Simulating cold-region hydrology in an intensively drained agricultural watershed in Manitoba, Canada, using the Cold Regions Hydrological Model
Marcos R. C. Cordeiro1, Henry F. Wilson2, Jason Vanrobaeys3, John W. Pomeroy4, and Xing Fang41Science and Technology Branch, Agriculture and Agri-Food Canada, 200-303 Main Street, Winnipeg, MB, R3C 3G7 2Science and Technology Branch, Agriculture and Agri-Food Canada, 2701 Grand Valley Rd., Brandon, MB, R7A 5Y3 3Science and Technology Branch, Agriculture and Agri-Food Canada, 101 Route 100, Morden, MB, R6M 1Y5 4Centre for Hydrology, University of Saskatchewan, 117 Science Place, Saskatoon, SK, S7N 5C8
Abstract. Eutrophication and flooding are perennial problems in agricultural watersheds of the northern Great Plains. A high proportion of annual runoff and nutrient transport occurs with snowmelt in this region. Extensive surface drainage modification, frozen soils, and frequent backwater or ice damming impacts on flow measurement represent unique challenges to accurately modeling watershed scale hydrological processes. A physically-based, non-calibrated model created using the Cold Regions Hydrological Modelling platform (CRHM) was parameterized to simulate hydrological processes within a low slope, clay soil, and intensively surface drained agricultural watershed. These characteristics are common to most tributaries of the Red River of the North. Analysis of the observed water level records for the study watershed (La Salle River) indicate that ice cover and backwater issues at time of peak flow may impact the accuracy of both modeled and measured stream flows, highlighting the value of evaluating a non-calibrated model in this environment. Simulations best matched the streamflow record in years when peak and annual discharges were equal to or above the medians of 6.7 m3 s−1 and 1.25 × 107 m3, respectively, with an average Nash-Sutcliff efficiency (NSE) of 0.76. Simulation of low-flow years (below the medians) was more challenging (average NSE < 0) with simulated discharge overestimated by 90 % on average. This result indicates the need for improved understanding of hydrological response in the watershed under drier conditions. Improved simulation of dry years was achieved when infiltration was allowed prior to soil thaw indicating the potential importance of preferential flow. Representation of in-channel dynamics and travel time under the flooded or ice-jam conditions should also receive attention in further model development efforts. Despite the complexities of the watershed being modeled, simulations of flow for average to high flow years and other components of the water balance were robust [snow water equivalency (SWE) and soil moisture]. A sensitivity analysis of the flow routing model suggests a need for improved understanding of watershed functions under both dry and flooded conditions due to dynamic routing conditions, but overall CRHM is appropriate for simulation of hydrological processes in agricultural watersheds of the Red River. Falsifications of snow sublimation, snow transport, and infiltration to frozen soils processes in the validated base model indicate that these processes were very influential to stream discharge generation.
Cordeiro, M. R. C., Wilson, H. F., Vanrobaeys, J., Pomeroy, J. W., and Fang, X.: Simulating cold-region hydrology in an intensively drained agricultural watershed in Manitoba, Canada, using the Cold Regions Hydrological Model, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-462, in review, 2016.