The hydrological response of groundwater to rainfall plays a key role in the initiation of deep-seated bedrock landslides; however, the mechanisms require further investigation due to the complexity of groundwater movement in fissured bedrock. In this study, an active translational landslide along nearly horizontal rock strata was investigated. The hydrological response of groundwater to rainfall was analyzed, using the data from a four-year real-time field monitoring program from June 2013 to December 2016. The monitoring system was installed along a longitudinal of the landslide with severe deformation and consisted of two rainfall gauges, nine piezometers, three water-level gauges, and two GPS data loggers. Much research effort has been directed to exploring the relationship between rainfall and groundwater response. It is found that both the pore-water pressure (PWP) and groundwater level (GWL) responses were significantly influenced by the rainfall pattern and the hydrological properties of the underlying aquifer. The rapid rise and fall of PWP and GWL were observed in the rainy season of 2013 with high-frequency, long-duration, and high-intensity rainfall patterns, especially in the lower of the landslide dominated by the porous aquifer system. In contrast, a slower and prolonged response of PWP and GWL to rainfall was observed in most monitoring boreholes in 2014 and 2015 with two rainstorms of short duration and high intensity. In the lower of the landslide, the peak GWL exhibited a stronger correlation with the cumulative rainfall than the daily rainfall in a single rainfall event whereas the peak groundwater level fluctuation (GWLF) exhibited a strong correlation with API with a half-life of 7 days. In the middle of the landslide, however, relatively lower correlation between rainfall and groundwater response was observed. Three types of groundwater flow were identified based on the recession coefficients of different segments of water-level hydrographs in the landslide area, corresponding to the quick flow through highly permeable gravely soil and well-developed vertical joints in the bedrock, the slow and diffuse flow through the relatively less-permeable bedrock, and the transition between them in the aquifer system.

In this study, summer rainfall contributions to streamflow were quantified in the sub-arctic, 30% glacierized Tarfala (21.7km(2)) catchment in northern Sweden for two non-consecutive summer sampling seasons (2004 and 2011). We used two-component hydrograph separation along with isotope ratios (O-18 and D) of rainwater and daily streamwater samplings to estimate relative fraction and uncertainties (because of laboratory instrumentation, temporal variability and spatial gradients) of source water contributions. We hypothesized that the glacier influence on how rainfall becomes runoff is temporally variable and largely dependent on a combination of the timing of decreasing snow cover on glaciers and the relative moisture storage condition within the catchment. The results indicate that the majority of storm runoff was dominated by pre-event water. However, the average event water contribution during storm events differed slightly between both years with 11% reached in 2004 and 22% in 2011. Event water contributions to runoff generally increased over 2011 the sampling season in both the main stream of Tarfala catchment and in the two pro-glacial streams that drain Storglaciaren (the largest glacier in Tarfala catchment covering 2.9km(2)). We credit both the inter-annual and intra-annual differences in event water contributions to large rainfall events late in the summer melt season, low glacier snow cover and elevated soil moisture due to large antecedent precipitation. Together amplification of these two mechanisms under a warming climate might influence the timing and magnitude of floods, the sediment budget and nutrient cycling in glacierized catchments. Copyright (c) 2012 John Wiley & Sons, Ltd.

Results are presented of an inter-basin comparison of cold-season (October-April/March) river flow characteristics for 17 undisturbed catchments in Siberia for the period 1980-1998. Flow and recession metrics for each basin and mean annual cold-season catchment-averaged drainage depth, Q(cold) (mm), were analyzed with various basin attributes in an attempt to detect potential controls of recession behavior. There is a marked behavioral distinction between basins on non-continuous (n = 6) permafrost coverage (discontinuous/sporadic/isolated) and those on continuous (n = 11) permafrost. The first group is characterized by slow recession, relatively high discharge in April before spring freshet, and high values for Q(cold) up to about 80 mm, which corresponds to more than 10% of total annual rainfall. Although positive correlations with several catchment attributes (annual precipitation regime; peat land fraction) are found, higher abundance of through-taliks and greater active layer depth (ALD) are presumed to be the most likely controls of the distinctive hydrological behavior of catchments containing non-continuous permafrost. Within the group of catchments on continuous permafrost, characteristics of cold-season flow vary conspicuously as some rivers exhibit very fast recession and cessation of flow for 3-4 months, while others show strongly reduced, but continuous discharge throughout the cold season. Our analysis shows that lake area fraction, peatland fraction and morphological metrics may play a role in favoring prolonged cold-season flow in this group. Whether prolonged cold-season flow in areas of continuous permafrost also signals contributions to river flow from intra- and/or sub-permafrost groundwater remains an intriguing but so far unresolved question. (C) 2013 Elsevier B.V. All rights reserved.