Abstract
AbstractSurface saturated areas are key features in generating run‐off. A detailed characterization of the expansion and contraction of surface saturation in riparian zones and its connectivity to the stream is fundamental to improve our understanding of the spatial and temporal variability of streamflow generation processes. In this first contribution of a series of two papers, we used ground‐based thermal infrared imagery for characterizing riparian surface saturation seasonal dynamics of seven different riparian areas in the Weierbach catchment (0.42 km2), a small forested catchment in Luxembourg. We collected biweekly panoramic images of the seven areas over a period of 2 years. We identified the extension of saturation in each collected panoramic image (i.e., percentage of pixels corresponding to saturated surfaces in each riparian area) to generate time series of surface saturation. Riparian surface saturation in all areas was seasonally variable, and its dynamics were in accordance with lower hillslope groundwater level fluctuations. Surface saturation in the different areas related to catchment outlet discharge through power law relationships. Differences in these relationships for different areas could be associated with the location of the areas along the stream network and to a possible influence of local riparian morphology on the development of surface saturation, suggesting a certain degree of intracatchment heterogeneity. This study paves the way for a subsequent investigation of the spatio‐temporal variability of streamflow generation in the catchment, presented in our second contribution.
Highlights
This result may suggest that variability in the unsaturated compartment of the catchment storage (SUNSAT − estimated from the Volumetric soil water content (VWC) of the soil profiles) could be related with the dynamics of riparian surface saturation in some areas, this particular relationship remains of difficult interpretation, and further investigation on the water sources of riparian surface saturation is currently ongoing
Considering the observed seasonal dynamics of surface saturation and the possible influence of lower hillslope Ground water (GW) fluctuations on surface saturation, we provide a perceptual model of how riparian surface saturation may evolve in the different monitored areas in Weierbach catchment during dry and wet periods, in the absence of precipitation (Figure 12)
This study is a contribution to the call for the development of a routine method for mapping surface saturated areas (Dunne et al, 1975) and to the need to start characterizing the spatial and temporal variability of riparian processes for a better understanding of catchments hydrological and biochemical functioning (Grabs et al, 2012; Ledesma et al, 2018; Tetzlaff et al, 2008; Vidon & Hill, 2004)
Summary
There is a reasonable understanding of how the overall hydrological response of the catchment is generated (Fenicia et al, 2014; Glaser et al, 2016; Klaus, Wetzel, Martínez-Carreras, Ector, & Pfister, 2015; MartínezCarreras et al, 2016; Schwab, Klaus, Pfister, & Weiler, 2018; Wrede et al, 2015), there is still a lack of understanding of the dynamics of small-scale riparian processes, like the spatial and temporal variability of riparian surface saturation, and of how these dynamics are related to the hydrological response (Scaini et al, 2017) In this first contribution of a series of two papers, we apply ground-based TIR imagery as a routine method for mapping surface saturation dynamics across multiple seasonal and hydrological conditions and across multiple sites in the riparian zone of the Weierbach catchment. In case of dry antecedent conditions, the catchment produces a single spiky peak of short duration (i.e., hours), whereas the response is bimodal during wet antecedent conditions—with a first peak followed by a broader second peak of longer duration (extending up to several days). Martínez-Carreras et al (2016) showed that the first peak is mainly composed of water from precipitation, throughfall, and rapid HRS connectivity through
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