Fall AGU 2001 Hydrogeophysics Session

Document Sample
Fall AGU 2001 Hydrogeophysics Session Powered By Docstoc
					   SPATIAL AND TEMPORAL VARIABILITY OF SOIL MOISTURE
      CONTENT OBTAINED USING GPR DATA: ACCURACY,
       RESOLUTION, AND IMPLICATIONS FOR PRECISION
                      VITICULTURE

S. Hubbard (1,2), K. Grote (2), I. Lunt (2), L. Pierce (3), and Y. Rubin (2)

(1) Lawrence Berkeley National Laboratory, Berkeley, CA 94720
    sshubbard@lbl.gov,
(2) Dept. of Civil and Environmental Engineering, UC Berkeley, Berkeley, CA
    94720
(3) California State University, Monterey Bay , Seaside, California 93955

        The ability to optimize winegrape production necessitates
an understanding of the factors that influence their spatial and
temporal variability. In the U.S. and in Australia, the majority of
precision viticulture has focused on investigating the link between
winegrape parameters and above-ground factors, such as the
training, cultivation, and harvest timing of the grapes. Through
trial and error and over hundreds of years, French winemakers
have learned that certain soils and meteorological conditions
produce finer wines than others. However, within new-world wine
producing areas, where much of the active development and
experimentation of grape growing and wine making is performed,
very little emphasis has been given to investigating the role of soil
properties on winegrapes. This is partly due to that fact that
heretofore, most soil characterization has been performed using
invasive methods (such as by digging backhoe pits). These
techniques are invasive and laborious, and yet still provide
information at a single point in time/space only, which is often
insufficient to capture the field-scale variability in soil properties
that are observed in winegrapes.

         We have investigated the applicability of ground
penetrating radar (GPR) methods to provide very high resolution
estimates of near surface water content within two California
vineyard study sites: the Robert Mondavi Vineyard in Napa
County and the Dehlinger Vineyard within Sonoma County. Using
the travel time of ground- and reflected wave events, we estimated
the dielectric constant and subsequently the soil water content of
the soil layers in very high resolution at both sites. Comparison of
our GPR-obtained estimates with conventional measurements of
water content, soil texture and plant vigor measurements
illustrated that the GPR estimates are accurate and reliable, and
that water content, soil texture and plant vigor are correlated. Use
of the GPR-obtained information in ecosystem numerical models
suggested that high-resolution water content information is crucial
for optimal management of vineyards. In this study, we illustrate
the potential of GPR as a tool for investigating the spatial
variability of soil water content, as well as the impact of utilizing
high resolution water content information for precision viticulture
practices.

				
DOCUMENT INFO