3.1.1.1 Outside the irrigation
season
Figure 3 and Figure 4 show the SM time series at 5, 20, and 50 cm depth
and SMP at 20 cm depth for S09 and S10, respectively. The interquartile
range (Q25-Q75), calculated from 24
measurements (12 nodes with two profiles each) for every depth, shows
considerable variability in SM, especially in S10 and at 50 cm depth.
This reflects the high heterogeneity of soil texture and gravel content
that was observed during soil sampling. When comparing the observed SM
dynamics in the two orchards, S09 showed 4-12 vol% higher SM on average
compared to S10 throughout the measurement period. The soil textural
analysis of both orchards clearly showed a higher clay and organic
matter content, and lower gravel content in S09 compared to S10 (Table
1). Frequent rainfall during the winter months (631 and 606 mm in 2021
and 2022 respectively) kept the soil close to saturation with average
SMP around -8.5 kPa in both orchards. Starting in April the soil
gradually became drier causing a steep decline in SMP to around -500 kPa
(S09) and -300 to -400 kPa (S10) by mid-May. The decline resulted from
low rainfall amounts and increased evaporation demand along with water
consumption from the grasses in the alleys and the fruit trees. In
addition to the observations, the simulation results using both the
standard CLM5 irrigation routine and the irrigation data stream are
shown for the corresponding CLM5 soil layers in Figure 3 and Figure 4.
Table 4 lists the model quality parameters used to evaluate the
simulation results. The model simulations outside the irrigation season,
using either irrigation approach, corresponded well to the observed SM
in S09. However, in S10, CLM5 overestimated SM in the soil profile by on
average 4.5-7.3 vol%. The observed differences in SM between both
orchards were not captured by the model where SM values in S10 were only
1-2 vol% higher. In April and May, just before the start of the
irrigation season, the simulations showed the strongest deviation from
observed values for both orchards as the soil drying was much less
pronounced in the simulations.