Pan-European Calculation of Hydrologic Stress Metrics in Rivers: A First Assessment with Potential Connections to Ecological Status

Abstract

The hydrologic regime of a river is one of the factors determining its ecological status. This paper tries to indicate the present hydrologic stress occurring across European rivers on the basis of model integration. This results in a pan-European assessment at the resolution of the functional elementary catchment (FEC), based on simulated daily time-series of river flows from the model PCR-GLOBWB. To estimate proxies of the present hydrologic stress, two datasets of river flow were simulated under the same climate, one from a hypothetic least disturbed condition scenario and the second from the anthropogenic scenario with the actual water management occurring. Indicators describing the rivers' hydrologic regime were calculated with the indicators of hydrologic alteration (IHA) software package and the river total mean flow and the relative baseflow magnitude over the total flow were used to express the deviations between the two scenarios as proxy metrics of rivers' hydrologic alteration or hydrologic stress. The alteration results on Europe's FEC-level background showed that Southern Europe is more hydrologically stressed than the rest of Europe, with greater potential for hydrology to be clearly associated with river segments of unreached good ecological status and high basin management needs.Water 2019, 11, 703 2 of 17 shapes the patterns of erosion and sedimentation, and influences the type and dynamics of the river channels, banks and floodplains [1]. The hydrologic regime affects water chemistry through processes of retention, dilution or concentration. By this, it constitutes the habitat template for the riverine biota. Hydrology is thus an indispensable component of riverine ecology, and anthropogenic alteration of the hydrologic regime entails ecological detriment [2].Riverine hydrology is altered by humans in various ways [3,4]. At the local to regional scale, water abstraction, water diversion, water drainage and channelization modify the flow regime for the benefit of domestic, industrial or agricultural supply. In particular, dams represent one of the major anthropogenic disturbances of the rivers' hydrologic regimes [5]. At the river basin scale, the water retention capacities are reduced by converting natural vegetation into land used for agriculture or urbanization. At the continental scale, patterns of precipitation and evaporation shift due to a changing climate, with important changes in climate extremes over time. These alterations impact on the riverine ecosystems and lead to changes in natural flows, including water scarcity or overabundance with implications for ecological status and ecosystem services [6,7].However, full understanding of the effects of hydrologic alteration is still not available [8]. On the one hand, this relates to the intricate features of riverine hydrology covering the elements of timing, magnitude, duration and frequency, all of which are integral components of the ecosystem [9]. On the other hand, this relates to the lack of comprehensive datasets, e.g., from strea...

Multiple stressors determine river ecological status at the European scale: Towards an integrated understanding of river status deterioration

“…Hydrological stressor data were generated with the global model PCR‐GLOBWB (Sutanudjaja et al, 2018). Two datasets of daily time series of river discharges covering the period 2001–2010 were simulated under the same climate (Panagopoulos et al, 2019). The first dataset resulted from a least‐disturbed condition scenario, excluding all water uses such as irrigation, abstractions, industry or water management as well as the presence and hydrological impacts from reservoirs.…”

“…More specifically, we expected nutrient enrichment to be particularly relevant for the ecological status of lowland rivers, whose catchments are often characterized by high agricultural intensities (Hypothesis 2.1; e.g. Lemm & Feld, 2017); hydrological alteration to be particularly relevant for river types with small and F I G U R E 1 Overview of the locations of 52,847 sub-catchment units and their ecological status class (grey area: no data available) medium size catchments or rivers in the Mediterranean, which are frequently affected by damming or water abstraction for irrigation (Hypothesis 2.2;Couto & Olden, 2018;Huđek et al, 2020;Panagopoulos et al, 2019); and toxic substances to mainly affect small streams in intensively used areas (Hypothesis 2.3;Beketov et al, 2013;Schäfer et al, 2013). We furthermore expected that riparian land use particularly impacts ecological status of small streams, which are more strongly affected by the immediate surrounding as compared to larger rivers, for which cumulative stressors at catchment scale are more relevant (Hypothesis 2.4;Fuller & Death, 2018).…”

Unravelling Precipitation Trends in Greece since 1950s Using ERA5 Climate Reanalysis Data

“…Several studies have reported declining river flows and changes in the water quantity during the past decades [57,58], but it remains unclear how reducing precipitation is linked with hydrological alterations. This is more prominent in the Mediterranean since river damming and water abstractions are major environmental problems that are responsible for changing flow patterns and reduced water quantity [59][60][61]. For instance, Mentzafou et al [57] showed significant relationships between precipitation and discharge with similar fluctuation patterns for major Greek rivers but concluded that a more in-depth analysis that considers the water uses will reveal the actual causes of flow regime changes.…”

Assessing multiple stressor effects to inform climate change management responses in three European catchments

“…Since dissolved oxygen concentration is inversely related to water temperature, warming is expected to affect dissolved oxygen saturation (Cox and Whitehead 2009). Additionally, hypoxia in running waters may occur not only because of organic pollution and eutrophication but also due to drought and extreme low flow events, conditions that are becoming more common in Southern Europe (Gudmundsson et al 2017;Panagopoulos et al 2019). We acknowledge that such complexities will be difficult to resolve in our modelling approach, not least because of the potential for covariance between stressors.…”