Modelling future changes to the hydrological and thermal regime of unaltered streams using projected changes in climate to support planning for sensitive species management

Abstract

Climate change will alter stream habitats through precipitation and air temperature changes and potentially threaten species that rely on contemporary streamflow and stream temperature regimes. Habitat projections are therefore critical to inform management decisions. Past and ongoing research has improved streamflow and temperature modelling in ungauged regions, but no studies merge these advancements with climate modelling for regional streamflow and stream temperatures predictions that describe stream habitat change. Here, we predict change in streamflow and stream temperature at the reach scale using projections from downscaled global climate models (GCMs) and the ‘business as usual’ carbon emission scenario. We focus on unaltered streams in six southern California watersheds using data from baseline (1982–2014) and projected end‐of‐century (2082–2100). Stream temperature is projected to increase regionally, with high‐elevation stream reaches increasing most rapidly. There is less consistency in the streamflow projections, but a spatial and temporal homogenization of stream flow characteristics was predicted, that is, flows become more similar across the region with less inter‐annual variation. Additionally, there is a regional trend towards larger high flow magnitudes and more storm events. Despite the increased frequency and magnitude of storm events, high‐elevation streams are predicted to become drier for a greater portion of the year. Conversely, low‐elevation streams are predicted to have longer hydroperiods. Mapping future streamflow and stream temperatures at the reach scale can direct conservation efforts to streams that remain suitable, restoration to areas that decrease in suitability for target species, and support water policies that consider future stream condition.

Climate change and local anthropogenic activities have altered river flow regimes across Canterbury, New Zealand

“…Prediction of hydrological changes under different climate conditions whilst assuming xed catchment characteristics can be informative (e.g. Rogers et al, 2021). However, human actions can also alter hydrological conditions directly by manipulating river ows (e.g.…”

Thermal Suitability of the Los Angeles River for Cold Water Resident and Migrating Fish Under Physical Restoration Alternatives

“…In addition, while many rehabilitation projects do concentrate on improving water quality to address water contamination, stream temperature is often overlooked (Purcell et al, 2002;Walsh et al, 2005;Pander and Geist 2013). Rivers are often highly thermally polluted due to industrial discharges (e.g., thermoelectric power plants return flows; Madden et al, 2013) or due to associated land-use change e.g., deforestation and urbanization; (Parker and Krenkel, 1969;Wunderlich, 1972;Walsh et al, 2005;Poshtiri and Pal, 2016;Rogers et al, 2021). Increasing air temperatures from climate change are expected to increase river temperatures as well (Eaton and Scheller, 1996).…”

Thermal tolerances of Popenaias popeii (Texas hornshell) and its host fish from the Rio Grande Basin, Texas

“…Over time, changes in occupancy may lead to range shifts, and eventually extirpation followed by extinction [7][8][9] . Conservationists and natural resource managers have been acutely aware of the role stream temperature plays in the physiology of aquatic biota 10,11 , but have not fully appreciated the conservation implications of this relationship for a number of taxa. However, this is beginning to change given the threat of global climate change combined with increases in human water usage 12,13 .…”