This is the peer reviewed version of the following article: Soulsby, C., Bradford, J., Dick, J., McNamara, J. P., Geris, J., Lessels, J., Blumstock, M., and Tetzlaff, D. (2016) Using geophysical surveys to test tracer-based storage estimates in headwater catchments. Hydrol. Process., 30: 4434–4445., which has been published in final form at DOI: 10.1002/hyp.10889. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.