Numerical modelling study on non-steady-state groundwater flow systems in response to changing rainfall
-
摘要:
区域地下水流系统的发育受地质、气候和地形多种因素的影响。以往的地下水流系统研究主要探讨了地质、地形和稳态气候条件下所形成的局部、中间和区域流动系统的组成特征, 对非稳态的地下水流系统认识不足。聚焦于研究地下水流系统对降雨变化的动态响应规律, 使用HydroGeoSphere构建了剖面二维地下水地表水耦合数值模型, 模拟在降雨的周期性和随机性叠加动态驱动下非稳态渗流场形成的地下水流系统。模拟结果表明, 各层级流动系统的空间范围都会随着降水波动而发生变化。局部地下水流系统在雨季并非都处于扩张状态, 在旱季也并非都处于收缩状态。各个局部流动系统的同时刻穿透深度之间可能具有无关、正相关或负相关关系, 这取决于各个局部流动系统响应降雨变化的滞后性。中间流动系统在非稳态条件下非常活跃, 其排泄出口、补给入口和循环路径随时间变化, 并强烈影响局部流动系统。通过5种不同含水层参数和降雨情景的模拟对比, 发现地下水流系统的滞后性和穿透深度的相关性对含水层各向异性特征较为敏感。下一步, 需要更加深入地研究地下水流系统在季节尺度、多年乃至跨世纪时间尺度气候波动过程中的非稳态响应规律。
Abstract:Objective Geological, climatic, and topographical conditions control regional groundwater flow systems. Previous researchers have made significant advancements in developing the theory of groundwater flow systems under steady-state climatic conditions. However, there has been limited progress in comprehensively understanding transient groundwater flow systems.
Methods To address this gap, we constructed a two-dimensional numerical model that couples groundwater and surface water using HydroGeoSphere. We then examined the relationships among the subsystems of transient groundwater flow systems in response to variations in rainfall.
Results The results demonstrate that the areas occupied by subsystems change with rainfall fluctuations. Local groundwater flow systems may neither expand during wet seasons nor contract during dry seasons. The relationships among the penetration depths, which indicate the elevation of the lowest point in a local flow system, can be positive, negative, or unrelated. This variation mainly arises from the high activity of intermediate groundwater flow systems under transient conditions, where their inputs, outputs, flow paths, and areas of recharge and discharge vary with rainfall fluctuations. These relationships are also sensitive to factors such as geology (hydraulic conductivity, specific storage), climate (rainfall rate), and topography (local and regional).
Conclusion Based on a sensitivity analysis of five scenarios, changes in local flow systems are more influenced by aquifer anisotropy. Future research should prioritize conducting a more comprehensive analysis of the non-steady-state response patterns exhibited by groundwater flow systems, considering climate fluctuations on a seasonal scale, over multiple years, and even across centuries.
-
Key words:
- groundwater flow system /
- local flow system /
- penetration depth /
- rainfall fluctuation
-
表 1 局部抛物线型地形的控制参数
Table 1. Values of a, b and c used to control the local topographic undulation
(xi, xi+1)/m a/10-5 b/m c/m (0, 712.75) a1=2.35 b1=-714.29 c1=12 (712.75, 1 337.75) a2=3.07 b2=712.75 c2=12 (1 337.75, 1 792.75) a3=4.84 b3=1 792.30 c3=10 (1 792.75, 2 792.75) a4=1.00 b4=1 792.75 c4=10 (2 792.75, 3 177.5) a5=9.46 b5=3 177.37 c5=14 (3 177.5, 3 976.7) a6=2.19 b6=3 176.70 c6=14 (3 976.7, 4 421) a7=4.56 b7=4 421.14 c7=9 (4 421, 5 254.66) a8=1.30 b8=4 421.33 c8=9 (5 254.66, 5 671) a9=7.49 b9=5 671.33 c9=13 (5 671, 6 227.11) a10=4.21 b10=5 671.56 c10=13 (6 227.11, 6 727.11) a11=4.40 b11=6 727.11 c11=11 表 2 局部流动系统穿透深度变化滞后降雨波动的月数
Table 2. Time lag (month) of the change in the penetration depth of local flow systems to rainfall fluctuations
流动系统 模拟情景 情景1 情景2 情景3 情景4 情景5 WL1 5 3 4 4 4 L2 4 2 4 9 3 L3 4 3 4 4 4 L4 4 0 4 9 4 L5 4 9 3 4 4 L6 4 0 0 9 2 L7 4 3 11 0 0 L8 4 9 9 9 4 L9 1 2 10 4 0 L10 1 0 0 9 0 L11 1 9 0 0 -
[1] Tóth J. Groundwater as a geologic agent: An overview of the causes, processes, and manifestations[J]. Hydrogeology Journal, 1999, 7(1): 1-14. doi: 10.1007/s100400050176 [2] 梁杏, 张人权, 靳孟贵. 地下水流系统: 理论、应用、调查[M]. 北京: 地质出版社, 2015.Liang X, Zhang R Q, Jin M G. Groundwater flow systems: Theory, application and investigation [M]. Beijing: Geological Publishing House, 2015(in Chinese). [3] Domenico P A, Palciauskas V V. Theoretical analysis of forced convective heat transfer in regional groundwater flow[J]. Bulletin of the Geological Society of America, 1973, 84(12): 3803-3814. doi: 10.1130/0016-7606(1973)84<3803:TAOFCH>2.0.CO;2 [4] Wang H, Jiang X W, Wan L, et al. Hydrogeochemical characterization of groundwater flow systems in the discharge area of a river basin[J]. Journal of Hydrology, 2015, 527: 433-441. doi: 10.1016/j.jhydrol.2015.04.063 [5] Zhang X L, Jiao J J, Li H L, et al. Effects of downward intrusion of saline water on nested groundwater flow systems[J]. Water Resources Research, 2020, 56(10): W28377. [6] 张人权, 梁杏, 靳孟贵, 等. 多级次地下水流系统的最小能耗率原理初探[J]. 地质科技通报, 2022, 41(1): 11-18. doi: 10.19509/j.cnki.dzkq.2022.0002Zhang R Q, Liang X, Jin M G, et al. Preliminary discussion on the principle of minimum energy consumption rate controlling hierarchical groundwater flow systems[J]. Bulletin of Geological Science and Technology, 2022, 41(1): 11-18(in Chinese with English abstract). doi: 10.19509/j.cnki.dzkq.2022.0002 [7] 万力, 王旭升, 蒋小伟. 地下水循环结构的动力学研究进展[J]. 地质科技通报, 2022, 41(1): 19-29. doi: 10.19509/j.cnki.dzkq.2022.0003Wan L, Wang X S, Jiang X W. Advances in dynamics of groundwater circulation patterns[J]. Bulletin of Geological Science and Technology, 2022, 41(1): 19-29(in Chinese with English abstract). doi: 10.19509/j.cnki.dzkq.2022.0003 [8] 蒋小伟, 万力, 王旭升, 等. 区域地下水流理论的发展历程与教材演变[J]. 地质科技通报, 2022, 41(1): 43-49. doi: 10.19509/j.cnki.dzkq.2022.0004Jiang X W, Wan L, Wang X S, et al. Evolution of the theory of regional groundwater flow and updates in textbooks[J]. Bulletin of Geological Science and Technology, 2022, 41(1): 43-49(in Chinese with English abstract). doi: 10.19509/j.cnki.dzkq.2022.0004 [9] Vandenberg A. Regional groundwater motion in response to an oscillating water table[J]. Journal of Hydrology, 1980, 47(3): 333-348. [10] Kollet S J, Maxwell R M. Demonstrating fractal scaling of baseflow residence time distributions using a fully-coupled groundwater and land surface model[J]. Geophysical Research Letters, 2008, 35(7): L07402. [11] Haitjema H M, Mitchell-Bruker S. Are water tables a subdued replica of the topography?[J]. Ground Water, 2005, 43(6): 781-786. [12] Zhang X L, Jiao J J, Guo W. How does topography control topography-driven groundwater flow?[J]. Geophysical Research Letters, 2022, 49(20): e2022GL101005. [13] Zhang X L, Li H L, Jiao J J, et al. Fractal behaviors of hydraulic head and surface runoff of the nested groundwater flow systems in response to rainfall fluctuations[J]. Geophysical Research Letters, 2022, 49(2): e2021GL093784. [14] Tóth J. A theoretical analysis of groundwater flow in small drainage basins[J]. Journal of Geophysical Research, 1963, 68(16): 4795-4812. [15] Tóth J. Gravitational systems of groundwater flow: Theory, evaluation and utilization[M]. Cambridge: Cambridge University Press, 2009. [16] Liang X, Quan D J, Jin M G, et al. Numerical simulation of groundwater flow patterns using flux as upper boundary[J]. Hydrological Processes, 2013, 27(24): 3475-3483. [17] 张蔓菲, 孙蓉琳, 梁杏. 通量上边界渗透系数随埋深增加指数衰减的地下水流系统[J]. 地质科技情报, 2015, 34(4): 189-193. https://www.cnki.com.cn/Article/CJFDTOTAL-DZKQ201504028.htmZhang M F, Sun R L, Liang X. Effect of Decay exponential in hydraulic conductivity with depth on groundwater flow system based on flux upper boundary[J]. Geological Science and Technology Information, 2015, 34(4): 189-193(in Chinese with English abstract). https://www.cnki.com.cn/Article/CJFDTOTAL-DZKQ201504028.htm [18] Dai X, Xie Y Q, Simmons C T, et al. Understanding topography-driven groundwater flow using fully-coupled surface-water and groundwater modeling[J]. Journal of Hydrology, 2021, 594: 125950. [19] Zhao K Y, Jiang X W, Wang X S, et al. An analytical study on nested flow systems in a Tóthian basin with a periodically changing water table[J]. Journal of Hydrology, 2018, 556: 813-823. [20] Brunner P, Simmons C T. HydroGeoSphere: A fully integrated, physically based hydrological model[J]. Groundwater, 2012, 50(2): 170-176. [21] Goderniaux P, Davy P, Bresciani E, et al. Partitioning a regional groundwater flow system into shallow local and deep regional flow compartments[J]. Water Resources Research, 2013, 49(4): 2274-2286. [22] Jiang X W, Wang X S, Wan L, et al. An analytical study on stagnation points in nested flow systems in basins with depth-decaying hydraulic conductivity[J]. Water Resources Research, 2011, 47(1): W01512. [23] Robinson N I, Love A J. Hidden channels of groundwater flow in Tóthian drainage basins[J]. Advances in Water Resources, 2013, 62: 71-78.