Lester McKee (PhD) Watershed Program Manager San Francisco Estuary Institute (SFEI)

1. Land Use Influences on Water, Sediment and Nutrients in the Napa Valley Watershed: Conceptual Models and Examples Lester McKee (PhD) Watershed Program Manager San Francisco Estuary Institute (SFEI)

2. San Francisco Estuary Institute Presentation Outline • Historic conceptual model for water and sediment • Modern conceptual model for water and sediment • Examples of impacts • Conceptual models for nutrients • Examples of nutrient impacts

5. San Francisco Estuary Institute Overview of Changes • Channel have been: • Straightened • Strengthened or lined • Connected • Drainage density has been increased • Result • More water drains of faster • Sediment supply is more connected • Nutrients and other chemical residues drain off faster

6. Soda - Realignment of Road and Creek

7. Lower Soda Creek Silverado-Napa R. Reach

8. Lower Soda Creek Silverado-Napa R. Reach 1942 1999

9. San Francisco Estuary Institute St. Helena

13. Sulphur - Alluvial Fan Reaches • Storage of large volumes of sediment • Discontinuation of gravel mining in 2002 • Aggradation and potential flood risks

14. Sulphur - Lowest Reaches • Highly affected by the town of St. Helena • Entrenched • Large amount of bank revetment • Water quality affected by runoff • Invasive species, primarily Arundo donax • Some areas with no riparian vegetation

15. Carneros Ck. Revetment

16. Carneros Ck. Bank Erosion

17. Carneros Ck. Bank Erosion

18. San Francisco Estuary Institute Nutrients

19. San Francisco Estuary Institute Null Hypothesis H(0) Land use or human population have no influence on nitrogen or phosphorus concentrations in flowing water bodies within the Napa River watershed. • Accept H(0) if there was reasonable doubt that anthropogenic factors strongly influence water quality • If reject H(0) then we would need to develop and test alternate hypotheses (i.e. develop monitoring/management questions)

20. San Francisco Estuary Institute Conceptual Models to Test Null Hypotheses Against • Nutrient concentrations should be below WQ standards • Seasonal variation should be minor (<10x) • Little spatial variation either between subwatersheds or in a downstream direction • Nitrate << organic nitrogen • Phosphate << organic phosphorus

21. SamplingLocations*selected for beneficial uses and coverage

22. WQ Guidelines NOx 1,129 µg/L TDN 500 µg/L Phosphate 30 µg/L TDP 30 µg/L

23. San Francisco Estuary Institute Seasonal Variation

24. Downstream Variation

26. Reasons for Rejecting H(0): • Except in headwater reaches, concentrations of NOx, NH3 and PO43- were high relative to expected concentrations in pristine watersheds. • Concentrations of NOx varied greatly between sampling locations and increased in a downstream direction in relation to anthropogenic factors. • Total dissolved nitrogen was dominated by NOx and total dissolved phosphorus was dominated by PO43-. • Approximately 85% of the sampling locations exceeded EPA guidelines in Level III Eco-Region 6 for TN (500 µg/L) and ~92% of the sampling locations exceeded EPA guidelines in Level III Eco-Region 6 for TP (30 µg/L). • NOx concentrations were highest during the winter months indicating considerable seasonal variation greater than would be expected in a natural system. • NOx correlated significantly with population and urban environmental variables during the winter, spring and early summer and during the wet season only with agricultural and commercial land use variables

27. San Francisco Estuary Institute Conclusions • Work to-date on water, sediment, and nutrients in the Napa River watershed suggests a level of impact associated with historic and current human land and water use • The questions that stakeholders and the public have to answer is: • Is this acceptable given multiple societal needs? • What goals do we set for the future?