Abteilung Systemanalyse, Integrated Assessment und Modellierung

This paper presents some of the reasons for studying the history of hydrology and for the formation of the International Association of Hydrological Sciences (IAHS) History of Hydrology Working Group. In particular, we consider the importance of recording the histories of hydrological data, catchments, diversity in hydrology (of both people and topics), and what can be gained from the historical literature in hydrology. We also consider why the classical concepts of catchment response to rainfall have evolved slowly in hydrology, despite identified limitations, and how the major impetus for change in the 1970s, in the form of techniques for measuring environmental tracers, effectively came from developments outside the discipline. We conclude by speculating whether the questions posed by recent machine learning studies might lead to further change and understanding.

The interplay between abiotic (resource supply, temperature) and biotic (grazing) factors determines growth and loss processes in phytoplankton through resource competition and trophic interactions, which are mediated by morphological traits like size. Here, we study the relative importance of grazers, water physics, and chemistry on the daily net accumulation rates (ARs) of individual phytoplankton from natural communities, grouped into six size classes from circa 10 to 500 μm. Using a Random Forest modelling approach and 4 years of daily data from a lake, we find that water temperature is generally a pivotal control of all phytoplankton ARs. At the same time, nutrients and light are important for the smallest and the largest classes. Mesozooplankton abundance is a key predictor of the AR for small phytoplankton, with microzooplankton being important for the middle-size range. In our data, large and small phytoplankton have different (seasonal) blooming patterns: small forms are favoured by low temperature and grazing, and high phosphorus levels. Larger forms show positive ARs at high temperatures and low phosphorus (being relatively insensitive to zooplankton grazing). These results help us understand the opportunities and limitations of using size to explain and model phytoplankton responses to biotic and abiotic environmental change.

This study investigates the drought of three major terminal lakes: Great Salt Lake, Salton Sea, and Lake Urmia, driven by socio-hydrological lock-in—a phenomenon characterized by feedback loops between human activities and environmental processes. Previous research has linked this drying to socio-hydrological lock-in, where rational actions by individuals collectively lead to suboptimal outcomes, exacerbating water scarcity and ecological degradation. Despite existing studies, a critical knowledge gap remains in understanding how these feedback mechanisms operate across different socio-economic and ecological contexts. This research seeks to address this gap through an integrative analysis of historical data and case studies, highlighting the interplay between increased water demand for agriculture, population growth, and governance challenges. The resultant shrinkage of these lakes exposes saline playas, generating salt-rich dust with severe ecological and health impacts, including soil salinization and respiratory illnesses. By comparing the socio-hydrological lock-in across diverse regions, this study provides insights into preventing and mitigating these cycles. It emphasizes the necessity for holistic water management strategies that integrate both supply and demand-side measures. The key contribution of this research lies in its systematic exploration of the feedback mechanisms driving socio-hydrological lock-ins, offering a foundation for developing sustainable water resource management policies globally. This work aims to influence policy and practice by highlighting the need for integrated, long-term strategies that balance economic pursuits with environmental sustainability, ensuring resilience in water management amidst mounting environmental challenges.

Assessment of potential impacts of chemicals on the environment traditionally involves regulatory standard data requirements for acute aquatic toxicity testing using algae, daphnids, and fish (e.g., Organisation for Economic Co-operation and Development [OECD] test guidelines 201, 202, and 203, respectively), representing different trophic levels. In line with the societal goal to replace or reduce vertebrate animal testing, alternative bioassays were developed to replace testing with fish: the fish cell line RTgill-W1 acute toxicity assay (OECD test guideline 249) and the zebrafish embryo acute toxicity test (zFET, OECD test guideline 236). However, previous studies revealed the lower sensitivity of the RTgill-W1 cell line assay and zFET for some neurotoxic chemicals and allyl alcohol, which is presumably biotransformed in fish to the more toxic acrolein (which is predicted well through the cell line assay). To provide an additional alternative to acute fish toxicity, in this study we analyzed historic ecotoxicity data for fish and daphnids from the EnviroTox Database. We found a considerable variability in acute fish median lethal concentration and acute daphnids median effect concentration values, particularly for neurotoxic chemicals. Comparing sensitivity of these taxonomic groups according to different neurotoxicity classification schemes indicates that fish rarely represent the most sensitive trophic level of the two. Exceptions here most prominently include a few cyclodiene compounds, which are no longer marketed, and a chemical group that could be identified through structural alerts. Moreover, daphnids are more sensitive than fish to acrolein. This analysis highlights the potential of the Daphnia acute toxicity test, which is usually a standard regulatory data requirement, in safeguarding the environmental protection level provided by the RTgill-W1 cell line assay and the zFET. This research, rooted in decades of efforts to replace the fish acute toxicity test, shifts the focus from predicting fish toxicity one-to-one to emphasizing the protectiveness of alternative methods, paving the way for further eliminating vertebrate tests in environmental toxicology.

We review the main methods used to study spin glasses. In the first part, we focus on methods for fully connected models and systems defined on a tree. These include the replica method, the Thouless-Anderson-Palmer formalism, the cavity method, and the dynamical mean-field theory. In the second part, we deal with the description of low-dimensional systems, mostly in three spatial dimensions, which are mostly studied through numerical simulations. We conclude by mentioning some of the main open problems in the field.

Weunveil the multifractal behavior of Ising spin glasses in their low-temperature phase. Using the Janus II custom-built supercomputer, the spin-glass correlation function is studied locally. Dramatic fluctuations are found when pairs of sites at the same distance are compared. The scaling of these fluctuations, as the spin-glass coherence length grows with time, is characterized through the computation of the singularity spectrum and its corresponding Legendre transform. A comparatively small number of site pairs controls the average correlation that governs the response to a magnetic field. We explain how this scenario of dramatic fluctuations (at length scales smaller than the coherence length) can be reconciled with the smooth, self-averaging behavior that has long been considered to describe spin-glass dynamics.