Improved Vertical Streambed Flux Estimation Using Multiple Diurnal Temperature Methods in Series

Area of Science:

• Environmental Science
• Hydrology
• Geophysics

Background:

• Estimating vertical fluxes between groundwater and surface water is crucial for understanding hydrological systems.
• Traditional methods using amplitude ratios (Ar) or phase shifts (Δϕ) of diurnal temperature signals often yield conflicting results.
• Recent analytical solutions combining Ar and Δϕ have reduced uncertainty but can be sensitive to signal identification.

Purpose of the Study:

• To develop an improved method for estimating vertical fluxes between groundwater and surface water.
• To address limitations in identifying amplitude ratios and phase shifts from temperature data.
• To enhance the reliability and accuracy of flux calculations using diurnal temperature signals.

Main Methods:

• An add-on program for VFLUX 2 was developed to integrate amplitude ratio (Ar) and phase shift (Δϕ) methods.
• Thermal diffusivity was determined from a reliable period using the combined Ar Δϕ method.
• Fluxes were recalculated using the Ar method with the determined thermal diffusivity.
• Sensor spacing calculations were used to identify unreliable flux estimates and assess streambed scour.

Main Results:

• The integrated approach maximizes the benefits of both Ar and Ar Δϕ methods.
• Recalculating fluxes using the Ar method after determining thermal diffusivity improved parameter estimates.
• Sensor spacing calculations proved useful for identifying unreliable flux periods and assessing streambed scour.
• The combined methods in series were particularly effective for conditions with fluxes exceeding 1 m/d.

Conclusions:

• The presented VFLUX 2 add-on program offers a robust solution for improving groundwater-surface water flux estimations.
• This approach enhances the reliability of flux calculations, especially in challenging conditions.
• The method provides valuable insights into hydrological processes and streambed conditions.