The theoretical framework for an ET mapping algorithm is presented along with application of this methodology in two restored and two degraded meadow systems. The algorithm takes advantage of high resolution (FLIR) thermography data and local weather station data to partition the measured available heat flux into the sensible and latent heat components of energy budget in a spatially distributed manner. The sensible heat flux is driven by the difference between the land surface temperature and the air temperature; therefore, FLIR imagery and weather station data can be used to estimate this component. The latent heat flux is directly related to ET and can be calculated as the residual of the energy budget.
The method performed with an estimated accuracy of ±10% for this application and holds potential as a routine monitoring technique for riparian systems. For the first time, the practitioners conducting the restoration (the Feather River Coordinated Resource Management Group) were given a quantitative estimate of changes to the evapotranspiration component of the water budget as a result of restoration efforts. As a result of restoration, this component nearly doubles from about 1.5-4 mm/day xeric vegetation, which dominates degraded meadows (dryland grasses and sagebrush) to 5-6.5 mm/day for healthy wet meadow vegetation (sedges and rushes). Very high resolution data sets (1 m) such as this one will be critical for hydroecological studies by elucidating patterns in vegetative water use and serving as a basis for evaluation of the effectiveness of riparian restoration.
Flowchart for ET mapping algorithm (ETMA)