嘎达苏小流域雨洪资源利用涵养地下水可行性应用研究

Feasibility study on stormwater resource utilization for groundwater recharge in Gadasu small watershed

摘要

【目的】雨洪资源利用对于加强小流域综合治理,缓解半干旱区水资源短缺问题至关重要。由于小流域生态系统对地下水变化高度敏感,因此雨洪资源利用补给地下水潜力的评估尤为重要,这也是半干旱区地下水库建设可行性研究的核心内容。【方法】以北方半干旱区的小流域地下水库工程为背景,利用修正后的曲线径流数模型(SCS-CN),分析1981—2023年降雨产生的地表径流量,采用皮尔逊三型(P-Ⅲ)曲线适线法选取25%、50%、75%降雨频率产生的地表径流量作为不同工况代表值,并基于MODFLOW边界条件法构建地表水-地下水耦合数值模型,探讨不同工况下地下水流场的变化情况,量化地下水库调节汛期雨洪,促进以丰补枯的潜力。【结果】结果显示:(1)采用区域解析雨量代替雨量站观测雨量,可以解决观测数据异常值多、离散性大的问题,月、季度降雨拟合系数平均值为0.73;(2)修正的SCS-CN模型初损率λ=0.02,预测地表径流结果与水文比拟法设计径流量基本一致;(3)通过雨洪资源涵养地下水可以大幅度提升地下水位高度,不同降雨保证率条件下地下水位可稳定抬升1.66 m,蓄滞洪区拦蓄径流量呈几何倍数增加,占总径流量的41.9%、73.2%和109.15%。【结论】结果表明:修正后的SCS-CN模型能够准确预测干旱区和半干旱区降雨产生的地表径流,尤其适用于数据不易测量、土壤信息匮乏的小型农业流域。采用切换边界条件法构建的地表水-地下水耦合模型可以更好地反映雨洪涵养工程建设前后上游地下水流场的变化情况。同时,蓄滞洪区收集的雨洪资源能够将汛期洪水转化为非汛期供水,实现雨洪资源的合理利用。因此,地表径流的收集潜力对于地下水库的建设非常重要,在一定程度上决定了工程研究的可行性。研究可为北方半干旱区及类似山区小流域综合治理提供理论支撑与技术参考。

Abstract

[Objective] The utilization of stormwater resources plays a critical role in enhancing integrated small watershed management and alleviating water shortage in semi-arid regions. The small watershed ecosystems are highly sensitive to groundwater level fluctuations, making the evaluation of stormwater resource utilization for groundwater recharge essential. This also constitutes a key aspect of feasibility studies for underground reservoir construction in semi-arid regions. [Methods] An underground reservoir project in a small watershed within northern semi-arid regions was selected as the study background.Surface runoff generated by rainfall from 1981 to 2023 was analyzed using a modified SCS-CN(curve number) model. The Pearson Type Ⅲ(P-Ⅲ) curve fitting method was employed to determine representative runoff values at 25%, 50%, and 75% rainfall frequencies under different conditions. A coupled surface water-groundwater numerical model was established using the MODFLOW boundary condition method to simulate groundwater flow field variations under different conditions. Furthermore, the potential of groundwater reservoirs to regulate stormwater during flood seasons and balance seasonal water availability was quantified. [Results] The result showed that:(1) utilizing regional analytical rainfall data instead of rain gauge observations effectively addressed issues of data anomalies and high dispersion, with average monthly and seasonal rainfall fitting coefficients of 0. 73.(2) The initial abstraction ratio in the modified SCS-CN model was determined to be 0. 02, and the predicted runoff result closely matched design runoff values derived from the hydrological analogy method.(3) Groundwater recharge through stormwater conservation significantly increased groundwater levels, with a stable rise of 1. 66 m under different rainfall frequency conditions.Additionally, runoff retention in flood detention areas showed exponential growth, accounting for 41. 9%, 73. 2%, and 109. 15%of total runoff, respectively. [Conclusion] The result demonstrate that the modified SCS-CN model accurately predicts rainfallinduced surface runoff in arid and semi-arid regions, especially for small agricultural watersheds where direct measurements are challenging and soil information is limited. The coupled surface water-groundwater model established using the switching boundary condition method effectively captures variations in upstream groundwater flow fields before and after the implementation of stormwater conservation project. Furthermore, stormwater collected in detention areas can be converted into a water supply for the non-flood season, ensuring the rational utilization of stormwater resources. Therefore, the collection potential of surface runoff is crucial for the construction of underground reservoir and largely determines project feasibility. The findings provide theoretical support and technical references for integrated watershed management in northern semi-arid regions and similar mountainous small watersheds.

关键词

雨洪资源利用 / 修正SCS-CN模型 / 降雨 / 径流 / 地表水-地下水耦合模型 / 地下水流场 / 地下水库

Key words

stormwater resource utilization / modified SCS-CN model / rainfall / runoff / coupled surface water-groundwater model / groundwater flow field / underground reservoir

基金资助

国家自然科学基金项目(51374046)