Root Zone Water Fluxes for Victorian Landscapes

Background | Objectives | Methodology | Outputs | Implications | Next users of project outputs | Contacts

Background
Policy makers and natural resource managers are increasingly requiring spatially distributed information to support policy development, creation of policy instruments and management decisions on surface water and groundwater, wetlands and riparian zones, salinity, nutrients, and irrigation modernisation. Northern Victorian irrigated landscapes are undergoing significant, continuous and rapid changes in land use and water management practices in response to changing climatic conditions, markets and government policies. Hydrological processes at field to catchment scales are similarly undergoing major changes. As a result, new data and data acquisition approaches are required in order to reliably model and manage Goulburn Murray Irrigation District (GMID) (external link) catchments. Spatially distributed root zone water flux data, in particular reliable estimates of deep percolation under different land uses, soil types, watertable and climatic conditions are fundamental for modelling and managing the GMID.

Objectives To provide monthly to annual estimates of root zone water fluxes for different climatic conditions, land uses, soils and watertable depths in GMID irrigation regions. To assess the uncertainty and sources of uncertainty of root zone water flux estimates. To develop simple approaches for repeatable estimation of monthly to annual deep percolation and surface runoff at field to regional scales. Methodology The project will provide fundamental root zone flux information at spatial and temporal resolutions appropriate for management. It will do this by integrating a range of spatial data sets, including remotely sensed estimates of evapotranspiration, with a spatially distributed hydrological model.

The methodology will allow for future, progressive refinement of root zone flux estimates when new or more accurate data become available. The information generated by the project will significantly add to our existing knowledge base for achieving sustainable management of irrigated landscapes.

The model application will feature the following three innovations: The use of remote sensing data including actual evapotranspiration estimates obtained using DPI-SEBAL and land use information based on remotely sensed Enhanced Vegetation Index time series. The application of sub-catchment scale base flow and surface runoff data (separated using isotopic/chemistry information) to better estimate groundwater and surface water related model parameters respectively. The calibration of only a few, global, catchment scale pedotransfer function parameters instead of many local, spatially distributed SWAT model parameters, which will reduce the number of model parameters to be estimated.

Outputs
This is a three year project in its first year of implementation. Anticipated outputs from the project include:

• reliable and repeatable field to regional scale root zone water flux estimates in irrigation landscapes,
• field to regional scale root zone water fluxes for different land use / soil type / watertable / climate conditions,
• estimates of uncertainty in root zone water fluxes and sources, and
• "rules of thumb" for deep percolation and runoff estimates under different conditions.

Implications
Northern Victorian irrigated landscapes are undergoing significant, continuous and rapid changes in land use and water management practices. Reliable and repeatable field to regional scale root zone water flux estimates in irrigation landscapes will:

• improve the performance and credibility of distributed catchment and groundwater models used to make decisions about irrigated land and water management,
• better inform surface and groundwater management policies,
• provide guidance for future monitoring data acquisition, and
• provide information about likely risks and uncertainties of land and water management actions and strategies.

Next users of project outputs
Policy makers and natural resource managers who make use of the spatial distributed information directly.

Policy makers and natural resource managers who undertake or commission distributed hydrological modelling.

Developers of distributed hydrological models of the Riverine Plains.

Contacts Dr. Thabo Thayalakumaran or Dr. Benny Selle Landscape and Water Sciences Future Farming Systems Research Division Department of Primary Industries Ferguson Road, Tatura, VIC, 3616. Phone : (03) 5624 2317 or 5824 5534 Email: thabo.kumaran@dpi.vic.gov.au benny.selle@dpi.vic.gov.au

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