LOMOS-mini: A coupled system quantifying transient water and heat exchanges in streambeds

Abstract

The LOMOS-mini is a new experimental system monitoring transient water and heat fluxes in the hyporheic zone at a sub-daily resolution. Given the coupling of high-frequency hydraulic head gradient and temperature measurements, its innovation when compared to currently available monitoring systems is to operate under transient conditions and to allow the quantification of coupled water and heat exchanges with an unprecented fine temporal resolution, such as the rainfall event time scale. The LOMOS-mini is low-cost, easy to construct from individual microelectronic components and has an autonomy of several months in the field. Its robust implementation protocol makes it suitable for a wide variety of geological environments, from soft loamy, sandy, clayey streambeds to compact colluvial environments. Hydraulic head gradients are measured using the pressure sensor technology presented in Greswell et al. (2009). The sensibility of pressure estimates to ambient temperature is demonstrated; the measurement error is evaluated to decrease by up to one order of magnitude when accounting for temperature in the calibration relationship. Coupled with a physically-based hydrothermal model, the LOMOS-mini provides transient estimates of vertically distributed Darcy fluxes, conductive and advective heat fluxes. The methodology is illustrated on a colluvial streambed case study.