Community Hydrologic Model: Structure

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Community Hydrologic Model Structure

• Reed Maxwell
• LLNL

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Challenges to CHM

• Application pore-scale groundwater contaminant
  transport to global hydrology
• Physics and scale balance laws not scale
  invariant
• Computing desktop to supercomputer
• Calibration, Optimization needs to be flexible
  to connect w/ management codes
• User Communities each with different needs,
  goals and perspectives

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Huge range in scales
Regional Scale 132x88x0.5km DxDy1km Dz0.5m
Plot Scale 17x10x3.8m DxDy0.34m Dz0.038m
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Timescales and scaling in Groundwater

• Range of paths and scales in groundwater
• Water moves as K/q10-4-10-5 m/s
• Pressure propagates as Kb/Ss100-101 m/s
• System responds over a wide range of scales
  (Kirchner et al 2000, 2001 Alley et al 2002)
• Topography and land surface processes have strong
  influence

Z (m)
Land surface
20
40
0
Travel time (y)
Kirchner et al (2000)
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Thoughts on Model Structure

• Object oriented
• Open source
• Parallel with efficient solvers, linear scaling
• Flexible grid options
• Flexible physics options
• Flexible input
• Not in a vacuum able to be coupled to other
  models, processes

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Open Source Programming Tools

• QGIS
• an open source and free "Programmable Geographic
  Information System"
• a mapping tool, a GIS modeling system, and a GIS
  application programming interface (API) all in
  one
• a platform independent Open Source Geographic
  Information System that runs on Linux, Unix, Mac
  OSX, and Windows
• libraries for raster and vector geospatial
  formats
• Object relational database is handled using
  PostgreSQL
• GRASS compatible
• Qt/C
• - tools for programming the interface and
  visualization

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PIHM GIS Interface
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ParFlow Structure
TCL input script Set database keys for
simulation, any other manipulations.

• pfrun command
• Executes parflow.tcl script
• Write database (.pfidb) file
• Set up parallel run parameters
• Execute run script

• run script
• Execute ParFlow using platform specific options
• Port standard output to a file

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Model Input Structure

• TCL/TK scripting language
• All parameters input as keys using pfset command
• Keys used to build a database that ParFlow uses
• ParFlow executed by pfrun command
• Since input file is a script may be run like a
  program

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SolidFile Geometry (input file)
pfset GeomInput.Names
"solidinput" pfset GeomInput.solidinput.InputType
SolidFile pfset GeomInput.solidinput.GeomNames
domain pfset GeomInput.solidinput.FileName
fors2_hf.pfsol pfset Geom.domain.Patches
"infiltration z-upper x-lower y-lower
x-upper y-upper z-lower"
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Octree used to delineate geometries
Source Wikipedia
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SolidFile Geometry
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CATHY Model Governing equations channel and
hillslope routing Orlandini Rosso, WRR
2001

• "Constant critical support area" overland flow
  cells with upstream drainage area A lt A else
  channel flow
• Leopold Maddock relationships
• Muskingum-Cunge solution scheme (explicit and
  sequential) etc
• (need Pe?? and Cu?1)

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Penn State Integrated Hydrologic Model PIHM
Qu and Duffy 2007
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ParFlow enables simulating groundwater flow in
large subsurface regimes

• Two Modes fully and variably saturated (via
  Richards EQ) flow solver
• Efficient multigrid preconditioned linear solver
• Kinsol nonlinear solver
• Parallel code specifically designed to run on
  large institutional computer facilities
• Enables large, highly-resolved, simulations
• Coupled overland flow and land surface
  interactions

Ground Surface
Infiltration Front
Vadose Zone
Saturated Zone
Water Table
Ashby and Falgout, 1996 Jones and Woodward,
2001 Kollet and Maxwell, 2006
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Coupled Model PF.CLM
Atmospheric Forcing
Land Surface
Flow Divide

• PF.CLM Parflow (PF) Common Land Model (CLM)
  Kollet and Maxwell (2008), Kollet and Maxwell
  (2006), Maxwell and Miller (2005), Dai et al.
  (2003), Jones and Woodward (2001) Ashby and
  Falgout (1996)
• Surface and soil column/root zone hydrology
  calculated by PF (removed from CLM)
• Overland flow/runoff handled by fully-coupled
  overland flow BC in PF (Kollet and Maxwell, AWR,
  2006)
• CLM is incorporated into PF as a module- fully
  coupled, fully mass conservative, fully parallel

Air
Root Zone
Vadose Zone
Vegetation
Water Table
Routed Water
Flow Lines
Groundwater
Dynamically coupled, 2D/3D OF/LS/GW Model
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Integration of Atmospheric Processes PF.ARPS

• Understanding two-way feedbacks subsurface ?
  atmosphere
• Integrate ARPS (Advanced Regional Prediction
  System) into ParFlow
• ARPS (Xue et al., 1995, 2000, 2001)
• Large eddy simulation code
• solves the three-dimensional, compressible,
  non-hydrostatic Navier-Stokes equations
• Land Surface Model ISBA (Interaction Soil
  Biosphere Atmosphere)

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Scaled Parallel Efficiency
Perfect efficiency double problem size and
processor same run time gt E 1
Kollet and Maxwell, AWR (2006)
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Many options for subsurface conceptual model
Loam
Sand
Loamy Sand
Clay Loam
Soil
Aquifer
Aquitard/bedrock

• Completely general, 3D subsurface variably
  saturated GW model
• Any parameter combinations, effective,
  heterogeneous, stochastic
• Many scales, features can be incorporated, no
  predefined GW or vadose zones

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Conceptual Model GeoDataBase A Priori Data
Conceptual Model Groundwater flow in the
Allegheny Plateau Section.
Example of the GIS for the surface geology
coverage.
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Little Washita watershed in OK provides a good
field site for coupled model

• Site of several Southern Great Plains (SGP) field
  campaigns
• Located at bottom Atmospheric Radiation
  Measurement (ARM) site
• Most complete data set to validate model

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Offline Model Spinup and Dynamics

• Run offline, PF.CLM coupled model
• WY 1999 used as forcing (NARR)
• Spinup Run over successive years until
  beginning-ending water and energy balances drop
  below threshold
• Results can be
• compared to data
• used to understand dynamics
• used for initialization

Kollet and Maxwell (2008a)
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Water Table Depth, Cross Section

• Water table driven by topography
• Very deep (40m) at hilltops (drier)
• Very shallow in valleys (wetter)
• Cross section shows variation of WT and Saturation

hilltops
valleys
groundwater
Maxwell, Chow and Kollet, AWR (2007)
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We see a connection between groundwater and the
lower atmosphere
27h

• Cross-section at y15km
• Shallow WTwetter
• Wettercooler
• Temperature variationswind variations
• Wind variationsBL variations

Maxwell, Chow and Kollet, AWR (2007)
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Influence of Groundwater Dynamics on Energy Fluxes
(yearly averaged)
Kollet and Maxwell (2008a)
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Understanding Residence Times Spatiotemporal
Scaling of Baseflow Contributions
Kollet and Maxwell (2008b)
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Summary CHyMP Model Structure

• Object oriented
• Flexible
• Range of interface, data, needs
• Range of Scales
• Growing community of models, experiences
• Interesting science questions

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CHyMP Model Challenges

• Community
• Intercomparison
• Education
• Data