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

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EXECUTIVE SUMMARY (CONTINUED FROM PAGE 2.2) the highest on record. (Fig. 10.1) • The depth of the maximum chlorophyll concentration decreased in 2008 to a mean of 115 feet. (Fig. 10.4) • Periphyton (attached algae) concentrations were similar to values recorded in 2007, with the exception of Zephyr Point, which experienced a 2-3 fold increase to the highest values ever recorded at that site. (Fig. 10.9) CLARITY Clarity remains the indicator of greatest interest for Lake Tahoe because it tracks both degradation and the community’s efforts to restore clarity to historic levels. Secchi depth (the point below the lake surface at which a 10-inch white disk disappears from view) has been measured continuously since 1968, and is the longest continuous measure of Lake Tahoe’s water clarity. In 2008, the annual average Secchi depth was 69.6 feet, virtually identi- TERC.UCDAVIS.EDU cal to the value recorded in 2007. In the last eight years, Secchi depth measurements have been better than predicted by the long-term linear trend. There is statistical support that Lake Tahoe’s clarity decline has slowed significantly, and is now best represented by a curve. (Fig. 11.1) EDUCATION AND OUTREACH The public can learn about the science behind Lake Tahoe restoration at TERC’s Incline Village education center (the Thomas J. Long Foundation Education Center). In 2008, over 9,200 people participated in our education and outreach activities. (Fig. 12.1) TAHOE: STATE OF THE LAKE REPORT 2009 2.3
ABOUT LAKE TAHOE AND THE TAHOE BASIN • Maximum depth: 1,645 feet (501 meters), making it the 11th deepest lake in the world and 2nd deepest lake in the United States • Average depth: 1,000 feet (305 meters) • Lake surface area: 191 square miles (495 square kilometers) • Watershed area: 312 square miles (800 square kilometers) • Length: 22 miles (35 kilometers) • Width: 12 miles (19 kilometers) • Length of shoreline: 72 miles (116 kilometers) • Volume of water: 39 trillion gallons • Number of inflowing streams: 63, the largest being the Upper Truckee River TERC.UCDAVIS.EDU • Number of outflowing streams: one, the Truckee River, which leaves the lake at Tahoe City, Calif., flows through Truckee and Reno, and terminates in Pyramid Lake, Nev. • Average residence time of water in the lake: about 600 years • Average elevation of lake surface: 6,225 feet (1,897 meters) • Highest peak in basin: Freel Peak, 10,891 feet (3,320 meters) • Latitude: 39 degrees North • Longitude: 120 degrees West • Age of the lake: about 2 million years • Permanent population: 66,000 (2000 Census) • Number of visitors: 3,000,000 annually TAHOE: STATE OF THE LAKE REPORT 2009 3
Page 1 and 2: TAHOE: STATE OF THE LAKE REPORT 200
Page 3 and 4: INTRODUCTION The University of Cali
Page 5: EXECUTIVE SUMMARY (CONTINUED FROM P
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 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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