Collaborative Research: River Stage Tomography for Automatic Characterization of Fluxes between Surface and Groundwater Reservoirs: A Pilot Study

准确的水和化学物质平衡知识是正确管理流域水资源的关键。经过几十年的实地调查和模拟，地下水储量、地表和地下水库之间的通量以及流域/流域上空地面和大气之间的通量仍然高度不确定。为了解决这一问题，需要在表征、监测和建模方法方面取得突破。在这项建议中，我们提出了一种新的水力层析成像方法，利用河流水位的时空变化和河流附近相应的地下水响应来表征、监测和预测地下水位带及更远的区域。这项新技术能够以目前尚不可行的方式，对河流/地下水边界的通量进行三维成像和确定通量，并确定潜水和地下系统的特征。如果这项拟议的概念验证研究成功，这项技术最终可以推广到流域/分水岭尺度问题。本研究的目的是论证基于河段涨落的水力层析成像是探测河流附近大尺度地下非均质性的有效概念和可行技术。我们打算展示这一概念和技术可以在与河流相互作用的无承压含水层中实现其目标。提出的任务包括：1)修改现有的水文层析成像反演算法，以适应时空变化的边界条件，这些边界条件代表了时空变化的河流水位；2)通过数值模拟检验时空变化的河流水位对非均质非承压含水层中地下水位的影响；3)在改进的反演算法中使用这些模拟的井水位线来测试其探测地下水位非均质性的能力；4)利用现有的两个砂箱进行实验室研究，研究结果应表明，尽管河流水位可能在时间和空间上迅速变化，但只要河流水位的变化得到很好的表征，层析反演法就是一种有效和合理的方法。

The accurate knowledge of water and chemical mass balances is the key to proper management of water resources in a watershed. After decades of field investigations and modeling, groundwater storage, fluxes between surface and subsurface reservoirs, and fluxes between land surface and atmosphere over a basin/watershed still remain highly uncertain. A breakthrough in characterization, monitoring, and modeling approaches is needed to resolve this issue. In this proposal, we propose a novel hydraulic tomography approach to characterize, monitor, and predict the hyporheic zone and beyond, using spatial-temporal variations in river stages and the corresponding groundwater responses near a river. This new technology allows three-dimensional imaging and determination of fluxes across the river/groundwater boundaries and characterization of the hyporheic and subsurface system in a manner that is presently not feasible. If this proposed proof-of-concept study is successful, the technology can ultimately be extended to basin/watershed scale problems. The goal of the study is to demonstrate that hydraulic tomography based on river stage fluctuations is a valid concept and a viable technology for detecting large-scale subsurface heterogeneity near the river. We intend to show that the concept and technology can accomplish its goal in unconfined aquifers that interact with rivers. Proposed tasks include: 1) the modification of existing hydrologic tomography inversion algorithm to accommodate temporally and spatially varying boundary conditions, which represent the temporally and spatially varying river stages; 2) the examination of the effects of temporal and spatial varying river stage on groundwater level in synthetic heterogeneous unconfined aquifers through numerical simulations; 3) the use of these simulated well hydrographs in the modified inversion algorithms to test its ability to detect heterogeneity within the hyporheic zone; and 4) the conduct of laboratory studies using two existing sandboxes with a synthetic heterogeneous unconfined aquifer.Results from the study should demonstrate that while river stages may change rapidly in time and space, the tomographic inversion is a valid and logical approach as long as the variation of the river stages is well characterized.