RBM

The particle tracking stream temperature model River Basin Model (RBM) solves the time-dependent one-dimensional heat advection equation using a mixed Eulerian-Lagrangian approach (Yearsley, 2009; Yearsley, 2012). Water temperature is calculated for a specific stream segment based on the upstream water temperature and inflow into the stream segment, the dominant heat exchange at the air-water surface, and the inflow and temperature of water advected from tributaries (Figure 1). Solutions are obtained by tracking individual water parcels along their flow characteristics and storing the output at discrete points on a fixed grid.

RBM was previously modified for application on a worldwide level and to include effects of heat effluents from thermoelectric power plants and reservoir impacts on water temperature (van Vliet et al., 2012a). RBM uses output from the Variable Infiltration Capacity (VIC) hydrological model. The VIC-RBM modelling framework is applied on a 1/2° x 1/2° spatial resolution globally and was used to study impacts of climate change (Figure 2) (van Vliet et al., 2013a; van Vliet et al., 2016c) and impacts of thermal pollution (Raptis et al., 2016) on water temperatures globally. Global water temperature and streamflow projections of VIC-RBM were also used to quantify the consequences for cooling water use and electricity supply (van Vliet et al., 2016b; van Vliet et al., 2013c; van Vliet et al., 2016c; van Vliet et al., 2012b) and impacts on freshwater fish habitats globally (van Vliet et al., 2013b). VIC-RBM was also used for developing climate information services (van Vliet et al., 2015) and for quantifying impacts of recent droughts on power generation globally (van Vliet et al., 2016a).

Figure 1. Concept of RBM stream temperature model and schematic of reverse particle tracking method. Abbreviations are used for water temperature (Tw) and flow (Q) of tributaries (trb), subsurface (sub) and thermal effluents (effl), net shortwave solar radiation (HnS), net longwave atmospheric radiation (HnL), evaporative/latent heat flux (Hevap) and conductive/sensible heat flux (Hcond) (van Vliet, 2012).
Figure 1. Concept of RBM stream temperature model and schematic of reverse particle tracking method. Abbreviations are used for water temperature (Tw) and flow (Q) of tributaries (trb), subsurface (sub) and thermal effluents (effl), net shortwave solar radiation (HnS), net longwave atmospheric radiation (HnL), evaporative/latent heat flux (Hevap) and conductive/sensible heat flux (Hcond) (van Vliet, 2012).
Figure 2: Impacts of climate change on annual mean streamflow and water temperature for RCP8.5 for 2040–2069 relative to 1971–2000 (based on van Vliet et al, 2016c).
Figure 2: Impacts of climate change on annual mean streamflow and water temperature for RCP8.5 for 2040–2069 relative to 1971–2000 (based on van Vliet et al, 2016c).

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