Interactive application to visualize the error and vertical distribution of soil moisture sensor layouts compared to in situ soil cores.
*Press "Compute" to update layout after adding or removing sensor depths.
Observed soil water storage is computed from volumetric water content measured in 1-m long in situ soil cores segmented in the field at 5-cm intervals. These measurements are linearly interpolated to a 1-cm vertical resolution for visualization purposes. In the figure, the 1-cm intervals are displayed using the midpoint of each segment (0.5, 1.5, 2.5, …, 98.5, 99.5 cm). Estimated storage is calculated by assigning the volumetric water content at each selected sensor depth to a specific layer of the soil profile, where the thickness of that layer is determined by the midpoints between adjacent sensors and the user-defined bottom of the profile. Each sensor value is obtained by averaging the observed volumetric water contents of the two adjacent 1-cm layers above and below the sensor depth (e.g., the volumetric water content of a sensor at 5 cm is calculated by averaging the observed values of the 4-5 cm and the 5-6 cm segments). Relative error is computed using the profile storage as follows: |Estimated - Observed| / Observed * 100
Note that using midpoint-based layers produces the same total soil water storage as a linearly interpolated profile. Linear interpolation is therefore shown only to help visualize the estimated soil moisture distribution. Above the shallowest sensor and below the deepest sensor, soil moisture is assumed to be equal to the nearest sensor value rather than extrapolated.
Consider a profile depth of 50 cm with sensors placed at 5, 20, and 40 cm.
The depth intervals represented by each sensor are defined as follows:
In this configuration, the deepest sensor (40 cm) captures the lower portion of the profile and the estimated profile reproduces both the vertical distribution of soil moisture and total storage reasonably well across the entire 0–50 cm depth.
Now consider the same 50-cm profile, but with sensors placed at 5, 10, and 20 cm.
The resulting depth intervals are:
In this case, the sensor at 20 cm is used to represent the entire 15–50 cm portion of the profile. Because no sensor is located below 20 cm, the estimated soil moisture below that depth is assumed to be uniform and equal to the value at 20 cm. This typically leads to a poor representation of deeper soil moisture conditions.
Krueger, E. S., Ashrafi, A., Patrignani, A., Wyatt, B. M., Fiebrich, C. A., Luttrell, C. M., Azizi, S. A., & Ochsner, T. E. (2026). Optimizing soil moisture sensor installation depths and number of sensors for in situ monitoring networks. Vadose Zone Journal.
For comments and suggestions about this website contact: Erik Krueger (erik.kruger@okstate.edu) and Andres Patrignani (andrespatrignani@ksu.edu)