Imperial College London

Emeritus Professor Howard Wheater

Faculty of EngineeringDepartment of Civil and Environmental Engineering

Emeritus Professor in Civil and Environmental Engineering
 
 
 
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Contact

 

+44 (0)20 7594 6066h.wheater CV

 
 
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Assistant

 

Miss Judith Barritt +44 (0)20 7594 5967

 
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Location

 

229Skempton BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

435 results found

Woldegiorgis BT, Baulch H, Wheater H, Crossman J, Clark M, Stadnyk T, Bajracharya Aet al., 2023, Impacts of Uncontrolled Operator Splitting Methods on Parameter Identification, Prediction Uncertainty, and Subsurface Flux Representation in Conceptual Hydrological Models, Water Resources Research, Vol: 59, ISSN: 0043-1397

The proper numerical representation of physical processes in mechanistic hydrological models is essential to produce robust predictions. A common problem with numerical schemes in hydrological models is that multiple concurrent fluxes are calculated sequentially. Although the importance of errors introduced by inappropriate numerical schemes is well recognized in the literature, many hydrological models calculate concurrent fluxes sequentially. Here, two versions of the HYPE model are used to investigate the limitations of sequential calculations. A fourth order Gear-Nordsieck solution of the continuous state-space formulation of HYPE (I-HYPE) is developed to provide a robust solution, and a fixed-step implicit Euler scheme (IE-HYPE) is implemented to provide a computationally efficient and robust approximation of the I-HYPE simulations. In contrast to I-HYPE, results show that the original HYPE and the sequential calculation implemented in the continuous state-space formulation of HYPE (SQ-HYPE) typically simulate no interflow when soil moisture levels exceed the field capacity. The discrepancy between SQ-HYPE and I-HYPE grows with the size of the computation time step, and this implies a compromised representation of flow paths by sequential schemes. IE-HYPE provides responses comparable with I-HYPE for both daily and hourly time steps. IE-HYPE and SQ-HYPE are compared in terms of their groundwater representation, parameter identifiability, and predictive skills for two catchments. The sequential models have larger groundwater contributions to flow than IE-HYPE because the splitting errors in SQ-HYPE limit the interflow flux. IE-HYPE estimates of the groundwater flux are more consistent with literature values of groundwater contributions to flow for the basins studied.

Journal article

Abdelhamed MS, Elshamy ME, Razavi S, Wheater HSet al., 2023, Challenges in Hydrologic-Land Surface Modeling of Permafrost Signatures—A Canadian Perspective, Journal of Advances in Modeling Earth Systems, Vol: 15

Permafrost thaw/degradation in the Northern Hemisphere due to global warming is projected to accelerate in coming decades. Assessment of this trend requires improved understanding of the evolution and dynamics of permafrost areas. Land surface models (LSMs) are well-suited for this due to their physical basis and large-scale applicability. However, LSM application is challenging because (a) LSMs demand extensive and accurate meteorological forcing data, which are not readily available for historic conditions and only available with significant biases for future climate, (b) LSMs possess a large number of model parameters, and (c) observations of thermal/hydraulic regimes to constrain those parameters are severely limited. This study addresses these challenges by applying the MESH-CLASS modeling framework (Modélisation Environmenntale communautaire—Surface et Hydrology embedding the Canadian Land Surface Scheme) to three regions within the Mackenzie River Basin, Canada, under various meteorological forcing data sets, using the variogram analysis of response surfaces framework for sensitivity analysis and threshold-based identifiability analysis. The study shows that the modeler may face complex trade-offs when choosing a forcing data set; for current and future scenarios, forcing data require multi-variate bias correction, and some data sets enable the representation of some aspects of permafrost dynamics, but are inadequate for others. The results identify the most influential model parameters and show that permafrost simulation is most sensitive to parameters controlling surface insulation and runoff generation. But the identifiability analysis reveals that many of the most influential parameters are unidentifiable. These conclusions can inform future efforts for data collection and model parameterization.

Journal article

Annand HJ, Wheater HS, Pomeroy JW, 2023, The influence of roads on depressional storage capacity estimates from high-resolution LiDAR DEMs in a Canadian Prairie agricultural basin, Canadian Water Resources Journal, ISSN: 0701-1784

The Canadian Prairies are a post-glacial agricultural landscape, where millions of small depressions store surface water, form wetlands and control runoff contributing area. Their management is key to flood and drought hydrology, groundwater recharge, ecological integrity, migratory bird habitat and agricultural productivity. Depression drainage and infilling is common in the region, where it is often used to increase cropped area. The regularly spaced, rural ‘grid-road‘ network also impedes drainage, but associated culvert drainage can mitigate those effects. Management of depressions can be informed by hydrological modelling, but accurate surface water storage capacity estimates are needed to ensure accurate model results. Simple representation of road embankments in digital elevation models (DEMs) neglects the effects of culvert drainage. Here, a raster-based depression-filling algorithm was used to delineate depressions from three LiDAR-derived DEMs: a 10-m DEM with roads intact, a 2-m DEM with roads intact, and a 2-m DEM with roads breached at culvert locations. Road breaching was conducted manually in the 2-m DEM to remove artifact depressions that form alongside roads where culverts exist. Results indicated that increasing DEM resolution from 10-m to 2-m in a 393.5 km2 basin did not significantly change depression area or storage capacity estimates; however, breaching roads in the 2-m DEM decreased depression area by 29% (from 98.5 km2 to 69.8 km2) and estimated storage capacity by 48% (from 47.4 × 106 m3 to 23.8 × 106 m3), compared to leaving roads intact in the 2-m DEM. Depressions delineated from the 2-m roads-breached DEM also covered 48% more area and offered 53% more storage capacity than Canadian Wetland Inventory (CWI) aerial-photograph delineated wetlands, which occupied 47.1 km2 with an estimated storage capacity of 15.5 × 106 m3. The implications of these results for the ability of hydrological models to calculate runo

Journal article

Wheater HS, Peach DW, Suárez F, Muñoz JFet al., 2023, Understanding the Silala River—Scientific insights from the dispute over the status and use of the waters of the Silala (Chile v. Bolivia), Wiley Interdisciplinary Reviews: Water

The flows of surface water and groundwater from the Andes to the Atacama Desert are a vital source of freshwater, supporting ecosystems and human activities, but few substantive studies have addressed the hydrological and hydrogeological functioning of these systems. A dispute between Chile and Bolivia concerning the transboundary Silala River, recently heard before the International Court of Justice, The Hague, provided a unique opportunity for new scientific studies, reviewed in this Special Issue. First, findings from field studies that address the geological and geomorphological evolution of the Silala River basin and its current status, the key hydrological processes (including infiltration, actual evaporation from wetlands and alluvial plains, and surface water-groundwater interactions), and the hydrogeological characterization of the major aquifers are reviewed. The dispute arose because Bolivia disagreed that the Silala was a transboundary river, subject to international law. As the Court proceedings evolved, this was accepted by Bolivia, but effects on surface flows of historical channelization in the Bolivian headwater wetlands remained a point of legal and technical disagreement. Bolivia asserted large increases in surface flow, based on modeling by their consultants, DHI. Chile held that these effects are small. In the second part of this paper, we summarize the modeling evidence. Chile's use of DHI's models, and its own hydrological and groundwater modeling of the basin, fully support Chile's position. We conclude with discussion of the Court's judgment, the challenges of physically-based modeling of small changes in complex systems, and associated implications for judicial practice. This article is categorized under: Human Water > Water Governance Science of Water > Hydrological Processes Science of Water > Water and Environmental Change.

Journal article

Wheater HS, Pomeroy JW, Pietroniro A, Davison B, Elshamy M, Yassin F, Rokaya P, Fayad A, Tesemma Z, Princz D, Loukili Y, DeBeer CM, Ireson AM, Razavi S, Lindenschmidt K-E, Elshorbagy A, MacDonald M, Abdelhamed M, Haghnegahdar A, Bahrami Aet al., 2022, Advances in modelling large river basins in cold regions with Modelisation Environmentale Communautaire-Surface and Hydrology (MESH), the Canadian hydrological land surface scheme, HYDROLOGICAL PROCESSES, Vol: 36, ISSN: 0885-6087

Journal article

Abdelhamed MS, Elshamy ME, Wheater HS, Razavi Set al., 2022, Hydrologic-land surface modelling of the Canadian sporadic-discontinuous permafrost: Initialization and uncertainty propagation, HYDROLOGICAL PROCESSES, Vol: 36, ISSN: 0885-6087

Journal article

Wong JS, Zhang X, Gharari S, Shrestha RR, Wheater HS, Famiglietti JSet al., 2021, Assessing Water Balance Closure Using Multiple Data Assimilation- and Remote Sensing-Based Datasets for Canada, JOURNAL OF HYDROMETEOROLOGY, Vol: 22, Pages: 1569-1589, ISSN: 1525-755X

Journal article

DeBeer CM, Wheater HS, Pomeroy JW, Barr AG, Baltzer JL, Johnstone JF, Turetsky MR, Stewart RE, Hayashi M, van der Kamp G, Marshall S, Campbell E, Marsh P, Carey SK, Quinton WL, Li Y, Razavi S, Berg A, McDonnell JJ, Spence C, Helgason WD, Ireson AM, Black TA, Elshamy M, Yassin F, Davison B, Howard A, Theriault JM, Shook K, Demuth MN, Pietroniro Aet al., 2021, Summary and synthesis of Changing Cold Regions Network (CCRN) research in the interior of western Canada - Part 2: Future change in cryosphere, vegetation, and hydrology, HYDROLOGY AND EARTH SYSTEM SCIENCES, Vol: 25, Pages: 1849-1882, ISSN: 1027-5606

Journal article

Razavi S, Gober P, Maier HR, Brouwer R, Wheater Het al., 2020, Anthropocene flooding: Challenges for science and society, Hydrological Processes, Vol: 34, Pages: 1996-2000, ISSN: 0885-6087

Journal article

Asong ZE, Elshamy ME, Princz D, Wheater HS, Pomeroy JW, Pietroniro A, Cannon Aet al., 2020, High-resolution meteorological forcing data for hydrological modelling and climate change impact analysis in the Mackenzie River Basin, EARTH SYSTEM SCIENCE DATA, Vol: 12, Pages: 629-645, ISSN: 1866-3508

Journal article

Costa D, Baulch H, Elliott J, Pomeroy J, Wheater Het al., 2020, Modelling nutrient dynamics in cold agricultural catchments: A review, Environmental Modelling and Software, Vol: 124, ISSN: 1364-8152

The hydrology of cold regions has been studied for decades with substantial progress in process understanding and prediction. Simultaneously, work on nutrient yields from agricultural land in cold regions has shown much slower progress. Advancement of nutrient modelling is constrained by well-documented issues of spatial heterogeneity, climate dependency, data limitations and over-parameterization of models, as well as challenges specific to cold regions due to the complex (and often unknown) behaviour of hydro-biogeochemical processes at temperatures close to and below freezing where a phase change occurs. This review is a critical discussion of these issues by taking a close look at the conceptual models and methods behind used catchment nutrient models. The impact of differences in model structure and the methods used for the prediction of hydrological processes, erosion and biogeochemical cycles are examined. The appropriateness of scale, scope, and complexity of models are discussed to propose future research directions.

Journal article

Marsh CB, Pomeroy JW, Spiteri RJ, Wheater HSet al., 2020, A Finite Volume Blowing Snow Model for Use With Variable Resolution Meshes, WATER RESOURCES RESEARCH, Vol: 56, ISSN: 0043-1397

Journal article

Marsh CB, Pomeroy JW, Wheater HS, 2020, The Canadian Hydrological Model (CHM) v1.0: a multi-scale, multi-extent, variable-complexity hydrological model - design and overview, GEOSCIENTIFIC MODEL DEVELOPMENT, Vol: 13, Pages: 225-247, ISSN: 1991-959X

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Elshamy ME, Princz D, Sapriza-Azuri G, Abdelhamed MS, Pietroniro A, Wheater HS, Razavi Set al., 2020, On the configuration and initialization of a large-scale hydrological land surface model to represent permafrost, HYDROLOGY AND EARTH SYSTEM SCIENCES, Vol: 24, Pages: 349-379, ISSN: 1027-5606

Journal article

Gharari S, Clark MP, Mizukami N, Wong JS, Pietroniro A, Wheater HSet al., 2019, Improving the Representation of Subsurface Water Movement in Land Models, JOURNAL OF HYDROMETEOROLOGY, Vol: 20, Pages: 2401-2418, ISSN: 1525-755X

Journal article

Mantyka-Pringle C, Leston L, Messmer D, Asong E, Bayne EM, Bortolotti LE, Sekulic G, Wheater H, Howerter DW, Clark RGet al., 2019, Antagonistic, synergistic and direct effects of land use and climate on Prairie wetland ecosystems: Ghosts of the past or present?, Diversity and Distributions, Vol: 25, Pages: 1924-1940, ISSN: 1366-9516

Aim: Wetland loss and degradation threaten biodiversity to an extent greater than most ecosystems. Science-supported responses require understanding of interacting effects of land use and climate change on wetland biodiversity. Location: Alberta, Canada. Methods: We evaluated how current climate, climate change (as a ghost of the past), land use and wetland water quality relate to aquatic macroinvertebrates and birds. Results: Climatic relationships and climate–land use interactions were observed on chironomid abundance, but not macroinvertebrate taxa richness (MTR) or odonate abundance, which responded to land use and water chemistry. Chironomid abundance was positively associated with cropland and negatively associated with total precipitation. Higher cropland cover and dissolved organic carbon synergistically interacted with total precipitation to affect chironomids. MTR was negatively related to salinity, yet greater area of non-woody riparian vegetation attenuated salinity effects on MTR. Odonate abundance was negatively related to total phosphorus. Higher grassland cover also increased the negative relationship of total phosphorous to odonate abundance. Climatic relationships and climate–land use interactions were observed on bird species richness (BSR) and abundance of several bird functional groups. Higher BSR and abundances of several bird groups were positively related to average rainfall and greater warming temperatures over time. Area of non-crop cover and wetlands was positively associated with most bird groups and BSR. Warming temperatures over time ameliorated the negative relationship of higher cropland or less shrubland on aerial insectivores and other bird groups. Main conclusions: Climate patterns and climate change are as important as land use pressures with stronger impacts on birds. Climate change was more influential than current climate and provided novel empirical evidence that progressively warmer, wetter conditions is benefitin

Journal article

Costa D, Pomeroy J, Baulch H, Elliott J, Wheater Het al., 2019, Using an inverse modelling approach with equifinality control to investigate the dominant controls on snowmelt nutrient export, Hydrological Processes, Vol: 33, Pages: 2958-2977, ISSN: 0885-6087

There is great interest in modelling the export of nitrogen (N) and phosphorus (P) from agricultural fields because of ongoing challenges of eutrophication. However, the use of existing hydrochemistry models can be problematic in cold regions because models frequently employ incomplete or conceptually incorrect representations of the dominant cold regions hydrological processes and are overparameterized, often with insufficient data for validation. Here, a process-based N model, WINTRA, which is coupled to a physically based cold regions hydrological model, was expanded to simulate P and account for overwinter soil nutrient biochemical cycling. An inverse modelling approach, using this model with consideration of parameter equifinality, was applied to an intensively monitored agricultural basin in Manitoba, Canada, to help identify the main climate, soil, and anthropogenic controls on nutrient export. Consistent with observations, the model results suggest that snow water equivalent, melt rate, snow cover depletion rate, and contributing area for run-off generation determine the opportunity time and surface area for run-off–soil interaction. These physical controls have not been addressed in existing models. Results also show that the time lag between the start of snowmelt and the arrival of peak nutrient concentration in run-off increased with decreasing antecedent soil moisture content, highlighting potential implications of frozen soils on run-off processes and hydrochemistry. The simulations showed TDP concentration peaks generally arriving earlier than NO3 but also decreasing faster afterwards, which suggests a significant contribution of plant residue Total dissolved Phosphorus (TDP) to early snowmelt run-off. Antecedent fall tillage and fertilizer application increased TDP concentrations in spring snowmelt run-off but did not consistently affect NO3 run-off. In this case, the antecedent soil moisture content seemed to have had a dominant effect on overw

Journal article

Yassin F, Razavi S, Elshamy M, Davison B, Sapriza-Azuri G, Wheater Het al., 2019, Representation and improved parameterization of reservoir operation in hydrological and land-surface models, Hydrology and Earth System Sciences, Vol: 23, Pages: 3735-3764, ISSN: 1027-5606

Reservoirs significantly affect flow regimes in watershed systems by changing the magnitude and timing of streamflows. Failure to represent these effects limits the performance of hydrological and land-surface models (H-LSMs) in the many highly regulated basins across the globe and limits the applicability of such models to investigate the futures of watershed systems through scenario analysis (e.g., scenarios of climate, land use, or reservoir regulation changes). An adequate representation of reservoirs and their operation in an H-LSM is therefore essential for a realistic representation of the downstream flow regime. In this paper, we present a general parametric reservoir operation model based on piecewise-linear relationships between reservoir storage, inflow, and release to approximate actual reservoir operations. For the identification of the model parameters, we propose two strategies: (a) a "generalized" parameterization that requires a relatively limited amount of data and (b) direct calibration via multi-objective optimization when more data on historical storage and release are available. We use data from 37 reservoir case studies located in several regions across the globe for developing and testing the model. We further build this reservoir operation model into the MESH (Modélisation Environmentale-Surface et Hydrologie) modeling system, which is a large-scale H-LSM. Our results across the case studies show that the proposed reservoir model with both parameter-identification strategies leads to improved simulation accuracy compared with the other widely used approaches for reservoir operation simulation. We further show the significance of enabling MESH with this reservoir model and discuss the interdependent effects of the simulation accuracy of natural processes and that of reservoir operations on the overall model performance. The reservoir operation model is generic and can be integrated into any H-LSM.

Journal article

Rokaya P, Peters DL, Bonsal B, Wheater H, Lindenschmidt KEet al., 2019, Modelling the effects of climate and flow regulation on ice-affected backwater staging in a large northern river, River Research and Applications, Vol: 35, Pages: 587-600, ISSN: 1535-1459

In cold region environments, ice-jam floods (IJFs) pose a severe risk to local communities, economies, and ecosystems. Previous studies have shown that both climate and regulation affect IJF probabilities, but their relative impacts are poorly understood. This study presents a probabilistic modelling framework that couples hydrologic and hydraulic models to assess the relative role of regulated and naturalized flows on ice-affected backwater staging. The framework is evaluated at an IJF-prone town on the Peace River in western Canada, which has been regulated since 1972. Naturalized flows were generated for the comparison, and ice-affected backwater profiles were calculated along jams of varying length and location and for different combinations of model parameters and boundary conditions. Results show significant differences in backwater staging (~2 m for a return period of T = 1:10 year) between two study time periods (1973–1992 vs 1993–2012) as compared with two different hydraulic flow conditions (regulated vs naturalized), suggesting a larger role of climate than regulation in backwater staging. However, regulation was found to offset flood risk during the 1973–1992 period and exacerbate flood risk during the 1993–2012 period.

Journal article

Rokaya P, Morales-Marín L, Bonsal B, Wheater H, Lindenschmidt KEet al., 2019, Climatic effects on ice phenology and ice-jam flooding of the Athabasca River in western Canada, Hydrological Sciences Journal, Vol: 64, Pages: 1265-1278, ISSN: 0262-6667

In cold region environments, any alteration in the hydro-climatic regime can have profound impacts on river ice processes. This paper studies the implications of hydro-climatic trends on river ice processes, particularly on the freeze-up and ice-cover breakup along the Athabasca River in Fort McMurray in western Canada, which is an area very prone to ice-jam flooding. Using a stochastic approach in a one-dimensional hydrodynamic river ice model, a relationship between overbank flow and breakup discharge is established. Furthermore, the likelihood of ice-jam flooding in the future (2041–2070 period) is assessed by forcing a hydrological model with meteorological inputs from the Canadian regional climate model driven by two atmospheric–ocean general circulation climate models. Our results show that the probability of ice-jam flooding for the town of Fort McMurray in the future will be lower, but extreme ice-jam flood events are still probable.

Journal article

Rokaya P, Wheater H, Lindenschmidt KE, 2019, Promoting sustainable Ice-Jam flood management along the peace river and Peace-Athabasca Delta, Journal of Water Resources Planning and Management, Vol: 145, ISSN: 0733-9496

The regulation of rivers has always been a controversial issue, with potential benefits but also environmental impacts. In western Canada, the construction of W.A.C. Bennett Dam in the headwaters of the Peace River has raised concerns over the ecological health of the Peace-Athabasca Delta (PAD), a socioeconomically and ecologically important delta with national and international significance. The major concern is the reduced frequency of ice-jam floods, which are particularly effective in replenishing the high-elevation basins of the PAD. Previous studies have suggested that releasing water at opportune times from the dam could promote ice-jam flooding of the δ however, ice-jam flood events can also be severe and devastating to riverside communities and economies. Thus, a critical and challenging question is how to promote flooding in the downstream deltaic ecosystem where it is essential without necessarily increasing the flood risk in upstream communities of the Peace River. This study reviews previous approaches and explores possible reservoir operation schemes with an integrated hydrologic and hydraulic river ice modeling framework to minimize flood risk and maximize flood potential at desired locations. It is demonstrated that by increasing reservoir release in the breakup period, it is possible to increase the likelihood of ice-jam flooding in the PAD without necessarily causing ice-jam floods in the upstream communities. However, the timing of the flow release, taking into account the receding ice front and local hydrometeorological conditions, is critical.

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Costa D, Pomeroy J, Wheater H, 2018, A numerical model for the simulation of snowpack solute dynamics to capture runoff ionic pulses during snowmelt: The PULSE model, Advances in Water Resources, Vol: 122, Pages: 37-48, ISSN: 0309-1708

© 2018 Elsevier Ltd Early ionic pulse during spring snowmelt can account for a significant portion of the total annual nutrient load in seasonally snow-covered areas. Ionic pulses are a consequence of snow grain core to surface ion segregation during metamorphism, a process commonly referred to as ion exclusion. While numerous studies have provided quantitative measurements of this phenomenon, very few process-based mathematical models have been proposed for diagnostic and prognostic investigations. A few early modelling attempts have been successful in capturing this process assuming transport through porous media with variable porosity. However, this process is represented in models in ways that misalign with the mechanistic view of the process described in the literature. In this research, a process-based model is proposed that can simulated ionic pulses in runoff by emulating solute leaching from snow grains during melt and the subsequent vertical solute transport by meltwater through the snowpack. To facilitate its use without the need for snow-physics’ models, simplified alternative methods are proposed to estimate some of the variables required by the model. The model was applied to two regions, and a total of 4 study sites, that are subject to significantly different winter climatic and hydrological conditions. Comparison between observations and simulation results suggest that the model can capture well the overall snow melt runoff concentration pattern, including both the timing and magnitude of the early melt ionic pulse. The model enables the prediction of concentration profiles of the dry (snow) and liquid (wet) fractions within the snow matrix for the first time. Although there is a computational cost associated with the proposed modelling framework, this study demonstrates that it can provide more detailed information about the reallocation and transport of ions through snowpacks, which can ultimately be used to improve nutrient transport p

Journal article

Morales-Marín L, Wheater H, Lindenschmidt KE, 2018, Potential changes of annual-averaged nutrient export in the South Saskatchewan River Basin under climate and land-use change scenarios, Water (Switzerland), Vol: 10

© 2018 by the author. Climate and land-use changes modify the physical functioning of river basins and, in particular, influence the transport of nutrients from land to water. In large-scale basins, where a variety of climates, topographies, soil types and land uses co-exist to form a highly heterogeneous environment, a more complex nutrient dynamic is imposed by climate and land-use changes. This is the case of the South Saskatchewan River (SSR) that, along with the North Saskatchewan River, forms one of the largest river systems in western Canada. The SPAtially Referenced Regression On Watershed (SPARROW) model is therefore implemented to assess water quality in the basin, in order to describe spatial and temporal patterns and identify those factors and processes that affect water quality. Forty-five climate and land-use change scenarios comprehended by five General Circulation Models (GCMs) and three Representative Concentration Pathways (RCPs) were incorporated into the model to explain how total nitrogen (TN) and total phosphorus (TP) export could vary across the basin in 30, 60 and 90 years from now. According to model results, annual averages of TN and TP export in the SSR are going to increase in the range 0.9-1.28 kg km-2 year-1 and 0.12-0.17 kg km-2 year-1, respectively, by the end of the century, due to climate and land-use changes. Higher increases of TP compared to TN are expected since TP and TN are going to increase ~36% and ~21%, respectively, by the end of the century. This research will support management plans in order to mitigate nutrient export under future changes of climate and land use.

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Marsh CB, Spiteri RJ, Pomeroy JW, Wheater HSet al., 2018, Multi-objective unstructured triangular mesh generation for use in hydrological and land surface models, COMPUTERS & GEOSCIENCES, Vol: 119, Pages: 49-67, ISSN: 0098-3004

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Xu L, Gober P, Wheater HS, Kajikawa Yet al., 2018, Reframing socio-hydrological research to include a social science perspective, JOURNAL OF HYDROLOGY, Vol: 563, Pages: 76-83, ISSN: 0022-1694

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Sapriza-Azuri G, Gamazo P, Razavi S, Wheater HSet al., 2018, On the appropriate definition of soil profile configuration and initial conditions for land surface-hydrology models in cold regions, HYDROLOGY AND EARTH SYSTEM SCIENCES, Vol: 22, Pages: 3295-3309, ISSN: 1027-5606

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Asong ZE, Wheater HS, Bonsal B, Razavi S, Kurkute Set al., 2018, Historical drought patterns over Canada and their teleconnections with large-scale climate signals, HYDROLOGY AND EARTH SYSTEM SCIENCES, Vol: 22, Pages: 3105-3124, ISSN: 1027-5606

Journal article

Sadeghian A, Chapra SC, Hudson J, Wheater H, Lindenschmidt K-Eet al., 2018, Improving in-lake water quality modeling using variable chlorophyll a/algal biomass ratios, Environmental Modelling and Software, Vol: 101, Pages: 73-85, ISSN: 1364-8152

© 2017 Elsevier Ltd Algal simulations in many water quality models perform poorly because of oversimplifications in the process descriptions of the algae growth mechanisms. In this study, algae simulations were improved by implementing variable chlorophyll a/algal biomass ratios in the CE-QUAL-W2 model, a sophisticated two-dimensional laterally-averaged water quality model. Originally a constant in the model, the chlorophyll a/algal biomass ratio was reprogrammed to vary according to the nutrient and light limiting conditions in the water column. The modified model was tested on Lake Diefenbaker, a prairie reservoir in Saskatchewan, Canada, where, similar to many other lakes in the world, field observations confirm variable spatiotemporal ratios between chlorophyll a and algal biomass. The modified version yielded more accurate simulations compared to the standard version and provides a promising algorithm to improve results for many lakes and reservoirs globally.

Journal article

Morales-Marin LA, Wheater HS, Lindenschmidt KE, 2018, Estimating Sediment Loadings in the South Saskatchewan River Catchment, WATER RESOURCES MANAGEMENT, Vol: 32, Pages: 769-783, ISSN: 0920-4741

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Haghnegahdar A, Razavi S, Yassin F, Wheater Het al., 2017, Multicriteria sensitivity analysis as a diagnostic tool for understanding model behaviour and characterizing model uncertainty, Hydrological Processes, Vol: 31, Pages: 4462-4476, ISSN: 0885-6087

Copyright © 2017 John Wiley & Sons, Ltd. Complex hydrological models are being increasingly used nowadays for many purposes such as studying the impact of climate and land-use change on water resources. However, building a high-fidelity model, particularly at large scales, remains a challenging task, due to complexities in model functioning and behaviour and uncertainties in model structure, parameterization, and data. Global sensitivity analysis (GSA), which characterizes how the variation in the model response is attributed to variations in its input factors (e.g., parameters and forcing data), provides an opportunity to enhance the development and application of these complex models. In this paper, we advocate using GSA as an integral part of the modelling process by discussing its capabilities as a tool for diagnosing model structure and detecting potential defects, identifying influential factors, characterizing uncertainty, and selecting calibration parameters. Accordingly, we conduct a comprehensive GSA of a complex land surface–hydrology model, Modélisation Environmentale–Surface et Hydrologie (MESH), which combines the Canadian land surface scheme with a hydrological routing component, WATROUTE. Various GSA experiments are carried out using a new technique, called Variogram Analysis of Response Surfaces, for alternative hydroclimatic conditions in Canada using multiple criteria, various model configurations, and a full set of model parameters. Results from this study reveal that, in addition to different hydroclimatic conditions and SA criteria, model configurations can also have a major impact on the assessment of sensitivity. GSA can identify aspects of the model internal functioning that are counter-intuitive and thus help the modeller to diagnose possible model deficiencies and make recommendations for improving development and application of the model. As a specific outcome of this work, a list of the most influential para

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