Topic 4: Drought, low flow and warming – hydrological effects and impacts on the ecological state and functioning of river systems

Introduction/background

Drought is one of the most harmful natural hazards. Drought-induced low flows and warming can lead to a cascade of hydrochemical processes that can impair water quality and threaten a wide range of ecosystem services. So far, information is scarce about drought-response chains within and across the social system and the ecosystem. There is also a lack of knowledge about the resilience and resistance of existing and emerging drought-response chains to environmental and social change. 

Main objective/research question/hypothesis

The aim of this PhD topic is to shed light on the ecological response of IRLs to low flow and warming. For this purpose, an in-depth catchment study will be conducted to address the following research questions: (i) what are the spatio-temporal dynamics of low flow and stream temperature indices in the river system in response to drought and heat events; (ii) how does water quality respond to the hydrological signal and which water quality indices are ecologically most relevant; (iii) how do structural and functional ecological indicators respond to hydrological and physico-chemical indices, and how relevant are these indicators for detecting changes in the ecological state and functioning? In close cooperation with Topic 3 (“Intermittent flow”), the PhD study will provide a new perspective on drought processes and impact chains in IRLs. It will contribute to a better understanding of the vulnerability and resilience of river systems as a basis for drought management plans. 

Approach/methods and time frame

The study focuses on eastern Austria, which is severely affected by droughts. The following analysis will be performed. A1) Statistical space-time modelling to characterise temporal dynamics and average and extreme conditions of streamflow and temperature in the river network. A2) Water quality monitoring to obtain physico-chemical indices at nodes of the river network. A3) Data collection and assessment of structural indicators, such as functional traits and biomass of macrozoobenthos, microbial biomass, and organic carbon stocks; and functional indicators such as microbial respiration and production, and organic matter decomposition. A4) Statistical assessment of the link between hydrological characteristics, water quality indices, structural and functional ecological indicators. Timeframe: Four years, with flow, water quality and structural indicator monitoring (year 1), space-time models (year 2), multivariate indicator assessment (year 3), publications (year 4).