Enhancing Root Water Uptake and Mitigating Salinity through Ecological Water Conveyance: A Study of Tamarix ramosissima Ledeb. Using Hydrus-1D Modeling

In an arid climate with minimal rainfall, plant growth is constrained by water scarcity and soil salinity. Ecological Water Conveyance (EWC) can mitigate degradation risks faced by riparian plant communities in these regions. However, its effects on long-term dynamics of root zone soil water content, salt levels, and root water uptake remain unclear. This study examined how groundwater affects salt and water dynamics, in addition to root water uptake, under different scenarios involving Tamarix ramosissima Ledeb. The research was conducted in the lower reaches of the Tarim River in northwestern China. The Hydrus-1D model was used, following the EWC strategy. The results show that the distribution of T. ramosissima roots was significantly influenced by soil water and salt distributions, with 56.8% of roots concentrated in the 60–100 cm soil layer. Under water stress conditions, root water uptake reached 91.0% of the potential maximum when considering water stress alone, and 41.0% when accounting for both water and salt stresses. Root water uptake was highly sensitive to changes in Depth-to-Water Table (DWT), notably decreasing with lower or higher DWT at 40% of the reference level. EWC effectively enhances root water uptake by using water to leach salts from the root zone soil, with optimal results observed at 500–600 mm. This study advocates for sustainable EWC practices to support vegetation and combat desertification in the lower reaches of arid inland rivers.