Reed M. Maxwell1, Stefan J. Kollet1, Qingyun Duan1 and Fotini K. Chow2

1Atmospheric, Earth, and Energy Sciences Dept, Lawrence Livermore National Lab

2Civil and Environmental Engineering Dept, University of California, Berkeley

This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

UCRL-PRES-XXXXXX

A dynamically-coupled groundwater, land surface and regional climate model to predict seasonal

watershed flow and groundwater response

Three talks for the price of one

• Brief overview on RC/LS/OF/GW coupled model project underway at LLNL

• Some details of a new coupled overland flow-groundwater work (Kollet and Maxwell, 2005)

• Example problem that illustrates distributed LS/OF/GW modeling

Results of first coupled* model study show important gains resulting from process feedback

• Runoff

• Soil moisture

• Water balance

Observations

Coupled

Coupled Model provides much more accurate predictions of:

0

50

100150

200

250

J-68 D-68 D-69 D-70

Ru

no

ff (

mm

/mo

nth

)

Observations Coupled Uncoupled

Uncoupled

-1

*Maxwell and Miller, J. Hydromet,6(3), 2005. Others have shown similar results.

This project integrates four models in a unique way

Land surface modelLand surface model

This project integrates four models in a unique way

Groundwater model

Groundwater model

Land surface modelLand surface model

This project integrates four models in a unique way

Groundwater model

Groundwater model

Land surface modelLand surface model

Overland flowOverland flow

This project integrates four models in a unique way

Groundwater model

Groundwater model

Land surface modelLand surface model

Overland flowOverland flow

Land surface modelLand surface model

Overland flowOverland flow

Regional climate modelRegional climate model

This project integrates four models in a unique way

Groundwater model

Groundwater model

Land surface modelLand surface model

Overland flowOverland flow

Land surface modelLand surface model

Overland flowOverland flow

Regional climate modelRegional climate model

Explicitly incorporates fluxes at air/land-surface/subsurface interfaces

Moisture/heat fluxMoisture/heat flux

EvapotranspirationEvapotranspiration

Infiltration/SeepageInfiltration/Seepage

Precipitation/AdvectionPrecipitation/Advection

Runoff/RoutingRunoff/Routing

Project tasks, details

• Run RCM over central US w/ a detailed study area over Little Washita watershed– SGP/ARM site

– Data to validate all models (need lots)

• P1 run in a nested mode, RCM and GW/LS/OF models uncoupled (control run)– RCM (ARPS) passes LS forcing to coupled model

– Coupled model spun up w/ obs, forced by RCM

• P2 fully couple models, re-run– Verify that models are coupled and balancing mass and energy

– Look at water, heat fluxes across the LS and at weather and weather generating processes

Surface contours for 1 km resolution grid, 07/08/99 12 UTC

RCM/ARPS Results

• Norman Oklahoma sounding comparison 07/08/99, 12 UTC

θ [K] U [m/s] φ[degrees] q [g/kg]

Sacramento Model Calibration for Little Washita

Borehole data used to create 3D geostatistical realization of the subsurface

Free-surface overland-flow boundary condition, coupled groundwater overland flow

• Lots of motivation for coupled model– Watershed modeling

– Climate

– Water quality

• Most (all?) coupled models rely on interface between SW and GW– “conductance concept”

– Hard to find field data to support this

– Need for a more general formulation

• Desire for parallel model w/ a robust non-linear solver– Integrate into ParFlow

– Take advantage of infrastructure

Kollet and Maxwell, Advances in Water Resources, in press, 2005.

The Conductance Concept

xqxqvt ers

s

)(

pse xxq

es

pwpws qmqq

t

S

tSS '

New Overland Flow Boundary in ParFlow

s

wws qq

t

S

tSS

)(0,0,

xqvt

zkxk r

Kollet & Maxwell, 2005

Verification Examples

Panday & Huyakorn, 2004

2D Tilted V-Catchment:90 min rain, 90 min recession

1D Slope:200 min rain, 100 min recession

Jabar & Mohtar, 2004

Simulation Examples II

Low-K slab

Simulation Examples III

Random (Gaussian) Heterogeneity Five Realizations

Kgeo = qrain

Scaled Parallel Efficiency

E(np,p) = T(n,1) / T(np,p)

Integrating land surface processes into ParFlow an Example

• We add in LS processes (parts of CLM) into ParFlow– Hydro, Runoff handled by PF as detailed earlier

– Fully distributed

– Fully parallel

• Use a well-resolved, large scale 2D “Classic” Example problem to investigate coupled model performance and behavior– Dx=100m; Dz=2m; 40km x 0.54km domain

– Toth Problem: sinusoidal topography in a large basin

– J. Toth, 1963. A theoretical analysis of groundwater flow in small drainage basins. J. Geophys. Research 68:4795-4842.

• Forced uniformly with PILPS midlatitude for one year

Toth problem uses an sinusoidal topography

Initial Pressure July Pressure

Coupled model forced by PILPS midlatitude, produces realistic looking hydrograph

Averaged, Cumulative ET

Distributed Ground Surface Temperature

Initialization

Non-uniform thaw

Distribution of temps, non-uniform water content

Non-uniform freezing

Distributed Water and Heat Fluxes

Summary

• We are working on lots of stuff, but have a lot yet to do– Coupled RC/LS/OF/GW project in Y1/control run phase, soon will

start dynamic coupling

– Coupled overland flow and groundwater method looks very promising

– Integrating LS processes into GW provides interesting distributed results need to compare to field site (Little Washita, Valdai)

– Still overall question regarding quantifying impacts and scale of coupled processes