Pelican River Watershed District 2016 Water Quality Monitoring Summary

Transcription

1 Pelican River Watershed District 2016 Water Quality Monitoring Summary 1

2 Introduction The Pelican River Watershed District (PRWD), is one of 46 watershed districts established in Minnesota whose purpose is to conserve the natural resources of the state by land use planning, flood control, and other conservation projects utilizing sound scientific principles for the protection of the public health and welfare and the prudent use of the natural resources. Due to the deteriorating water quality in area lakes and streams in the 1950s and 1960s, residents petitioned the state of MN to establish a watershed district in the upper Pelican River watershed area to address the water quality issues. Established on May 27, 1966, PRWD was the first watershed district formed to address water quality issues rather than flooding issues. The District is 120 square miles in size and is located primarily in Becker County (95%), with a small portion (5%) in Ottertail County. The Pelican River watershed is part of the Ottertail River basin which eventually discharges to the Red River of the North. Eight major lakes include the Floyd Lake Chain, Big/Little Detroit Lakes, Long Lake, Lake Sallie and Lake Melissa. These lakes also serve as the economic engine for the NW region of Minnesota, providing recreational opportunities for residents and visitors, including fishing, boating and swimming. The Pelican River Watershed District is located within the North-Central Hardwood Forest Ecoregion. This region is an area of transition between the forested areas to the north and east, and the agricultural areas to the south and west. The terrain varies from rolling hills to smaller plains and is abundant with glacial lakes, wetlands, and remnant hardwood forests. The plains areas of the region are a mix of row crops, livestock grazing, and native prairie land. Much of the land surrounding the lakes has been developed for housing and recreation, resulting in an increase of the nutrient runoff associated with the lawns and impervious surfaces. The lakes in this region are typically found to be mesotrophic but are occasionally found to be slightly eutrophic, especially during mid-late summer, in shallower systems, and in more highly developed areas. The Pelican River Watershed is a headwaters watershed of the Ottertail River Basin, meaning the location is upstream from most other watersheds in the basin. The status of a headwaters watershed comes with benefit and responsibility; the benefit being that waters of the Pelican River aren t negatively affected by upstream development, land use, or industry. However, downstream resources and communities are affected by the land use implications, policies, and decisions made within this drainage system. By caring for our own resources, we also act as good neighbors. The Pelican River Watershed District is dedicated to protecting and improving not only the resources within its jurisdiction, but helping protect the downstream neighbors as well. This is done through collaborative conservation efforts, working with local, state, and federal agencies, to help reduce and manage stormwater runoff, educate the public with benefits of responsible development, and promote healthy lakes and rivers. The District pursues projects which meet the mission, to enhance the quality of water in the lakes, by actively seeking state and federal Grant Funding to stretch and best utilize local tax dollars. Introduction 2 Methods & Guidelines 3 Climatological Summary & Water Level 4 Water Quality Results 5-11 Special Projects

3 Methods and Guidelines The Pelican River Watershed District began a comprehensive water quality monitoring program in 1995, monitoring lakes and streams throughout the District. The primary objective is to identify areas of decreased and impaired water so that nutrient reduction efforts can be focused to improve those locations. A secondary goal of the program was to develop a database of water samples that could be reviewed to identify trends in water quality in the area. Discovering and reversing decreasing trends before the waterbody becomes impaired is one aspect of the monitoring program strategy. The District keeps all water records in a database in-house, including many water clarity samples collected through the MPCA s Citizen Lake Monitoring Program. In addition to the PRWD database, District staff reviews and submits all water quality data that is obtained to the MPCA s surface water database annually. Lake Monitoring With a total of 144 lakes within its jurisdiction, it is important to prioritize lakes and develop a monitoring plan. Most are small, pothole lakes with little to no residential development around them, or they are landlocked and not connected to any surface waterway, making them a low priority. There are 27 lakes which have been identified as having high value, whether economical or environmental, and these lakes are monitored on a rotating basis. The repeating schedule is used to focus monitoring efforts, while keeping costs within budget, and ensures that all priority lakes are sampled a minimum of three years within a 10-year period. Monitored lake are sampled on a bi-weekly basis, May-September. Water clarity is measured using a Secchi Disk, while Total Phosphorous and Orthophosphate samples are obtained using a 2- meter integrated sampler. Dissolved Oxygen, Temperature, and ph profiles are created by taking readings every 1-meter throughout the water column using a YSI Multiparameter Sonde. Citizen Lake Monitoring Program PRWD gains valuable supporting information collected by volunteers through the Minnesota Pollution Control Agency s Citizen Lake Monitoring Program. The program gathers water quality data using a Secchi Disk to observe water clarity throughout the summer months. This information is included in the PRWD s water quality database and is incredibly valuable to the District, especially in years that monitoring by PRWD is not scheduled. The District assists Citizen Lake Monitoring Volunteers by offering technical assistance and supplies through the program. Stream and Public Drainage Ditch Monitoring The Pelican River Watershed District also monitors stream water quality within its jurisdiction. Water quality samples are collected on a bi-weekly basis, beginning during the spring melt through September. Stream flow is measured throughout the year at some of the locations, where nutrient and sediment loading information is of value. Routine water chemistry samples are taken bi-weekly. Specific analytes vary depending on the source of the water and the project goals, but typically include Total Phosphorous, Orthophosphate, and Total Suspended Solids (sediment). In addition to chemistry analysis, water level is observed and documented at each sampling as well as stream flow measurement at many of the sites. Continuous water level logging equipment is deployed alongside rain gauges to observe stream response to rain events and to record high water conditions. In addition to the routine monitoring schedule, PRWD obtains samples following large storm events, rainfall greater than 1, to observe potential increases in nutrient and sediment inputs during high stormwater runoff and stream flows. 3

4 Climatological Summary and Water Level Local weather patterns have a strong effect on local water resources. Precipitation has one of the strongest influences, creating stormwater runoff that can deliver sediment and nutrients to the streams and lakes, which can result in decreased water clarity and increased algal growth. Water levels in local lakes and streams are also directly affected by the amount of precipitation received. Local temperature can effect local water quality by causing increases, or decreases, in water temperatures resulting in changes in algal growth. The Pelican River Watershed District records precipitation data in two locations to observe local precipitation and any variations of precipitation totals within the District. PRWD also receives local weather observation reports from KDLM radio station, which, in addition to precipitation data, records high/low temperature and snowfall totals, dating back to For constancy, the data observed and recorded by KDLM is used for weather trend analysis. Precipitation and Weather Summary 2016 was the warmest year recorded, with averages, both highs and lows, about 3 degrees above the 20-year average (51 and 32 degrees). February and March were the warmest months, both reaching high temperatures 9 degrees above average (13 and 27 degrees). December was the only month which recorded temperatures lower than average, one degree below average for both high and low temperatures. Low snowfall totals during the winter season contributed to a precipitation deficit early in the year inches of snow fell that winter, with only 2 inches falling in March and April. This amount was significantly lower than the average of 50.5 inches. The spring and early summer were relatively dry, with a 4 inch rainfall deficit. The drought conditions ended in July with a significant rain event spanning several days, July 10-12, during which 4.9 inches of rain was recorded at the KDLM radio station. During the same storm event, PRWD rain monitoring equipment located on Campbell Creek at Co Rd 149, measured 6.8 inches. This shoes the large amount of variability of rainfall totals within a short distance, less than 4 miles in this case. The rainfall total in July was nearly 10 inches, 5.8 inches greater than average. High levels of rainfall continued through August and September, bringing precipitation totals to 5 inches greater than average. Water Level Summary In a typical year, lakes are recharged with spring meltwater and spring rainfall. With increased water inputs, lake levels will rise late-april and May, usually reaching its highest level late-may to early-june. Local weather patterns obviously play a major role in lake water levels and this water level pattern will fluctuate. Due to limited snowfall and spring rains at the beginning of the 2016 season, all District lake and stream levels were significantly below average, especially prior to July. Detroit Lake water level was below the Ordinary High Water Level even after the spring melt, which is about.8 feet below typical water levels for that time of year, late-april-early-may. It was not until late-july, after heavy rainfalls, that the water level began to rise. Lake Melissa had a similar water measurements as Detroit Lake. Melissa water levels began at a similar level to previous years, but with the lack of spring meltwater and rainfall, the level fell gradually until the July rains began. Even with the rains, levels remained below average. 4

5 Water Quality Results Summary Water quality is the core component of the Pelican River Watershed District, it relates to the creation and ultimately to all other aspects of District activities. Central to water quality is our monitoring program of District lakes and streams. All decisions that are made regarding the activities and programs of PRWD are based on water quality data. The primary nutrient of concern in District lakes is phosphorous, which is a naturally occurring element. Increases in both urban and agricultural development can cause this nutrient to become more concentrated and increase nutrient loads to lakes and rivers. Impervious surfaces, grass clippings, pet waste, sediment, and fertilizers can all be carried by stormwater runoff to lakes and rivers, negatively impacting water quality. Phosphorous is the limiting plant nutrient in area lakes, meaning that higher level of phosphorous will provide more nutrients for algal growth. The photo to the right shows an algal bloom as a result of increased nutrient inputs due to stormwater runoff. This parameter is most commonly measured as Total Phosphorous (TP) for a water sample, which include both organic and inorganic forms. The organic portion of the Total Phosphorous is Orthophosphate (reported as OP), also known as the dissolved portion of the Total Phosphorous, which is a form of the nutrient that is most easily taken up by plants (algae). Chlorophyll-a (Chl-a) is a pigment found in all plants and is essential in photosynthesis. By measuring Chlorophyll-a, you are directly measuring the amount of algae in a sample. While algae is a natural aquatic plant, it can have negative side effects to water quality in high concentrations. Recreational activities can become unpleasant or not possible when algae blooms are present. Certain varieties of algae produce chemicals that can be toxic to humans and pets. Decomposition of dead algae can use up oxygen in the water column, making it unavailable for fish and other species, which could result in die-off. Water clarity (reported as Secchi depth) is the most easily measured and least costly parameter. Water clarity is measured using a Secchi disk; which is a white, 8-inch circle, that is lowered over the side of a boat, to observe the vertical visibility into the water. Because phosphorous is the primary driver of algal growth and increased algal growth decreases water clarity, the two parameters are strongly coupled. In most lakes, there is a direct relationship between Secchi depth and Total Phosphorous levels. Suspended solids and sediment can also have an impact on water clarity, especially following large rain events, in systems with highly erodible stream inputs. Figure 1: Results from 2016 monitoring data compared to the 20-year average of monitored lakes. Results reported are an average from annual lake monitoring data. 5

6 TSI (TP) TSI (Secchi) TSI (Chl-a) TSI Average Big Floyd North Floyd Little Floyd Little Detroit Melissa Johnson Reeves Long Fox St. Clair The results of the TSI analysis on the 2016 monitoring data show that PRWD lakes are predominantly mesotrophic (TSI 40-50) with some lakes very near, or just beyond the eutrophic threshold. The only exception for these results is St. Clair Lake, which is impaired for excessive nutrients, and has been designated a Total Maximum Daily Load (TMDL) by the Minnesota Pollution Control Agency (MPCA). Floyd Lake Floyd Lake is a 1,163 acre lake with a heavily developed shoreline. The Minnesota DNR has classified Floyd as a General Development Lake, meaning it has the least restrictive developmental standards. Floyd is divided by a natural channel into two distinct sections; the north arm of the lake is known local as North Floyd, which is significantly different from the southern Big Floyd. The lake receives water inputs from a relatively large sub-watershed area, totaling 6,291 acres, which includes the agricultural land north of the lake. The agricultural area north of the lake is drained by Campbell Creek, which is a large contributor of nutrients and sediment for the lake and has a strong effect on water quality. For water quality analysis, PRWD views these as two separate lakes, Big Floyd and Little Floyd. 6 Big Floyd At 882 acres in size, Big Floyd is significantly larger than the connected North Floyd. Big Floyd has a maximum depth of 26 feet, which also happens to be the PRWD monitoring location. There are no significant river or stream inputs to the lake. Most the surface water inputs to the lake are from stormwater runoff. The shoreline is highly developed with predominantly single family homes. There is one public access that is located on the south end of the lake. North Floyd The North arm of Floyd Lake is 281 acres in size. This part of the lake reaches 32 feet in depth. The shoreline is less developed than Big Floyd, but in recent years, previously natural shoreline areas on the north side of the lake are being developed into single family homes. Campbell Creek flows into the NE side of this lake, contributing nutrients and sediments, causing lower transparency than Big Floyd to the South.

7 Water Quality Big Floyd Lake had below average water clarity (10.9 feet compared to a 12.2-foot average) which is the lowest mean summer average since Although clarity was much less than average, the value is still within the expected range of seasonal variation. The results of the TSI analysis put the lake in the middle of the mesotrophic category, which is to be expected, and true historically for this lake. Little Floyd water clarity was better than average with a mean summer depth of 9.7 feet (8.0 foot average). Low water flow from Campbell Creek early in the summer resulted in near record clarity early in the season. Clarity was reduced following large summer rains, but average clarity was still high. The summer rains also resulted in increased runoff, and nutrient loads, causing increased total phosphorous levels. While mean summer phosphorous levels and water clarity values were slightly different than the historic average, the values were still within a range that is to be expected with seasonal variability. Little Floyd Lake Little Floyd Lake is a 214-acre lake with a moderately developed shoreline just north of the city of Detroit Lakes. In recent years, additional development has been observed in previously undeveloped land on the north and southwest shorelines. This waterbody has a small sub-watershed area, 342 acres, therefore, receives most of its surface water input by way of the Pelican River from North Floyd Lake. The outlet of this lake is controlled by a permanent concrete weir along the west shoreline continuing down the Pelican River and has a maximum depth of 34 feet. The littoral area of the lake accounts for 95 acres (45%) of the lakes area. There is an abundant native plant community, with no known invasive species. Little Floyd Lake was classified as mildly eutrophic based on the Tropic State Index for phosphorous, chlorophyll-a, and water clarity. The water quality results were slightly below average; total phosphorous and water clarity both about 10% poorer that seen historically. The results remain within a range of annual variability and there is no significant trend for overall change in water quality. Early season water clarity readings were above average. Those readings quickly fell following near record rainfall in July. Phosphorous levels were also affected by the summer rains, resulting in a 50% increase in Total Phosphorous levels between the July 15 th and July 29 th sampling dates. Nutrient levels did fall back to normal levels; however, water clarity remained poor for the remainder of the monitoring season, most likely as a result of increased nutrient and sediment inputs from stormwater runoff. 7

8 Detroit Lake At 3,067 acres, Detroit Lake is the largest lake within the PRWD, with the City of Detroit Lakes lying directly to the north. The entirety of the lake lies within the municipal boundaries of the City. As typical with urban area lakes, its shoreline is extensively developed with residential homes, commercial businesses and some industrial buildings. The Lake is divided in to two distinct parts, known locally and monitored as two separate waterbodies, Big Detroit and Little Detroit. The two are separated by a shallow gravel bar with an area to the north which had been dredged in the past to provide easy passage for watercraft. The two waterbodies typically have consistently different water clarity and nutrient levels. Historically, Little Detroit has been observed to have better water quality results than the larger and deeper Big Detroit. Big Detroit was not sampled in 2016, and water quality results for Little Detroit were slightly above average. Water clarity results were nearly 1-foot better than average (7% increase) while total phosphorous levels were slightly lower than average (8% decrease). The strong relationship between the total phosphorous level and the water clarity can be seen below. Zebra Mussels were confirmed present in Detroit Lake in August The extent of the spread is still unknown as well as the potential effect of water quality; however, it is expected that there will be an increase in water clarity, leading to increased aquatic plant growth to a greater depths. Lake Melissa Lake Melissa is the second largest lake within the District at 1,850 acres, reaching a maximum depth of 37 feet. Melissa has a highly develop shoreline, which, in recent years, has seen more development and the conversion from small, seasonal cottages, to larger, year-round homes. The Pelican River passes through the lake, entering on the north end from lake Sallie, outlet into on the south end to Mill Pond. Landcover in the Lake Melissa drainage is primarily forested and grassland (52%) with 21.3% of the land being developed and 17% used for cultivated crops. In 2014, Zebra Mussels were confirmed in the lake. The District has continued routine water quality monitoring to determine the extent of the impact they may have on water quality. Water clarity in 2016 was the second highest average on record with PRWD, only.4 feet less than the record in 2004 of 14.5 feet. The phosphorous levels were also better than average by nearly 30%, continuing a 4-year above average trend for both clarity and nutrient levels. The extent in the role that Zebra Mussels will play in the longterm trend in water quality is still unclear, but it does appear that clarity will certainly increase since their introduction. 8

9 Long Lake In 2016, water clarity and phosphorous levels were better than average. Early season drought produced minimal inputs of sediment and nutrients to the lake, resulting in very high water clarity. Clarity and nutrient levels did return to typical ranges with the onset of heavy July rains and increased stormwater runoff; however, the mean summer average values still remained better than the historic average. Johnson/Reeves Lake Johnson and Reeves are classified and sampled as two separate lakes, however, due to their proximity and connectivity, they are always sampled on the same sample rotation and exhibit similar water quality trends. Johnson and Reeves Lake are both classified as Natural Environment with moderate shoreline development, which has increased in recent years. Johnson Lake is 183 acres in size with a maximum depth of 30 feet, it outlets to Reeves Lake, which is 113 acres and reaches 43 feet deep. Both lakes are heavily bordered with a wetland fringe and floating bogs. The bogs often shift within the lake with wind a water currents, often closing the channel between the lakes. There is no public access to the lakes, however there are several small private accesses that allow many lakeshore owners to use motor boats. The drainage area has a high land to lake ratio of 136:1, and receives surface water inputs primarily from surface water runoff. The lakes are well protected with the land use being predominantly forested and grasslands, total nearly 81% of the drainage area land cover. 3.5% of the land is developed and less than 6% is used as cropland. Long Lake is a narrow lake located at the western edge of the City of Detroit Lakes, just south of Highway 10. The lake is 409 acres in size with a shoreline comprised mainly of private homes, resorts, and campgrounds. There are three protected management areas along the lake as well as a City Park. The City of Detroit Lakes annexed much of the lake, bringing sewer utilities to those areas. Landcover in the lake s drainage areas is primarily forested and grassland (57%), developed land (18%), and cultivated crops (21%). The primary surface water source is from stormwater runoff, however, there is a small stream on the north side of the lake that originates in Wine and Oar lake. Because of its large shoreline to area ratio, it is very sensitive to shoreline developmental changes. Efforts should be made to minimize stormwater runoff to the lake, maintaining shoreline vegetation, ensuring compliance of private septic systems, and reducing or eliminating fertilizer use. Water clarity on both lakes was lower than average in Johnson Lake clarity was about 1 foot lower than average while Reeves was over 2 feet below average. It is apparent that the heavy rainfall in July caused a sharp decline in water clarity and nutrient level in both lakes, while the phosphorous levels were slightly above average, both were within the range of natural variability. 9

10 Fox Lake Fox Lake is a small, moderately developed lake located just west of Lake Sallie. The lake is 143 acres in size and reaches a depth of 24 feet. It is connected to and flows into Lake Sallie to the south through a small wetland stream. Fox Lake does not have a direct inlet and receives all of the surface water input from stormwater runoff from the surrounding drainage area. Between 1966 and 1999, land use around the lake changed drastically with the amount of residential homes increasing from 24 to 55, causing increased nutrient loading and declining water quality. An Agricultural area to the north and west also lead to increased nutrient and sediment load. Most of the land once used for crop production is now enrolled in Federal Conservation programs. This dramatic change in agricultural land use, along with updated septic systems between 2002 and 2006 led to sharp increases in water clarity and quality. Currently, the predominant land use is forested and grassland, which accounts for 74.8% of the land use in the lake drainage area. 13% of the land is used for cultivated crops and 10% has been developed. Because the drainage area to lake area is small, 28 to 1, the lake is very sensitive to changes in land use. Water quality in 2016 was similar to the previous sampling cycle in 2012, and was better than average for clarity and chemistry. Summer water clarity average was 14.1 feet, a 2.8-foot increase from average. Fox Lake remained well mixed throughout the summer, with bottom temperatures always within 4 F of the surface temperatures. Oxygen levels were well mixed throughout the water column. St. Clair Lake The effects of the heavy July and August rains had a much smaller effect on Fox Lake than other area lakes. Causes for this could include the presence of the natural shoreline buffer around the lake that helps reduce stormwater runoff and should be protected whenever possible. St. Clair is a small, shallow lake located in the City of Detroit Lakes. Only about 160 acres in size, 100% of the lake area is classified as littoral. The maximum water depth is 9 feet with a mean depth of 5.2 feet. In 1915 the lake was drained from about 600 acres to its current size in an attempt to control the smell it was producing as a result of receiving sewage from the city for more than 75 years. A sewage treatment facility was constructed in 1976, which still discharged effluent wastewater to the lake. In some locations, nearly 12 feet of unconsolidated sediment is present on the lake bottom, which is consistent with nearly 125 year of receiving sewage from the City of Detroit Lakes. In an attempt to control internal nutrient loading from the sediments, the lake was treated with alum in 1998, which inhibits release of phosphorous in water from lake sediments. To help extend the life of the alum treatment and potential mixing of sediments, motorboats are not allowed except for research and data collection purposes by PRWD and the MN DNR. In 2014 the MPCA completed a Total Maximum Daily Load (TMDL) study identifying areas where nutrients input need to be reduced. The City of Detroit Lakes urban stormwater runoff was identified as a priority reduction and PRWD continues to work with the City to reduce to nutrients loading to St. Clair had the lowest water clarity and one of the highest nutrient levels (second to 2015) recorded since the alum treatment in There has been a steady decline in water quality beginning in 2010, which is consistent with the 10-year life expectancy of an alum treatment. Additional alum treatments are being explored to determine their effectiveness of further reducing internal loading. 10

11 Stream Summary There are three main stream corridors in the Pelican River Watershed District. Campbell Creek, which includes public drainage ditches 11 and 12, drains the northern portions of the Watershed. It is composed primarily of agricultural land, mixed with some forested and wetland areas. The Pelican River begins where Campbell Creek ends, in North Floyd Lake. After flowing through the City of Detroit Lakes, the Pelican River connects the major District lakes (Detroit, Sallie, and Melissa). Sucker Creek, which flows from a spring fed wetland and through a partially protected natural forested area, is the District s only designated Trout Stream. St. Clair Creek, also known as Public Ditch 14, runs though St. Clair Lake and empties into the Pelican River, just downstream from Detroit Lake. There are several other minor tributaries that make up the watershed, creating a system that is very well connected. Campbell Creek At monitoring station CC1, located at County Road 149, the District was observing the response time that the stream experiences during rain events, and how long before the stream returns to base flow. This indicates the rate at which the stormwater runoff moves across the landscape. The rain gauge at CC1 recorded over 6.5 of rainfall from July 9 to July 11. Campbell Creek responded rapidly, peaking nearly 5 feet above the stream height observed prior to the rain event. Within two days, the stream height fell over 3 feet. However, with additional summer rains, it remained well above base flow for over a month. As can be expected with drastic increase in stream levels, stream flows also increased. Between July 6 th and July 19 th, flows increased from 4 CFS to 53 CFS. During peak flow both Suspended Solids and Total Phosphorous concentration were nearly 10 times that of the samples prior to the storm event, signaling significant upstream streambank erosion. Pelican River Beaver dams and debris blockages plagued the Pelican River between the City of Detroit Lakes and the outlet of Little Floyd Lake. A total of 4 beaver dams were removed, which created high water and water backing up near some residential and agricultural areas. Downed trees and streambank erosion were caused by summer storms and created additional debris blockages requiring removal. St. Clair Creek St. Clair Creek, also known at Judicial Ditch 14, flows from St. Clair Lake, through a ditched wetland, and into the Pelican River, just downstream of Detroit Lake. Increases in phosphorous concentrations have steadily increased in recent years coming from St. Clair Lake, which is consistent with the results of the in-lake monitoring of St. Clair. A ditched wetland, just downstream from the lake, contributes additional phosphorous to the system, especially following heavy rain events. The wetland complex releases nutrients from decomposing plant matter that has been exposed to atmospheric oxygen after the ditching of the wetland. During rain event, increased water levels and flows flushes the wetland, contributing additional phosphorous to the Pelican River and Lake Sallie downstream. 11

12 Special Projects Flowering Rush Management Research 2016 was the final year of research to monitor the efficacy of the District Management Phase of the Flowering Rush Research Project. The research project began in 2010, studying the phenology and ecology of the variety of Flowering Rush that is found in the PRWD, along with herbicide trials to determine the most effective chemical to reduce the plant s population. In 2012, the most effective herbicide application protocols that were found in the study was used on a large-scale project with positive success, reducing both above and below ground plant biomass. The treatment protocol utilized a timed treatment approach, using two applications of the chemical annually, and was continued for 3 years, through In 2015, the District worked to develop new treatment protocols which would minimize the amount of herbicide used to maintain the plant population at an acceptable level. A point-intercept plant survey is conducted at each treatment site every spring to determine the extent of plant growth at that site. Treatment areas with Flowering Rush present at more than 25% of the survey points receive two herbicide applications that year. Sites with 25% or less, but more that 5%, receive one chemical application. Finally, sites with the plant present at 5% or less receive no treatment for that year. Each site is assessed for plant growth annually to determine treatment protocol thresholds. Results of the new management protocol after 2015 were positive, with reductions in both plant biomass and shoot densities for sites receiving two treatments, as expected. More importantly, sites that received only one treatment did not see any significant increase in plant biomass or shoot density. The results from the 2016 monitoring season are still being analyzed. Curly-leaf Pondweed Management Historically, PRWD had managed the in-lake Curly-leaf Pondweed infestation with the use of a mechanical harvester. In 2016 the District tried a more proactive approach. Because the plant has a unique growing cycle and grows much earlier than native pondweeds, a properly timed herbicide application can reduce the amount of invasive plant growth with minimal impact to the native species. A total of 54 acres where treated on Detroit Lake, 5.4 acres on Lake Sallie, 10 acres on Lake Melissa, 1 acre on Curfman Lake, and 3 acres on Muskrat Lake. Most of the treatment areas had positive results, the best results being the areas in less than 7 feet of water. The treatment area on Muskrat Lake was not as successful. It was found that the water current flowing through the lake does not allow for a long enough contact time of the chemical on the plant for the treatment to be effective. The District plans to continue the strategically timed application of herbicide to manage the invasive plant population. Shoreline Surveys PRWD conducts periodic assessments of the land use, lake use, and level of shoreline alteration on lots on District Lakes. In 2016, District staff completed surveys of Big Floyd, North Floyd and Little Floyd. Each parcel was documented for shoreline alterations, the use of the Shore Impact Zone (SIZ), and the amount/type of waterfront equipment. The amount of altered shoreline was documented into four categories, Natural Condition, Minimally Altered, Moderately Altered, and Greatly Altered. In 2016, North Floyd parcels were observed having altered shorelines (minimal, moderate, or greatly) at 24% of the sites, compared to Big Floyd at 88% and Little Floyd at 86% altered shorelines. The previous survey, completed in 2009, did not separate the lakes into two separate waterbodies. To compare the change over time, the results from the 2016 survey on Big and Little Floyd were combined as they were in The amount of greatly altered shoreline declined by 34 parcels between 2009 and On the other side, natural shorelines increased by 43 parcels. Moderately and Minimally altered shorelines remain very similar. The significance of this my vary due to the high level of interpretation of shoreline alteration. Protocols should be established to ensure a more consistent interpretation of the shoreline conditions. 12

13 Monitoring and documenting the type and quantity of waterfront equipment is the method that was used to observe the change in lake use over time. The information in the graph to the right shows the type of equipment that was observed per parcel on Floyd and Little Floyd. By comparing the quantity and type of equipment, assumptions can be made as to lakeshore owners use. It is apparent that Little Floyd and Big Floyd are more heavily used, with 90% of the parcels having docks. There is a positive correlation with the level of shoreline alteration and the amount of equipment per parcel. The amount of water boats and personal water craft were compared to the 2004 survey. The 2009 survey was not used in this comparison because the survey was done in late October when many of the boat had already been removed from the lake. The results of the comparison are shown below. The photos below are examples of a natural shoreline (left) and a greatly modified shoreline (right). The photo on the right was recorded to have a dock, motorboat, PWC, and two non-covered lifts (one for each watercraft). 13