Utah Lake Watch Report 2009

Utah Lake Watch Report 2009 Utah State University Water Quality Extension Prepared by: Eric Peterson 1 Introduction As a statewide monitoring program, Utah Lake Watch (ULW) enlists the help of volunteers to collect data used to evaluate the general condition of Utah’ s lakes and reservoirs and how that changes over time. The data collected are used by the Utah Division of Water Quality and lake managers to determine whether the lake’s water quality is good enough to support the benefits that our lakes provide, such as recreational uses, fisheries and esthetic benefits. This report discusses the water transparency data (Secchi depths) and other related data collected in 2009 by citizen monitors throughout Utah. In 2009, USU’s Water Quality Extension program also conducted a pilot study on the use of citizen volunteers to collect bacterial data. The results of the pilot study will be reported in a separate document. Major objectives of the program include: •acquiring baseline data for Utah’s lakes and reservoirs; •providing education to state citizens on the importance of healthy lakes, how lakes function, and how to monitor lakes; and •demonstrating the effectiveness of citizen monitoring in collecting water quality data which can be used to better manage and protect our lakes and reservoirs To mee t these o bjecti ves parti ci pan ts are t rai ned to measure th e transparency an d make some simple observations for a particular lake or reservoir. Transparency correlates to other indicators of a lake’s condition, such as the amount of suspended algae growing in the lake, the amount of nutrients entering the lake, and the seasonal patterns of plant growth. Methods Utah Lake Watch participants measure transparency using a Secchi disk. A Secchi disk is a white and black weighted disk attached to a line which is lowered into the water until it is no longer visible. The line is pulled slowly back up and the depth at which the Secchi disk reappears is recorded. This is referred to as the “Secchi depth.” Although the measurement is quite simple, in most cases the volunteer needs a boat to get to the location in the lake established by the Utah Division of Water Quality. Each volunteer is trained by USU Water Quality Extension. This training takes place at the lake or reservoir the volunteer will be monitoring. The training consists of a brief introduction to the Lake Watch program and its goals, followed by a demonstration of how to take a Secchi measurement, which is usually done from a boat dock for the training. 2 Volunteers are encouraged to take measurements on a regular basis from May until September. When these Secchi depths are taken at regular intervals throughout a summer, a picture of the seasonal changes in lake turbidity emerges. Secchi depths collected over multiple years can indicate whether a lake’s trophic state is changing over time. The participants record the Secchi depths and other simple observations on a data sheet, and return the data to USU Water Quality Extension at the end of the season. USU Water Quality Extension compiles the raw data, and summarizes all the findings into an annual report. The report and data are delivered electronically to the Utah Division of Water Quality. USU Extension also sends the individual lake summaries to the citizen volunteers. Results Because we depend entirely on volunteers, not all lakes are monitored each year. Since 2002, 37 different waterbodies have been monitored by Lake Watch volunteers (See Appendix B). Annual reports may be obtained by contacting USU Water Quality Extension, Utah Division of Water Quality, or on the USU Water Quality Extension website at www.extension.usu.edu/waterquality. In 2009, 13 lakes and reservoirs were successfully monitored. The results for each monitori ng event i n 2009 are separa te ly disp laye d for eac h in div idua l la ke or reservo ir in this report. In addition, all raw data collected by the 2009 volunteers is included in Appendix A. Figure 1 displays the average Secchi depth for each waterbody monitored in 2009, and Table 1 includes additional information about each waterbody. Bear Lake Site 1 had the maximum average depth for 2009 at 6. 3 meters, while Starvation Reservoir recorded the maximum individual reading with 8.3 meters. The minimum average depth was 0.32 meters at Utah Lake Site 2, which also recorded the lowest individual reading of 0.20 meters. The number of samples at each site varied, as well as the dates of collection as seen in Table 1. Discussion Lake transparency is a measure of how many tiny particles are suspended in the lake water. In most lakes these particles are primarily microscopic plants called algae. These algae increase and decrease throughout a year, as the plants grow and die. The maximum amount of algae each year is related to the nutrients in the reservoir, because these nutrients feed the plants. Most of these nutrients enter a lake through tributaries or through erosion or resuspension of sediments within a lake. 3 Average Secchi Depth Lake/Reservoir 0 1 2 3 epth (meters) 4 5 Secchi D 6 7 Figure 1. Average Secchi measurements for each lake or reservoir monitored in 2009 by ULW volunteers. 4 Table 1. Maximum, minimum, and average depths, along with the number of measurements collected at each site and the months of collection at the site. Number of Average Measurements Months of Lake / Reservoir Max (m) Min (m) (m) Collected Collection Bear Lake 1 7.50 5.10 6.30 6 June-September Bear Lake 2 3.15 2.40 2.93 12 May-August Burreston Pond 2.00 2.00 2.00 1 August Causey Reservoir 5.60 2.50 3.50 3 June-August Deer Creek Reservoir 6006.00 3603.60 5005.00 6 June-September Grantsville Reservoir 2.55 2.55 2.55 1 July Hyrum Reservoir 1.60 1.40 1.50 3 August-September Otter Creek Reservoir 2.20 1.25 1.64 5 July-August Pineview Reservoir 1 5.60 4.30 4.77 6 July-September Pineview Reservoir 2 5.70 2.10 4.30 8 May-September Red Fleet Reservoir 2.80 0.90 1.83 7 June-September Starvation Reservoir 8.30 2.20 5.10 15 April-September Steinaker Reservoir 4.50 2.10 3.10 7 June-September Utah Lake 1 0.41 0.24 0.33 4 June-August Utah Lake 2 0.40 0.20 0.32 3 June-July Yuba Reservoir 1.65 0.77 1.30 7 June-August 5 Eutrophication, or lake aging, is a natural process by which a lake fills in over thousands of years, mostly from eroded materials carried by the tributary streams, with the remains of plants and animals produced in the lake itself and other sources. Cultural eutrophication occurs when human influences increase the nutrients entering the lake from a variety of new sources, such as direct discharge of sewage, septic tank leakage, and runoff from areas affected by human development, such as agricultural lands, logged or mining areas, and urban areas. These increased nutrients cause excessive plant growth. Dissolved oxygen in the lake is consumed when these plants die and decay. This can lead to fish kills and loss of game fish, taste and odor problems if the water is treated for culinary purposes, loss of recreational value of the lake if weeds hinder boats and water skiers, and aesthetic problems from turbid water or decaying material on the shores. Scientists often classify lakes according to the degree of eutrophication. One commonly used system is called a “Trophic State Index” or “TSI”, developed by Carlson in 1977. Carlson developed this index by collecting data from hundreds of lakes and comparing nutrients in the lake with the microscopic algae concentrations and average Secchi depth. Table 2 summarizes the classification of lakes by trophic state index. This simplified system allows lake managers and scientists to compare lakes with each other and to evaluate changes in a lake over time. VlVolun teers are encourage dtd to tktake measuremen ts on a regu lar bas is from May un til September. When these Secchi depths are taken at regular intervals throughout a summer, a picture of the seasonal changes in lake turbidity emerges. Secchi depths collected over multiple years can indicate whether a lake’s trophic state is changing over time. Classification Definition Secchi Depth Chl TP TSI (m) (μg/L) (μg/L) Oligotrophic A waterbody having low turbidity and > 4 abundant dissolved oxygen (i.e. good < 2.6 < 12 < 40 water quality). Mesotrophic A waterbody having moderate turbidity and moderate dissolved oxygen (i.e. 2-4 2.6-7.3 12-24 40-50 moderate water quality). Eutrophic A waterbody having high turbidity and low dissolved oxygen (impaired water quality). 0.5-2 7.3-56 24-96 50-70 Hypereutrophic A waterbody that is extremely turbid and exceptionally low in dissolved oxygen (i.e. < 0.5 > 56 96-384 > 70 very poor water quality). Tbl2Table 2. ThiTrophic Sta te Class ifica tions (Car lson, 1996), wh ere Chl is the Chlorop hy ll concen tra tion, TP i s the Total Phosphorus concentration, and TSI is the calculated value of the Trophic State Index. 6 In this report, we converted the average Secchi depth to a TSI value. This value can be somewhat confusing because as the Secchi depths get smaller, the TSI values get larger. Several lakes and reservoirs monitored have relatively low TSI values including Bear Lake, Deer Creek, Starvation, Pineview, Causey, Steinaker, and Grantsville Reservoirs.

Load more