State of the Lake 2009 - Tahoe Environmental Research Center ...

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Depth (feet) Depth (feet) TERC.UCDAVIS.EDU 0 50 100 150 200 250 300 350 400 450 500 PHYSICAL PROPERTIES Water temperature profile In 2008 Water temperatures are measured at six-inch intervals every two to four weeks to produce Lake Tahoe’s thermal profile. In 2008, that profile followed a typical seasonal pattern. In TAHOE: STATE OF THE LAKE REPORT 2009 early March, the lake was coldest with a uniform temperature throughout its depth. This resulted in a complete mixing from the surface to the bottom (1,645 feet), the second successive Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec year in which this happened. Thermal stratification commenced in May and peaked in late August. From September onwards, the surface layer cooled and deepened. 65 60 55 50 45 40 Temperature ( °F) 8.7
Density Difference (kilograms per cubic meter) TERC.UCDAVIS.EDU PHYSICAL PROPERTIES Density stratification Since 1970 Density stratification in Lake Tahoe has generally increased since 1970, as shown by the trend below. Each bar represents the annual average density difference between deep (100 0.10 0.08 0.06 0.04 0.02 0.00 −0.02 −0.04 −0.06 −0.08 −0.10 1970 1975 1980 TAHOE: STATE OF THE LAKE REPORT 2009 to 165 feet) and shallow (0 to 33 feet) water, subtracted from the mean density. Density differences increase as Lake Tahoe’s surface waters warm, making them less dense or lighter. 1985 1990 1995 2000 Increasing density stratification causes deep mixing of the lake to occur less frequently. 2005 8.8
Page 1 and 2: TAHOE: STATE OF THE LAKE REPORT 200
Page 3 and 4: INTRODUCTION The University of Cali
Page 5 and 6: EXECUTIVE SUMMARY (CONTINUED FROM P
Page 7 and 8: ABOUT LAKE TAHOE AND THE TAHOE BASI
Page 9 and 10: MAP OF TAHOE BASIN DATA COLLECTION
Page 11 and 12: Rainbow, Brook, Brown and Lake trou
Page 13 and 14: 100% 90% 80% 70% 60% 50% 40% 30% 20
Page 15 and 16: ASIAN CLAM Asian Clam Excretion Exp
Page 17 and 18: ASIAN CLAM Asian Clam Size Distribu
Page 19 and 20: Temperature ( o F) 60 55 50 35 30 M
Page 21 and 22: Temperature ( o F) 70 60 50 40 30 2
Page 23 and 24: Inches 70 60 50 40 30 20 10 0 METEO
Page 25 and 26: Percent 80 70 60 50 40 30 20 10 0 M
Page 27 and 28: PHYSICAL PROPERTIES TERC.UCDAVIS.ED
Page 29 and 30: Feet 6232 6230 6228 6226 6224 6222
Page 31 and 32: Temperature ( o F) TERC.UCDAVIS.EDU
Page 33: Temperature ( o F) TERC.UCDAVIS.EDU
Page 37 and 38: Mean daily streamflow (cubic feet p
Page 39 and 40: NUTRIENTS AND PARTICLES TERC.UCDAVI
Page 41 and 42: TERC.UCDAVIS.EDU NUTRIENTS AND PART
Page 43 and 44: Metric Tons TERC.UCDAVIS.EDU 10 8 6
Page 45 and 46: Dissolved inorganic nitrogen (micro
Page 47 and 48: Nitrate−nitrogen (micrograms per
Page 49 and 50: BIOLOGY 10
Page 51 and 52: BIOLOGY Algae abundance Yearly sinc
Page 53 and 54: BIOLOGY Depth of chlorophyll maximu
Page 55 and 56: BIOLOGY TAHOE: STATE OF THE LAKE RE
Page 57 and 58: BIOLOGY Nutrient limitation of alga
Page 59 and 60: BIOLOGY Shoreline algae distributio
Page 61 and 62: TERC.UCDAVIS.EDU CLARITY Annual ave
Page 63 and 64: Depth (feet) TERC.UCDAVIS.EDU CLARI
Page 65: TERC.UCDAVIS.EDU OUTREACH AND EDUCA

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