A novel method to evaluate the effect of a stream restoration on the spatial pattern of hydraulic connection of stream and groundwater

Abstract

Keywords:Groundwater-stream water interactions Principal component analysis Signal propagation Hydraulic connectivity Clogging Riparian zone s u m m a r y Stream restoration aims at an enhancement of ecological habitats, an increase of water retention within a landscape and sometimes even at an improvement of biogeochemical functions of lotic ecosystems. For the latter, good exchange between groundwater and stream water is often considered to be of major importance. In this study hydraulic connectivity between river and aquifer was investigated for a four years period, covering the restoration of an old oxbow after the second year. The oxbow became reconnected to the stream and the clogging layer in the oxbow was excavated. We expected increasing hydraulic connectivity between oxbow and aquifer after restoration of the stream, and decreasing hydraulic connectivity for the former shortcut due to increased clogging. To test that hypothesis, the spatial and temporal characteristics of the coupled groundwater-stream water system before and after the restoration were analysed by principal component analyses of time series of groundwater heads and stream water levels. The first component depicted between 53% and 70% of the total variance in the dataset for the different years. It captured the propagation of the pressure signal induced by stream water level fluctuations throughout the adjacent aquifer. Thus it could be used as a measure of hydraulic connectivity between stream and aquifer. During the first year, the impact of stream water level fluctuations decreased with distance from the regulated river (shortcut), whereas the hydraulic connection of the oxbow to the adjacent aquifer was very low. After restoration of the stream we observed a slight but not significant increase of hydraulic connectivity in the oxbow in the second year after restoration, but no change for the former shortcut. There is some evidence that the pattern of hydraulic connectivity at the study site is by far more determined by the natural heterogeneity of hydraulic conductivities of the floodplain sediments and the initial construction of the shortcut rather than by the clogging layer in the oxbow.

Forensic hydrology: what function tells about structure in complex settings

“…Principal component analysis has been used in hydrology for many decades but has only rarely been applied to time series, in contrast to other disciplines like climatology. However, it has proven to be a powerful tool to identify and to quantify the impact of river water stage on riparian groundwater head (Lehr et al 2015), of groundwater production wells on adjacent lakes (Böttcher et al 2014), of different crops and tillage practices on soil water content (Hohenbrink et al 2016), or of climatic gradients on stream discharge (Thomas et al 2012). Application of PCA on a data set comprising soil matrix potential, groundwater head and stream discharge nicely illustrated the hydrological continuum within a catchment (Lischeid et al 2017).…”

Interação rio-aquífero e a meiofauna do ambiente hiporreico

“…Para este ambiente não existe uma definição conceitual única, pois seu estudo envolve diferentes variáveis, como: ecologia, morfologia, química, hidrologia, tempo de residência e até combinações entre essas varáveis (WILLIAMS, 1989;BOULTON et al, 2010;BIANCHIN et al, 2011;LARNED & DATRY, 2013;LEHR et al, 2015). Diante disso, é muito importante conhecer as características da zona hiporreica, visto que esse ambiente pode proporcionar um tratamento natural nas águas de recarga dos aquíferos.…”

Evaluation of Spatio-Temporal Patterns of Remotely Sensed Evapotranspiration to Infer Information about Hydrological Behaviour in a Data-Scarce Region

“…The similarity between the map of average ET and the scores of PC1 suggest that PC1 mainly reflects the mean behaviour of ET in the river basin. Similarly, PCA of time series often yields a first component that depicts the mean behaviour [17,18,59,70]. This component explained 63.0% of the variance of spatial and temporal patterns of ET, thus it represents the most prevailing conditions in the river basin.…”