Qin et al. (2026) Simulation Experiment on the Effect of Saline Reclaimed Water Recharge on Soil Water and Salt Migration in Xinjiang, China

Identification

• Journal: Water
• Year: 2026
• Date: 2026-01-16
• Authors: Jiangwen Qin, Tao Zhou, Jihong Zhang, Tao Zhao, Ankun Wang, Hongbang Liang, Wenhao Li, Meng Li
• DOI: 10.3390/w18020238

Research Groups

• College of Water Conservancy & Architectural Engineering, Shihezi University, Shihezi, China
• Key Laboratory of Modern Water-Saving Irrigation of Xinjiang Production & Construction Group, Shihezi University, Shihezi, China
• Corps Saline-Alkali Land Comprehensive Utilization Engineering Technology Center, Shihezi, China
• Corps Agricultural Water and Fertilizer Efficient Key Equipment Technology Innovation Center, Shihezi, China
• Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
• Department of Water Resources of Xinjiang Uygur Autonomous Region, Urumqi, China

Short Summary

This study experimentally determined the optimal salinity of reclaimed water for improving soil infiltration and desalination in Xinjiang's saline-alkali soils, identifying 2 g L−1 as the most effective concentration for enhancing water movement and salt leaching.

Objective

• To investigate how varying salinity levels of reclaimed water affect soil water infiltration, water-salt migration, and salt distribution in typical sandy loam saline-alkali soils of Xinjiang, China.
• To reveal the influence mechanism of salinity on soil water-salt distribution and clarify the effects of different salinity levels on soil infiltration capacity and water-salt migration patterns.
• To identify a suitable reclaimed water irrigation salinity level that provides scientific guidance for sustainable reclaimed water utilization in arid regions.

Study Configuration

• Spatial Scale: Laboratory-scale, one-dimensional vertical infiltration experiments using plexiglass soil columns (5 cm inner diameter, 70 cm soil height) filled with sandy loam collected from the 0–40 cm tillage layer of a reclaimed water experimental field in Hu yang he City, Xinjiang. Soil samples were sectioned at 5 cm depth intervals for analysis.
• Temporal Scale: Short-term infiltration experiments, typically up to 180 minutes or until the wetting front reached approximately 45.7 cm depth (two-thirds of the soil column length).

Methodology and Data

• Models used: Philip infiltration formula, Green–Ampt infiltration formula.
• Data sources:
  • Soil: Sandy loam collected from a reclaimed water experimental field in Hu yang he City, Xinjiang. Initial bulk density 1.47 g cm−3, initial volumetric moisture content 0.058 cm3 cm−3, saturated volumetric moisture content 0.397 cm3 cm−3, initial salt content 7.6 g kg−1, pH 7.9.
  • Reclaimed water: Treated municipal/industrial wastewater with an initial salinity of 4.32 g L−1 and pH 7.9. Experimental treatments included pure water (0 g L−1) and four reclaimed water salinity levels (1, 2, 3, and 4 g L−1), prepared by mixing with pure water.
  • Experimental setup: Indoor vertical infiltration simulation system comprising soil columns and a Mariotte bottle for constant head water supply.
  • Measurements: Cumulative infiltration, wetting front migration depth, soil mass water content, soil water storage, soil salt content (derived from electrical conductivity of 1:5 soil water extract), soil salt storage, desalination rate, desalination depth coefficient, qualified desalination depth coefficient, and soil pH.

Main Results

• Optimal Salinity for Infiltration: Reclaimed water with a salinity of 2 g L−1 demonstrated the most significant improvement in infiltration performance.
  • At 180 minutes, cumulative infiltration increased by 22.73% (to 7.61 cm) compared to pure water (5.88 cm).
  • The time required for the wetting peak to reach a specified depth was shortened by 21.74%, and infiltration depth increased by 27.78% compared to pure water.
• Soil Hydraulic Parameters: Philip's sorptivity (S) and Green-Ampt's saturated hydraulic conductivity (Ks) initially increased with salinity, peaking at approximately 2.37 g L−1, then decreased with further increases in salinity.
• Soil Moisture Distribution: The 2 g L−1 reclaimed water treatment resulted in the highest average moisture content (23.11%) and water storage (168.19 mm) in the wetted body, representing increases of 6.20% and 6.25%, respectively, compared to pure water.
• Soil Salinity Distribution:
  • Soil salinity increased with the salinity of the irrigation water, with salts accumulating near the wetting front, leading to a characteristic pattern of desalination in the upper layer (0–30 cm) and salt accumulation in the lower layer (>30 cm).
  • Reclaimed water reduced soil salinity in the 0–30 cm layer. When the salinity was ≤2 g L−1, the salt content in the 0–25 cm layer decreased below the crop salt tolerance threshold (<5 g kg−1).
  • For reclaimed water with salinity ≤2 g L−1, salt storage in the 0–30 cm layer was less than 7 kg ha−1, achieving a desalination rate exceeding 60%. The 2 g L−1 treatment showed the most pronounced desalination effect, with a maximum desalination rate of 62.82% in the 0–25 cm layer.
• Soil pH: Reclaimed water treatments generally increased soil pH in the 0–35 cm layer compared to the initial pH, with a subsequent decrease observed in the 35–50 cm layer.

Contributions

• Identified an optimal salinity threshold of 2 g L−1 for reclaimed water in Xinjiang's sandy loam, which significantly enhances infiltration performance (cumulative infiltration increased by 22.73%) and achieves efficient root-zone desalination (>60%).
• Provided a scientific basis and practical guidance for sustainable reclaimed water reuse in arid regions, particularly for urban greening, farmland irrigation, and saline-alkali land improvement.
• Quantitatively analyzed water and salt transport characteristics under different salinities using Green–Ampt and Philip infiltration formulas, offering an effective model and method for evaluating saline water infiltration.

Funding

• Science and Technology Program of XPCC (2025DA025, 2025YD17)
• Shihezi University Innovation and Development Special Project (CXFZ202304)
• High-level talent research startup project of Shihezi University (RCZK202319)

Citation

@article{Qin2026Simulation,
  author = {Qin, Jiangwen and Zhou, Tao and Zhang, Jihong and Zhao, Tao and Wang, Ankun and Liang, Hongbang and Li, Wenhao and Li, Meng},
  title = {Simulation Experiment on the Effect of Saline Reclaimed Water Recharge on Soil Water and Salt Migration in Xinjiang, China},
  journal = {Water},
  year = {2026},
  doi = {10.3390/w18020238},
  url = {https://doi.org/10.3390/w18020238}
}