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Campbell 2014 esa workshop
- 1. Paired watershed studies •Watersheds are unreplicated • It’s difficult to find suitable replicate watersheds and expensive to treat them • Uncertainty analysis can be used to report statistical confidence Andréassian 2004 Journal of Hydrology 29:1-27
- 2. W6 W5 • Net hydrologicflux = precipitation inputs minus stream outputs • W5 - whole tree harvest during winter of 1983-1984 • All trees >5 cm dbh were removed (boles and branches) • Purpose: evaluate impact of this more intensive management practice on nutrient removals and site productivity Uncertainty in the flux of Ca
- 3. Water year (June1) 1960 1970 1980 1990 2000 2010 Nethydrologicflux(kgha-1yr-1) -24 -21 -18 -15 -12 -9 -6 -3 0 W6 (reference) W5 (harvested) Ca response to harvesting Harvest Calcium data courtesy G.E. Likens
- 4. Sources of uncertainty Precipitation •Interpolation model • Collector undercatch • Chemical analysis • Gaps in chemistry Stream water • Watershed area • Rating curve • Gaps in discharge • Chemical analysis • Streamwater interpolation model
- 5. Precipitation interpolation method 01000 m 1000 1600 mm Precip. gage Watershed Precip. W6 W5 W4 W2 W3 W7 W8 W9 W1 W6 W5 W4 W2 W3 W7 W8 W9 W1 W6 W5 W4 W2 W3 W7 W8 W9 W1 W6 W5 W4 W2 W3 W7 W8 W9 W1 Kriging W6 W5 W4 W2 W3 W7 W8 W9 W1 Inverse distance weighting Thiessen polygon Spline Regression
- 6. Precipitation interpolation method W1W2 W3 W4 W5 W6 W7 W8 W9 Annualprecip.(mm) 1340 1360 1380 1400 1420 1440 1460 1480 1500 1520 Thiessen Kriging IDW Spline Regression Uncertainty = 0.6%
- 7. Chemical analyses Uncertainty =1.0% • Precision describes the variation in replicate analysis of the same sample • At Hubbard Brook, one sample of every 40 is analyzed four times
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- 10. Gaps in streamflow •7% of streamflow record is gaps • 65% due to the chart recorder (53% clock)
- 11. Streamflow Monte Carlo approach WatershedArea Net Hydrologic Flux Etc. Calculation
- 12. Ca response toharvesting Harvest Water year (June 1) 1960 1970 1980 1990 2000 2010 Nethydrologicflux(kgha-1yr-1) -24 -21 -18 -15 -12 -9 -6 -3 0 W6 (reference) W5 (harvested) Harvest
- 13. Ca response toharvesting W6 Ca Net hydrologic flux (kg/ha/yr) -25 -20 -15 -10 -5 0 W5Canethydrologicflux(kg/ha./yr) -25 -20 -15 -10 -5 0
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- 17. • Stream chemistrysampling interval • Rating curve at high flow Other sources of Uncertainty
- 18. Source of excessCa in W5 • Dissolution of calcium oxalate, which is common in plant tissue and is known to accumulate in forest soils (Bailey et al. 2002). • Dissolution of nonsilicate minerals, such as calcite and apatite, which are more rapidly weathered than silicate minerals (Hamburg et al. 2003).