Big Bear Municipal Water District. Lake Operations Summary

Transcription

1 Big Bear Municipal Water District Lake Operations Summary 2018

2 Big Bear Municipal Water District 2018 Lake Operations Summary The mission of the Big Bear Municipal Water District is to Manage the Lake for recreation and wildlife Big Bear Lake, Lake Management operations, in support of the Districts mission, consists of a multitude of management activities. This document serves as a summary of three broad activities; lake level stabilization, limnological monitoring, and invasive species management. Lake Level Stabilization The 2018 season began with below normal lake-levels. On January 2, 2018 the Lake was down feet. After the winter season was complete, the Lake reached feet below full on March 28, 2018 (Figure 1) before beginning to drop again. There was little rain and very little snowpack which led to low spring snow melt flows and a low lake level at the start of the 2018 boating season. Over the 2018 summer season, the lake level was a few feet below the average lake level over the 2017 boating season. The 2018 boating season ended with the lake at feet below full. The lake reached its lowest level on November 28 th at feet below full. The District paid Valley District $1,476,043 in 2018 in accordance with the 1996 in-lieu agreement to help stabilize the level of Big Bear Lake. There were no additional water releases in 2018 beyond the fish release requirement for Bear Creek. Historical lake levels can be viewed on the District web page. Figure 2 depicts lake levels from Figure 1 1 P age

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4 Limnological Monitoring District Staff weekly measure the Lake s limnological properties during the boating season (May- November) at 5 monitoring stations across the Lake. Measurements of the Lake s temperature and dissolved oxygen are taken using a YSI 556 MPS meter. Water clarity is also measured at each monitoring station using a Secchi Disk. The charts below (Figures 3, 4, and 5) show surface, mid depth and bottom water temperature and dissolved oxygen content for each of the five Lake monitoring stations (1=Boom Line, 2=Papoose Bay, 3=West Ramp, 4=Observatory and 5=Juniper Point). The District compiled and created graphs for a ten-year rolling period of the limnological properties of the Lake to compare trends. These graphs are located in the appendix of this report. Temperature Fig Surface Temperature and Dissolved Oxygen Dissolved Oxygen Station 1 TEMP Station 2 TEMP Station 3 TEMP Station 4 TEMP Station 5 TEMP Station 1 D.O. Station 2 D.O. Station 3 D.O. 3 P age

5 Temperature Fig Mid Range Temperature and Dissolved Oxygen Dissolved Oxygen Station 1 TEMP Station 2 TEMP Station 3 TEMP Station 4 TEMP Station 5 TEMP Station 1 D.O. Station 2 D.O. Station 3 D.O. Temperature Fig Bottom Temperature and Dissolved Oxygen Dissolved Oxygen Station 1 TEMP Station 2 TEMP Station 3 TEMP Station 4 TEMP Station 5 TEMP Station 1 D.O. Station 2 D.O. Station 3 D.O. 4 P age

6 Typically as the Lake surface warms, the Lake stratifies with cold dense oxygen depleted water forming a layer below the relatively warmer, less dense, oxygenated water above. Later in the year, surface and bottom water temperatures typically equilibrate and the waters mix bringing oxygen depleted and nutrient laden water up into the water column to spur algae growth. Water clarity drops dramatically and water column oxygen is also diluted when this occurs. Table 1 lists the dates that the Lake has mixed. Mixing typically occurs in late August or early September. The 2018 season saw normal states of stratification and mixing. The Lake first began to stratify in mid-june and remained slightly stratified by from late-june to mid-august. Around August 10, 2018 the Lake showed signs of de-stratification and slight mixing. On August 27, 2018, the entire Lake was completely mixed and showing uniform temperatures throughout the entire waterbody. By September 9, 2018 the lake began to lightly stratify until October 1, 2018 when the lake mixed thoroughly and remained mixed though the end of the year. Due to the timing of the Lake s mixing in 2018, algae rates were higher during those times. However, physically, aesthetically, and recreationally, the lake was not adversely impacted with algae growth. Temperature is the main variable effecting lake stratification and mixing. Other variables such as heavy winds and low lake level may help contribute to mixing. The 2018 season saw a more mixed Lake throughout. Given the amount of time the lake was mixed, and the amount of available nutrients in the water column, it was amazing to see a lake which have very little impact from algae growth. Winds may have helped keep the physical appearance of algae down since algae sinks and scatters when the wind blows the surface of the water. However, the lack of algae blooms was likely due to the aluminum sulfate treatment in This treatment capped available nutrients in deeper portions of the lake which reduced nutrient flux rates between the lake sediment and the water column. With those additional sediment nutrients made unavailable, algae did not have a sufficient means of nourishment to create a lake-wide bloom. Because of the low lake levels and very little inflow of new nutrients, previous populations of algae in years past, and aquatic vegetation may have been sequestering available nutrients which reduced algae populations this season. The conditions for algae were ripe this year, and the main variable on the lower populations of algae this season was nutrient availability. Surface water temperatures peaked on August 6, 2018 with degrees Fahrenheit at the west end and on July 23, 2018 with degrees Fahrenheit at the east end of the lake. Throughout 2018, the temperature differed by degrees Fahrenheit on average from the west to the east end. Lake temperatures normally varied from the mid-60s to low-70s at both the west and east ends of the Lake. Secchi readings vary widely year to year over the spring and summer months when the Lake is stratified. In 2018, Secchi depths maxed between July 9 and July 23, The depth readings become shallower as the season proceeds due to algal growth and mixing. Figure 6 is a chart showing average weekly Secchi water clarity results in P age

7 12 Fig Secchi 10 Depth in Feet Station 1 Station 2 Station 3 Station 4 Station 5 Year Table 1 Lake Mixing History Date Lake Mixed 2018 June 3, August 10-15, October 1 (close to not stratifying all year) 2017 August 14, September August 22, September Late June-Early July, Mid October 2014 Mid-August/Mid-September 2013 August 2012 Lake did not stratify 2011 September 6 and June September June 12 and August August August August September Lake did not stratify The District installed a Lake aeration system in the summer of The decision to purchase and install the system was the result of low lake levels, warm water temperature, high concentrations of algae and low dissolved oxygen content when the Lake is stratified. High Lake water temperatures and low dissolved oxygen concentrations stressed trout species, sometimes resulting in fish die off in large numbers. Table 2 provides a qualitative summary of fish die off prior and subsequent to the installation of the aeration system. 6 P age

8 Table 2 Big Bear Lake Fish Die Off History Year Qualitative Die Off of Trout Comments 2018 Insignificant 2017 Insignificant 2016 Insignificant 2015 Insignificant 2014 Insignificant 2013 Insignificant 2012 Insignificant 2011 Insignificant 2010 Insignificant 2009 Insignificant 2008 Insignificant 2007 Insignificant 2006 Insignificant 2005 Insignificant Sept New aerator is installed 2004 Very Significant per week 2003 Very Significant per week 2002 Significant per week 2001 Moderate per week 2000 Moderate per week 1999 Moderate per week 1998 Minor per week 1997 Minor per week 1996 Minor per week The system is a stationary floating 25 horse power pump located between the boom line and the dam that draws Lake water and discharges it into the air at the rate of 8600 gallons per minute. The water cools and is oxygenated as it falls through the air before returning to the Lake. The result is an approximate 40 acre oxygenated, cooler water refuge for trout fish species. Although the system typically operates during the cooler night and early morning hours, under extreme problematic conditions it is run 24 hours a day. Since installation and operation of the aeration system no significant fish die offs have occurred. Invasive Species Management The Invasive Species Management program can be broken down into 3 major activities; aquatic plant control, carp removal and quagga mussel prevention program. Aquatic Plant Control Activities associated with aquatic plant control have two components. Milfoil specific herbicides are commonly used to treat areas infested with Eurasian Water Milfoil. Native aquatic plant species are 7 P age

9 typically controlled mechanically using a weed harvester. Cuttings are delivered to a composting facility operated by the City of Big Bear Lake. Harvesting operations are used to maintain navigation channels and boat dock lake access. By harvesting and removing milfoil, the District receives credit by the Santa Ana Regional Water Quality Control Board for phosphorus and nitrogen TMDL reduction targets. The District has made considerable progress in reducing the population of milfoil plants in the Lake compared to the baseline year 2000 when more than 1000 acres of the lake were infested. Figure 7 is a chart summarizing acres of Milfoil mapped each year. Figure 7 Three methods of herbicide application are used. Each of the application methods utilizes a pontoon boat and two Lake Maintenance employees. The boat driver uses a GPS mapping system to assure applications are made within the mapped boundaries and at the prescribed concentrations. Large areas are treated using vortex physics of water pumped through an eductor nozzle at pressure to draw dry product from a hopper to mix granular herbicide with Lake water and spray it onto the Lake surface. Nozzles installed on either side of the back of the weed harvester barge distribute product in swaths 30 feet wide as the barge moves through the milfoil infested littoral zone. Metering of product delivery in this unit is based on the known delivery rate of the equipment and the speed of the barge moving through the infested area. The other method employs vortex physics but uses air instead of water. Typically called the Vortex by the District, this method is used for smaller more pinpoint applications. The unit has a blower that moves air across the bottom opening of a funnel shaped hopper. The air draws the product out of the hopper and is then directed through a hose to a hand held control and nozzle. Metering with this unit is based on an even distribution of a preloaded quantity of product in the hopper and the known dimension of the area to be treated. The liquid herbicide application is made 8 Page

10 below the water surface by injection from submerged discharge hoses. An electric metering pump draws herbicide from storage through calibrated hose nozzles trailing from the back of a moving work boat. In all cases application rates are computed using label instruction for plant species, treatment area and water depth and are in accordance with the District s Aquatic Pesticide Application Plan/NPDES permit. In 2018, two small herbicide applications were made. For both events, the herbicides used were a mixture of triclopyr and endothall. Most plant control came from harvesting in The reasons are given below. On odd-years, the District conducts a detailed density survey of aquatic vegetation within Big Bear Lake. Being an even-year, weed growth in 2018 was surveyed but density counts were not performed. The District had knowledge of what species were present in the lake and where they would likely create problems. The bigger concern came from the Lake s level and nutrient loading. The Lake s highest level in 2018 was at feet (14.60 feet below full) which occurred on March 28th. Because of the drought conditions and far below average winter, the District expected the Lake to drop approximately three and a half (3.5) feet over the summer months of The total range of lake level was 3.86 feet March 28 to November 28. The actual lowest lake level in 2018 occurred on November 28, 2018 at feet below full. Beginning the 2018 season at lower than average level, the District made an informed proactive decision to sparsely treat with aquatic herbicides for the 2018 season. Similar to the 2016 and 2017 season, the District feared that chemically treating the Lake s aquatic vegetation would result in heavy nutrient loading from the decaying vegetation. These decaying byproducts would be added to an already nutrientsaturated half-full lake, which could result in a massive algae bloom(s). The District weighed the options and decided it would be worse to have a massive algae bloom (possibly a harmful algae bloom HAB ) than to have the presence of more nuisance aquatic vegetation left in the Lake. Furthermore, the presence of more aquatic vegetation in the water column would help absorb some of the water s nutrients. The District conducted an alum treatment in May-June The legacy effects of the alum treatment would be better preserved if more nutrient was not added to the water column or the lake bottom. It was decided that the District would mechanically harvest and remove nuisance species rather than treat with herbicides. Though the District focused on utilizing heavy harvesting rotations, there were minimal treatments in No scalable treatment events occurred. Spot treatments were made only at marinas. The cost of herbicide used for spot treating the marinas totaled $1024. Employee expenses, fuel and depreciation for the 2018 program came to $ for a 2018 total program cost of $1,714. The District harvested heavily from June 15, 2018 to September 15, The District took calls from the public and surveyed the Lake daily to schedule and plan the logistics of the mechanical harvester. Because of the Lake s low level, only one launch ramp was accessible to off-load the harvester s cuttings to a dump truck. The limited ramp access made harvesting extremely time consuming for the summer season. A full harvester can only travel two (2) miles per hour, so cutting nuisance vegetation at one end of the Lake and transporting the cuttings to the ramp at the other end of the Lake proved to be a slow operation. This in turn diminished the amount of nuisance vegetation that could be cut. 9 P age

11 Though transportation was time-consuming, this year saw good control of Eurasian Water Milfoil, coontail, and widgeon grass by manually harvesting. In 2018, 54 acres were mapped and harvested, shown in Figure 8 below. There were 81 loads of aquatic vegetation removed by the District s harvester. These 81 loads totaled tons (553,800 lbs.) of wet-weight vegetation or tons (54,272 lbs.) of dry-weight vegetation. As plants are harvested the operator notes the species collected during his run. Using the weight and species of aquatic plant and average phosphorous and nitrogen content based on previous sampling and laboratory analysis results for each species, the District estimates total phosphorous and nitrogen removed by the harvesting operation each year, summarized in Table 3 below. Of the 2018 totals, approximately 163 lbs. of phosphorus and 1,357 lbs. of nitrogen were removed from the Lake. Weed harvesting expenses, including labor, fuel and depreciation, totaled $15,420. Table 3 Harvestor Totals Wet Weight Vegetation HARVESTOR TOTALS Dry Weight Vegetation Phosphorus Nitrogen LBS 553, , , TONS Figure 8 10 P age

12 Harvesting in 2018 was successful. Granted the lake level was low, the Lake was low to moderately impacted by milfoil and other nuisance aquatic macrophytes. Though 2018 saw less mappable and harvested acres than This is simply due to lower lake levels as lake levels drop there is less and less photic zone area for aquatic species to grow. The Lake experienced no significant algae blooms. There was no biological or recreational impairment due to algae during the 2018 season. This was in part due to: 1) allowing more aquatic macrophytes to remain in the water column helped to absorb nutrients that would have otherwise been available for algae growth, 2) the legacy effect of the 2015 alum treatment, and 3) continuous microscopy monitoring of the water column for algae types and cell counts with the District s FlowCam microscope. There was slight aesthetic impairment at times in some back bays during hot, calm days. However, as soon as wind picked up, the algae disappeared. Water samples were taken through-out the summer season: Table 4 FlowCam Algae Sampling Events FlowCam Algae Sampling Events Date Location Sample Runs 7/9/2018 TMDL 1 (Dam) 5 7/13/2018 Big Bear Marina 4 7/25/2018 West Ramp 1 7/26/2018 East Ramp 4 8/20/2018 TMDL 1 (Dam) 3 9/19/2018 Big Bear Marina 3 10/3/2018 Big Bear Marina 11 10/25/2018 TMDL 6 (Mid Lake) 4 10/26/2018 TMDL 6 (Mid Lake) 3 Carp Removal After observing the effectiveness of electro-shock fishing for Carp by a District contractor in 2007 the District purchased an electro-shock boat in 2008 and installed a commercial grinder placed over a sewer manhole in Shocked carp are netted and after the boat is filled they are ground up and disposed of in the sanitary sewer at the back of the District shop. The Big Bear Area Regional Wastewater Agency (BBARWA) charges the District $150 for every 1000 pounds of Carp discharged to the sewer. Electro-shock fishing began June 15, 2018 and continued to September 15, However due to mechanical problems with the generator on the electro-fishing boat, the District was unable to electrofish very many carp in the summer of The annual Carp Round-up event also removes carp from the lake. Cash and prizes are awarded for winners in the various divisions. Bow hunters came from California and the southwest to compete in this District sponsored event on the weekend of June 16-17, Including the 1,489 pounds of carp shot during the Carp Round-up, the District removed a total of 2,289 pounds of carp during summer Expenses for the carp removal program including the grinder, wages, fuel costs and BBARWA charges for carp disposal in 2018 totaled $289. Fish surveys conducted by the California Department of Fish and 11 P age

13 Wildlife indicate that the District s carp removal program has dramatically improved game fish populations. Table 5 and Figure 9 show the District s Carp removal statistics from Table 5 Carp Removal Statistics Year Carp Tournament (lbs) Electro Shock Fishing (lbs) Total Pounds Removed Cost (approx.) , ,289 $ ,327 9,890 13,217 $3, ,438 4,950 7,388 $2, ,913 32,800 41,713 $10, ,443 10,700 15,143 $4, ,931 7,050 10,981 $3, ,115 18,955 23,070 $10, ,000 20,491 31,491 $7, ,128 39,350 49,478 $14, ,350 36,000 42,350 $12, ,200 26,000 30,200 $8, ,119 96, ,119 $96,000 Figure 9 Quagga Mussel Prevention Program Starting with the boating season of 2008, the District implemented a quagga mussel prevention program aimed at preventing the spread of quagga mussels in Big Bear Lake. The general policy is clean, drained and dry before a vessel can launch. If a vessel does not meet these criteria, the vessel will be decontaminated at one of our public launch ramps. Private marinas along the lake are required to have 12 P age

14 a level 1 certified quagga mussel inspector available to inspect boats prior to launch. If they encounter a vessel that does not meet the criteria, they are sent to one of the public launch ramps for decontamination. The District has 3 decontamination stations. The East Ramp and West Ramp handle the bulk of the decontaminations. The third station is located at the District s main office and is only run on holidays or special events. The decontamination is conducted by flushing suspect areas of the vessel with hot water. The entire process can take as little as 5 minutes or up to 45 minutes depending on the size of the vessel and level of decontamination. In the spring of each year, the District s Level III quagga mussel inspection trainers conduct a Level I quagga mussel training class to certify new and returning inspectors. The class is a free-of-charge all-day course for both private marina employees and District staff. The District was awarded $400,000 in grant money for a Quagga/Zebra Mussel Prevention grant through the Department of Boating and Waterways in April This money funded projects and costs for 2016 seasonal ramp personnel salaries, doubling the decontamination capacity at the East Ramp by adding an additional decontamination pad and decontamination unit, purchasing new efficient and safer operating propane fired/electric driven decontamination units for the East and West launch ramps, implementing a more robust and secure reciprocal banding program, upgrading the District s phone system to include a quagga hotline for the public, and training our inspection staff to be Level II quagga inspectors with the new training material and protocol. The District was awarded an additional $345,000 under the same program in early 2017, which funded seasonal ramp personnel and operational costs, decon unit replacement parts, signage and training material, more banding supplies, and a FlowCam to monitor the Lake for quagga mussel veligers. In late 2017, the District was awarded an additional $385,000 to cover seasonal ramp personnel and operational costs, constructing a new enclosure at the Eat Ramp to house the new decontamination units, and purchase more banding supplies. The District consistently monitored water for the presence of quagga mussels in Big Bear Lake. If quaggas were found in Big Bear Lake early enough, the District could do its part to contain the quagga or zebra mussels so they would not contaminate any other neighboring body of water. The District sent water samples to the California Department of Fish and Wildlife Bodega Bay Shellfish Laboratory for analysis and samples were proven negative by the State. Furthermore, the District monitored for quagga mussels using cross-polarized light microscopy with the District s flow cam. Samples were collected and tested on the following dates (all results were negative): 13 P age

15 Table 6 Plankton Tow Sample Sheet 2018 Quagga Plankton Tow Sample Sheet for FlowCam Cross-Polarized Microscopy Date Location Sample Runs Positive/Negative Sampled By Analyzed By 7/9/2018 TMDL 1 (Dam) 5 Negative James Bellis James Bellis 7/13/2018 Big Bear Marina 4 Negative James Bellis James Bellis 7/25/2018 West Ramp 1 Negative James Bellis James Bellis 7/26/2018 East Ramp 4 Negative James Bellis James Bellis 8/20/2018 TMDL 1 (Dam) 3 Negative James Bellis James Bellis 9/19/2018 Big Bear Marina 3 Negative James Bellis James Bellis 10/3/2018 Big Bear Marina 11 Negative James Bellis James Bellis 10/25/2018 TMDL 6 (Mid Lake) 4 Negative James Bellis James Bellis 10/26/2018 TMDL 6 (Mid Lake) 3 Negative James Bellis James Bellis Also, the District monitored multiple substrate locations weekly in Other locations were checked for presence of quagga mussels throughout These areas include boats exiting the launch ramp, District vessels during maintenance, District docks, the face of the Bear Valley Dam, and random shoreline areas during dock inspections. All instances of substrate and other inspections came back negative in Because Big Bear Lake is still quagga/zebra free, the District is eligible to apply for further quagga/zebra prevention grant funding. The District intends to apply for more funding through the Department of Boating and Waterways Quagga/Zebra Mussel Prevention program as opportunities become available. The District employs 11 seasonal ramp attendants whose job is to inspect and decontaminate vessels as they arrive at the public launch ramps. In total, the District launched 7,758 boats in the 2018 boating season. Of these, 4,707 were inspected at the public launch ramps. Of this number 2,556 vessels were clean and no decontamination was necessary and 2,151 vessels were decontaminated. A total of 3,051 boats were banded. Figure 10 below depicts the lake use statistics for P age

16 Figure 10 Lake Use Statistics Big Bear Lake Lake Use Statistics MEMORIAL DAY THRU LABOR DAY MON-FRI DAILY AVERAGE BOAT COUNT MON-FRI MORNING MON-FRI AFTERNOON WEEKEND DAILY AVERAGE BOAT COUNT WEEKEND MORNING WEEKEND AFTERNOON MEMORIAL DAY THRU LABOR DAY MON-FRI DAILY AVERAGE SHORELINE USERS MON-FRI MORNING MON-FRI AFTERNOON WEEKEND DAILYAVERAGE SHORELINE USERS WEEKEND MORNING WEEKEND AFTERNOON APRIL-SEPTEMBER TOTAL VESSEL LAUNCHED EAST RAMP WEST RAMP APRIL-SEPTEMBER TOTAL VESSEL INSPECTION EAST RAMP WEST RAMP APRIL-SEPTEMBER TOTAL VESSEL DECONTAMINATED EAST RAMP WEST RAMP APRIL-SEPTEMBER TOTAL VESSEL CLEAN EAST RAMP WEST RAMP APRIL-SEPTEMBER TOTAL VESSEL BANDED EAST RAMP WEST RAMP ANNUAL PERCENTAGE OF USE: AM PRIVATE BOATS PRIV STILL FISHING 10% 11% 12% 18% 20% 20% 13% 16% 16% 14% 15% 14% PRIV TROLLING 24% 23% 25% 29% 30% 26% 15% 16% 12% 16% 12% 9% PRIV SKIING 10% 11% 10% 13% 10% 9% 5% 6% 7% 6% 6% 5% PRIV SAILING 0% 0% 1% 0% 0% 1% 1% 1% 1% 1% 1% 2% PWC 9% 8% 8% 8% 8% 7% 10% 11% 12% 12% 12% 12% PRIV OTHER 13% 17% 15% 16% 16% 18% 15% 15% 20% 20% 20% 28% TOTALS 66% 70% 71% 84% 84% 81% 59% 65% 68% 69% 66% 70% AM PM RENTAL BOATS RENT STILL FISHING 5% 4% 5% 4% 4% 7% 8% 6% 8% 7% 7% 5% RENT TROLLING 17% 15% 15% 9% 8% 7% 15% 15% 12% 10% 8% 4% RENT OTHER 11% 12% 9% 3% 4% 5% 17% 15% 12% 14% 19% 22% TOTALS 33% 31% 29% 16% 16% 19% 40% 36% 32% 31% 34% 31% PM AM PM ACTIVITY USE FISHING 56% 52% 58% 59% 61% 60% 51% 52% 48% 46% 41% 32% OTHER ACTIVITIES 44% 48% 42% 41% 39% 40% 49% 48% 52% 54% 59% 68% INSPECTION TOTALS CLEAN 33% 39% 28% 23% 21% 22% DECON 28% 31% 23% 22% 19% 18% BANDED 39% 30% 72% 55% 60% 60% 15 P age

17 Summary of 2018 Lake Management Operations Expenses In Lieu Agreement $1,476,043 Herbicide Treatment $1,714 Weed Harvesting $15,420 Carp Removal and Disposal $498 TOTAL $1,493, P age

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