1. 1 DETERMINATION OF SOURCES AND FLOWPATHS USING ISOTOPIC AND CHEMICAL 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

2. 2 HYDROLOGIC FLOWPATHS  Generally, 4 paths  Change over time  Change over space

3. 3 OBJECTIVES  understanding the mechanism of stream flow generation in snow-dominated alpine basins  determining uncertainties of hydrograph separation by using different mixing models and tracers

4. 4 RESEARCH SITE AND SAMPLE COLLECTION  Stream water - weekly grab samples  Snowmelt - snow lysimeter  Soil solution - zero tension lysimeter Delta 18 O, DOC, Solutes

5. 5 MASS BALANCE MODEL FOR WATER SOURCES AND FLOWPATHS C - tracer concentrations Q - discharge (runoff) i - tracers n - water source or flow path components t - stream flow How we use 2 to 4 component mixing model C i 1 Q 1 + C i 2 Q 2 + C i 3 Q 3 +.. + C i n Q n = C i t Q t Q 1 + Q 2 + Q 3 +.. + Q n = Q t

6. 6 End-Member Mixing Analysis (EMMA) and PCA Tracer concentrations distinct - time series plots Tracers conservative - mixing diagram Number of components - PCA Qualification of end-member characterization EMMA solutions for hydrograph separation

7. 7 SOURCE WATER SEPARATION - 2 COMPONENTS Calendar Day (1996) MartnelliGL4

8. 8 RESULTS FOR FLOW SOURCES Calendar Day (1996) Martinelli GL4

9. 9 FLOWPATH SEPARATION - EMMA MIXING DIAGRAM Mart

10. 10 FLOWPATH SEPARATION - EMMA MIXING DIAGRAM GL4

11. 11 FLOWPATH SEPARATION - QUALIFICATION OF 2C SEPARATION  Na +, Si, SO 4 2-, and K/Si are conservative at both catchments  2-component flowpath separations using Na +, Si, SO 4 2- are not successful in that characterization of the subsurface is difficult  Concentrations of those tracers vary a lot over soil horizons

12. 12 FLOWPATH SEPARATION - K/Si Calendar Day (1996) GL4 Overland vs. subsurface flow

13. 13 FLOWPATH SEPARATION - DOC GL4 Upper soil horizon vs. deeper flow

14. 14 FLOWPATH SEPARATION - 4 COMPONENTS 2/25/39/34 GL4 Martinelli 2/16/77/5

15. 15 EMMA PCA Diagram Martinelli GL4

16. 16 4-C SEPARATION - EMMA SOLUTIONS MartinelliGL4 Methods 3-Tracers ( 18 O,K/Si,DOC) Least square optimization (Na,Si,SO4,K/Si, 18 O, DOC) PCA Projection (U) (Na,Si,SO4,K/Si, 18 O,DOC)

17. 17 SUMMARY  New water accounts for 95% at Mart, while new water decreases to 65% at GL4  K/Si and DOC are efficient tracers to identify overland and upper soil horizon flow  3-tracer-4-component separation is superior to EMMA approach  Four flowpaths are successfully identified: overland, upper soil horizon, lower soil horizon, and base flow (2/16/77/5 at Mart; 2/25/39/34 at GL4)

18. 18 THANK YOU!