ABSTRACT:

This dataset contains questionnaire responses sent to a random sample of persons that announced vacancies through the About Hydrology mailinglist between 2013 and 2020. To protect the privacy of the respondents, these data are not publicly shared.

Hydrological models play a key role in contemporary hydrological scientific research. For this study, 400+ scientific hydrological vacancies were analyzed, to evaluate whether the job description already prescribed which model must be used, and whether experience with a specific model was an asset. Of the analysed job positions, 76% involved at least some modelling. Of the PhD positions that involved any modelling, the model is already prescribed in the vacancy text in 17% of the cases, for postdoc positions this was 30%. A small questionnaire
revealed that also beyond the vacancies where the model is already prescribed, in many Early-Career Scientist (ECSs) projects the model to be used is pre-determined and, actually, also often used without further discussion. There are valid reasons to pre-determine the model in these projects, but at the same time, this can have long-term consequences for the ECS: experience with the model will influence the research identity the ECS is developing, and influence future opportunities of the ECS - it might be strategic to gain experience with popular, broadly used models, or to become part of an efficient modelling team. This serves an instrumental vision on modelling. Seeing models as hypotheses calls for a more critical evaluation. ECSs learn the current rules of the game, but should at the same time actively be stimulated to critically question these rules.

ABSTRACT:

Drought-affected regions often contain high densities of small reservoirs, usually informally built, as drought-coping mechanism. These structures influence socio-hydrological dynamics and have the potential to alter hydrological processes relevant to drought emergence and development. This study aimed to analyze the influence of a high concentration of small reservoirs on the intensification and evolution of drought events. We present an innovative method, which we call “Drought Cycle Analysis”, that tracks the concomitance of precipitation and water storage deficit and associates this with four drought stages: Wet Period, Meteorological drought, Hydro-meteorological drought and Hydrological drought period. The methodology was tested for the Riacho do Sangue River watershed located in the semi-arid region of northeast Brazil. We used a combination of satellite imagery (Landsat 5, 7 and 8) and an empirical equation to estimate the volume stored in the dense network of small reservoirs. Using the Drought Cycle Analysis, we show that the unmonitored small reservoirs induced and modified drought events, extending the hydrological drought on average with 30%, while this extension can double for specific drought events. The Drought Cycle Analysis method proved useful for monitoring and comparing the evolution of different drought events, in addition to being applicable as an auxiliary tool in the improvement of water resources management of large reservoirs. This study demonstrates the importance of considering small reservoirs in water resource management strategy development for drought-prone regions.

ABSTRACT:

This database contains vacancies that were announced through the About Hydrology Mailinglist between 2013 and 2020.

Hydrological models play a key role in contemporary hydrological scientific research. For this study, 400+ scientific hydrological vacancies were analyzed, to evaluate whether the job description already prescribed which model must be used, and whether experience with a specific model was an asset. Of the analysed job positions, 76% involved at least some modelling. Of the PhD positions that involved any modelling, the model is already prescribed in the vacancy text in 17% of the cases, for postdoc positions this was 30%. A small questionnaire
revealed that also beyond the vacancies where the model is already prescribed, in many Early-Career Scientist (ECSs) projects the model to be used is pre-determined and, actually, also often used without further discussion. There are valid reasons to pre-determine the model in these projects, but at the same time, this can have long-term consequences for the ECS: experience with the model will influence the research identity the ECS is developing, and influence future opportunities of the ECS - it might be strategic to gain experience with popular, broadly used models, or to become part of an efficient modelling team. This serves an instrumental vision on modelling. Seeing models as hypotheses calls for a more critical evaluation. ECSs learn the current rules of the game, but should at the same time actively be stimulated to critically question these rules.

ABSTRACT:

Hydrological models are useful tools to explore the impact of climate change. To prioritize parameters for calibration and to evaluate hydrological model functioning, sensitivity analysis can be conducted. Parameter sensitivity, however, varies over climate, and therefore climate change could influence parameter sensitivity. In this study we explore the change in parameter sensitivity for the mean discharge and the timing of the discharge, within a plausible climate change rate. We investigate if changes in sensitivity propagate into the calibration strategy, and diagnostically compare three hydrological models based on the sensitivity results. We employed three frequently used hydrological models (SAC, VIC, and HBV), and explored parameter sensitivity changes across 605 catchments in the United States by comparing GCM(RCP8.5)-forced historical and future periods. Consistent among all hydrological models and both for the mean discharge and the timing of the discharge, is that the sensitivity of snow parameters decreases in the future. Which other parameters increase in sensitivity is less consistent among the hydrological models. In 45% to 55% of the catchments, dependent on the hydrological model, at least one parameter changes in the future in the top-5 most sensitive parameters for mean discharge. For the timing, this varies between 40% and 88%. This requires an adapted calibration strategy for long-term projections, for which we provide several suggestions. The disagreement among the models on the processes that become more relevant in future projections also calls for a strict evaluation of the adequacy of the model structure for long-term simulations.

ABSTRACT:

This folder contains the output files from:

L.A. Melsen and B. Güse (2019), Hydrological drought simulations: How climate and model structure control parameter sensitivity, Water Resources Research, doi: 10.1029/2019WR025230

The data contain hydrological drought indicators (e.g. median drought duration) for three different models (SAC, VIC, HBV), where these models were run with a sample of parameters for 605 basins in the US. Sensitivity analysis was applied to the indicators.

Study abstract:
Hydrological drought, defined as below average streamflow conditions, can be triggered by different mechanisms which are to a large extent dictated by the climate. Moreover, the simulation of hydrological droughts highly depends on the model structure and how drought triggering mechanisms are parameterized. In this large-sample hydrological study, we investigate how climate and model structure control hydrological drought simulations. We conducted sensitivity analysis on parameters of three frequently used hydrological models (HBV, SAC, and VIC) for the simulation of drought duration and drought deficit over 605 basins covering more than ten different K\"oppen-Geiger climates. The sensitivity analysis revealed that, as anticipated, different parameter are sensitive in different climates. However, not all expected drought mechanisms were reflected in the parameter sensitivity: especially the sensitivity of ET parameters does not align with the theory, and the role of snow parameters in snow-related droughts shows a distinction between degree-day based models and energy-balance models. Besides parameter sensitivity being different over climates, we also found that parameter sensitivity differed over the different models. Where HBV and SAC did display fairly similar behaviour, in VIC other model mechanisms were triggered. This implies that conclusions on driving mechanisms in hydrological drought cannot be based on hydrological models only, as different models would lead to different conclusions. Hydrological models can have heuristic value in drought research, to formulate new theories and identify research directions, but formulated theories on driving processes should always be backed up by observations.