How well does the NARR data simulate recharge to groundwater?

1. How well does the NARR data simulate recharge to groundwater? Lindsey Gulden Surface Water Hydrology April 26, 2005

2. Point of comparison for NARR recharge: Keese et al., 2005 • Results: average annual recharge 1961-1990 • 1-D recharge simulations • Unsaturated-zone model (UNSAT-H) Keese et al., 2005

3. Define “recharge” in NARR as NARR “BGRUN” (baseflow)

4. Methods… Evaporation 144 GRIB Files containing NARR monthly data (baseflow, precip., surface runoff, and evaporation) Myriaddata conversion steps Baseflow FORTRAN! VBA! Precipitation NCL! Blood, sweat tears ArcGIS grids, polygons

5. NARR-Noah avg. annual baseflow (mm/yr) 1979-90

6. NARR-Noah avg. annual precipitation (mm/yr) 1979-90

7. NARR-Noah average percent of precipitation that becomes recharge

8. Normalize baseflow data to precipitation

9. Intersect study-region polygons with NARR baseflow data

13. Preliminary conclusion • “Recharge” calculated by NARR is approximately half that calculated by UNSAT-H • Baseflow is moderately correlated between NARR and UNSAT-H

14. Many (~100), variably spaced layers Precise Ψ, K calculations based on soil texture Implicit surface runoff 3-dimensional variation in soil texture 4 soil layers Coarse calculations of Ψ, K Explicit surface runoff scheme Homogeneous soil across each 32-km grid cell Soil hydrology of Noah LSM Keese et al.’s UNSAT-H

15. Next steps . . . • Recalculate Keese et al.’s recharge for the overlapping time period (’79-’90) • Continue to analyze reasons for discrepancy • Propose modifications to Noah LSM that will improve vadose-zone moisture transport

16. Thanks!