Decadal simulation of winter deep percolation driven by snowmelt and precipitation using HYDRUS-1D

Deep percolation (DP) assessment is a critical component of groundwater recharge and plays a key role in sustaining groundwater resources in cold regions, where snowmelt and precipitation are the major drivers of subsurface water movement, particularly in coarse-textured soils. This experiment investigated winter season (November–April) DP (flux below the root zone) dynamics driven by rainfall and snowmelt (SNM) using HYDRUS-1D across common soil types for 10 years (2014–2015 to 2023–2024) of climatic data from two locations. Decadal hydrological data (rainfall with SNM) were used to estimate the interannual fluctuations in bottom flux, surface runoff, and evaporation for each soil type and location. Results indicated that water budget inputs (rainfall and SNM) and outputs (bottom flux from the root zone, surface runoff, and evaporation) varied across years, soil types, and locations. Higher water budget inputs led to increased bottom flux, with the magnitude greatly influenced by rainfall intensity and frequency over the years. Surface runoff and evaporation exhibited significant annual variability among soils and locations due to different hydraulic characteristics. Approximately 73% and 69% of the bottom flux from the root zone of the total inputs (rainfall + SNM) was observed for Entrican and Mendon locations. In Entrican, the decadal average bottom flux from the root zone was 62% and 83% for Riddles–Hillsdale sandy loam and Oakville fine sand, respectively. Contrary to this, in Mendon, the average decadal bottom flux from the root zone was 55% and 83% for Riddles–Hillsdale sandy loam and Oakville fine sand, respectively. Overall, the interannual variability of bottom flux varied from 37% to 76% for Oakville fine sand and from 75% to 89% for Riddles–Hillsdale sandy loam. This research highlights the critical role of soil hydraulic characteristics in the influence of climatic variability on soil water dynamics, especially the bottom flux from the root zone under changing climatic scenarios.