Quasi-distributed fiber-optic in-situ monitoring technology for large-scale measurement of soil water content and its application

In the last decades, rainfall thresholds for landslide occurrences were thoroughly investigated, producing several different test cases and relevant technical and scientific advances. However, a recent literature review on rainfall thresholds articles (Segoni et al., 2018), published in journals indexed in SCOPUS or ISI Web of knowledge databases in the period 2008-2016, highlighted significant advances and critical issues about this topic. Only in the 11% of the analysed papers (a total of 115) there were installed instruments for measuring physical parameters other than rainfall. The implication was that, in most cases, the occurrence of landslides was forecasted considering exclusively a rainfall correlation, completely neglecting soil characteristics.A reanalysis dataset (ERA5-Land) providing a consistent view of the evolution of land variables over several decades at an enhanced resolution has been used to evaluate the soil water content. Reanalysis combines numerical model data with observations from across the world into a globally complete and consistent dataset using the laws of physics. A comparison between in situ measurements with the results of the model has been carried out for two sites in Norway (Eidsvoll, Morsa catchmen) with 3 different vegetation types: grass, bush, tree. The results showed a good agreement between the modelled soil water content layer 2 and 3 (respectively representing 2 - 28 cm and 28 -100 cm depths) and, respectively, in-situ measurements at 30 and 50 cm depths.Then, 15 Norwegian basins with moraine and peat covers and, previous landslide occurrences in the period 2009-2018, have been selected for correlations. Combinations of rainfall and soil water contents that triggered and not-triggered landslides have been analysed. Rainfall-soil water content thresholds have been defined for the selected basins highlighting the important role played by soil water content, together with rainfall, in triggering landslides. The use of the soil water content contributed to increase the performance of the thresholds and to reduce the uncertainties of landslide forecast.This paper has been conceived in the context of the project "Klima 2050-Risk reduction through climate adaptation of buildings and infrastructure" http://www.klima2050.no/, and it is included into Work Package 3.3-Early warning systems.&#160;

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Field calibration of ThetaProbe (ML2x) and ECHO probe (EC-20) soil water sensors in a Black Vertosol

Soil Research ◽

10.1071/sr06156 ◽

2007 ◽

Vol 45 (3) ◽

pp. 233 ◽

Cited By ~ 10

Author(s):

J. L. Foley ◽

E. Harris

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Clay Soils ◽

Deep Drainage ◽

Swelling Clay ◽

Field Calibration ◽

Volumetric Measurements

Past studies have shown that soil-specific calibrations are required to attain a higher level of accuracy when measuring soil water content with ThetaProbe and ECHO probe soil water sensors, particularly in swelling clay soils. Both probes were assessed for their capacity to accurately monitor soil water in a deep drainage study on a Black Vertosol. Probes were trialled in situ and calibrated against hand-sampled volumetric measurements. The generic calibrations given by the manufacturers resulted in significant errors in water content estimates for both probes. Using the generic calibration, ECHO probes under-estimated water content by 0.10–0.2 m3/m3, whereas ThetaProbes under-estimated by 0.04 m3/m3 at the wet end and over-estimated by 0.08 m3/m3 at the dry end. The soil-specific calibrations significantly improved the accuracy of both probes. ThetaProbes were chosen for the drainage study. The calibration allowed for accuracy across the full wet–dry range to within 0.001–0.004 m3/m3 of volumetric measurements. ECHO probes were less accurate at the wet end, but still determined soil water content to within 0.02–0.05 m3/m3 of volumetric measurements.

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Evaluating Soil Water Content in a WRF-Noah Downscaling Experiment

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-12-0239.1 ◽

2013 ◽

Vol 52 (10) ◽

pp. 2312-2327 ◽

Cited By ~ 22

Author(s):

Peter Greve ◽

Kirsten Warrach-Sagi ◽

Volker Wulfmeyer

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Land Surface ◽

Root Zone ◽

Regional Scale ◽

Land Surface Model ◽

Surface Model ◽

Flux Partitioning

AbstractSoil water content (SWC) depends on and affects the energy flux partitioning at the land–atmosphere interface. Above all, the latent heat flux is limited by the SWC of the root zone on one hand and radiation on the other. Therefore, SWC is a key variable in the climate system. In this study, the performance of the Weather Research and Forecasting model coupled with the Noah land surface model (WRF-Noah) system in a climate hindcast simulation from 1990 to 2008 is evaluated with respect to SWC versus two reanalysis datasets for Europe during 2007 and 2008 with in situ soil moisture observations from southern France. When compared with the in situ observations, WRF-Noah generally reproduces the SWC annual cycle while the reanalysis SWCs do not. The biases in areal mean WRF-Noah SWCs relate to biases in precipitation and evapotranspiration in a cropland environment. The spatial patterns and temporal variability of the seasonal mean SWCs from the WRF-Noah simulations and from the two reanalyses correspond well, while absolute values differ significantly, especially at the regional scale.

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In situ estimation of actual évapotranspiration. A case study in Argos plain

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.16976 ◽

2018 ◽

Vol 40 (3) ◽

pp. 1409

Author(s):

P. Giannoulopoulos ◽

A. Poulovassilis

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Profile ◽

In Situ Monitoring ◽

Experimental Methodology ◽

Actual Evapotranspiration ◽

Winter Period ◽

Time Step ◽

Matrix Potential

The following work refers to an experimental methodology employed for in situ monitoring of specific soil water fluxes constituting water balance components. The test area is located in the plain of Argos - Greece, within an orange grove. A micrometeorological station was installed in the site, equipped with several sensors for real time monitoring of various atmospheric parameters as well as water content and temperature in the soil profile. The soil profile was made accessible for sampling through a rectangular pit which was excavated close to the station. The soil water content was monitored making use ofTDR sensors which were calibrated against the traditional neutron probe technique and also by soil sampling. Tensiometeres were also installed in four different depths for monitoring the matrix potential. A software programme was developed for the analysis and the evaluation of the data collected in a 10 - minute time step. The analysis of the data showed that the three - year average of Actual Evapotranspiration, in this irrigated field, was approximately 857 mm, out of which almost 600mm occur between April and September and 260 mm in the winter period. Those results show that there is no significant water surplus for deep infiltration and aquifer recharge in clayey and clay - loam soils in this region.

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