Imperial College London

Emeritus Professor Howard Wheater

Faculty of EngineeringDepartment of Civil and Environmental Engineering

Senior Research Investigator
 
 
 
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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

429 results found

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

Journal article

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.

Journal article

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.

Journal article

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

Journal article

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

Journal article

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

Journal article

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

Journal article

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

Journal article

Guerrero J-L, Pernica P, Wheater H, Mackay M, Spence Cet al., 2017, Parameter sensitivity analysis of a 1-D cold region lake model for land-surface schemes, Hydrology and Earth System Sciences, Vol: 21, Pages: 6345-6362, ISSN: 1027-5606

© 2017 Author(s). Lakes might be sentinels of climate change, but the uncertainty in their main feedback to the atmosphere-heat-exchange fluxes-is often not considered within climate models. Additionally, these fluxes are seldom measured, hindering critical evaluation of model output. Analysis of the Canadian Small Lake Model (CSLM), a one-dimensional integral lake model, was performed to assess its ability to reproduce diurnal and seasonal variations in heat fluxes and the sensitivity of simulated fluxes to changes in model parameters, i.e., turbulent transport parameters and the light extinction coefficient (Kd). A C++ open-source software package, Problem Solving environment for Uncertainty Analysis and Design Exploration (PSUADE), was used to perform sensitivity analysis (SA) and identify the parameters that dominate model behavior. The generalized likelihood uncertainty estimation (GLUE) was applied to quantify the fluxes' uncertainty, comparing daily-averaged eddy-covariance observations to the output of CSLM. Seven qualitative and two quantitative SA methods were tested, and the posterior likelihoods of the modeled parameters, obtained from the GLUE analysis, were used to determine the dominant parameters and the uncertainty in the modeled fluxes. Despite the ubiquity of the equifinality issue-different parameter-value combinations yielding equivalent results-the answer to the question was unequivocal: Kd, a measure of how much light penetrates the lake, dominates sensible and latent heat fluxes, and the uncertainty in their estimates is strongly related to the accuracy with which Kd is determined. This is important since accurate and continuous measurements of Kd could reduce modeling uncertainty.

Journal article

Costa D, Roste J, Pomeroy J, Baulch H, Elliott J, Wheater H, Westbrook Cet al., 2017, A modelling framework to simulate field-scale nitrate response and transport during snowmelt: The WINTRA model, Hydrological Processes, Vol: 31, Pages: 4250-4268, ISSN: 0885-6087

Copyright © 2017 John Wiley & Sons, Ltd. Modelling nutrient transport during snowmelt in cold regions remains a major scientific challenge. A key limitation of existing nutrient models for application in cold regions is the inadequate representation of snowmelt, including hydrological and biogeochemical processes. This brief period can account for more than 80% of the total annual surface runoff in the Canadian Prairies and Northern Canada and processes such as atmospheric deposition, overwinter redistribution of snow, ion exclusion from snow crystals, frozen soils, and snow-covered area depletion during melt influence the distribution and release of snow and soil nutrients, thus affecting the timing and magnitude of snowmelt runoff nutrient concentrations. Research in cold regions suggests that nitrate (NO3) runoff at the field-scale can be divided into 5 phases during snowmelt. In the first phase, water and ions originating from ion-rich snow layers travel and diffuse through the snowpack. This process causes ion concentrations in runoff to gradually increase. The second phase occurs when this snow ion meltwater front has reached the bottom of the snowpack and forms runoff to the edge-of-the-field. During the third and fourth phases, the main source of NO3transitions from the snowpack to the soil. Finally, the fifth and last phase occurs when the snow has completely melted, and the thawing soil becomes the main source of NO3to the stream. In this research, a process-based model was developed to simulate hourly export based on this 5-phase approach. Results from an application in the Red River Basin of southern Manitoba, Canada, shows that the model can adequately capture the dynamics and rapid changes of NO3concentrations during this period at relevant temporal resolutions. This is a significant achievement to advance the current nutrient modelling paradigm in cold climates, which is generally limited to satisfactory results at monthly or annual resolut

Journal article

Pan X, Helgason W, Ireson A, Wheater Het al., 2017, Field-scale water balance closure in seasonally frozen conditions, Hydrology and Earth System Sciences, Vol: 21, Pages: 5401-5413, ISSN: 1027-5606

Hydrological water balance closure is a simple concept, yet in practice it is uncommon to measure every significant term independently in the field. Here we demonstrate the degree to which the field-scale water balance can be closed using only routine field observations in a seasonally frozen prairie pasture field site in Saskatchewan, Canada. Arrays of snow and soil moisture measurements were combined with a precipitation gauge and flux tower evapotranspiration estimates. We consider three hydrologically distinct periods: the snow accumulation period over the winter, the snowmelt period in spring, and the summer growing season. In each period, we attempt to quantify the residual between net precipitation (precipitation minus evaporation) and the change in field-scale storage (snow and soil moisture), while accounting for measurement uncertainties. When the residual is negligible, a simple 1-D water balance with no net drainage is adequate. When the residual is non-negligible, we must find additional processes to explain the result. We identify the hydrological fluxes which confound the 1-D water balance assumptions during different periods of the year, notably blowing snow and frozen soil moisture redistribution during the snow accumulation period, and snowmelt runoff and soil drainage during the melt period. Challenges associated with quantifying these processes, as well as uncertainties in the measurable quantities, caution against the common use of water balance residuals to estimate fluxes and constrain models in such a complex environment.

Journal article

Yassin F, Razavi S, Wheater H, Sapriza-Azuri G, Davison B, Pietroniro Aet al., 2017, Enhanced identification of a hydrologic model using streamflow and satellite water storage data: a multicriteria sensitivity analysis and optimization approach, Hydrological Processes, Vol: 31, Pages: 3320-3333, ISSN: 0885-6087

Hydrologic model development and calibration have continued in most cases to focus only on accurately reproducing streamflows. However, complex models, for example, the so-called physically based models, possess large degrees of freedom that, if not constrained properly, may lead to poor model performance when used for prediction. We argue that constraining a model to represent streamflow, which is an integrated resultant of many factors across the watershed, is necessary but by no means sufficient to develop a high-fidelity model. To address this problem, we develop a framework to utilize the Gravity Recovery and Climate Experiment's (GRACE) total water storage anomaly data as a supplement to streamflows for model calibration, in a multiobjective setting. The VARS method (Variogram Analysis of Response Surfaces) for global sensitivity analysis is used to understand the model behaviour with respect to streamflow and GRACE data, and the BORG multiobjective optimization method is applied for model calibration. Two subbasins of the Saskatchewan River Basin in Western Canada are used as a case study. Results show that the developed framework is superior to the conventional approach of calibration only to streamflows, even when multiple streamflow-based error functions are simultaneously minimized. It is shown that a range of (possibly false) system trajectories in state variable space can lead to similar (acceptable) model responses. This observation has significant implications for land-surface and hydrologic model development and, if not addressed properly, may undermine the credibility of the model in prediction. The framework effectively constrains the model behaviour (by constraining posterior parameter space) and results in more credible representation of hydrology across the watershed.

Journal article

Masud MB, Khaliq MN, Wheater HS, 2017, Projected changes to short- and long-duration precipitation extremes over the Canadian Prairie Provinces, CLIMATE DYNAMICS, Vol: 49, Pages: 1597-1616, ISSN: 0930-7575

Journal article

Wada Y, Bierkens MFP, De Roo A, Dirmeyer PA, Famiglietti JS, Hanasaki N, Konar M, Liu J, Schmied HM, Oki T, Pokhrel Y, Sivapalan M, Troy TJ, Van Dijk AIJM, Van Emmerik T, Van Huijgevoort MHJ, Van Lanen HAJ, Vörösmarty CJ, Wanders N, Wheater Het al., 2017, Human-water interface in hydrological modelling: Current status and future directions, Hydrology and Earth System Sciences, Vol: 21, Pages: 4169-4193, ISSN: 1027-5606

© Author(s) 2017. This work is distributed under. Over recent decades, the global population has been rapidly increasing and human activities have altered terrestrial water fluxes to an unprecedented extent. The phenomenal growth of the human footprint has significantly modified hydrological processes in various ways (e.g. irrigation, artificial dams, and water diversion) and at various scales (from a watershed to the globe). During the early 1990s, awareness of the potential for increased water scarcity led to the first detailed global water resource assessments. Shortly thereafter, in order to analyse the human perturbation on terrestrial water resources, the first generation of largescale hydrological models (LHMs) was produced. However, at this early stage few models considered the interaction between terrestrial water fluxes and human activities, including water use and reservoir regulation, and even fewer models distinguished water use from surface water and groundwater resources. Since the early 2000s, a growing number of LHMs have incorporated human impacts on the hydrological cycle, yet the representation of human activities in hydrological models remains challenging. In this paper we provide a synthesis of progress in the development and application of human impact modelling in LHMs. We highlight a number of key challenges and discuss possible improvements in order to better represent the human-water interface in hydrological models.

Journal article

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