Fluxes from soil moisture measurements (FluSM v1.0): a data-driven water balance framework for permeable pavements

Abstract

Abstract. Water fluxes at the soil–atmosphere interface are a key piece of information for studying the terrestrial water cycle. However, measuring and modeling water fluxes in the vadose zone poses great challenges. While direct measurements require costly lysimeters, common soil hydrologic models rely on a correct parametrization, a correct representation of the involved processes, and the selection of correct initial and boundary conditions. In contrast to lysimeter measurements, soil moisture measurements are relatively cheap and easy to perform. Using such measurements, data-driven approaches offer the possibility to derive water fluxes directly. Here we present FluSM (fluxes from soil moisture measurements), which is a simple, parsimonious and robust data-driven water balancing framework. FluSM requires only a single input parameter (the infiltration rate) and is especially valuable for cases where the application of Richards-based models is critical. Since permeable pavements (PPs) present such a case, we apply FluSM on a recently published soil moisture data set to obtain the water balance of 15 different PPs over a period of 2 years. Consistent with findings from previous studies, our results show that vertical drainage dominates the water balance of PPs, while surface runoff plays only a minor role. An additional uncertainty analysis demonstrates the ability of the FluSM-approach for water balance studies, since input and parameter uncertainties only have a small effect on the characteristics of the derived water balances. Due to the lack of data on the hydrologic behavior of PPs under field conditions, our results are of special interest for urban hydrology.

Estimating karst groundwater recharge from soil moisture observations – a new method tested at the Swabian Alb, southwest Germany

“…In addition to the correlation analysis, we used a more physically oriented approach to describe the relation between soil moisture and recharge. We fitted the unit gradient model (Hillel, 1998) with its two parameters (B and k s ) (Schaffitel et al, 2021). Vertical water flow, considered here as a proxy for groundwater recharge, is defined as…”

“…In other non-karstic geological settings, soil moisture measurements conducted at a high temporal resolution have been used in a few studies to investigate infiltration-related processes (Demand et al, 2019;Martini et al, 2015). Schaffitel et al (2021) developed a data-driven water-balancing framework to derive water fluxes from meteorological data and soil moisture measurements. One of the steps of this framework was the calculation of the soil water balance, which included the fitting of a drainage model that could be used to predict drainage from soil moisture measurements.…”

Estimating karst groundwater recharge from soil moisture observations – A new method tested at the Swabian Alb, Southwest Germany

“…In addition to the correlation analysis, we used a more physically-oriented approach to describe the relation between soil moisture and recharge. We fitted the unit gradient model (Hillel, 1998) with its two parameters (B and ks) (Schaffitel et al, 2021). Vertical water flow, considered here as a proxy for groundwater recharge, is defined as:…”

“…Ɵr [vol %] and Ɵs [vol %] correspond to the residual water content and the saturated water content. In this study, the soil moisture minimum and maximum measured during soil moisture time series were used, as in Schaffitel et al, (2021). The relationship is based on the Burdine-Brooks-Corey parametrization of hydraulic conductivity (Brooks and Corey, 1964).…”

“…In other non-karstic geological settings, soil moisture measurements conducted at a high temporal resolution have been used in a few studies to investigate infiltration related processes (Demand et al, 2019;Martini et al, 2015). Schaffitel et al (2021) developed a data-driven water-balancing framework to derive water fluxes from meteorological data and soil moisture measurements. One of the steps of this framework was the calculation of the soil water balance, which included the fitting of a drainage model that could be used to predict drainage from soil moisture measurements.…”