Department of Applied Geology, Faculty of Earth Sciences, Kharazmi University, P.O. Box: 31979-37551, Tehran, Iran.
Soil Conservation and Watershed Management Research Institute (SCWMRI), Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran.
Sci Total Environ. 2020 May 10;716:137105. doi: 10.1016/j.scitotenv.2020.137105. Epub 2020 Feb 3.
Knowledge of soil water dynamics in the deep vadose zone provides valuable information on the temporal and spatial variability of groundwater recharge. However, semi-arid climate can complicate how the input of water, such as irrigation, can contribute to potential groundwater recharge. This study assessed the recharge rates and their timing under irrigated cropland from a semi-arid region of northern Iran. A deep drainage (10 m) experiment was performed and in situ soil water content was measured to analyze the soil water dynamics and model hydraulic parameters using HYSDRUS-1D. The best parameters selected from inverse parameter optimization were used to calibrate model and estimate the long-term (20-year) average groundwater recharge and the influence of the root zone, unsaturated zone and the time scale on the recharge processes. The simulated annual flux ranged from 24 mm to 268 mm (mean of 110 mm) at 2-m depth and ranged between 26 mm to 207 mm (mean of 95 mm) at the 10-m depth. High fluxes, observed between December and April, may be the result of greater precipitation combined with the irrigation return flow. The May-October period showed a gradual decrease in flux at the depth of 2 m. At the depth of 10 m, the flux showed some continuity (base flux) during the long-term recharge simulation. In total, 12.7% of the input water contributed to the recharge of the groundwater. The annual soil water fluxes were almost similar irrespective of depth below the root zone and the flux rates did not show any clear relation between the different components of the water budget at any depth. This approach improved our understanding of the recharge process in the deep vadose zone in a semiarid region and can help for the development of effective management of groundwater resources.
了解深层包气带中的土壤水分动态可为地下水补给的时空调变提供有价值的信息。然而，半干旱气候会使水的输入（如灌溉）如何有助于潜在的地下水补给变得复杂。本研究评估了伊朗北部半干旱地区灌溉农田的补给速率及其时间。进行了深层排水（10 米）实验，并原位测量土壤水分含量，使用 HYSDRUS-1D 分析土壤水分动态并模拟水力参数。从反演参数优化中选择的最佳参数用于校准模型并估算长期（20 年）平均地下水补给以及根区、非饱和区和时间尺度对补给过程的影响。模拟的年通量在 2 米深度处的范围为 24 毫米至 268 毫米（平均值为 110 毫米），在 10 米深度处的范围为 26 毫米至 207 毫米（平均值为 95 毫米）。12 月至 4 月之间观测到的高通量可能是由于更大的降水加上灌溉回流的结果。5 月至 10 月期间，2 米深处的通量逐渐减少。在 10 米深处，在长期补给模拟过程中通量显示出一定的连续性（基础通量）。总共有 12.7%的输入水有助于地下水的补给。无论根区以下的深度如何，每年的土壤水流通量几乎相似，通量率在任何深度都没有显示出与水分预算不同组成部分之间的任何明显关系。这种方法提高了对半干旱地区深层包气带补给过程的认识，并有助于地下水资源的有效管理。
