Water content estimated from point scale to plot scale

Akyürek, Sevda Zuhal
Demir, Gokben
Abgarmi, Bizhan
Binley, Andrew
Soil moisture controls the portioning of rainfall into infiltration and runoff. Here we investigate measurements of soil moisture using a range of techniques spanning different spatial scales. In order to understand soil water content in a test basin, 512 km2 in area, in the south of Turkey, a Cosmic Ray CRS200B soil moisture probe was installed at elevation of 1459 m and an ML3 ThetaProbe (CS 616) soil moisture sensor was established at 5cm depth used to get continuous soil moisture. Neutron count measurements were corrected for the changes in atmospheric pressure, atmospheric water vapour and intensity of incoming neutron flux. The calibration of the volumetric soil moisture was performed, from the laboratory analysis, the bulk density varies between 1.719 (g/cm3) -1.390 (g/cm3), and the dominant soil texture is silty clay loam and silt loamThe water content reflectometer was calibrated for soil-specific conditions and soil moisture estimates were also corrected with respect to soil temperature. In order to characterize the subsurface, soil electrical resistivity tomography was used. Wenner and Schlumberger array geometries were used with electrode spacing varied from 1m- 5 m along 40 m and 200 m profiles. From the inversions of ERT data it is apparent that within 50 m distance from the CRS200B, the soil is moderately resistive to a depth of 2m and more conductive at greater depths. At greater distances from the CRS200B, the ERT results indicate more resistive soils. In addition to the ERT surveys, ground penetrating radar surveys using a common mid-point configuration was used with 200MHz antennas. The volumetric soil moisture obtained from GPR appears to overestimate those based on TDR observations. The values obtained from CS616 (at a point scale) and CRS200B (at a mesoscale) are compared with the values obtained at a plot scale. For the field study dates (20-22.06.2017) the volumetric moisture content obtained from CS616 were 25.14%, 25.22% and 25.96% respectively. The values obtained from CRS200B were 23.23%, 22.81% and 23.26% for the same dates. Whereas the values obtained from GPR were between 32%-44%. Soil moisture observed by CRS200B is promising to monitor the water content in the soil at the mesoscale and ERT surveys help to understand the spatial variability of the soil water content within the footprint of CRS200B.
Citation Formats
S. Z. Akyürek, G. Demir, B. Abgarmi, and A. Binley, “Water content estimated from point scale to plot scale,” presented at the AGU 2017, 2017, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/71158.