909 - NEW, COUPLED MARMITES-MODFLOW MODEL IMPROVING SIMULATION OF SUBSURFACE EVAPOTRANSPIRATION

Alain Pascal FrancesITC, University Twente, Enschede, Netherlands

Maciek Waclaw LubczynskiITC, University Twente, Enschede, Netherlands

As subsurface evapotranspiration is poorly simulated in existing hydrological models, a new, coupled model composed of land surface and soil zone MARMITES model and groundwater MODFLOW-NWT model was developed with the aim of incorporating model-based partitioning and sourcing of evapotranspiration (ET), as part of spatio-temporal water balancing at the catchment scale. The partitioning of ET involves its separation into evaporation and transpiration while the sourcing of evaporation and transpiration involves separation of each of the two into soil and saturated zone components.

The MARMITES-MODFLOW coupled model was applied to the La Mata catchment (Salamanca, Spain) to demonstrate its capability to simulate complex hydrological systems. The catchment was characterized by a semi-arid climate with rainfall 500 mm y-1, granitic bedrock, shallow groundwater and sparse oak woodland. The model was calibrated in transient using daily data of two hydrological years. The water balance results of the partitioning and sourcing of ET involved (in % of rainfall): soil evaporation (34.7%), soil transpiration (8.0%), groundwater evaporation (8.5%) and groundwater transpiration (2.0%). Accordingly, the gross recharge was 28.5% and groundwater exfiltration 17.3%, implying low net recharge 0.7%.

The presented MARMITES-MODFLOW model constitutes a powerful tool to analyze catchment water dynamics and water balances in details, accounting separately for impacts of evaporation and transpiration on groundwater resources. The model generates spatio-temporally variable maps of unsaturated and saturated zone fluxes, well-depicting recharge and discharge zones. It can be particularly helpful in analyzing impacts of climate and land cover changes on groundwater resources and for mapping groundwater dependent ecosystems.

The MARMITES-MODFLOW is developed in Python, open-source and freely available at: http://code.google.com/p/marmites/.

Session S8.9 - Aqua 2015 - 42nd

IAH Congress

1

NEW, COUPLED MARMITES-MODFLOW MODEL IMPROVING SIMULATION OF SUBSURFACE EVAPOTRANSPIRATION

A.P. Francés, M.W. Lubczyński

with contributions of E. Balugani, L.Reyes-Acosta, Ch.v.d.Tol

ITC, University of Twente

Department of Water Resources (WRS)

PROBLEM STATEMENT

Evapotranspiration

partitioning

Sourcing

Net recharge (𝐸𝑥𝑓𝑔 = 0)

𝐸 = 𝐼 + 𝐸𝑠𝑢𝑟𝑓 + 𝐸𝑠𝑜𝑖𝑙 + 𝐸𝑝 + 𝑬𝒈

𝑇 = 𝑇𝑠𝑜𝑖𝑙 + 𝑇𝑝 + 𝑻𝒈

𝐸𝑇 = 𝐸 + 𝑇

𝑅𝑛 = 𝑅 − (𝑬𝒈 + 𝑻𝒈)

3/13

MARMITES-MODFLOW COUPLED MODEL

𝐸𝑇 partitioning and sourcing

Spatio-temporal water flux assessment

transient and distributed grid-based model

land surface hydrological processes

meteorological forcing, interception, surface storage, runoff and evaporation from open water

soil reservoir / unsaturated zone

hydrological processes

evaporation, transpiration, percolation and soil moisture

driving forces

rainfall, potential evaporation and potential transpiration

parameterization

vegetation, soil, percolation zone and aquifer reservoirs

state variables

hydraulic heads and soil moisture

Python programing language

https://github.com/AlainPascalFrances/marmites

MARMITES-MODFLOW COUPLED MODEL

MARMITES-MODFLOW COUPLING

5/13

EVAPORATION AND TRANSPIRATION PARTITIONING

6/13

Vegetation

𝑇 = 𝑇𝑠𝑜𝑖𝑙 + 𝑇𝑝 + 𝑇𝑔

Vegetation and soil types mapped in each grid cell using remote sensing images

Bare soil 𝐸 = 𝐸𝑠𝑜𝑖𝑙 + 𝐸𝑝 + 𝐸𝑔

groundwater evaporation

Exponential decay between

𝐸𝑔 𝑃𝐸𝑔 and the depth of

groundwater table 𝑑 (Shah et al,

2007).

EVAPORATION AND TRANSPIRATION SOURCING

7/12

groundwater transpiration

Example of simulated drying tree behavior

under water stress (notice, with reduction

of soil moisture, first 𝑇𝑔 increases then

decreases with 𝑇 decline).

8/13

semi-arid catchment (~6 km2)

weathered and fractured granite

shallow water table (~2 m)

limited human influence on

water resources

2 main tree species

>20 years monitoring

LA MATA STUDY CASE

water fluxes maps (average of 2 hydrological years)

= -

net recharge (𝑅𝑛)

gross recharge (𝑅𝑔)

𝐸𝑔

𝑇𝑔

𝐸𝑥𝑓𝑔

LA MATA STUDY CASE

10/13

water fluxes maps water fluxes time series

LA MATA STUDY CASE

RAINFALL

EVAPORATION

TRANSPIRATION

11/13

water fluxes maps water fluxes time series

LA MATA STUDY CASE

RAINFALL

RUNOFF

RECHARGE

EXFILTRATION

GW ET

12/13

water fluxes maps

water fluxes time series

water balance at the catchment

scale (Sankey diagrams)

LA MATA STUDY CASE

VEGETATION

SURFACE

SOIL

PERCOLATION

GROUNDWATER

Validation - poster ID 939 (S.5.8)

MARMITES-MODFLOW:

is an open-source code https://github.com/AlainPascalFrances/marmites

partitioning and sourcing of subsurface evapotranspiration

code with spatio-temporally water balance validated with field

independent methods (eddy covariance system, sap flow

measurements, stable isotopes, evaporation modelling);

Introducing processes of partitioning and sourcing of ET into modelling

protocol, makes ET simulation more realistic than ever before; more

realistic models such as M-M, will improve water management but also can

contribute to environmental sciences

Development of Earth Observation Methods can stimulate and fully

automatize the use of satellite remote sensing data as input for integrated

hydrological models

CONCLUSIONS

14/13