Remote sensing of land-use-specific actual evapotranspiration of entire catchments containing plantations (PNC286-1112)
In this FWPA co-funded project, researchers from CSIRO Land and Water determined water-usage across two large study sites that include forestry plantations in NSW (covering over 27,000 square kilometres) and the Green Triangle region of Victoria and South Australia (covering over 32,000 square kilometres).The researchers “blended” low frequency/high resolution Landsat data with high frequency/low resolution MODIS data. The “blended” high frequency/high resolution satellite data was used as input to an algorithm that accurately estimated actual evapotranspiration (AET) across the study sites for all land-uses.
At both study sites the research found that although forestry plantations had high relative rates of AET, due to their smaller area, the impact of forestry plantations at the catchment scale was less than other land uses like agriculture and native vegetation, which used greater volumes of water. Since forestry plantations are planted in higher rainfall parts of the catchment, the study found putting AET rates in a hydrologic context to be important for interpretation of results. When accounting for rainfall (P) variability (reporting water use as AET/P), forest plantations were found to be low water users at the NSW site. There was also high variability of water use across the forestry plantations, suggesting that forestry plantation water use needs to be considered on a site-by-site basis and within the hydrological context of the catchments they are operating in.
Integrating satellite-based estimates of actual evapotranspiration with forestry management and planning information should help plantation managers to better understand water use efficiency; surface water and groundwater usage; and how different forest management actions impact on water use.