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Modeling the hydrologic interactions between an aging reservoir and the surrounding groundwater.

机译：模拟老化的水库与周围地下水之间的水文相互作用。

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摘要

Aging reservoirs that have been subjected to severe sedimentation are growing in number worldwide. Searsville Reservoir, located within Jasper Ridge Biological Preserve at Stanford University, is one example. Given the many benefits, but also the potential problems, of sediment-impacted reservoirs, there is strong motivation to better understand these hydrologic systems to enhance management and investment decisions. Field data suggest that the interactions between the reservoir and the surrounding groundwater in the deposited sediments are very complex and dynamic. Water flux can be either from the sediment to the reservoir or vice versa or both, and the interactions are not only seasonal but also diurnal, forming an integrated hydrologic system. Computational modeling is essential for understanding the various hydrologic processes and also for predicting system responses to different management scenarios. This dissertation tackles several modeling challenges, solutions to which enhance our ability to understand integrated groundwater-reservoir systems. It also examines specific features of groundwater-reservoir systems and addresses important questions underlying management decisions for sediment-impacted reservoirs, using Searsville as a case study.;This dissertation is divided into the following three parts:;(1) Enhancing modeling techniques for integrated hydrological systems. The first part of this dissertation studies the feasibility of simulating a reservoir/lake as a high-conductivity variably-saturated porous medium, and presents guidelines for choosing modeling parameters for the reservoir/lake region. It concludes that when applied in variably-saturated models, this approach is most suitable for relatively simple geometries and lakes with slower and smaller fluctuations. It is also more applicable to research that studies the overall flow pattern and system fluxes, rather than the detailed flow pattern around the interaction of the lake and land surfaces.;It also explores the use of a multiphysics model in integrated hydrological modeling by implementing and verifying three important hydrologic boundary conditions: rainfall infiltration, seepage faces, and evapotranspiration fluxes. It demonstrates that with care and creativity these boundary conditions can be implemented accurately and efficiently. Therefore, boundary condition implementation should not limit the applicability of multiphysics model to a broad set of problems of interest to the hydrologic community.;(2) Examining diurnal evapotranspiration signals in coupled groundwater surfacewater systems. The second part of this dissertation analyzes the diurnal evapotranspiration signals in fully-coupled and interacting groundwater surface-water systems. It first performs numerical modeling using simplified and generic domains to understand the characteristics (i.e., the magnitudes, the timing and the phase relationships) of the diurnal signals. Using both data analysis and numerical modeling, it then examines the diurnal signals in the Searsville Reservoir surface-water elevation, in the piezometric head in the surrounding ground water, as well as in the incoming streamflow during summer. It illustrates the interactions of surface and subsurface water bodies and demonstrates the importance of intermittent incoming stream at Searsville in shaping the characteristics of the diurnal signals. It also concludes that, to extract ecohydrologic information from diurnal signals, one must consider the couplings between surface and subsurface water.;(3) Predicting subsurface hydrologic responses to alternative management scenarios. The last part of this dissertation investigates the upstream subsurface hydrologic responses to simplified hypothetical management scenarios in sediment-impacted reservoirs, using numerical models based on conditions at Searsville. It concludes that the vegetation community upstream is not highly sensitive to downstream management decisions because its water table remains relatively high and its total transpiration remains around the same. Sensitivity analysis reveals that systems with lower precipitation and/or higher reference transpiration and/or higher hydraulic conductivity in general are more sensitive to management decisions because they rely more heavily on the reservoir in maintaining the shallow water table in the deposited sediments.;Overall, the results of this dissertation contribute to our understanding and modeling of groundwater-reservoir interactions, which benefits the management of sediment-impacted reservoirs globally. Some of the results, such as those pertaining to the modeling techniques and evapotranspiration signals, are also applicable to riparian and other groundwater-lake systems.
机译：在世界范围内，遭受严重沉降的老化水库的数量正在增长。一个例子就是位于斯坦福大学贾斯珀里奇生物保护区内的西尔斯维尔水库。考虑到受泥沙影响的水库有许多好处，但也有潜在的问题，因此有很强的动力去更好地了解这些水文系统，以加强管理和投资决策。现场数据表明，沉积物中储层与周围地下水之间的相互作用非常复杂和动态。水流量既可以是从沉积物到水库的流量，反之亦然，也可以是两者兼而有之，相互作用不仅是季节性的，而且是昼间的，形成一个综合的水文系统。计算模型对于理解各种水文过程以及预测系统对不同管理方案的响应至关重要。本文解决了一些建模挑战，提出了解决方案，这些解决方案增强了我们理解地下水综合储藏系统的能力。并以西尔斯维尔为案例研究了地下水水库系统的具体特征，并探讨了受泥沙影响的水库管理决策的重要问题。论文分为以下三个部分：（1）增强综合模型技术水文系统。本文的第一部分研究了模拟储层/储层作为高电导率可变饱和多孔介质的可行性，并为选择储层/储层区域的建模参数提供了指导。结论是，当在可变饱和模型中应用时，该方法最适合于相对简单的几何形状和波动较慢且波动较小的湖泊。它也更适用于研究总体流型和系统通量的研究，而不是研究湖泊与陆地表面相互作用周围的详细流型的研究。它还通过实现和探索多物理场模型在综合水文建模中的用途。验证三个重要的水文边界条件：降雨入渗，渗流面和蒸散通量。它表明，通过谨慎和创造力，可以准确，有效地实现这些边界条件。因此，边界条件的实施不应将多物理场模型的适用性限制在水文界关注的广泛问题上。（2）检查地下水耦合系统中的日蒸散信号。本文的第二部分分析了全耦合和相互作用的地下水地表水系统中的日蒸散信号。它首先使用简化和通用域执行数值建模，以了解昼夜信号的特征（即幅度，定时和相位关系）。然后，通过数据分析和数值建模，它可以检查Searsville水库地表水高程，周围地下水的测压头以及夏季流入的水流中的昼夜信号。它说明了地表水和地下水体的相互作用，并说明了在Searsville间歇性进入的水流对塑造昼夜信号特征的重要性。研究还得出结论，要从昼夜信号中提取生态水文信息，必须考虑地表水与地下水之间的耦合。（3）预测地下水文对替代管理方案的响应。本文的最后一部分使用基于西尔斯维尔条件的数值模型，研究了对沉积物影响的水库中简化的假设管理方案的上游地下水文响应。结论是上游的植被群落对下游的管理决策并不高度敏感，因为其地下水位仍然相对较高，总蒸腾量保持不变。敏感性分析表明，通常降水量较低和/或参考蒸腾量较高和/或水力传导率较高的系统对管理决策更为敏感，因为它们在维持沉积物浅层地下水位时更依赖储层。本文的结果有助于我们对地下水-水库相互作用的理解和建模，这有利于全球范围内受泥沙影响的水库的管理。一些结果，例如与建模技术和蒸散信号有关的结果，也适用于河岸和其他地下水湖系统。

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