1. Effects of Drought on Lake Almanor Water Quality
Dr. Gina Johnston and
Mr. John McMurtry
California State University, Chico
October 21, 2014

2. Effects of Drought on Lake Almanor Water Quality
Three Major Effects Have been Observed since 2009:
Increase in abundance of algae, especially blue-green algae (cyanobacteria)
Increase in temperature of the surface water (epilimnion) in the summer
Decrease in dissolved oxygen in the summer throughout the water column

3. Blue-green algae (Cyanobacteria)
Blue-green algae (Cyanobacteria) are very small, structurally simple plants that occur naturally in aquatic environments.
Some can produce toxins potentially harmful to humans and other animals.
When conditions are right, algae can reproduce rapidly in what is known as an algal bloom. Blooms can cause visible surface scum to form, produce noticeable tastes and smells, and harm other aquatic life.
A cyanobacterial bloom is especially dangerous due to the possible toxins produced by many species.
Conditions that increase the chances of an algal bloom:
• Little water movement, in terms of both horizontal flow and vertical mixing
• High levels of nutrients – phosphorus and nitrogen
• Warmer water temperatures

4. Some B-G Genera Found in Lake Almanor: Lyngbya

5. Some B-G Genera Found in Lake Almanor: Anabaena

6. When there are too many algae – a bloom

7. Algal Surface Scums and Odors

8. Lake Almanor Algal Populations 2009-2014

9. Summer Water Temperature and Dissolved Oxygen: 2009-2014
2009:Look at T and O in 8-12 meter range

10. Summer Water Temperature and Dissolved Oxygen: 2009-2014
2009:Look at T and O in 8-12 meter range

11. Summer Water Temperature and Dissolved Oxygen: 2009-2014
2014: Look at T and O in 8-12 meter range

12. Environmental Requirements of Brown Trout
Temperature: 5° C – 20° C
(Best growth in cool water)
Oxygen: greater than 5 ppm
(reduction in growth rate below 5 ppm)

13. Trout Habitat, July 2009, Lake Almanor

14. Trout Habitat, July 2014, Lake Almanor

15. Effects of Drought on Lake Almanor Water Quality
Increase in algae, especially cyanobacteria, due to warmer water temperature
Decrease in acceptable trout habitat in summer, due to warmer water temperature and lower dissolved oxygen