Protect and Enhance the Nations Natural Resource Base and Environment
Understanding The Processes That Contribute To Reduced Visibility In Lake Tahoe
Issue (Who cares and why?)
Reduced water quality in high altitude pristine environments such as the Sierra Nevada has been attributed to increased algal growth caused by nutrient inputs in surface and groundwater from disturbance and development. As a result, hundreds of thousands of taxpayer dollars are currently being spent on litigation trying to settle disputes between environmental, residential and commercial interests. In order to live in harmony with each other, as well as with the natural environment, we must first identify specific cause/effect interactions that result in environmental degradation. Few studies have addressed the natural pollution potential of pristine sub-alpine forested watersheds. This research identifies the pollution potential from natural contributions of soluble inorganic and organic nitrogen and phosphorus. The study involves the field collection of natural groundwater recharge from snowmelt and summer precipitation, and the laboratory leaching of intact soil cores taken from forested, open and riparian areas of the Sierra Nevada. Findings will also apply to other high altitude environments throughout the State, and greatly assist in the resolution of conflicting natural resource values.
What has been done?
Two pristine locations were selected for study: Little Valley, Nevada and Incline Creek, Nevada. Areas of specific investigation within each general location consisted of forested, open and riparian watershed conditions. In situ colloid-bound Nitrogen (N) and Phosphorus (P) in soil solution during saturated groundwater recharge from spring snowmelt and high intensity summer precipitation were measured using zero tension lysimeters. The in vitro discharge of colloid-bound N and P under saturated flow conditions were characterized by analyzing the outflow effluent during leaching of intact undisturbed soil columns. In vitro distribution and discharge of colloid-bound N and P under vadose conditions through sectionable undisturbed soil columns were similarly characterized by analyzing the sectional distribution and the outflow effluent during unsaturated water flow. The resulting data base was incorporated into a newly developed transport model for predictive estimation of colloidal-bound N and P discharge phenomena.
Comprehensive intact core soil samples were taken throughout the Incline Creek watershed. Each sample was leached under laboratory conditions within 48 hours of sampling and interval leachate samples were collected and analyzed for inorganic and suspended/dissolved-organic N and P. Data then underwent statistical examination for interpretive analysis. Future efforts include examination of the effects of fire on physio-chemical nutrient transport processes.
Impact
Rivers and lakes are central to the lives and livelihoods of Nevada and Californians. We depend upon our rivers and lakes to supply drinking water, irrigate farmland, and generate electricity. We also value our rivers and lakes for their ability to support an intricate web of biologically significant communities and to provides us with places of beauty to recreate. Increasingly, Nevada and Californians recognize the need for diligent stewardship of natural river and lake processes to maintain these vital resources.
Carried by runoff, plant nutrients such as nitrogen and phosphorus can enter the water, promoting algae and other aquatic plants to grow rapidly and become nuisances or result in low levels of dissolved oxygen, killing fish. To effectively control water quality, it's best to develop and implement a river, lake and watershed management plan. For such a plan to succeed, basic research like this project is required. Without it officials are forced to make uninformed decisions for controlling nutrient input.
Contact
Watkins Miller
Natural Resources and Environmental Science/186
University of Nevada
Reno, Nevada 89557
wilymalr@unr.edu