Fig. 1. The time response curve and scattergram is shown for Plot 2423's wetness index, y(t). For both estimation methods, the wetness duration index is 36.5. The model has R² = 0.974 for 31 observations (P < 0.0001). The selected regression model is two splined line segments with a common join point; formally, it can be written as follows:

The gray band is the 95% confidence interval, the dashed line represents the model estimates, and the black circles are the wetness index values estimated by scaling the soil matric potential observations.