|Tuesday, June 01|
Comparative performance of a new Assembled Watershed Runoff Model vs. traditional continuous simulation watershed models. Application case: Buck Creek watershed, British Columbia
* Stephen Clark, Klohn Crippen Berger, Canada
Diana Alvarez, Canada
"A continuous simulation hydrology model is an essential tool for understanding watershed processes that influence annual runoff volumes, and the magnitude and timing of high flows and low flows. Continuous simulation models can, and should, be calibrated to long records of measured data, and can be used to project future changes to the watershed (e.g., timing and volume of spring runoff) with climate change. An example of the application of these models is in a mine water balance, which may require estimates of water availability to meet demands, tracking impounded volumes in water and tailings storage facilities, and flow rates to support calculations of contaminant concentrations (when coupled with a water quality model). The aim of these models is to capture the physical watershed processes, such as evaporation, infiltration, surface runoff and groundwater discharges, resulting in an accurate representation of both high-flow and low-flow conditions. In northern latitudes, annual runoff volumes are dominated by spring snowmelt. Therefore, accurate representation of snow accumulation and melt processes is often necessary to match modelled with measured flows. A new Assembled Watershed Runoff Model (AWRM) was developed in GoldSim™ that aims to accurately model high flows, low flows, and snowmelt timing, addressing some shortfalls in other traditional continuous simulation hydrology models. The inputs of the AWRM are: daily precipitation, minimum and maximum daily temperature, and site latitude. A number of elevation bands can be modelled through the use of temperature-elevation and precipitation-elevation relationships. Snow accumulation is based on principles from the SNOW-17 model, while melt rates are based on a modified version of the melt equation in the UBC Watershed Model. Evaporation processes are based on Hargreaves’ equation. Infiltration and groundwater discharges are modelled based on principles from the Soil Moisture Accounting (SMA) model employed in HEC-HMS. This paper describes the key concepts and equations used in the AWRM and demonstrates its effectiveness by calibrating to measured snow pillow and flow gauge data in the Buck Creek watershed in central British Columbia. The model results are compared against those of calibrated traditional hydrology models: Rango Snowmelt Runoff Model (SRM) and HEC-HMS SMA. The results of this exercise indicate that the AWRM accurately captures the timing and volume of spring snowmelts, as well as a large autumn rain-on-snow event, while modelling peak flows and low flows with reasonable accuracy. Quantitative statistics indicate higher performance than the traditional hydrology models over 22 years of snow pillow measurements and 26 years of discharge measurements. "
Assessing the hydrological control attributes of wetlands in the Lake Champlain-Richelieu River basin
* Alain Rousseau, INRS, Canada
Stéphane Savary, Canada
Jean Morin, Canada
Olivier Champoux, Canada
Simon Lachapelle, Canada
"The Richelieu River (RR) and Lake Champlain (LC) sub-watersheds make up the Lake Champlain-Richelieu River (LCRR) watershed. About 16% and 84% of the 23,900-km2 LCRR basin lies in Canada and in the USA, respectively. The RR sub-watershed contributes to roughly 10% of the annual discharge into the St. Lawrence River; while the total discharge flowing out of the Lake Champlain contributes the remaining 90%. In the LC basin, there is a well-documented, exceptional, event that clearly showed that wetlands can alleviate flood, namely the Otter Creek watershed between Middlebury and Rutland, Vermont, during Tropical Storm Irene, August, 28, 2011; and a global effect at the watershed scale as illustrated in several theoretical studies. In the former study, wetlands and floodplains protected Middlebury, from as much as 1.8 million US $ in flood damage during Tropical Storm Irene (Watson et al., 2016). The study was the first to calculate the economic benefits that wetlands and floodplains provided during the major storm that struck the USA East Coast in recent years. Researchers analyzed 10 flood events to estimate the value of the Otter Creek floodplain near Middlebury. According to the study, the natural barrier saves the town an average of 126,000 to 450,000 US $ per year, or up to 78 percent of potential damages. Using the aforementioned background information, the objective of this study was to assess the effect of wetlands of tributaries of the Vermont and New York States’ sub-watersheds on reducing runoff volumes, peak flows and net basin supplies to Lake Champlain. To single out the flow regulation effect provided by the wetlands, the isolated and riparian wetland parameterization schemes provided by HYDROTEL were turning on and off. The simulation results were analyzed in terms of net basin supplies (NBS, inflows from all sub-watersheds and hillslopes discharging into LC, plus precipitation and evaporation); flows (annual and seasonal high and 7-day low flows) and water levels in LC and the RR at the St. Jean Marina (NBS as input to the daily LC water balance model (WBM) developed by Environment and Climate Change Canada, ECCC). The results of this study clearly quantify the hydrological services provided by the actual 1684 km2 of wetlands (covering 7% and draining 34% of the basin) and illustrated their key role currently played in the attenuation of NBSs, peak flows, and water levels, especially during the 2011 flood and theoretically the breath of their effect when using 64 years of meteorological data. Results demonstrate that existing wetlands can reduce on average the annual high flow of the LC tributaries by 9% up to 47%; reducing thereafter on average the annual LC NBS high flow by 22% on average, the annual RR high flow by 6%, the LC annual high water level by 12 cm and the RR annual high water level by 9 cm. "
A multi-model assessment of climate change impacts on the Oldman water system in Alberta
* Ali Sharifinejad, Polytechnique Montreal, Canada
Elmira Hassanzadeh, Canada
Masoud Zaerpour, Canada
Changing climatic conditions have altered streamflow regimes, and consequently, affected the reliability of water allocation plans in various regions. The impacts of climate change on water systems are commonly evaluated using the outputs of Global Circulation Models (GCMs) in the hydrological models. In this study, we aim to analyze the behavior of a Canadian water system under changing climatic conditions. Using a set of hydrological models, we also highlight the importance of the hydrologic system’s spatial representation in the climate change impact assessments. For this purpose, HBV-based models using semi-distributed and lumped representations of the hydrological system are developed for the region. The projections of an ensemble of GCMs under two different future scenarios are then used in these developed hydrological representations to project natural flow conditions throughout the 21st century. The projected natural flow series are fed into a water allocation model to estimate the water system behavior and scrutinize the changes in the regulated flow’s hydrological signatures. The Oldman River Basin in Alberta is chosen as the case study due to its strategic role in supporting regional water demands and controlling flooding events. Results show that the spatial discretization of the hydrologic system has considerable impacts on the estimations of water system conditions in the future. Regardless, it is found that despite the expected increase in the regulated flow’s quantiles, the water deficit in the vicinity of the Oldman Reservoir would deteriorate. Due to the intensified flooding events and aggravated water scarcity downstream of the reservoir in the future, the Oldman Reservoir’s operation plans should be revisited to mitigate the climate change impacts in the study area.
Benchmarking evapotranspiration equations over a lake-wetland duo in Southern Quebec
* Henrique Vieira, Concordia University, Canada
Ali Nazemi, Canada
Evapotranspiration is a key component of the water cycle, affecting both water quantity and quality. Accurate quantification of evapotranspiration in time and space is therefore paramount for provision of effective water resources management, particularly under a warmer climate. Despite significant progress made, quantification of evapotranspiration involves a large uncertainty. In this investigation, we consider Lake Memphremagog, a transboundary water body between Quebec and Vermont, along with one of its adjacent wetlands as a test bed to (1) measure evaporative fluxes at the two nearby sites using the Eddy Covariance method, (2) to model evapotranspiration fluxes at the two sites based on a large ensemble of already established equations, and (3) to intercompare and evaluate their performance in capturing measured fluxes using a multi-objective approach. Our preliminary findings have shown that evaporation in the lake is strongly correlated with aerodynamic forcing, whereas evapotranspiration in the nearby wetland is more affected by radiative forcing; however, a detailed investigation will formally reveal the extent to which each model captures evapotranspiration in each landscape, across various time scales, different times of the day and seasons. The results of this study will be informative in terms of understanding the key variables affecting evaporative fluxes emitted from two different water saturated landscapes that are under the same climatic conditions. The insights on evapotranspiration forcing acquired through this study along with the assessment of existing evapotranspiration models will help practitioners to develop more accurate models for quantifying evaporative fluxes over lakes and wetlands, which are two important water resources in Canada, particularly under warming conditions. More specifically, our findings will directly contribute to integrated water management practice at Lake Memphremagog that has immediate water security concerns in terms of both water quality and quantity.
Existing methods and models to project hydropower production in the Congo River Basin
* Samane Lesani, Polytechnique Montreal University, Canada
Musandji Fuamba, Canada
Elmira Hassanzadeh, Canada
The Congo River Basin is the second-largest watershed in the world, containing about one-third of Africa’s freshwater resources. Most importantly, the Congo River, which flows through ten countries before reaching the Atlantic Ocean, plays a strategic role in sustaining hydroelectricity generation in Africa. However, climate change has already affected the hydroclimatic conditions of the Congo Basin with major implications for power generation. Therefore, an improved understanding of climate change impact on the Congo River Basin is required to propose effective hydroelectricity production plans for this region. This study reviews the existing methods and models used to project hydropower production in the Congo River Basin. For this purpose, the components of climate change impact assessment, namely climate, hydrological, and hydropower estimation models are evaluated. In brief, the applied climate models, downscaling techniques, as well as reanalysis data are explored. Moreover, the developed hydrological models for this area are categorized based on their structure, temporal and spatial scales, data requirements, as well as considered calibration procedures. Finally, existing methods to estimate hydropower production are reviewed, and an integrated climate-hydrological-power production model is proposed. This study will provide a state-of-the-art picture of hydropower projection under a changing climate in the Congo River Basin. Moreover, this study will give a useful insight to the research community in selecting approaches for impact assessment studies in other large basins over the world.