Development of Tools and Methods for the Characterization of the Groundwater-Surface Water Interface

This study focuses on water exchange, and associated processes, at the groundwater-surface water interface (GWSWI). The contributions of the study, as a whole, can be divided into two groups: scientific contributions and technical contributions. Scientifically, there are three main contributions. Firstly, the data presented below map a stream reach to show separate the effects of water flow and contaminant concentrations on contaminant mass discharge. The field demonstration of this concept, at the sub-meter scale, is novel. Secondly, the data included in the comparison of methods suggest the variability of flow across the GWSWI is large when compared with the differences related to replication of measurements. This suggests the importance of mapping in detail to ensure that all the controlling points of discharge are included. Thirdly, SBPVP measurements made a field-based mass loading calculation for a vertical flow bioreactor possible. It was found that the attenuation capacity of this system was about three orders of magnitude greater than the theoretical attenuation capacity suggested. Technically, there are five main contributions. Firstly, the design and validation of a new measurement tool to quantify flow across the groundwater-surface water interface (the streambed point velocity probe, or SBPVP). Secondly, a demonstration and comparison of the SBPVP in the field with three other, more commonly used methods. Thirdly, the development of a new method to quantify contaminant discharge into a stream using the SBPVP. Fourthly, a demonstration that the new approach can provide highly detailed information about the distribution of contaminant mass discharge, which could be of value to risk assessment and remediation design. Fifthly, the application of the SBPVP to the characterization of a vertical flow bioreactor for the purpose of assessing its performance. Given these contributions, the study presents a new tool for investigating the groundwater-surface water interface and describes various applications (and their associated scientific advances) in detail