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Monitoring Daily Vegetation-Soil-Water Balance Components using the VegET Model

Gabriel Senay [e-mail] (Updated: April, 2009)

The VegET model (Senay, 2008) integrates commonly used water balance algorithms with remotely sensed Land Surface Phenology (LSP) parameter to conduct operational vegetation water balance modeling of rainfed crop and grassland systems at the LSP’s spatial scale using readily available global weather data sets for rainfall (Xie and Arkin, 1997) or NOAA’s new precipitation product (blend of NEXRAD and station data) for the US
(http://www.srh.noaa.gov/rfcshare/precip_about.php) and reference evapotranspiration (Senay et al., 2008)

The VegET model conducts daily water balance on a pixel-by-pixels basis and produces several agro-hydrologic products. The following products are routinely posted on a website for season monitoring and early warning applications:

Product Type: 1) Soil Water Index (SWI) 2) Water Requirement Satisfaction Index (WRSI) 3) Cumulative ETa 4) Cumulative ETa Anomaly 5) Cumulative ETa Forecast Anomaly

Note: the growing season for the US is assumed to occur from April 1 through October 31 of each year. Thus, products that require cumulative values start from April 1. The model initializes the soil moisture 60 days prior to April 1st.

Graphics Label: 1) NatVeg: indicates the modeling pixel is for a landscape with natural vegetation. A mix of crop and natural vegetation under a rained influence, i.e., no irrigation is considered in this product.

2) Date Example: 2009-04-20 indicates this product is produced by taking into account agro-hydrologic processes from the beginning of an assumed growing season (April 1 for USA) till the current date of April 20 in 2009. The end-of-season for USA is considered to be end of October.

Brief Description of Operational Graphical Products, posted on the website: http://earlywarning.usgs.gov/usewem/

1. Soil Water Index (SWI)

The values in