| Summary: | Includes bibliographical references. 2017 Summer. Accurate quantification of water movement, both in magnitude and direction, is a necessary component of evaluating any hydrologic system. Groundwater flow patterns are usually determined using a network of piezometers or wells, which can be limited due to logistical or regulatory constraints. In the unsaturated zone, tensiometers can be used to determine unsaturated flow, but require knowledge of site-specific soil moisture curves. In either case, piezometers and tensiometers measure potentials from which flow is inferred rather than directly measuring water movement. An emerging alternative is to measure small currents that are generated as water moves through earth material. These currents generate small voltage differences detectable at the ground surface. Measurement of these voltage differences is the basis of the self-potential (SP) method. Signals can be measured using only two electrodes, or through installation of an array of electrodes. Here we present the results of multiple SP surveys designed to help address open hydrologic questions at multiple temporal (single snapshot, monthly surveys and continuous measurements) scales. In the first project, SP surveys are used to map complex flow patterns contributing to preferential hillslope drainages in an area of continuous permafrost. In the second, a subsurface electrode array is used to measure small changes in vertical and horizontal unsaturated flow rates induced by tree transpiration. Finally, through the example of repeat SP surveys collected in a remote sub-alpine meadow, we demonstrate how additional field data sets and coupled fluid flow and electrical models can constrain interpretations of SP data.
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