9 Soil Moisture
211
model produced estimates (from measured rainfall) produce adequate definition of
the antecedant rainfall or soil moisture condition.
A Multisensor Aircraft Campaign (MAC) was conducted in July of 1990 with a
focus on microwave sensors, soil moisture and humid region hydrology. The experiment was conducted at the u.s. Department of Agriculture, Agricultural Research Service's Northeast Watershed Research Center experimental watershed
near Klingerstown P A. The passive microwave measurements showed a good
correlation with the ground data and may yield a reliable technique for calibrating
hydrologic models (Wood et aI., 1993) and improve the water budget calculations
of a basin (Lin et aI., 1994).
Multisensor Aircraft Campaigns for hydrology (W ASHIT A 92 and 94) were
conducted in June of 1992 and April and October of 1994 over the Little Washita
Watershed, a u.s. Department of Agriculture (USDA) research facility near
Chickasha, Oklahoma. The Little Washita Watershed is a 610 sq. km drainage
basin situated in the southern part of the Great Plains in southwest Oklahoma. This
MAC focused on both passive microwave and Synthetic Aperture Radar (SAR).
The Passive microwave instrument was theL-band Electronically Steered Thinned
Array Radiometer (EST AR) while the SARs were the JPL AIRSAR (polarimetric
C, Land P band) and the Shuttle Imaging Radar (SIR-C/X-SAR) which had X, C
and L bands. An even more dramatic example of hydrologically significant soil
moisture was derived with the ESTAR during the WASHITA 92 (Jackson et aI.,
1995). From a hydrologic perspective we were able to follow a drying period from
very wet to dry over a period of ten days. It had rained for 26 consecutive days in
Oklahoma when we arrived and initial conditions were very wet. The drying pattern as well as the spatial variability reflected by different soil properties is shown
in Colour Plate 9-.A. Colour Plate 9.A illustrates the spatial and temporal changes
in soil moisture measured with EST AR during 1992 in which we were able to
follow a dry down from an extremely wet condition. Colour Plate 9.B illustrates
the changes in soil moisture observed in1994 with the shuttle imaging radar.
The patterns illustrated in Colour Plate 9.A and their similarity to the soil texture
map has inspired research to investigate if certain physical and hydrologic properties might be determined from a temporal series of the rates of change in soil
moisture. The 1992 EST AR data have been analyzed to produce estimates of soil
texture (represented by the percent sand to clay ratio, and the saturated hydraulic
conductivity (Mattikalli et aI., 1998). Examples of these results are shown in Colour Plate 9.C.
Verhoest et aI., (1998) used a principal components analysis to separate the effects of vegetation, topography and soil moisture from each other using eight ERS1&2 scenes over the Zwalm catchment in Belgium. The resulting product (Colour
Plate 9.D) is an excellent rendition of what one would expect from a partial contributing area process. The dark blue areas represent the storm runoff contributing
areas and the orange and yellow represent regions that could be considered to be
recharge areas and not areas that produce storm runoff.
211
model produced estimates (from measured rainfall) produce adequate definition of
the antecedant rainfall or soil moisture condition.
A Multisensor Aircraft Campaign (MAC) was conducted in July of 1990 with a
focus on microwave sensors, soil moisture and humid region hydrology. The experiment was conducted at the u.s. Department of Agriculture, Agricultural Research Service's Northeast Watershed Research Center experimental watershed
near Klingerstown P A. The passive microwave measurements showed a good
correlation with the ground data and may yield a reliable technique for calibrating
hydrologic models (Wood et aI., 1993) and improve the water budget calculations
of a basin (Lin et aI., 1994).
Multisensor Aircraft Campaigns for hydrology (W ASHIT A 92 and 94) were
conducted in June of 1992 and April and October of 1994 over the Little Washita
Watershed, a u.s. Department of Agriculture (USDA) research facility near
Chickasha, Oklahoma. The Little Washita Watershed is a 610 sq. km drainage
basin situated in the southern part of the Great Plains in southwest Oklahoma. This
MAC focused on both passive microwave and Synthetic Aperture Radar (SAR).
The Passive microwave instrument was theL-band Electronically Steered Thinned
Array Radiometer (EST AR) while the SARs were the JPL AIRSAR (polarimetric
C, Land P band) and the Shuttle Imaging Radar (SIR-C/X-SAR) which had X, C
and L bands. An even more dramatic example of hydrologically significant soil
moisture was derived with the ESTAR during the WASHITA 92 (Jackson et aI.,
1995). From a hydrologic perspective we were able to follow a drying period from
very wet to dry over a period of ten days. It had rained for 26 consecutive days in
Oklahoma when we arrived and initial conditions were very wet. The drying pattern as well as the spatial variability reflected by different soil properties is shown
in Colour Plate 9-.A. Colour Plate 9.A illustrates the spatial and temporal changes
in soil moisture measured with EST AR during 1992 in which we were able to
follow a dry down from an extremely wet condition. Colour Plate 9.B illustrates
the changes in soil moisture observed in1994 with the shuttle imaging radar.
The patterns illustrated in Colour Plate 9.A and their similarity to the soil texture
map has inspired research to investigate if certain physical and hydrologic properties might be determined from a temporal series of the rates of change in soil
moisture. The 1992 EST AR data have been analyzed to produce estimates of soil
texture (represented by the percent sand to clay ratio, and the saturated hydraulic
conductivity (Mattikalli et aI., 1998). Examples of these results are shown in Colour Plate 9.C.
Verhoest et aI., (1998) used a principal components analysis to separate the effects of vegetation, topography and soil moisture from each other using eight ERS1&2 scenes over the Zwalm catchment in Belgium. The resulting product (Colour
Plate 9.D) is an excellent rendition of what one would expect from a partial contributing area process. The dark blue areas represent the storm runoff contributing
areas and the orange and yellow represent regions that could be considered to be
recharge areas and not areas that produce storm runoff.