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

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Metric Tons TERC.UCDAVIS.EDU 60 50 40 30 20 10 0 NUTRIENTS AND PARTICLES 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 TAHOE: STATE OF THE LAKE REPORT 2009 Nitrogen contribution by Upper Truckee River Since 1989 Nitrogen (N) is important because it, along with phosphorus (P), stimulates algal growth. (Fig. 9.1 shows the major sources of N and P to Lake Tahoe) The Upper Truckee River is the largest of the 63 streams that flow into Lake Tahoe, contributing about 25 percent of the inflowing water. The river’s contribution of dissolved inorganic nitrogen (nitrate and ammonium) and total organic nitrogen loads are shown here. The year-to-year variations primarily reflect changes in precipitation. For example, 1994 had 16.6 inches of precipitation and a low nitrogen load, while 1995 had 60.8 inches of precipitation and a very high nitrogen load. Low rainfall in 1999 2000 Water Year 2001 2002 2003 2004 2005 2006 2007 2008 resulted in a low nitrogen load. The watershed burned in the Angora Fire (June 2007) drains directly to the Upper Truckee River. 2008 was the first year after the fire and nitrogen load was not elevated as a result of that event. (One metric ton = 2,205 pounds.) 2008 Dissolved inorganic nitrogen Total organic nitrogen 9.3
Metric Tons TERC.UCDAVIS.EDU 10 8 6 4 2 0 NUTRIENTS AND PARTICLES 1989 1990 1991 1992 1993 1994 1995 1996 1997 TAHOE: STATE OF THE LAKE REPORT 2009 Phosphorus contribution by Upper Truckee River Yearly since 1989 Soluble reactive phosphorus (SRP) is that fraction of phosphorus immediately available for algal growth. As with nitrogen (Fig. 9.3), the year-toyear variation in load largely reflects the changes in precipitation. Low rainfall in 2008 resulted in a relatively low phosphorus load. Unlike nitrogen and suspended sediment, phosphorus was somewhat higher in 2008 versus 2007. The possible influence of the Angora Fire is being investigated. 1998 1999 2000 Water Year 2001 2002 2003 2004 2005 2006 Total phosphorus is the sum of SRP and other phosphorus, which includes organic phosphorus and phosphorus associated with particles. (One metric ton = 2,205 pounds.) 2007 2008 Soluble reactive phosphorus Other phosphorus 9.4
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 and 36: Density Difference (kilograms per c
Page 37 and 38: Mean daily streamflow (cubic feet p
Page 39 and 40: NUTRIENTS AND PARTICLES TERC.UCDAVI
Page 41: TERC.UCDAVIS.EDU NUTRIENTS AND PART
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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