.697

TP 0.83 0.093

Statistical Trend Results for the Six Smaller Subwatersheds

16

Mgnt Units Station Year Range Parameter p-value Slope


(alpha ≤ 0.05)

Status


Piersons-Marsh- Wassermann

Piersons Lake 2002-2016

SD 0.425 0.044

CHLA 0.080 -0.522

TP 0.583 -0.188

Wassermann Lake 2001-2016

SD 0.373 0.014

CHLA 0.620 -0.816

TP 0.344 -0.856

Church Lake 2006-2016

SD 0.063 -0.204

CHLA n/a n/a

TP 0.536 -3.203

East Auburn Inlet 2005-2016






(alpha ≤ 0.05)

Status


Carver Park Reserve

Zumbra-Sunny Lake

2001-2016

SD 0.0004 0.168 Yes Improving

CHLA 0.003 -0.636 Yes Improving

TP 0.060 -0.607

Steiger Lake 2002-2016

SD 0.064 0.058

CHLA 0.945 -0.085

TP 0.193 -0.531



(alpha ≤ 0.05)

Status


Auburn-North Lundsten

East Auburn 2006-2016

SD 1.000 0.004

CHLA 0.348 -0.699

TP 0.754 -0.662

West Auburn 2002-2016

SD 0.138 0.037

CHLA 0.621 -0.131

TP 0.075 -0.528

North Lundsten 2006-2016

SD 0.088 -0.733

CHLA 0.721 0.658

TP 1.000 -0.380

North Lundsten Outlet

2005-2016

Yield 0.837 0.019



Statistical Trend Results for the Six Mile Creek Subwatershed

17



(alpha ≤ 0.05)

Status


Turbid-South Lundsten

Turbid Lake 2006-2016

SD 0.474 -0.030

CHLA 0.020 2.840 Yes Degrading

TP 0.032 3.813 Yes Degrading

Parley-Mud

Parley Lake 2006-2016

SD 0.519 0.004

CHLA 0.692 -0.900

TP 1.000 0.034

Mud Lake Outlet 2005-2016

Yield 0.631 0.012


TSS 3.988E-07 -4167 Yes Improving

Station Station Name Year Range Parameter p-value


(alpha ≤ 0.05)

Status Slope

Painter Creek Subwatershed

CPA01 West Branch

Rd 2005-2016

Yield 0.373 0.013

TP 0.008 Yes Degrading 5547

TSS 0.067 -1630

Statistical Trend Results for the Painter Creek Subwatershed

Station Station Name Year Range Parameter p-value Slope


(alpha ≤ 0.05)

Status

Long Lake Creek Subwatershed

LDY01 Dickey’s Lake 2009-2016

SD 0.27 -0.048

CHLA 0.54 0.241

TP 0.54 1.367

LLO01 Long Lake 2001-2016


CHLA 0.92 0.028

TP 0.07 1.875

LTG01 Lake Minnetonka:

Tanager Lake 2001-2016

SD 0.84 -0.001

CHLA 0.84 0.435

TP 0.32 0.607

Statistical Trend Results for the Long Lake Creek Subwatershed

18



(alpha ≤ 0.05)

Status

Lake Minnetonka Subwatershed

LWL01 Lake

William 2009-2016

SD 0.308 0.045

CHLA 0.386 -0.415

TP 1.000 -0.051

Lake Minnetonka Subwatershed: Group 1

LCS01 Carsons Bay 2004-2016



TP 0.044 -0.647 Yes Improving

LGB01 Grays Bay 2004-2016


CHLA 0.300 -0.196

TP 0.058 -0.712

LLF01 Lafayette Bay 2005-2016



TP 0.169 -0.848

LGI01 Lower Lake

South 2001-2016



TP 0.079 -0.460

LAL01 St. Albans

Bay 2001-2016




LWA01 Wayzata Bay 2001-2016


CHLA 0.115 -0.118

TP 0.137 -0.304

Statistical Trend Results for the Lake Minnetonka Subwatershed



(alpha ≤ 0.05)

Status


LBL01 Black Lake 2006-2016

SD 0.087 0.108

CHLA 0.161 -0.888

TP 0.137 -0.924

LCO01 Cooks Bay 2001-2016

SD 0.137 0.057

CHLA 1.000 -0.024

TP 0.137 -0.51

LCR01 Crystal Bay 2001-2016


CHLA 0.224 -0.32

TP 0.163 -0.406

19



(alpha ≤ 0.05)

Status


LMA01 Maxwell Bay 2001-2016

SD 0.137 0.05

CHLA 0.060 -0.49

TP 0.137 -0.519

LPT01 Priests Bay 2006-2016

SD 0.275 0.05

CHLA 0.213 0.469

TP 0.482 0.717

LSP02 Spring Park

Bay 2006-2016


CHLA 0.062 -0.612


LCI01 West Upper

Lake 2001-2016

SD 0.163 0.058

CHLA 0.417 -0.221

TP 0.100 -0.452



(alpha ≤ 0.05)

Status


LFO01 Forest Lake 2001-2016

SD 0.279 0.012

CHLA 0.893 -0.109

TP 0.260 -0.632

LHL01 Halsted Bay 2001-2016

SD 0.260 -0.015

CHLA 0.500 1.18

TP 0.558 -0.335

LJE01 Jennings Bay 2001-2016

SD 0.928 0.001

CHLA 0.499 1.032

TP 0.964 0.146

LPE01 Peavey Lake 2001-2016


CHLA 0.300 -0.401


LSU03 Stubbs Bay 2006-2016

SD 1.000 -0.004

CHLA 0.640 -1.396

TP 0.640 0.719

LWE01 West Arm 2001-2016

SD 0.822 -0.002

CHLA 0.192 0.721

TP 0.718 0.534

20

Mgnt Unit Station Name Year Range Parameter p-value Slope


(alpha ≤ 0.05)

Status


Minnehaha Creek Head-waters

Grays Bay Dam

2005-2016

Yield 0.373 0.023


TSS 4.050E-08 -2981 Yes Improving

Minnetonka Mills

I-494 2005-2016

Yield 0.537 0.014


TSS 0.028 2305 Yes Degrading

Minnehaha Greenway

W 34 St 2005-2016

Yield 0.537 0.015


TSS 0.880 -138

Excelsior Blvd 2005-2016

Yield 0.537 0.010





(alpha ≤ 0.05)

Status


Cedar

Cedar Lake 2002-2016


CHLA 0.921 -0.013

TP 0.519 0.127

Twin Lakes 2002-2016

SD 0.621 0.009

CHLA 0.125 2.556

TP 0.060 -3.119

Isles Lake of the

Isles 2001-2016

SD 0.192 0.027



Calhoun (Bde Maka Ska)

Lake Calhoun

(Bde Maka Ska)

2001-2016

SD 0.685 -0.025

CHLA 0.149 -0.081

TP 0.786 0.054

Harriet Lake Harriet 2001-2016

SD 0.558 -0.054

CHLA 0.893 -0.018


Statistical Trend Results for the Minnehaha Creek Subwatershed

21



(alpha ≤ 0.05)

Status


Minnehaha Parkway

W. 56th St. 2005-2016

Yield 0.721 0.017



21st/ Minnehaha

Parkway 2007-2016






(alpha ≤ 0.05)

Status


Nokomis Lake

Nokomis 2001-2016

SD 0.821 -0.008



Hiawatha

Lake Hiawatha

2004-2016

SD 0.2 0.023

CHLA 0.25 -0.905

TP 0.08 -1.142

Powderhorn Lake

2002-2016


CHLA 0.228 1.965

TP 0.661 1.278

Minnehaha Falls

Hiawatha Ave 2005-2016

Yield 0.373 0.019


TSS 0.814 -352

Note: Brownie, Grass and Diamond lakes were not statistically analyzed for the 2016 report.

2016 research and monitoring report€¦ · ment releases an annual report summarizing the water...

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