Gregor Laaha

Gregor Laaha
University of Natural Resources and Life Sciences Vienna | boku · Institute of Applied Statistics and Computing

Associate Professor

About

105
Publications
28,221
Reads
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2,982
Citations
Citations since 2016
51 Research Items
2284 Citations
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
Additional affiliations
April 2010 - present
University of Natural Resources and Life Sciences Vienna
Position
  • Professor (Associate)

Publications

Publications (105)
Article
The main objective of the paper is to understand the contributions to the uncertainty in low flow projections resulting from hydrological model uncertainty and climate projection uncertainty. Model uncertainty is quantified by different parameterizations of a conceptual semi-distributed hydrologic model (TUWmodel) using 11 objective functions in th...
Article
Full-text available
The objective of this paper is to present a new strategy for assessing climate impacts on low flows and droughts. The strategy is termed a three-pillar approach as it combines different sources of information. The first pillar, trend extrapolation, exploits the temporal patterns of observed low flows and extends them into the future. The second pil...
Article
Full-text available
Drought; Hydrology; Impacts; Management; 2015 European drought
Article
Full-text available
In 2015 large parts of Europe were affected by a drought. In two companion papers we summarize a collaborative initiative of members of UNESCO’s EURO FRIEND-Water program to perform a timely pan-European assessment of the event. In this second paper, we analyse the event of 2015 relative to the event of 2003 based on streamflow observations. Analys...
Article
Full-text available
A lack of winterization of power system infrastructure resulted in substantial rolling blackouts in Texas in 2021, but debate about the cost of winterization continues. Here we assess if incentives for winterization on the energy-only market are sufficient. We combine power demand estimates with estimates of power plant outages to derive power defi...
Preprint
Full-text available
In climates with a warm and a cold season, low-flows are generated by different processes, which violates the homogeneity assumption of extreme value statistics. In this second part of a two-part series, we extend the mixed probability estimator of the companion paper (Laaha, G., 2022) to deal with dependency of seasonal events. We formulate a copu...
Article
Full-text available
Accurate predictions of seasonal low flows are critical for a number of water management tasks that require inferences about water quality and the ecological status of water bodies. This paper proposes an extreme gradient tree boosting model (XGBoost) for predicting monthly low flow in ungauged catchments. Particular emphasis is placed on the lowes...
Article
Full-text available
Standardized drought indices such as the Standardized Precipitation Index (SPI) or the Standardized Precipitation and Evapotranspiration Index (SPEI) are frequently used around the world to assess drought severity across a continent or a larger region covering different meteorological regimes. But how standard are these standardized indices? In thi...
Article
Full-text available
Drought events and their impacts vary spatially and temporally due to diverse pedo-climatic and hydrologic conditions, as well as variations in exposure and vulnerability, such as demographics and response actions. While hazard severity and frequency of past drought events have been studied in detail, little is known about the effect of drought man...
Preprint
Accurate predictions of seasonal low flows are critical for a number of water management tasks that require inferences about water quality and the ecological status of water bodies. This paper proposes an extreme gradient tree boosting model (XGBoost) for predicting monthly low flow in ungauged catchments. Particular emphasis is placed on the lowes...
Article
Full-text available
Restoring the longitudinal connectivity of rivers through fish passes is of great importance for achieving good ecological status of surface waters. However, the key stimuli determining the findability of the entrance of these structures is still subject to debate. In this article, the influence of water temperature, light and acoustic stimuli in a...
Preprint
Full-text available
In this paper future changes of surface water availability in Austria are investigated. We use an ensemble of downscaled and bias-corrected regional climate model simulations of the EURO-CORDEX initiative under moderate mitigation (RCP4.5) and Paris agreement (RCP2.6) emission scenarios. The climatic water balance and its components (rainfall, snow...
Article
Considering the probability of occurrence of an extreme cold event similar to that in February 2021, winterization of the Texan power system pays off for risk-neutral utilities in the medium term. Risk aversion can cause under-investment, and policymakers should therefore take into account extreme event risks in decision-making and implement measur...
Article
Full-text available
In the course of eliminating continuum breaks at watercourses, the findability of the entrance to fish passes continues to be a relevant research topic. In addition to the positioning, the functionality of the entrance is defined in various guidelines, primarily by the flow or flow impulse. This publication, which is part of a research project at v...
Article
Full-text available
Statistical learning methods offer a promising approach for low-flow regionalization. We examine seven statistical learning models (Lasso, linear, and nonlinear-model-based boosting, sparse partial least squares, principal component regression, random forest, and support vector regression) for the prediction of winter and summer low flow based on a...
Article
Full-text available
Habitat fragmentation is one of the drivers for amphibian population declines globally. Especially in industrialized countries roads disrupt the seasonal migration of amphibians between hibernation and reproduction sites, often ending in roadkills. Thus, a timely installing of temporary mitigation measures is important for amphibian conservation. W...
Preprint
Full-text available
Drought events and their impacts vary spatially and temporally due to diverse pedo-climatic and hydrologic conditions, as well as variations in exposure and vulnerability, such as demographics and response actions. While hazardous severity and frequency of past drought events have been studied in detail, little is known about the effect of drought...
Preprint
Full-text available
Statistical learning methods offer a promising approach for low flow regionalization. We examine seven statistical learning models (lasso, linear and non-linear model based boosting, sparse partial least squares, principal component regression, random forest, and support vector machine regression) for the prediction of winter and summer low flow ba...
Article
Full-text available
River systems have undergone a massive transformation since the Anthropocene. The natural properties of river systems have been drastically altered and reshaped, limiting the use of management frameworks, their scientific knowledge base and their ability to provide adequate solutions for current problems and those of the future, such as climate cha...
Preprint
Full-text available
A lack of winterization of power system infrastructure resulted in significant rolling blackouts in Texas in 2021. We therefore assess if incentives for winterization on the energy only market have been sufficient, combining power demand estimates with estimates of power plant outages toderive power deficits and scarcity prices. The loss of load in...
Article
Full-text available
Intermittent rivers are prevalent in many countries across Europe, but little is known about the temporal evolution of intermittence and its relationship with climate variability. Trend analysis of the annual and seasonal number of zero-flow days, the maximum duration of dry spells and the mean date of the zero-flow events is performed on a databas...
Article
Full-text available
Numerous indices exist for the description of hydrological drought. The EURO FRIEND-Water Low flow and Drought Group has repeatedly discussed changing paradigms in the perception and use of existing and emerging new indices for hydrological drought identification and characterization. Group members have also tested the communication of different in...
Book
Full-text available
SMIRES is a COST Action addressing the Science and Management of Intermittent Rivers & Ephemeral Streams (coord. T. Datry, INRAE, and G. Singer, University of Innsbruck; http://www.smires.eu). This COST Action had brought together scientists from various research field and stakeholders to develop a European multidisciplinary network for synthesisin...
Technical Report
Full-text available
SMIRES is a COST Action addressing the Science and Management of Intermittent Rivers & Ephemeral Streams (coord. T. Datry, INRAE, and G. Singer, University of Innsbruck; http://www.smires.eu). This COST Action had brought together scientists from various research field and stakeholders to develop a European multidisciplinary network for synthesisin...
Article
Full-text available
The findability of entrances of fish passes for fish, following their instinct movements triggered by key stimuli serve as a basis for addressing a wide range of research issues. The present project is part of a multi-stage study which aims to determine key stimuli which are responsible for finding the entrance of fish passes. Mainly the attraction...
Chapter
Full-text available
In diesem Beitrag werden die Bereiche Umweltdatenmanagement und Umweltstatistik vorgestellt und ihre Anwendung in der Umweltökonomie beispielhaft gezeigt. Dafür sind Kenntnisse und Fertigkeiten zu Management, Modellierung und Bewertung von Umweltdaten mit Raum- und Zeitbezug wichtig. Im Bachelorstudium UBRM werden dazu Grundlagen vermittelt, die im...
Article
Full-text available
This study investigates the atmospheric drivers of severe precipitation deficits in the Greater Alpine Region during the last 210 years utilizing a daily atmospheric circulation type reconstruction. Precipitation deficit tends to be higher during periods with more frequent anticyclonic (dry) and less frequent cyclonic (wet) circulation types, as wo...
Article
Atmospheric and streamflow drought back to 1600 were reconstructed with provenance-verified regional Pinus-sylvestris and Pinus-nigra chronologies of earlywood, latewood and ring width, detrended by signal-free regional curve standardization, from the Weinviertel, a dry region in Eastern Austria. Linear regression models with Weinviertel latewood i...
Article
Full-text available
One of the main aims of accident data analysis is to derive the determining factors associated with road traffic accident occurrence. While current studies mainly use variants of count data regression to achieve this aim, the problem can also be considered as a binary classification task, with the dichotomous target variable indicating events (acci...
Article
Aiming for refined drought characterization, the validation of targeted drought indices is of vital importance. In this study, we compared the performance of established drought indices-the SPI (Standardized Precipitation Index) and the SPEI (Standardized Precipitation Evapotranspiration Index)-with standardized drought indices using a recently dev...
Article
Full-text available
Background Red foxes (Vulpes vulpes L.) have become successful inhabitants of urban areas in recent years. However, our knowledge about the occurrence, distribution and association with land uses of these urban foxes is poor, partly because many favoured habitats are on private properties and therefore hardly accessible to scientists. We assumed t...
Article
Full-text available
The Spanish slug (Arion vulgaris, also known as A. lusitanicus) is considered one of the most invasive species in agriculture, horticulture and private gardens all over Europe. Although this slug has been problematic for decades, there is still not much known about its occurrence across private gardens and the underlying meteorological and ecologic...
Article
Full-text available
Background Amphibians and reptiles are among the most endangered vertebrate species worldwide. However, little is known how they are affected by road-kills on tertiary roads and whether the surrounding landscape structure can explain road-kill patterns. The aim of our study was to examine the applicability of open-access remote sensing data for a...
Article
Full-text available
In 2015 large parts of Europe were affected by drought. In this paper, we analyze the hydrological footprint (dynamic development over space and time) of the drought of 2015 in terms of both severity (magnitude) and spatial extent and compare it to the extreme drought of 2003. Analyses are based on a range of low flow and hydrological drought indic...
Article
Compared to the alpine regions of Austria, the eastern part of the country is overall warmer and drier with some tree species growing at the dry limit within their ecological range. This suggests that tree rings may be a valuable proxy for hydroclimatic variability. In this study, we develop ring-width, earlywood-width and latewood-width chronologi...
Article
Full-text available
The assessment of road infrastructure exposure to extreme weather events is of major importance for scientists and practitioners alike. In this study, we compare the different extreme value approaches and fitting methods with respect to their value for assessing the exposure of transport networks to extreme precipitation and temperature impacts. Ba...
Article
Full-text available
The summer drought of 2015 affected a large portion of continental Europe and was one of the most severe droughts in the region since summer 2003. The summer of 2015 was characterized by exceptionally high temperatures in many parts of central and eastern Europe, with daily maximum temperatures 2 °C higher than the seasonal mean (1971–2000) over mo...
Article
Full-text available
Stream water temperature limits the growth and survival of aquatic organisms; whereby riparian shading plays a key role in inhibiting river warming. This study explains the effects of riparian shading on summer water temperatures at a pre-alpine Austrian river, during heatwave and non-heatwave periods at low flow conditions. A vegetation-shading in...
Article
Full-text available
The assessment of road infrastructure exposure to extreme weather events is of major importance for scientists and practitioners alike. In this study, we compare the different extreme value approaches and fitting methods with respect to their value for assessing the exposure of transport networks to extreme precipitation and temperature impacts. Ba...
Article
Full-text available
Road traffic has severe effects on animals, especially when road-kills are involved. In many countries, official road-kill data are provided by hunters or police; there are also road-kill observations reported by citizen scientists. The aim of the current study was to test whether road-kill reports by hunters stem from similar landscapes than those...
Article
Full-text available
The objective of this paper is to present a framework for assessing climate impacts on future low flows that combines different sources of information, termed pillars. To illustrate the framework three pillars are chosen: (a) extrapolation of observed low-flow trends into the future, (b) rainfall-runoff projections based on climate scenarios and (c...
Article
Full-text available
The main objective of the paper is to understand the contributions to the uncertainty in low-flow projections resulting from hydrological model uncertainty and climate projection uncertainty. Model uncertainty is quantified by different parameterisations of a conceptual semi-distributed hydrologic model (TUWmodel) using 11 objective functions in th...
Article
Full-text available
The summer drought of 2015 affected a large portion of continental Europe and was one of the most severe droughts in the region since summer 2003. The summer was characterized by exceptionally high temperatures in many parts of central and eastern Europe, with daily maximum temperatures 2 °C warmer than the seasonal mean (1971–2000) over most of we...
Poster
Full-text available
Around the world, drought events with severe socio-economic impacts seem to have a link with winter snowpack. That is the case for the current California drought, but analysing historical archives and drought impact databases for the US and Europe we found many impacts that can be attributed to snowpack anomalies. Agriculture and electricity produc...
Article
Long-term contribution of soil loss events depends on both - the magnitude and the occurrence probability - but oftentimes a limited observation period impedes the assessment of the temporal soil loss distribution.In this research, the event based soil loss from two plot-locations in Lower Austria (Mistelbach and Pixendorf) was linked with the even...
Article
Accurately predicting future low flows offers an important basis for water management and environmental policy. However, given the considerable degree of uncertainty involved in current climate prognoses, alternative sources of information should also be taken into account. Accordingly, an innovative three-pillar approach was developed in the conte...
Article
Full-text available
For drought management and prediction, knowledge of causing factors and socio-economic impacts of hydrological droughts is crucial. Propagation of meteorological conditions in the hydrological cycle results in different hydrological drought types that require separate analysis. In addition to the existing hydrological drought typology, we here defi...
Article
Full-text available
Knowledge of low streamflow statistics is necessary for effective water management in regions prone to extreme hydrologic events such as Iran. This study employs a data set of 23 river flow time series from Sefidrood Drainage Basin, Iran, to examine regional hydrological drought based on the low flow index 7Q10. Hierarchical agglomerative cluster a...
Article
Full-text available
p>For drought management and prediction, knowledge of causing factors and socio-economic impacts of hydrological droughts is crucial. Propagation of meteorological conditions in the hydrological cycle results in different hydrological drought types that require separate analysis. In addition to the existing hydrological drought typology, we here de...