Quick Summary
- State of the Lake is annual 鈥榬eport card鈥 for Lake Tahoe
- Clarity in 2018 appears back on track, but learning from lessons of 2017
- 2017 had record-breaking air and lake temperatures. Was one of wettest years, too.
- Tahoe in 2100 could be 9 degrees hotter
After a year marked by extreme weather and plunging clarity levels, the 完美体育 Tahoe Environmental Research Center today released its annual .
The 2018 report summarizes data collected in 2017 as part of the center鈥檚 ongoing, decades-long measurement programs, while also presenting current research on emerging issues.
This includes updates about the dramatic change in Lake Tahoe鈥檚 clarity in 2017, a study to characterize the nearshore and its impacts on algae, climate change indications, forest health and restoration, and an upcoming comparative study between Lake Tahoe and Lake Geneva.
鈥淲hile 2017 may be viewed as an anomalous year, it has reinforced the fact that progress toward environmental restoration of Lake Tahoe will be punctuated by extreme years in future decades,鈥 said Geoffrey Schladow, director of the 完美体育 Tahoe Environmental Research Center, or TERC. 鈥淢onitoring these extreme years and applying the lessons learned will be critical to ensuring that the lake and its watershed have the resilience needed to thrive under future conditions.鈥
Highlights include:
Clarity
Lake Tahoe鈥檚 average annual clarity in 2017 was at its lowest level, 59.7 feet, since regular measurements began in 1968. This was likely due to the one-two punch of the end of a five-year drought followed by a winter of record-high precipitation levels that extended well into the spring. More sediment washed into the lake in 2017 than the previous five years combined.
Clarity readings from the first half of 2018 indicate that clarity is back in its normal range, suggesting 2017 was an outlier. Nonetheless, the report said the decline highlighted the reality that extreme climatic and hydrologic events will become more common in the future and that current monitoring efforts need to be reviewed and upgraded to prepare for them.
An ecological approach to clarity
Past efforts to restore lake clarity primarily have focused on land-use management. The report said recent research shows a parallel ecological approach could accelerate progress. For example, a pilot project in Emerald Bay is testing whether removing invasive Mysis shrimp could restore the native food web and help sustain clarity improvements.
Record-busting weather
Winter monthly air temperatures were cooler than recent years, but average temperatures were warmer during summer. In 11 of the 12 months, air temperatures were higher than the 1910-2017 average.
Lake temperature was the warmest on record. Surface water temperatures in July 2017 were the warmest ever recorded at 68.4 degrees, which was 6.1 degrees more than in 2016.
Water Year 2017 (Oct. 1, 2016-Sept. 20, 2017) was the second wettest on record, with 68.9 inches compared to the long-term average of 31.6 inches.
Nitrogen and phosphorus loads were also at record levels in 2017 due to high streamflow. Suspended sediment was also high, particularly in Ward and Blackwood creeks.
Climate change
TERC climate change resea