Wednesday, March 25, 2015

Updates to the Climatic Water Deficit Toolbox - part III (final)

Soil available water supply is used to allow some of the water to be stored in the soil from one month to the next. Coarse soil textures hold the least water and fine soil textures the most. A fraction of the soil water can be extracted when PET exceeds the soil water. Usually the depth of soil for which plant-available water is assumed to be 1.5 meters. In the maps below soil water content is modeled for April, June, and August with green colors showing the highest soil water.

Actual evapotranspiration is estimated using a Thornthwaite water balance model. The Thornthwaite approach only requires monthly temperature and precipitation and doesn't require daily data or wind speed like the Penman-Monteith. The maps below show estimates of AET for April, June, and August with greens representing the highest values.

The climatic water deficit is calculated as the difference between PET and AET and can be thought of as the unmet demand for water expereinced by plants. The maps below are for April, June, and August and browns show areas of highest water deficit.

Climographs can be assembled showing water supply, AET, PET, and CWD for a site. Below are two example climographs. One is for low elevation Smith Valley and the other is for high elevation Pickel Meadow. Can you guess which is which?

To cite this tool:

Dilts, T.E. (2015) Climatic Water Deficit Toolbox for ArcGIS 10.1 - version 03/25/2015. DOI: 10.13140/RG.2.1.4579.0246

Available for download at: