Water and Solute Fluxes and their Structural Controls at Margins of Floodplain Aquifers

在中等气候条件下典型的中部集水区，洪泛平原的地下水主要流向下游。然而，洪泛区含水层的水文功能也取决于主要水文地质特征的存在与否，当地地下水系统受到其边缘的水和溶质通量的强烈影响。该项目的目标是阐明决定这些通量的水文地质驱动因素，并评估边缘对漫滩含水层总体水平衡和溶质周转的相对重要性。研究将在靠近t<s:1>宾根（德国西南部）的Ammer洪泛区进行，该洪泛区是气候温和的中段洪泛区的典型代表，CRC1253 CAMPOS内的申请人已经对其进行了研究。为了可靠地模拟和预测河漫滩含水层（包括其边缘）的水文功能，有必要了解这些边缘的输水结构特征的空间位置、几何形状和水文地质性质。因此，我们将描述洪泛区边缘的构造控制，决定水和溶质通过洪泛区含水层的通量。在这方面，我们的目标是采用劳动力和成本效益高的方法来绘制洪泛区边缘结构特征的空间范围和几何形状（使用地球物理测量），并表征它们与洪泛区含水层的水力连通性（使用水力测试）。我们特别关注已确定的洪泛区边缘的构造控制，研究了穿越洪泛区边缘的水通量和相应的溶质负荷，以量化它们在洪泛区含水层中的相对贡献。我们将特别研究水文边界条件的时间动态，以确定在哪些条件下会发生显著的水交换。实验结果将为洪泛区含水层的一致数值模型提供信息，用于预测水文地质测量信号和解释估计的动态交换通量结果。最后，我们将整理在不同调查步骤中收集到的地质信息，并在我们之前的工作中进行全面的地质解释，以确定指导地质过程，这些地质过程决定了漫滩边缘控制交换通量的渗透性特征的存在和有效性。这一步将有助于推广我们的发现，并将其转移到其他网站。

In typical midland catchments in moderate climate, groundwater flow in floodplains is mainly down-valley oriented. However, the hydrological functioning of floodplain aquifers also depends on the presence or absence of major hydrogeological features, and the local groundwater systems are strongly influenced by water and solute fluxes across their margins. The goal of this project is to elucidate the hydrogeological drivers that determine these fluxes and assess the relative importance of the margins for the overall water balance and solute turnover in floodplain aquifers. The research will be conducted in the Ammer floodplain close to Tübingen (Southwest Germany), which is a typical representative for a mid-section floodplain in moderate climate and has already been studied by the applicants within CRC1253 CAMPOS. To reliably model and predict the hydrological functioning of a floodplain aquifer including its margins, it is essential to know the spatial position, geometry, and hydrogeological properties of water-transmitting structural features at these margins. We will therefore characterize the structural controls at the floodplain margins determining the flux of water and solutes through the floodplain aquifers. In this regard, we aim at labor- and cost-efficient methods to map the spatial extent and geometry of structural features at floodplain margins (using geophysical surveying) and characterize their hydraulic connectivity to the floodplain aquifers (using hydraulic tests). With special focus on the identified structural controls at the floodplain margins, we investigate the water fluxes and corresponding loads of solutes crossing the floodplain margins to quantify their relative contributions within the floodplain aquifer. We will especially investigate the temporal dynamics of the hydrological boundary conditions to identify under which conditions significant water exchange occurs. The experimental findings will inform a consistent numerical model of the floodplain aquifer for predicting signals of hydrogeological measurements and interpreting the results of the estimated dynamic exchange fluxes. Finally, we will compile the geological information gathered in the different investigation steps and in our previous work to perform a comprehensive geological interpretation to identify the guiding geological processes that determine the presence and effectiveness of permeable features at floodplain margins controlling exchange fluxes. This step will facilitate generalizing our findings and transferring it to other sites.