Seasonal Variability in Soil Parameters | Computational Hydrology for Decision Support

The Illinois State Water Survey partnered with the Illinois Sustainable Technology Center on a study funded by the USDA National Institute of Food and Agriculture grant program to evaluate the seasonal variability of water moving through the soil zone. In this study, led by Mike Krasowski, novel observations and methods were created to simulate the seasonal differences in soil properties that were essential to the movement of water from land surface to the water table.

This work included evaluation of a SoilVue 10 soil moisture probe.

Conceptual diagram of how the soil moisture probe was installed in an agricultural field relative to tile drains and the saturated zone of the field. The soil moisture sensor is well above and does not meet either the tile drain or saturated zone.

Conceptual diagram of SoilVue 10 soil moisture probe installation

A CH4DS researcher uses a hand auger to install a soil moisture probe in the field. Grass near the probe is dried and yellow. Agricultural fields in the background have been harvested and tilled, while windmills spin in the skyline. — Installation of a soil moisture probe to analyse hydrodynamics in an agricultural setting.

Daniel installing soil moisture sensor

This study allowed the ISWS to make considerable progress on uncertainty evaluation using a genetic algorithm to explore parameters. By chaining models together, we were able to explore the best fit models by season. This work found seasonally variable parameters were essential to capturing changes, specifically in the summer conditions to capture short term spikes.

Model simulations using (a) constant and (b) seasonal hydraulic parameter (SHP) architectures.

Two time series plots of soil moisture content at 40 centimeters depth. The upper plot (a) shows model soil moisture results when the model is calibrated with constant hydraulic parameters. Meanwhile, the lower plot (b) depicts model estimates when calibrated with seasonal hydraulic parameters. The models with seasonal hydraulic parameters better match the field observations, including similarly timed peaks in soil moisture content.