Key Points :
- The CLM5 irrigation scheme is applied at the point and regional scale
and enhanced with the option to use prescribed irrigation data
- Soil moisture dynamics were simulated well using the prescribed data
while the default irrigation could not fully reproduce field practices
- Regional simulations using different irrigation scenarios suggest
substantial water saving potential for improved irrigation management
Abstract
Irrigation strongly influences land-atmosphere processes from regional
to global scale. Therefore, an accurate representation of irrigation is
crucial to understand these interactions and address water resources
issues. While irrigation schemes are increasingly integrated into land
surface models, their evaluation and further development remains
challenging due to data limitations, e.g. irrigation amounts and timing,
and soil moisture (SM). This study assessed the representation of
irrigation and its effect on crop yield in the Community Land Model
version 5 (CLM5) through implementation of an irrigation data stream
that allows to directly use observed irrigation data. Simulations were
conducted at the point scale for two instrumented apple orchards using
the CLM5 irrigation routine as well as the implemented data stream.
Furthermore, irrigation requirements and the effect of deficit
irrigation on crop yield and crop water use efficiency (CWUE) at the
regional scale were simulated and discussed. The irrigation data stream
performed better in representing observed SM dynamics compared to the
standard irrigation routine that could be further improved by
implementing more flexible irrigation schedules and irrigation
efficiency. At the regional scale, simulated irrigation and yield showed
a high sensitivity to climatic changes caused by the topographic
gradient. While a 25 % reduction in irrigation had negligible negative
effect on simulated yield and CWUE, a reduction of 50 % notably reduced
both variables. These effects varied with climatic conditions, soil
properties and timing of irrigation. These results showcase how CLM5
could be utilized for irrigation and water resources management.