Abstract
Abstract. One of the purposes of the Cold Regions Hydrological Modelling platform (CRHM) is to diagnose inadequacies in the understanding of the hydrological cycle and its simulation. A physically based hydrological model including a full suite of snow and cold regions hydrology processes as well as warm season, hillslope and groundwater hydrology was developed in CRHM for application in the Marmot Creek Research Basin (~ 9.4 km2), located in the Front Ranges of the Canadian Rocky Mountains. Parameters were selected from digital elevation model, forest, soil, and geological maps, and from the results of many cold regions hydrology studies in the region and elsewhere. Non-calibrated simulations were conducted for six hydrological years during the period 2005–2011 and were compared with detailed field observations of several hydrological cycle components. The results showed good model performance for snow accumulation and snowmelt compared to the field observations for four seasons during the period 2007–2011, with a small bias and normalised root mean square difference (NRMSD) ranging from 40 to 42% for the subalpine conifer forests and from 31 to 67% for the alpine tundra and treeline larch forest environments. Overestimation or underestimation of the peak SWE ranged from 1.6 to 29%. Simulations matched well with the observed unfrozen moisture fluctuation in the top soil layer at a lodgepole pine site during the period 2006–2011, with a NRMSD ranging from 17 to 39%, but with consistent overestimation of 7 to 34%. Evaluations of seasonal streamflow during the period 2006–2011 revealed that the model generally predicted well compared to observations at the basin scale, with a NRMSD of 60% and small model bias (1%), while at the sub-basin scale NRMSDs were larger, ranging from 72 to 76%, though overestimation or underestimation for the cumulative seasonal discharge was within 29%. Timing of discharge was better predicted at the Marmot Creek basin outlet, having a Nash–Sutcliffe efficiency (NSE) of 0.58 compared to the outlets of the sub-basins where NSE ranged from 0.2 to 0.28. The Pearson product-moment correlation coefficient of 0.15 and 0.17 for comparisons between the simulated groundwater storage and observed groundwater level fluctuation at two wells indicate weak but positive correlations. The model results are encouraging for uncalibrated prediction and indicate research priorities to improve simulations of snow accumulation at treeline, groundwater dynamics, and small-scale runoff generation processes in this environment. The study shows that improved hydrological cycle model prediction can be derived from improved hydrological understanding and therefore is a model that can be applied for prediction in ungauged basins.
Highlights
The Canadian Rockies are an important water source for northern North America; they form the headwaters of the eastward flowing Saskatchewan and Athabasca Rivers, whose water supplies are crucial to the urban centres of Alberta and Saskatchewan such as Edmonton, Calgary, Saskatoon, and Regina as well as to the agricultural sector and oil sands mining operations
The Marmot Creek Research Basin (MCRB) was divided into four subbasins that are represented by four separate RBs (Fig. 4) for which a modelling structure comprising of Muskingum routing was used to route the streamflow output from these RBs along the main channels in the MCRB: Cabin Creek, Middle Creek, Twin Creek, and Marmot Creek
No calibration from streamflow was used in setting any parameters in the model, but the results of extensive scientific investigations of basin snow and hydrology were used where available and applicable
Summary
The Canadian Rockies are an important water source for northern North America; they form the headwaters of the eastward flowing Saskatchewan and Athabasca Rivers, whose water supplies are crucial to the urban centres of Alberta and Saskatchewan such as Edmonton, Calgary, Saskatoon, and Regina as well as to the agricultural sector and oil sands mining operations. Another advantage of models like CRHM is that they may be evaluated using multiple objectives to avoid equifinality problems (Bevan and Freer, 2001) by allowing a much more powerful evaluation of the model as a representation of many aspects of the hydrological cycle (Dornes et al, 2008b) Considering these issues, the objectives of this paper are the following: (1) to propose a comprehensive physically based model to simulate all the relevant hydrological processes for a headwater basin of the Canadian Rocky Mountains; (2) to evaluate the model performance against the field observations, including winter snow accumulation, spring snowmelt, spring and summer soil moisture fluctuation, streamflow discharge, and groundwater level fluctuation without any parameter calibration from streamflow records. It is expected that this will assess our understanding of hydrology in this environment, but substantially advance the practice of hydrological prediction for ungauged basins, and provide a predictive tool that is sufficiently robust for describing hydrological responses in nonstationary environments
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