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

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Depth (feet) TERC.UCDAVIS.EDU 0 200 400 600 800 1000 1200 1400 1600 PHYSICAL PROPERTIES Depth of mixing Yearly since 1973 Lake Tahoe mixes each winter as surface waters cool and sink downward. In a lake as deep as Tahoe, the wind energy of winter storms helps to determine how deeply the lake mixes. Mixing depth has profound impacts on lake ecology and 1973 1975 1977 1979 1981 1983 1985 1987 1989 TAHOE: STATE OF THE LAKE REPORT 2009 water quality. Deep mixing brings nutrients to the surface, where they promote algae growth. It also moves oxygen to deep waters, promoting aquatic life throughout the water column. The deepest mixing typically occurs in late February to early March. 1991 1993 1995 1997 1999 2001 2003 2005 2007 In 2008, Lake Tahoe mixed all the way to the bottom at the mid-lake station. This was the second successive year of deep mixing. Complete mixing during two or more successive years has only occurred three times since 1973. 2009 8.9
Mean daily streamflow (cubic feet per second) TERC.UCDAVIS.EDU PHYSICAL PROPERTIES 450 400 350 300 250 200 150 100 50 0 Truckee River at Tahoe City Upper Truckee River TAHOE: STATE OF THE LAKE REPORT 2009 Upper Truckee River vs. Truckee River Mean Daily Streamflow Water Year 2008 The seasonal pattern (hydrograph) for the Upper Truckee River, as it flows into Lake Tahoe, was dominated by the annual snowmelt that occurs in the spring. In 2008, discharge peaked in mid-May. The low measured flow in the period October to February reflects the lack of significant rainfall, common for dry years such as 2008. The annual pattern of flow leaving Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Lake Tahoe via the Truckee River at Tahoe City includes natural patterns of drainage into the lake as well as human management of lake level to meet downstream water demands. 8.10
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 and 34: Temperature ( o F) TERC.UCDAVIS.EDU
Page 35: Density Difference (kilograms per c
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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