1. Isotope mass balance – Mica Creek Paul Koeniger, Tim Link, John Marshall 03/28/2006 – Mica Creek Group Meeting Department of Forest Resources – University of Idaho, Moscow USA

2. Combination of watershed hydrology and isotope techniques for an isotopic mass balance in forested watersheds - Snow sampling / spring snowmelt - Base flow sampling - Water vapour - evaporation vs. transpiration (- Isotopes as applied tracers: soil water-xylem-transpiration) Isotope hydrological mass balance (Mica creek): P*C P = (E*C E + T*C SW ) + R*C R + GWr*C SW { +/-  SW*C SW } C: Isotope concentration P: precipitationR: runoff E: evaporation T: transpiration GWr: groundwater (recharge)SW: soil water What we plan to do … 

3. Isotopes in precipitation: available data IAEA (2001). GNIP Maps and Animations, Accessible at http://isohis.iaea.org Bowen (2003). Accessible at http://www.waterisotopes.org

4. Isotopes in precipitation - Three to 5 sampling points in monthly resolution (altitude effect) - Reference station in Moscow (weekly) - Snow sampling campaign in winter - Event sampling

5. Isotopes in snow - Altitude effect in snow - Spatial variability - Snow profiles - Spring snowmelt event

6. Stream flow (Coplen and Kendall 2000: U.S. Geological Survey Open-File Report 00-160) Isotopes in stream flow: available data? Clearwater River / Spalding

7. Stream flow - Continuous (monthly) sampling at 3 to 5 locations (control site, partial-, clear cut) Event sampling – residence time distributions - Base flow “ Isotope hydrological and hydro chemical characterization of base flow at Mica creek” – best in Sept. / Oct. 2006 - Salt dilution discharge measurements - 18 O, 2 H (and 3 H/ 3 He or 3 H) - Conductivity, pH, chloride, water chemistry

8. Evaporation – transpiration – water vapor isotopes - Soil water Continuously - should represent transpiration - Transpiration Xylem Water labeling of sap flow: with 18 O possibilities for in situ equilibration techniques ?? with 2 H – sugar exchange?? - Evaporation Water vapor collecting techniques

9. Water balance components are crucial for isotope mass balance Isotopes in precipitation: reference station in Moscow -> regionalization Isotopes in stream flow, soil water, xylem: sampling is ongoing Isotopes in snow: results are soon to come … Evaporation / transpiration component is probably the biggest challenge Conclusions