Sensitivity-Informed Parameter Selection for Improved Soil Moisture Estimation from Remote Sensing Data

TL;DR

This paper presents a sensitivity-informed framework for selecting estimable soil hydraulic parameters from remote sensing data, leading to significantly improved soil moisture estimation accuracy in large-scale agricultural fields.

Contribution

It introduces a novel combination of sensitivity analysis, orthogonal projection, and data assimilation to reliably estimate key soil parameters from sparse remote sensing data.

Findings

Soil moisture estimation accuracy improved by 24-43%.

Predictive model performance increased by 50%.

Estimated parameters align well with experimental measurements.

Abstract

Improving the accuracy of soil moisture estimation is required for advancing irrigation scheduling and water conservation efforts. Central to this task are soil hydraulic parameters, which govern moisture dynamics but are rarely known precisely and must therefore be inferred from observational data. In large-scale agricultural fields, estimating the complete set of these parameters is often impractical due to the sparse and noisy nature of available measurements. To address this challenge, this work develops a framework that uses sensitivity analysis and orthogonal projection to identify parameters that are both reliably estimable from available data. These parameters, together with the spatial distribution of soil moisture, are jointly estimated by assimilating observational data into a cylindrical-coordinate version of the Richards equation using an extended Kalman filter. The soil moisture measurements are obtained from microwave remote sensors mounted on center pivot irrigation systems - an emerging and practical technology for capturing field-scale variability. Numerical simulations and field experiments conducted on a large-scale site in Lethbridge, Alberta, Canada, demonstrate that the proposed method improves soil moisture estimation accuracy by 24-43% and enhances predictive model performance by 50%. Furthermore, the estimated parameters - particularly saturated hydraulic conductivity - exhibit good agreement with experimental measurements.