Agriculture Reference
In-Depth Information
and Europe, with the
1-
D Integrated Crit-
ical Zone (ICZ) model. The PIHM code is a
multi-process hydrologic model and geo-
graphic information system (GIS) toolkit
for building unstructured numerical mesh
with initial estimates of parameters over
the catchment domain. Major hydro-
logical processes are fully coupled by the
semi-discrete finite volume approach,
simulating water, energy and solute trans-
port at the catchment scale (Qu and Duffy,
2007; Kumar
et al
., 2009, 2010). PIHM can
also solve for plant water uptake compo-
nents, groundwater-stream exchange and
recharge over the catchment stream network
(
Fig. 8.3
). The transport equations in PIHM
allow the simulation of residence time and
age of water in soils, groundwater and
streams.
The 1D-ICZ model simulates key soil
ecosystem functions such as biomass pro-
duction, carbon and nutrient sequestra-
tion, water transformation and filtration
and belowground biomass production. The
1D-ICZ is a combination of four submod-
els: (i) a flow, transport and bioturbation
model, HYDRUS 1D, which simulates flow,
heat and solute transport in the unsatur-
ated zone; (ii) a chemical equilibrium
model and weathering to account for the
Tr anspiration
Precipitation
Infiltration
Evaporation
Precipitation
Unsaturated zone
Evaporation
Recharge
Capillary lift
Solar radiation
Lateral flow
Saturated zone
Groundwater flow
Precipitation
Down flow
Bedrock
Evaporation
Infiltration
Recharge
Groundwater flow
Bedrock
Fig. 8.3.
Spatial discretization used for the numerical representation of the watershed in PIHM. Interact-
ing hydrologic processes are assigned to each prismatic element (top left) and on each linear river
element (top right). The local system of ordinary differential equations (ODEs) corresponding to the
processes acting on a unit prismatic element is termed as 'model kernel. (From Qu and Duffy, 2007.)
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