Regional Response to Global Warming: Water Temperature Trends in Semi-Natural Mountain River Systems

Abstract

River water temperature (TW) is a key environmental factor that determines the quality of the fluvial environment and its suitability for aquatic organisms. Atmospheric warming, accompanied by more frequent extreme weather phenomena, especially heat waves and prolonged drought, may pose a serious threat to the river environment and native river ecosystems. Therefore, reliable and up-to-date information on current and anticipated changes in river flow and thermal conditions is necessary for adaptive water resource management and planning. This study focuses on semi-natural mountain river systems to reliably assess the magnitude of water temperature change in the Polish Carpathians in response to climatic warming. The Mann–Kendall test was used to detect trends in water temperature series covering the last 35 years (1984–2018). Significant, rising trends in annual water temperature were found for all studied sites, with differences in intensity (0.33–0.92 °C per decade). Trends in TW were strongest in summer and autumn (0.75–1.17 and 0.51–1.08 °C per decade), strong trends were found in spring (0.82–0.95 °C per decade), and weaker in winter (0.25–0.29 °C per decade). Simultaneous air temperature trends were broadly consistent with water temperature trends. This indicates the urgent need for adaptive management strategies to counteract thermal degradation of the fluvial environment under study.

Machine-learning methods for stream water temperature prediction

“…where t is the time in days, t y is the number of days per year, Q is the mean discharge, θ = Q/Q is the dimensionless discharge and a 1,...,8 are the model parameters. This differential equation is numerically integrated at each time step using the Crank-Nicolson numerical scheme (Crank and Nicolson, 1947) and the model parameters are calibrated using particle swarm optimization (Kennedy and Eberhart, 1995).…”

Current and projected impacts of the parasite Tetracapsuloides bryosalmonae (causative to proliferative kidney disease) on Central European salmonid populations under predicted climate change

“…The future impact of PKD on brown trout, grayling, and salmon populations is greatly dependent on how water temperature, precipitation, and evaporation change in the context of the climate crisis (Borgwardt et al., 2020; Masson‐Delmotte et al., 2018). Water temperatures in central Europe have already increased by 1–2°C (Daufresne & Boët, 2007; Kędra, 2020; Michel et al., 2020; Webb & Nobilis, 2007) and patterns of precipitation have changed in quality (increasingly torrential rain, less snow) and seasonality (decreases in summer, increases in winter) (Masson‐Delmotte et al., 2018). Under these conditions, salmonids are estimated to have already lost half of their population density (Arndt et al., 2019; Burkhardt‐Holm & Zehnder, 2018; Waldner et al., 2020).…”

Sensitivity of mountain catchments to global warming: a case study of the San Basin, Poland

“…Such integrated catchment management, which is currently lacking in the Carpathian catchments, should probably focus on identifying and maintaining key processes and resources to: (1) improve water circulation in the catchment, (2) improve soil water retention and (3) improve water infiltration and groundwater storage. Because persistent periods of abnormal warm weather are likely to increase in Europe (EEA, 2019) as well as in the study area (Kędra, 2020), groundwater discharge, which maintains base flow, will be an important source of water that shapes Q during drought. In this context, the ongoing urbanisation process in the upper San catchments, with a significant increase in built-up areas since 1990 (Kędra and Szczepanek, 2019), seems unfavourable, because sealing the surface disrupts water circulation, reduces infiltration, groundwater recharge and the resulting base flow and accelerates overland runoff (Allan and Castillo, 2007).…”