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

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

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

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

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

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

NARR-Noah average percent of precipitation that becomes recharge

Normalize baseflow data to precipitation

Intersect study-region polygons with NARR baseflow data

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

Soil hydrology Keese et al.’s of Noah LSM UNSAT-H 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 Both calculate soil moisture transfer according to the richard’s equation Both calculate ET using Penman Monteith methods

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

Thanks!