Multi-year time series of daily solute and isotope measurements from three Swiss pre-Alpine catchments

Time series analyses of solute concentrations in streamwater and precipitation are powerful tools for unraveling the interplay of hydrological and biogeochemical processes at the catchment scale. While such datasets are available for many sites around the world, they often lack the necessary temporal resolution or are limited in the number of solutes they encompass. Here we present a multi-year dataset encompassing daily records of major ions and a range of trace metals in both streamwater and precipitation in three catchments in the northern Swiss Pre-Alps. These time series capture the temporal variability observed in solute concentrations in response to storm events, snow melt, and dry summer conditions. This dataset additionally includes stable water isotope data as an extension of a publicly available isotope dataset collected concurrently at the same locations, and together these data can provide insights into a range of ecohydrological processes and enable a suite of analyses into hydrologic and biogeochemical catchment functioning

Twenty-three unsolved problems in hydrology (UPH) – a community perspective

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through on-line media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focussed on process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come

Insights into streamflow generation mechanisms using high-frequency analysis of isotopes and water quality in streamflow and precipitation

ISSN:1029-7006ISSN:1607-796

The effects of model complexity and calibration period on groundwater recharge simulations

ISSN:1029-7006ISSN:1607-796

A lab in the field: high-frequency analysis of water quality and stable isotopes in stream water and precipitation

ISSN:1027-5606ISSN:1607-793

What is the best time to take stream isotope samples for event-based model calibration?

Environmental tracer data, such as the stable water isotopic composition of streamwater and precipitation, are valuable for understanding runoff generation processes and calibrating hydrological models. Despite recent technical advancements, the collection and analysis of streamwater and precipitation samples still involve significant costs and efforts. Consequently, it is useful to study how many samples need to be collected as a basis for model calibration and what the most informative sampling times are. In previous studies, we used the Birkenes hydrological model and synthetic data to explore the value of a few stream isotope samples for event-based model calibration. Our results showed that the information from two or three selected isotope samples, and particularly a sample taken during the falling limb of the hydrograph, improved model performance significantly compared to calibration against streamflow data only. In this follow-up study, we used a unique Swiss dataset with high-frequency isotope measurements of precipitation and streamwater during six rainfall-runoff events to determine which stream isotope samples were most informative for model calibration. Several benchmarks were used to judge model validation performance. Our results showed that for 83% of the 42 possible combinations of calibration and validation events two strategically selected streamwater samples improved model performance compared to the lower benchmark when only stream stage data were used for calibration. The most informative samples also improved the calibration of a mixing-related parameter. When the model was calibrated and validated for the same event, the most informative samples for model calibration were those from the early part of the falling limb, which confirmed the results of the previous studies with synthetic data. Pre-event isotope samples were more informative when the model was calibrated for one event and then validated against other events or all events combined. Our results suggest that relatively inexpensive event-based data for model calibration can be obtained for so-far ungauged catchments by placing a water level logger in the stream and collecting precipitation isotope data and a few streamflow samples. These samples should preferably include a pre-event sample and a sample from the early falling limb. However, similar analyses for a wider range of sites and events, in combination with a selection of models with different structures and assumptions, are needed to confirm these results and to optimise sampling strategies further

The “big brother” hydrologist is watching snow hydrology in forests and open space

ISSN:1029-7006ISSN:1607-796