Estimation Of ET Based On Reconstructed Atmospheric Conditions And Remotely Sensed Information Over Last Chance Creek Watershed, Feather River Basin, California

摘要

The restoration of meadow land using the pond and plug technique of gully elimination was performed in nine-mile segments along Last Chance Creek, Feather River Basin, California. In order to assess the impact of these restoration activities on water balance, it is crucial to estimate ET in a sparsely gauged watershed like Last Chance Creek watershed. As this watershed is covered mostly by pasture, shrub, riparian vegetation, and forest, it is difficult to apply the common ET estimation methods for croplands. In this presentation, a procedure to estimate ET from naturally vegetated land based on reconstructed atmospheric data and remote sensed information will be discussed. The ET from natural vegetation is mainly dictated by three factors: atmospheric conditions, vegetation conditions, and soil water conditions. The atmospheric conditions were reconstructed using a hydrodynamic atmospheric model. The vegetation pattern information, obtained by local survey, which may be at the best spatial resolution available, was combined with the satellite remote sensed data from MODIS (MOD15 and MYD15) in order to construct spatially and temporally varied LAI maps for the watershed. Using LAI and surface roughness height, the potential ET, based upon the reconstructed atmospheric conditions, was adjusted for every vegetation type. The soil water condition was estimated using a spatially averaged soil water flow model in which the soil heterogeneity at the subgrid scale was explicitly parameterized. It is shown that the ET over natural vegetation during the historical critical dry and wet period (1982- 1993) in the watershed was successfully estimated and incorporated into the assessment.