Controls on spatial and temporal variability in streamflow and hydrochemistry in a glacierized catchment

Abstract

Abstract. Understanding the hydrological and hydrochemical functioning of glacierized catchments requires the knowledge of the different controlling factors and their mutual interplay. For this purpose, the present study was carried out in two sub-catchments of the glacierized Sulden River catchment (130 km2; eastern Italian Alps) in 2014 and 2015, characterized by a similarly sized but contrasting geological setting. Samples were taken at different space and timescales for analysis of stable isotopes in water, electrical conductivity, and major, minor and trace elements. At the monthly sampling scale, complex spatial and temporal dynamics for different spatial scales (0.05–130 km2) were found, such as contrasting electrical conductivity gradients in both sub-catchments. For the entire Sulden catchment, the relationship between discharge and electrical conductivity showed a monthly hysteretic pattern. Hydrometric and geochemical dynamics were controlled by interplay of meteorological conditions, topography and geological heterogeneity. A principal component analysis revealed that the largest variance (36.3 %) was explained by heavy metal concentrations (such as Al, V, Cr, Ni, Zn, Cd and Pb) during the melting period, while the remaining variance (16.3 %) resulted from the bedrock type in the upper Sulden sub-catchment (inferred from electrical conductivity, Ca, K, As and Sr concentrations). Thus, high concentrations of As and Sr in rock glacier outflow may more likely result from bedrock weathering. Furthermore, nivo-meteorological indicators such as daily maximum air temperature and daily maximum global solar radiation represented important meteorological controls, with a significant snowmelt contribution when exceeding 5 ∘C or 1000 W m−2, respectively. These insights may help in better understanding and predicting hydrochemical catchment responses linked to meteorological and geological controls and in guiding future classifications of glacierized catchments according to their hydrochemical characteristics.

‘Teflon Basin’ or Not? A High-Elevation Catchment Transit Time Modeling Approach

“…Although we used δ 18 O ice melt data measured in the field to derive δ 18 O ice melt input data for ESCIMO, the spatio-temporal variability, as observed in empirical studies [10,61,62], provides an alternative source of uncertainty. An isotopic lapse rate was not directly estimated from the ice melt samples, rather it was estimated from the mean winter precipitation lapse rate.…”

“…An isotopic lapse rate was not directly estimated from the ice melt samples, rather it was estimated from the mean winter precipitation lapse rate. We used temporally invariant δ 18 O values of ice melt due to missing temporally distributed data throughout the four-year period, but temporal variability has also not yet been described intensively [10,61,62]. Our estimate (0.221% /100 m) compared well to values presented in other studies; e.g., He et al [46] directly estimated an isotopic glacier melt lapse rate from δ 18 O measurements at −0.226% per 100 m in a 17% glacierized high-elevation catchment in the Tien Shan and used it for their modeling study.…”

Water supply in times of climate change—Tracer tests to identify the catchment area of an Alpine karst spring, Tyrol, Austria

“…This extension could explain the observed discharge rates and temperatures at the Tuxbachquelle. Hydrological studies in other Alpine regions showed that rock glaciers can impact the water quality extensively and can yield a base runoff of 70 to 100 L/s during summer months (Nickus et al 2015;Thies et al 2013Thies et al , 2017Engel et al 2019).…”

Seasonal source water and flow path insights from a year of sampling in the Chamkhar Chhu basin of Central Bhutan

“…This agrees with our expectation that groundwater increases in importance with greater distance from the cryospheric water sources in the glacierized headwaters. In addition to decreasing meltwater contributions, the increasing catchment size is a proxy for increasing storage and longer flow paths in the bedrock (Muir, Hayashi, and McClymont 2011;Engel et al 2019). However, there is a small reversal in this trend below approximately 3,000 m where unreacted water increases its proportion of river flow once again.…”