FLOWPATHS AND WATER SOURCES IN A FRACTURED ROCK ENVIRONMENT

1. FLOWPATHS AND WATER SOURCES IN A FRACTURED ROCK ENVIRONMENT Mark Williams Geography, INSTAAR, ENVS

2. TWO CASE STUDIES • NWT-LTER: North Boulder Creek flowpaths and sources (science) • ACID MINE DRAINAGE: Plumbing of the Mary Murphy Mine, Chalk Creek, Colorado (application)

4. LEGACY OF EXTRACTIVE INDUSTRIES

5. RECREATION

6. NIWOT RIDGE NADP

7. WESTERN MOUNTAINS AT RISK

9. HYDROLOGIC UNKNOWNS • Flowpaths • Residence time • Circulation depth • Reservoir sizes • Groundwater fluxes • Fractured rock environment increases difficulty of understanding mountain plumbing

10. FLOW SOURCES AND FLOWPATHS USING ISOTOPIC AND GEOCHEMICAL TRACERS, GREEN LAKES VALLEY, ROCKY MOUNTAINS Fengjing Liu and Mark Williams Department of Geography and Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO80309

11. RESEARCH SITE: TOPOGRAPHY

12. RESEARCH SITE: SAMPLING Sample Collection Stream water - weekly grab samples Snowmelt - snow lysimeter Soil solution - zero tension lysimeter Green Lake 4 • Sample Analysis • Delta 18O, and major solutes

13. MIXING MODEL - GENERAL EXPRESSION Ci1Q1 + Ci2Q2 + Ci3Q3 + .. + CinQn = CitQt Q1 + Q2 + Q3 + .. + Qn = Qt C - tracer concentrations Q - discharge (runoff) i - tracers n - water source or flowpath components t - stream flow Note: The equations apply to n tracers for (n + 1) flow components.

14. MIXING MODEL - MATRIX EXPRESSION For a single observation xi= liB xi is any single observation of stream water chemistry with p tracers); MatrixB describes p tracer concentrations of k flow components ; li is the proportion of k components contributing to stream flow, where sum of all the k elements is equal to 1.Solving for li gives: li= xiB-1 Note: This equation also applies to EMMA with n end-members and (n-1) PCA components projected by stream flow chemistry with tracers equal or greater than (n - 1).

15. STREAM CHEMISTRY AND DISCHARGE

16. d18O IN SNOW AND STREAM FLOW

17. NEW WATER AND OLD WATER Old Water = 18% Old Water = 64%

18. END-MEMBER MIXING ANALYSIS (EMMA) AND PCA • Tracers conservativity - demonstrated by mixing diagrams of pairwise tracers; • Number of qualified end-members - routine PCA analysis using stream flow chemistry of conservative tracers. If the first 2 PCA components explain 90% of total variance, 3 end-members are sufficient. • End-member characterization - justified by U distance between end-member projections and their original values; the shorter the better. • EMMA solutions - evaluated by prediction of tracer concentrations in the stream flow.

19. MIXING DIAGRAM: PAIRED TRACERS

20. MIXING DIAGRAM: EMMA PCA COMPONENTS

21. FLOWPATHS: TRADITIONAL MIXING MODEL Mart GL4 Surface 33% 44% Soils 23% 12% Groundwater 44% 44%

22. FLOWPATHS: EMMA Mart GL4 Surface 49% 36% Soils/Talus 16% 36% Groundwater 35% 28%

23. COMPARISON OF NEW WATER WITH SURFACE FLOW

24. PREDICTION OF NO3- IN STREAM: MARTINELLI

25. PREDICTION OF NO3- IN STREAM: GREEN LAKE 4

26. DUAL ISOTOPES OF NO3-

27. SOURCES OF NO3-: MARTINELLI

28. SOURCES OF NO3-: GREEN LAKE 4

29. SUMMARIES • New water dominates the 8 ha Martinelli basin, while old water dominates the 220 ha Green Lake 4 basin; • Subsurface flow is dominant flow component, particularly at Green Lake 4 catchment; • A rapid subsurface flow from new water exists at Martinelli basin, but not at Green Lake 4 basin; • Talus flow is a significant flow component at Green Lake 4 catchment, accounting for more than 1/3 of the total flow; • Nitrate predictions using both TMM and EMMA flow components indicate that plant assimilation of N strongly occurred during summer at Green Lake 4 catchment; • Both hydrograph separations and dual isotopic data show that nitrate is primarily from atmospheric source during spring snowmelt period and terrestrial source after that at both basins.