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Browsing by Author "Pomeroy, John W."

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    Observations and management implications of crop and water interactions in cold water-limited regions
    (Journal of Hydrology, 2024-11) Harder, Phillip; Helgason, Warren D; Johnson, Bruce; Pomeroy, John W.
    Crop and water interactions strongly influence crop production in water-limited dryland agricultural systems in cold regions, such as the Canadian Prairies. A water balance approach was used to quantify crop water use, identify the source of water and corresponding hydrological processes, and evaluate the effectiveness of management techniques to increase agricultural productivity. Detailed water balance observations for 19 site-years were collected at four sites. Crop water use was consistently greater than or equal to growing season precipitation and displayed substantial interannual variation. On average, growing season precipitation provided 66% of crop water use whilst antecedent soil moisture from water surpluses in shoulder and winter seasons and preceding wet years supplied the remainder. Up to 70% of crop water use was derived from non-growing season water sources when high precipitation winters preceded dry growing seasons. Observations of soil moisture, snow accumulation, precipitation, and evaporative fluxes showed substantial spatial and temporal variability in antecedent soil moisture contributions to crop growth, which has implications for agricultural management. The relative importance of antecedent soil water to crop growth decreased with increased growing season precipitation. The water balance observations were used to constrain the water-limited yield potential associated with the optimisation of stubble and crop residue management practices. Increasing retention of snowfall with stubble management and suppression of soil evaporation with increased crop residue cover was estimated to increase potential crop water availability on average by 20% but, depended on seasonal dynamics, ranging between 4 and 48%. These results articulate the complex interactions between cold and warm season hydrological processes that drive dryland agricultural production in Western Canada and constrain the potential for stubble and residue management practices to mitigate crop water extremes.
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    The hysteretic and gatekeeping depressions model − A new model for variable connected fractions of prairie basins
    (Elsevier, 2025-06) Shook, Kevin; Pomeroy, John W.
    The Prairie Pothole Region of western North America has unusual hydrology and hydrography. Its level, post-glacial topography means that many drainage basins are dominated by internally drained depressions, rather than having conventional dendritic drainage networks of stream channels. Modelling the hydrology of these regions is difficult because the relationship between depressional storage and the connected fraction of a basin is hysteretic. Existing models are either computationally intensive and require high-resolution Digital Elevation Model (DEM) data which may not exist or require calibration and cannot reproduce the hysteresis between the basin connected fraction and depressional storage. The Hysteretic and Gatekeeping Depressions Model (HGDM) has been developed to simplify modelling of prairie basins with variable connected/contributing fractions. The model uses “meta” depressions to model the hysteretic responses of small depressions and a discrete model of large depressions, which cause “gatekeeping”, meaning that they prevent upstream flows from reaching the outlet until the depressions are filled. The HGDM was added to the Cold Regions Hydrological Modelling (CRHM) platform which is one of the few models that has successfully simulated land surface hydrology in the Canadian Prairies. CRHM + HGDM is tested by modelling streamflows at Smith Creek, a basin in southeastern Saskatchewan, Canada. It is demonstrated that CRHM + HGDM can reproduce the relationship between the connected/contributing fractions of sub-basins and their depressional storage at least as well as existing models. Importantly, it appears that HGDM can be used with coarse-resolution DEMs, which may permit its use in the many locations where higher-resolution data is unavailable. The simplicity and limited parameterization needs of HGDM may allow for broader representation of depressions and variable contributing area in prairie hydrology.