Description of an indirect method (IDPR) to determine spatial distribution of infiltration and runoff and its hydrogeological applications to the French territory

Regional coupled surface–subsurface hydrological model fitting based on a spatially distributed minimalist reduction of frequency domain discharge data

“…Figure 7 superimposes estimates of β at each discharge gauging station (dots) and the IDPR map produced by Mardhel et al (2021). First, an overall spatial coherence is observed between these two indicators.…”

“…Hence, very little information is available to compare our β estimates against and, ultimately, to validate them. Fortunately, the French Geological Survey (BGRM) has developed a systematic method to qualify the propensity of terrains to either infiltrate water or to generate runoff, as described by Mardhel et al (2021). The method takes advantage of the mismatch evaluated between thalweg locations inferred from digital elevation models and the actual location of drainage networks used to build a normalized index called IDPR (Network Development and Persistence Index).…”

“…The lower its value, the more a terrain is prone to infiltration and vice versa. Mardhel et al (2021) calculated this index for the entire French metropolitan area at high resolution (25 m). We take this opportunity to qualitatively assess the consistency of β estimates, which, in a way, is very complementary to the IDPR, being much less spatially resolved but providing an actual operable value to the flow partitioning, which is of primary importance for modeling purposes.…”

Calibration of groundwater seepage against the spatial distribution of the stream network to assess catchment-scale hydraulic properties

“…These indicators are essentially local and readily accessible from information on topography and stream networks. We propose more integrative indicators based on the distance between the observed and simulated stream networks computed along the steepest slope between them, as does the IDPR (Network Development and Persistence Index), to identify zones predominantly favorable to infiltration or runoff (Mardhel et al, 2021). The advantages of this procedure are to account for the topographical structure within the definition of the distances and to constrain the comparison to the best compromise between the over-and undersaturation, mainly driven by D so and D os , respectively.…”

“…Previous studies have focused on the comparison of an observed hydrographic network with a simulated hydrographic network computed from different methods. The organization of stream networks has been predicted directly from a digital elevation model (DEM) based on a predefined accumulation threshold value determining whether an upstream surface is capable of producing significant flow (Mardhel et al, 2021;Le Moine, 2008;Schneider et al, 2017;Luo and Stepinski, 2008;. Lumped parameter models, such as TOPMODEL (Beven and Kirkby, 1979), have also been extensively used to predict the spatial patterns of seepage areas (Merot et al, 2003) allowing us to constrain the subsurface hydraulic properties (Blazkova et al, 2002;Güntner et al, 2004;Franks et al, 1998).…”