ISSN 1000-3665 CN 11-2202/P

    新水情影响下华北平原深层地下水水平衡演变与更新能力分析

    Evolution of deep groundwater balance and renewability analysis in the North China Plain under new hydrological conditions

    • 摘要: 地下水是支撑华北平原社会经济发展的重要供水水源,深层地下水长期超采、水头大幅度下降,引发系列生态环境地质问题。2014年以来,常态化生态补水、地下水超采综合治理和连续强降水等新水情通过置换水源、农业节水以及强降水灌溉农业等方式减少了华北平原深层地下水开采量,深层地下水水平衡发生显著变化。基于深层地下水区域水平衡分析方法,探讨了水平衡关键指标变化特征,分析了新水情对深层地下水平衡的影响效应。利用14C年龄、中更新统岩相古地理分布特征2个地质背景指标和渗透系数、水平水力梯度、深浅层水头差以及越流系数4个水力评价指标对深层地下水更新能力进行综合评价。在地下水水位降落漏斗和地面沉降防控基础上,识别地下水水位恢复阈值,科学评价深层地下水可利用量。结果表明:2005—2020年,在新水情影响下,深层地下水渗流速度增大49.4%,侧向补给量增加0.29×108 m3/a,越流补给量增加0.14×108 m3/a,中东部深层地下水水位仍处于下降状态是主要原因;地下水年均开采量减少0.20×108 m3/a,地下水储量减速降低2.59×108 m3/a;从空间分析,西部山前渗透系数较大使得其更新性好于中东部,从时间分析,开采量的变化使得垂向越流通量和水平侧向径流的组成及数量发生了变化,2020年深层地下水更新能力较2005年总体增强;深层地下水可利用量为8.52×108 m3/a,主要分布于山前平原的中更新统冲洪积扇区。依据深层地下水补径排条件、开发利用程度差异,以不同水文地质单元开展水平衡演变分析,2015年以来深层地下水失衡状况得到缓解,但尚未得到根本扭转。研究结果对认识北方平原区深层地下水循环规律和可持续开发利用等方面具有借鉴意义。

       

      Abstract: Groundwater serves as a vital water resource supporting the socio-economic development of the North China Plain. Long-term overexploitation of deep groundwater and a significant decline in groundwater levels have led to a series of ecological and environmental geological problems. Since 2014, new hydrological conditions—such as water source replacement, regular ecological water replenishment, and comprehensive management of overexploitation of groundwater— have influenced deep groundwater dynamics by reducing extraction through alternative water supplies, agricultural water-saving measures, and heavy precipitation-based irrigation. Consequently, the deep groundwater balance has undergone substantial changes. This study used groundwater balance calculation to study the characteristics of key indicators of water balance changes. Using two geological background indicators, 14C age and the distribution characteristics of the middle Pleistocene lithofacies paleogeography, and four hydrologic evaluation indicators, permeability (K), hydraulic gradient (I), the difference in groundwater levels between shallow and deep layers (ΔH), and the interflow coefficient, the renewal capacity of deep groundwater was evaluated. Based on groundwater depression cones and land subsidence, thresholds for groundwater level recovery are identified to scientifically estimate the sustainable yield of deep groundwater. The results show that between 2005 and 2020, under the influence of new hydrological conditions, the seepage velocity of deep groundwater increased by 49.4%, the lateral replenishment increased by 0.29×108 m3/a, and interflow replenishment increased by 0.14×108 m3/a. These are primarily because the deep groundwater level in the middle and eastern part is still declining; The average annual exploitation of groundwater decreased by 0.20×108 m3/a and the rate of groundwater storage decline slowed down from 12.29×108 m3/a to 9.7 ×108 m3/a. Spatial analysis indicates that the renewal capacity in the piedmont plains is better than that in the central and eastern regions because of the larger hydraulic conductivity. Temporal analysis shows that the renewal capacity of deep groundwater in 2020 has generally increased compared to 2005. The composition and quantity of vertical interflow replenishment and horizontal lateral replenishment change with the change of mining yield. The availability of deep groundwater was evaluated to be 8.52×108 m3/a, primarily concentrated in the middle Pleistocene alluvial fan region of the piedmont plains. Based on the conditions of recharge, flow, and discharge of deep groundwater, as well as differences in the degree of development and utilization, the imbalance of deep groundwater has been alleviated since 2015, fundamental reversal has not yet been achieved. This study provides critical insights into deep groundwater circulation dynamics and offers guidance for the sustainable development and management of groundwater resources in the North China Plain.

       

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