Soil water content estimation from point scale to plot scale

Demir, Gökben
Estimating soil moisture is crucial for understanding vadose zone and surface hydrology dynamics. In this study, soil moisture measurement is investigated by using a range of techniques spanning different spatial scales in a test basin in the south of Turkey. A cosmic ray sensor soil moisture probe (CRS) and a water content reflectometer (CS-616) have been installed for retrieving volumetric soil moisture data continuously. Lab analyses have been performed for calibrating the installed instruments and to obtain the pore water electrical conductivity range in the study area. The average pore water conductivity value is obtained as 933 μS/cm, and it is observed that the variation of the pore water conductivity is not directly related to clay content. Electrical resistivity imaging (ERI) was used to map water content variation in a 2-D shallow unsaturated zone within the footprint of the CRS. Schlumberger and WennerAlpha electrode array with 0.50 m electrode spacing were used along 19.5 m resistivity profiles in the field surveys. Soil moisture measurements were done with CS-616 at these profile locations, concurrently. Archie’s Law has been used to reveal the relationship between soil moisture and resistivity. Archie’s cementation index (m) and saturation index (n) were calculated for the footprint as 1.57 and 1.152, respectively. This study reveals that ERI has limited sensitivity to the moisture content in the study area, whereas the CRS shows good agreement with the values obtained from the installed CS-616 at point-scale, and rainfall amount observed at a nearby meteorological station.


Opportunities and challenges in using soil moisture from cosmic ray neutron sensing for rainfall-runoff modelling
Duygu, Mustafa Berk; Akyürek, Sevda Zuhal; Department of Civil Engineering (2021-9-08)
Retrieving or estimating soil moisture is one of the most important elements of hydrology, since most of the hydrological studies consider the absence (drought) or excessiveness (flood) of water stored in the soil. Water stored in a basin has a very strong relation with the amount of soil moisture thus knowing the soil moisture significantly facilitates the estimation of other parameters of the hydrological cycle. For agricultural decision making systems, it is also vital to know whether the plants receive ...
Obtaining soil-water characteristic curves by numerical modeling of drainage in particulate media /
Shoarian Sattari, Amir; Toker, Nabi Kartal; Department of Civil Engineering (2014)
The soil water characteristic curve (SWCC) reflects fundamental drainage properties of partially saturated soils by revealing the relation between soil suction and water content. Although during the past decades, various experimental methods have been proposed for obtaining the SWCC, these approaches are generally time consuming, expensive and highly dependent on operator skills. One solution to this has been sought through various empirical or physico-empirical formulations that link the SWCC to common soi...
Swell pressure prediction by suction methods
Kandemir, A; Erol, O; Erzin, Y (1997-09-12)
Soil suction is the most relevant soil parameter for characterization of the swell behaviour. An attempt has been made to predict the swell pressures from soil suction measurements. Bentonite-Kaolinite clay mixtures were prepared to obtain soils in a wide range of plasticity indices. Suction measurements using thermocouple physchrometer technique and constant volume swell tests in oedometers were made on statically compacted specimens. Soil suction is correlated to plasticty index, water content and dry den...
Swell pressure prediction by suction methods
Erzin, Yusuf; Erol, Orhan (2007-07-10)
Soil suction is the most relevant soil parameter for characterization of the swell behavior. An attempt was made to predict swell pressures from soil suction measurements. In this study, Na-bentonite was mixed with kaolinite in the ratios of 5, 10, 15, 20 and 25% of dry kaolinite weight to obtain soils in a wide range of plasticity indices (i.e. 30, 50, 68, 84 and 97%). Suction measurements using thermocouple psychrometer technique were made on statically compacted specimens. The dependence of soil suction ...
Vegetation water content during SMEX04 from ground data and Landsat 5 Thematic Mapper imagery
Yılmaz, Mustafa Tuğrul; Goins, Lyssa D.; Ustin, Susan L.; Vanderbilt, Vern C.; Jackson, Thomas J. (Elsevier BV, 2008-02-15)
Vegetation water content is an important parameter for retrieval of soil moisture from microwave data and for other remote sensing applications. Because liquid water absorbs in the shortwave infrared, the normalized difference infrared index (NDII), calculated from Landsat 5 Thematic Mapper band 4 (0.76-0.90 mu m wavelength) and band 5 (1.55-1.65 mu m wavelength), can be used to determine canopy equivalent water thickness (EWT), which is defined as the water volume per leaf area times the leaf area index (L...
Citation Formats
G. Demir, “Soil water content estimation from point scale to plot scale,” M.S. - Master of Science, Middle East Technical University, 2018.