Improving the SHAW model’s performance in seasonally freeze-thaw irrigation districts by integrating the capillary bundle model

Le résumé fourni par la source

Accurate simulation of soil water-heat-salt dynamics during freeze–thaw cycles is critical for water/salinity management in arid shallow-groundwater regions. We develop SHAW-FH-CBM—a modified model integrating the capillary bundle model (CBM) with frost heave (FH) physics based on a laboratory test for soil freezing characteristic curve (SFCC) measurement—to overcome limitations in existing SHAW/SHAW-FH models. Validated against field data (Hetao Irrigation District, winters in 2019–2021), SHAW-FH-CBM uniquely captures two key processes: (1) Early freezing: frost heave rapidly elevates topsoil moisture (≤10 cm depth) to 0.6 m 3 m −3 , underestimated by the SHAW model due to erroneous hydraulic parameters. (2) Stable freezing: soil moisture declines to 0.35 m 3 m −3 through evaporation, missed by SHAW/SHAW-FH where ice impedance model (IIM) outputs zero hydraulic conductivity below critical temperatures (–0.75 to –5.2 °C). In contrast, CBM enables water flux (∼10 −11 cm s −1 ) and salt accumulation in frozen soil via salinity-dependent SFCCs. SHAW-FH-CBM improves soil moisture/salt simulation accuracy by 36–41 %, providing a validated tool for cold-region agricultural water management.

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