Soil water sensing methods - Usefulness for evapotranspiration monitoring and links to remote sensing

November 25, 2013 | 09:15 h - 10:45 h

Second ZEF/ZFL colloquium with Steven R. Evett, Lead Scientist and Acting Research Leader of the Soil and Water Management Research Unit at the Conservation & Production Research Laboratory in Bushland, Texas, USA.

Date: Monday, November 25, 9.15 a.m.

Venue: ZEF, Walter-Flex-Straße 3, 53111 Bonn

Abstract:

Soil water sensing methods are widely used to characterize the rhizosphere and below, but only a few are capable of delivering water content data with accuracy for the entire soil profile such that evapotranspiration (ET) can be determined by soil water balance with minimal error.

The methods evaluated here are a) the neutron probe (NP), which when field calibrated and appropriately used can resolve ET over weekly or longer intervals with acceptable accuracy for most uses, b) the Cosmic Ray Soil Moisture Observing System (COSMOS), which responds to surface soil water content changes in a circular area of radius up to several hundred meters, c) capacitance sensors, and d) time domain methods.

Heretofore prohibitively expensive and difficult to use deeply, time domain methods are becoming reasonably priced. Relatively inexpensive sensors using both time domain reflectometry and time domain transmission methods are on, or coming to, the market, including one that measures deeply enough for ET determination by soil water balance. Recent experiments at Bushland, Texas, demonstrate current challenges and successes in implementing this down-hole technology for soil profile water content determination and water balance computations.

These can be used to characterize field-scale ET which may be useful for remote sensing studies.

Publications : http://www.cprl.ars.usda.gov/swmru-publications.php

Information: www.ars.usda.gov