Challenges in determining soil moisture and evaporation fluxes using distributed temperature sensing methods.

Area of Science:

• Environmental Science
• Hydrology
• Geophysics

Background:

• Protecting arid zone groundwater-dependent ecosystems requires accurate soil moisture and evaporation monitoring.
• Existing methods for quantifying these variables need further assessment and improvement.

Purpose of the Study:

• To develop and evaluate a new method for determining groundwater evaporation rates.
• To combine actively heated fiber-optic (AHFO) sensing with vadose zone modeling for enhanced environmental monitoring.

Main Methods:

• Utilized the actively heated fiber-optic (AHFO) method to estimate soil moisture (θ) profiles.
• Employed vadose zone modeling, initially assuming the evaporation front remains at the soil surface.
• Achieved a spatial resolution of ~6.5 mm for soil moisture measurements.

Main Results:

• The AHFO method provided soil moisture estimates with an error of 0.026 m³ m⁻³.
• Numerical modeling showed discrepancies in the soil moisture profile compared to measurements, particularly at the surface.
• Sensitivity analyses indicated a need for higher precision in soil hydraulic parameter determination.

Conclusions:

• The proposed method shows promise for estimating groundwater evaporation but requires refinement.
• Future improvements should incorporate soil heat-vapor-water dynamics and relax the surface evaporation front assumption.
• Enhancing the AHFO calibration curve can reduce errors and broaden applicability across soil textures.