Assessing hydrological sensitivity of grassland basins in the Canadian Prairies to climate using a basin classification–based virtual modelling approach
Summary (2 min read)
Introduction
- Modelling a specific basin to evaluate 45 processes or to simulate the effects of change entails large computational and labour costs and requires observations of the basin response with sufficient spatial and temporal coverage.
- Prairie precipitation trends indicate more rain and less snow in the spring and fall (Shook and Pomeroy, 2012) and runoff generation has been shown to be shifting from snowmelt- to rainfall-driven in eastern Saskatchewan (Dumanski et al., 2015).
- Recent analysis of hydrometric stations across the 80 region identified sub-regional trends in streamflow associated with drying in the west and south and wetting in the east and north, associated with physical landscape characteristics and climate (Whitfield et al. 2020).
- This paper aims to demonstrate the utility of a basin classification–based virtual modelling approach for assessing the sensitivity of 110 Canadian Prairie catchments to climate.
Basin Classification
- The classification of Canadian Prairie basins was based on the analyses of Wolfe et al. (2019), which divided over 4000 basins, each approximately 100 km2 in area, into seven broad classes, based on a suite of physio-geographic characteristics .
- This was done because climate is introduced through the long meteorological time series used to drive the virtual basin model and in order to study climate sensitivity any classification that included historical climates could introduce bias.
- Exclusion of climate had a limited impact on the basin classification, with the seven classes of basins 140 identified closely following the original classification.
- The High Elevation Grasslands (HEG) class was selected for the development of the virtual basin model.
- The suffix “- w” in the HRU name indicates HRUs in the wetland catena.
Model set-up and parameterization
- The Cold Regions Hydrological Modelling platform (CRHM) was selected to develop the virtual 165 basin model, as CRHM is particularly suited for simulating the hydrology of the Canadian Prairies.
- With the correct suite of modules, each representing a key hydrological process, CRHM has proven very capable of representing prairie 170 hydrological processes and accurately emulating water fluxes in this landscape (Fang and Pomeroy, 2009; Fang et al., 2010).
- Runoff from the ‘wetland’ catena portion of the virtual basin (~33% of area) features a wetland complex HRU 190 within a landscape catena following a sequence from cultivated, to grassland, shrubland, and woodland HRUs .
- For other HRUs, a minimum value of 0.001 was set to simulate the canopy effects of Prairie vegetation (crop residue, grass) on radiation for snowmelt.
Model application
- To ensure that the role of climate variability across HEG was captured in streamflow simulations the model was run over a 46-year baseline period (1960–2006) driven using data from seven 255 locations.
- The locations were within and nearby the geographical extent of the HEG classification, and represented the variation in climate across the region .
- For this 290 reason, spring snow water equivalent (SWE) values from snow courses and mean annual hydrographs from hydrometric gauges at multiple sites within the HEG class were compared to virtual basin model outputs to establish that the virtual basin model was capturing the correct timing and magnitudes of important states and fluxes.
- This method has the advantages of being 325 computationally inexpensive, while avoiding bias, and preserving the covariances among variables, which are important in modeling cold-regions processes (Shook and Pomeroy, 2010).
- These scenarios were used with the model to quantify sensitivity of snow accumulation and annual runoff to climate change.
Results
- The HEG class occupies much of the western portion of the Canadian Prairies, and includes the 340 majority of southern Alberta and several isolated patches in both Saskatchewan and Manitoba .
- The date of annual peak SWE advances as annual air temperature warms .the authors.the authors.
- Under a warmer and wetter climate (6°C 495 warming and 30% increase in annual precipitation) runoff in western portions still experience decreases, but runoff in climates such as Brandon’s increase and remain the same in climates such as Saskatchewan’s .
- The consequence for streamflow is a 44% decline in annual volume in a drier HEG climate such as Medicine Hat’s (Table 4).
Conclusions
- Virtual experiments have proven to be suitable to diagnose the hydrological response of basins in 595 this landscape.
- The virtual basin model outputs are available from the authors by request.
- CS and CJW conceived the study, also known as Author contributions.
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"Assessing hydrological sensitivity ..." refers methods in this paper
...Actual evapotranspiration was simulated using the Penman– Monteith equation (Monteith, 1965), and evaporation from typically saturated surfaces subject to advection, such as wetlands and stream channels, was calculated using the Priestley and Taylor equation (Priestley and Taylor, 1972)....
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789 citations
"Assessing hydrological sensitivity ..." refers methods in this paper
...The basin delineations used in the study were taken from the HydroSHEDs dataset (Lehner and Grill, 2013), which provides geographically contiguous delineations of basins for the world, including the Prairie ecozone....
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...The basin delineations used in the study were taken from the HydroSHEDs dataset (Lehner and Grill, 2013), which provides geographically contiguous delineations of basins for the world, including the Prairie ecozone....
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693 citations
"Assessing hydrological sensitivity ..." refers background in this paper
...Basin classification can regionalize hydrological model outputs, based on the assumption that basins can be classified by their 50 characteristics and that basins of the same class respond similarly to changes in climate inputs or their landscapes (e.g., McDonnell and Woods, 2004; Wagener et al., 2007)....
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...…that basins can be classified by their characteristics and that basins of the same class respond similarly to changes in climate inputs or their land- Published by Copernicus Publications on behalf of the European Geosciences Union. scapes (e.g. McDonnell and Woods, 2004; Wagener et al., 2007)....
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426 citations
"Assessing hydrological sensitivity ..." refers background or methods in this paper
...CRHM is a modular, process-based, spatially semi-distributed hydrological model, which includes the key cold regions and warm season hydrological processes that operate in western Canada and elsewhere (Pomeroy et al., 2007)....
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...Fetch distances were set using values recommended in Pomeroy et al. (2007)....
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...Fang and Pomeroy (2007) and Pomeroy et al. (2007) attempted to determine the sensitivities of snow accumulation and runoff to drought at Bad Lake, Saskatchewan....
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Frequently Asked Questions (2)
Q2. What future works have the authors mentioned in the paper "Assessing hydrological sensitivity of grassland basins in the canadian prairies to climate using a basin classification–based virtual modelling approach" ?
Outputs of virtual experiments are less useful in predicting exact future system states than in specifying how alternative climate possibilities would alter hydrological behaviour. 630 Data Availability: All model forcing datasets used in this research are publicly available and can be accessed via the references and links provided.