City of Seattle State of the Waters 2007 Volume II: Small Lakes State of the Waters 2007 Volume II Table of Contents Part 1 Introduction .............................................................................................1 Understanding the State of Seattle Waters.............................................................................................. 1 Contents of the State of the Waters Report............................................................................................. 2 Overview of Seattle-Area Water Bodies................................................................................................. 3 Watercourses and Streams ................................................................................................................ 3 Lakes................................................................................................................................................. 3 Estuaries............................................................................................................................................ 4 Marine Ecosystems........................................................................................................................... 4 Part 2 A Brief Primer on Lake Ecosystems..........................................................7 Lake Ecosystem Processes ..................................................................................................................... 7 Trophic Status and Eutrophication.................................................................................................... 8 7KHUPDO6WUDWL¿FDWLRQ ....................................................................................................................... 9 Lake Zonation................................................................................................................................. 10 Disruptions to Lake Ecosystems........................................................................................................... 12 Altered Hydrology.......................................................................................................................... 13 Water Quality.................................................................................................................................. 13 Sediment Quality ............................................................................................................................ 14 Sediment Dynamics........................................................................................................................ 14 Shoreline Connectivity ................................................................................................................... 14 Nonnative Species .......................................................................................................................... 15 Part 3 Assessing the State of the Waters .........................................................17 Water and Sediment Quality Assessment Methods .............................................................................. 17 Water Quality Indicators................................................................................................................. 17 Data Compilation............................................................................................................................ 18 Data Quality Assurance Review ..................................................................................................... 19 Data Analysis.................................................................................................................................. 20 Habitat Assessment Methods................................................................................................................ 24 Part 4 Conditions in Seattle’s Small Lakes........................................................25 Bitter Lake ............................................................................................................................................ 25 Water and Sediment Quality Conditions ........................................................................................ 27 Habitat Conditions.......................................................................................................................... 33 Green Lake ........................................................................................................................................... 34 Water Quality Conditions ............................................................................................................... 36 Sediment Quality Conditions.......................................................................................................... 40 Habitat Conditions.......................................................................................................................... 43 Table of Contents i City of Seattle State of the Waters 2007 Volume II: Small Lakes Haller Lake ........................................................................................................................................... 48 Water Quality Conditions ............................................................................................................... 50 Habitat Conditions.......................................................................................................................... 51 Part 5 Small Lakes Comparison and Conclusions .............................................53 Water and Sediment Quality Conditions .............................................................................................. 54 Habitat Conditions................................................................................................................................ 55 Part 6 References and Glossary ........................................................................57 References and Information Sources.................................................................................................... 57 Glossary of Terms................................................................................................................................. 61 ii Table of Contents City of Seattle State of the Waters 2007 Volume II: Small Lakes Tables 7DEOH 8VHVDQGEHQH¿WVRI6HDWWOHODNHVDQGZDWHUTXDOLW\LQGLFDWRUVRIODNHFRQGLWLRQV............18 7DEOH :DWHUTXDOLW\GDWDVRXUFHVIRU6HDWWOH¶VVPDOOODNHV............................................................19 7DEOH %HQH¿FLDOXVHGHVLJQDWLRQVDSSOLFDEOHWR6HDWWOH¶VVPDOOODNHVXQGHUVWDWH ZDWHUTXDOLW\VWDQGDUGV ........................................................................................................21 7DEOH 7URSKLFVWDWHLQGH[YDOXHVXVHGWRDVVHVVODNHZDWHUTXDOLW\FRQGLWLRQV.............................22 Table 5. Bitter Lake metals concentrations sampled during a storm event compared to human health risk criteria. ....................................................................................................29 Table 6. Bitter Lake organic compounds detected in stormwater samples. .......................................29 Table 7. Bitter Lake sediment metals concentrations compared to freshwater sediment guidelines..............................................................................................................................30 Table 8. Bitter Lake sediment organic compounds concentrations compared to freshwater sediment guidelines. ...........................................................................................31 7DEOH *UHHQ/DNHZDWHUTXDOLW\GDWDIRU0D\±6HSWHPEHU...................................................38 7DEOH*UHHQ/DNHVXPPHUIHFDOFROLIRUPEDFWHULDOHYHOV± .........................................39 Table 11. Green Lake sediment metals concentrations compared to freshwater sediment guidelines. .............................................................................................................41 Table 12. Green Lake sampling stations with exceedances of freshwater sediment guidelines. .............................................................................................................42 Table 13. Green Lake sediment organic compounds concentrations compared to freshwater sediment guidelines....................................................................................... 44-45 Table 14. Haller Lake drainage sample results from Meridian storm drain compared to other Seattle stormwater data. ..........................................................................................51 7DEOH&RPSDULVRQVRIZDWHUTXDOLW\DQGVHGLPHQWTXDOLW\FRQGLWLRQVLQ6HDWWOH¶V small lakes. ...........................................................................................................................53 7DEOH/LVWLQJVRI6HDWWOH¶VVPDOOODNHVDVWKUHDWHQHGRULPSDLUHGZDWHUERGLHV under Clean Water Act Section 303(d). ................................................................................54 Figures Figure 1. Seattle small lakes. .................................................................................................................5 Figure 2. Conceptual model of oligotrophic and eutrophic lake ecosystems. .......................................8 Figure 3. Conceptual model of the seasonal thermocline in lakes.........................................................9 Figure 4. Bitter Lake. ...........................................................................................................................26 )LJXUH %LWWHU/DNHZDWHUTXDOLW\PRQLWRULQJGDWDVXPPDU\IRU±