The dynamics in the ETact becomes apparent when viewing the following animation. The significant temporal variability is caused by changes in weather conditions, leaf area development and the changing soil moisture and soil salinity status. The monthly ET and biomass production data is organized by county, but could be compiled for other geographic areas, such as watersheds.
Monthly ETact and BIO values per county (Arc/View shape, 0.2MB)
An alternative option for organizing the data is to express the temporal variability per land use category. A high resolution 30m land use database from 1992 made by the USGS National Land Cover Characterization team has been used for this purpose (see http://edcwww.cr.usgs.gov/programs/lccp/natllandcover.html ). The 21 land use classes have been resampled to reduce the number of classes to 12. The MODIS ET images have been disaggregated using the fixed specific presence of certain land use classes in each MODIS pixel. The monthly ET results of the six dominant land use classes are demonstrated. This graph describes the aerially averaged monthly ET for each land use class (50% of the pixels in that class have lower and 50% have higher ETact values).
The variation within each land use class can be significant due to the soil moisture status during the summer season. The evaporative demand of the atmosphere during June and July reaches its maximum, and depending on the water availability to the roots, this demand may or may not be met. Although the average wetland has an ETact of 200mm/month in July, the very top values are 350mm/month (+95% confidence) and the lowest values of dried down natural ecosystems have no moisture left for evaporation.
Total annual evapotranspiration values were computed from monthly MODIS images; 12 original images were used to create this composite map that contains the annual accumulated values. SEBAL computes actual evapotranspiration (ETact) and dry matter production (BIO) simultaneously. The CIMIS network of automatic weather stations has been used in conjunction with the DAYMET high resolution climate … Continue reading
Using MODIS satellite data, SEBAL was used to compute actual evapotranspiration and the biomass production for the entire state of California for 2002. FREE samples of this coarse-resolution (1000m) data are available below for different time scales. Additionally, high-resolution (30m) data for Kesterson National Wildlife Refuge are available for downloading. These two data samples illustrate … Continue reading
The SEBAL model has during the course of years been extended with different output layers, making it more useful to a larger spectrum of analysts. Whereas a River Basin Commission might be interested in water depletions only (i.e. ETact), the irrigation engineer and farmers want to see a map of crop water stress (i.e. ETpot-ETact). … Continue reading
According to its mission statement, the Oakdale Irrigation District (OID) in California’s San Joaquin Valley is committed to “providing dependable irrigation and domestic water service to its constituents at the lowest and most efficient cost possible. The District is committed to excellence in resource management and all aspects of its operation.” SEBAL technology was utilized … Continue reading
The Yakima River flows for over two hundred miles through south central Washington, and, with its tributaries, drains about 6,150 square miles or 4 million acres. The river originates in Kittitas County from Keechelus and Kachess Lakes on the east side of the Cascade Mountains near Snoqualmie Pass. The Yakima River flows southeast through the … Continue reading
SEBAL has been employed on more than 150 projects in 15 countries, including nine projects in the United States. The U.S. projects are summarized in the table below. River Basin State(s) Year(s) of Study Year(s) of Images Client Use of ET maps Bear River Idaho, Utah, Wyoming 2000 1985 IDWR Bear River Compact Compliance on … Continue reading
Digital version of the full papers will be send to you upon request ( firstname.lastname@example.org )(email@example.com) Bastiaanssen, W.G.M., M. Menenti, R.A. Feddes and A.A.M. Holtslag, 1998. The Surface Energy Balance Algorithm for Land (SEBAL): Part 1 formulation, J. of Hydr. 212-213: 198-212 Bastiaanssen, W.G.M., H. Pelgrum, J. Wang, Y. Ma, J. Moreno, G.J. Roerink and … Continue reading
Landsat Enhanced Thematic Mapper Temporal resolution – 16 days Spatial resolution – – – 30m (RED, NIR, SWIR, b1-5,7) 60m (TIR, b6) 15m (VIS, b8) Spatial coverage – 180×180 km Operational since – 1985 (Landsat5) 1999 (Landsat7) Cost – US$600 – 1500 per image More info – www.eurimage.com www.landsat.org NOAA AVHRR (Advanced Very-High Resolution Radiometer) Temporal resolution – 14 times per day Spatial … Continue reading
Irrigated crops The Bear River Basin covers portions of Idaho, Utah, and Wyoming and contains about 470,000 acres of crop and pasture land. For the basin, a comparison was made between SEBAL-based ET and available lysimeter data for two growing seasons. For 1985 four Landsat-TM images during the growing season (July 14, August 15, September … Continue reading