Light at the end of the well: A compact and low-cost DIY water level meter

Goundwater level data are a crucial element of water resources assessments. Corresponding measurements are often carried out with electric water level tapes, which are – despite their simple concept – relatively expensive. Here, I present a low-cost alternative, consisting of an ordinary measuring tape and an off-the-shelf “LED bait” (actually used for fishing). The latter is simply attached to the tape with a binder clip and starts flashing upon water contact. At reasonable depth-to-water conditions (<30 m), this light signal can be seen from the wellhead. While the basic concept of a light-emitting, self-contained probe had already been harnessed in the 1930s by the company Spohr (Frankfurt, Germany), its use has been greatly facilitated by the emergence of LED baits that are available for a few Euros. Repurposing a consumer product, designed for an entirely different purpose, has hence enabled a fit-for-purpose device that can be built by anyone at a fraction of the costs of a traditional electric water level tape. This water level meter “hack” provides a DIY tool for researchers and practitioners on a tight budget and a compact backup for others. Moreover, school or citizen science projects could benefit from this easy-to-build and low-cost alternative. Further details can be found in a related publication (Michelsen, 2021). References Michelsen, N., 2021. A compact and low-cost do-it-yourself water level meter. Hydrological Processes, 35(5), e14205, DOI: 10.1002/hyp.14205