The potential role of rural land use in mitigating flood risk and protecting water supplies conti... more The potential role of rural land use in mitigating flood risk and protecting water supplies continues to be of great interest to regulators and planners. The ability of hydrologists to quantify the impact of rural land use change on the water cycle is however limited and we are not able to provide consistently reliable evidence to support planning and policy decisions. This shortcoming stems mainly from lack of data, but also from lack of modelling methods and tools. Numerous research projects over the last few years have been attempting to address the underlying challenges. This paper describes these challenges, significant areas of progress and modelling innovations, and proposes priorities for further research. The paper is organised into five inter-related subtopics: (1) evidence-based modelling; (2) upscaling to maximise the use of process knowledge and physics-based models; (3) representing hydrological connectivity in models; (4) uncertainty analysis; and (5) integrated catch...
Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences, 2002
Recent floods in the UK have raised public and political awareness of flood risk. There is an inc... more Recent floods in the UK have raised public and political awareness of flood risk. There is an increasing recognition that flood management and land-use planning are linked, and that decision-support modelling tools are required to address issues of climate and land-use change for integrated catchment management. In this paper, the scientific context for fluvial flood modelling is discussed, current modelling capability is considered and research challenges are identified. Priorities include (i) appropriate representation of spatial precipitation, including scenarios of climate change; (ii) development of a national capability for continuous hydrological simulation of ungauged catchments; (iii) improved scientific understanding of impacts of agricultural land-use and land-management change, and the development of new modelling approaches to represent those impacts; (iv) improved representation of urban flooding, at both local and catchment scale; (v) appropriate parametrizations for hydraulic simulation of in-channel and flood-plain flows, assimilating available ground observations and remotely sensed data; and (vi) a flexible decision-support modelling framework, incorporating developments in computing, data availability, data assimilation and uncertainty analysis.
Across Europe, elevated phosphorus (P) concentrations in lowland rivers have made them particular... more Across Europe, elevated phosphorus (P) concentrations in lowland rivers have made them particularly susceptible to eutrophication. This is compounded in southern and central UK by increasing pressures on water resources, which may be further enhanced by the potential effects of climate change. The EU Water Framework Directive requires an integrated approach to water resources management at the catchment scale and highlights the need for modelling tools that can distinguish relative contributions from multiple nutrient sources and are consistent with the information content of the available data. Two such models are introduced and evaluated within a stochastic framework using daily flow and total phosphorus concentrations recorded in a clay catchment typical of many areas of the lowland UK. Both models disaggregate empirical annual load estimates, derived from land use data, as a function of surface/near surface runoff, generated using a simple conceptual rainfall-runoff model. Estimates of the daily load from agricultural land, together with those from baseflow and point sources, feed into an in-stream routing algorithm. The first model assumes constant concentrations in runoff via surface/near surface pathways and incorporates an additional P store in the river-bed sediments, depleted above a critical discharge, to explicitly simulate resuspension. The second model, which is simpler, simulates P concentrations as a function of surface/near surface runoff, thus emphasising the influence of non-point source loads during flow peaks and mixing of baseflow and point sources during low flows. The temporal consistency of parameter estimates and thus the suitability of each approach is assessed dynamically following a new approach based on Monte-Carlo analysis.
System Identification, Environmental Modelling, and Control System Design, 2012
Page 1. Chapter 22 Modelling Environmental Change: Quantification of Impacts of Land Use and Land... more Page 1. Chapter 22 Modelling Environmental Change: Quantification of Impacts of Land Use and Land Management Change on UK Flood Risk HS Wheater, C. Ballard, N. Bulygina, N. McIntyre, and BM Jackson 22.1 Introduction ...
Given the difficulties of ground-based observation in the north of Canada, many researchers rely ... more Given the difficulties of ground-based observation in the north of Canada, many researchers rely heavily on satellite-based, remotely-sensed data sources. The Saskatchewan River Delta (SRD), located on the border of Saskatchewan and Manitoba, is a flat area of low elevation with a complex series of abandoned and active river channels, lakes and wetlands, including the Cumberland Marshes, a bird breeding area of world importance. Tracking hydrological changes over the previous fifty years in this delta and modeling and predicting future change requires data which is currently lacking from conventional ground-based sources. Additionally, existing Digital Elevation Model (DEM) data, which was derived from Radar and extracted from aerial stereo photo images, does not properly represent the water coverage of the area. Radar, including Light Detection and Ranging (LIDAR), does not penetrate water, and also produces “noise” from ground vegetation and trees. Aerial photos show only the wate...
Cold regions provide water resources for half the global population yet face rapid change. Their ... more Cold regions provide water resources for half the global population yet face rapid change. Their hydrology is dominated by snow, ice and frozen soils, and climate warming is having profound effects. Hydrological models have a key role in predicting changing water resources but are challenged in cold regions. Ground‐based data to quantify meteorological forcing and constrain model parameterization are limited, while hydrological processes are complex, often controlled by phase change energetics. River flows are impacted by poorly quantified human activities. This paper discusses the scientific and technical challenges of the large‐scale modelling of cold region systems and reports recent modelling developments, focussing on MESH, the Canadian community hydrological land surface scheme. New cold region process representations include improved blowing snow transport and sublimation, lateral land‐surface flow, prairie pothole pond storage dynamics, frozen ground infiltration and thermod...
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2013
In this paper, we discuss the multiple dimensions of water security and define a set of thematic ... more In this paper, we discuss the multiple dimensions of water security and define a set of thematic challenges for science, policy and governance, based around cross-scale dynamics, complexity and uncertainty. A case study of the Saskatchewan River basin (SRB) in western Canada is presented, which encompasses many of the water-security challenges faced worldwide. A science agenda is defined based on the development of the SRB as a large-scale observatory to develop the underpinning science and social science needed to improve our understanding of water futures under societal and environmental change. We argue that non-stationarity poses profound challenges for existing science and that new integration of the natural sciences, engineering and social sciences is needed to address decision making under deep uncertainty. We suggest that vulnerability analysis can be combined with scenario-based modelling to address issues of water security and that knowledge translation should be coupled w...
Arid and semi-arid regions are defined as areas where water is at its most scarce. The hydrologic... more Arid and semi-arid regions are defined as areas where water is at its most scarce. The hydrological regime in these areas is extreme and highly variable, and they face great pressures to deliver and manage freshwater resources. However, there is no guidance on the decision support tools that are needed to underpin flood and water resource management in arid areas. UNESCO initiated the Global network for Water and Development Information for arid lands (GWADI), and arranged a workshop of the world's leading experts to discuss these issues. This book presents chapters from contributors to the workshop, and includes case studies from the world's major arid regions to demonstrate model applications, and web links to tutorials and state of the art modelling software. This volume is a valuable reference for researchers and engineers working on the water resources of arid and semi-arid regions.
Over the last 50 years there have been significant changes in the rural landscape of the UK as a ... more Over the last 50 years there have been significant changes in the rural landscape of the UK as a result of agricultural intensification. Obvious landscape features include the removal of hedgerows, in-creased field size and changing cropping patterns. In the lowlands, arable ...
Trade-offs between precision of numerical solutions to deterministic models of the environment, a... more Trade-offs between precision of numerical solutions to deterministic models of the environment, and the number of model realizations achievable within a framework of Monte Carlo simulation, are investigated and discussed. A case study of a model of river thermodynamics is employed. It is shown that the tractability of Monte Carlo simulation relies on adaptation of the numerical solution time-step, giving results with a guaranteed error in the time domain as well as near-optimum speed of calibration under any chosen accuracy criteria. Time-step control is implemented using two adaptive Runge-Kutta methods: a second order scheme with first order error estimator, and an embedded fourth-fifth order scheme. In the case study, where the effects of sparse and imprecise data dominate the overall modeling error, both the schemes appear adequate. However, the higher order scheme is concluded to be generally more reliable and efficient, and has wide potential to improve the value of applying the Monte Carlo method to environmental simulation. The problem of reconciling spatial error with the specified temporal error is discussed.
A novel stochastic method for reconstructing daily precipitation timesseries using tree-ring data... more A novel stochastic method for reconstructing daily precipitation timesseries using tree-ring data from the western Canadian Boreal Forest.Dendrochronologia
be larger than that associated with the choice of the driving AOGCM for most of the precipitation... more be larger than that associated with the choice of the driving AOGCM for most of the precipitation characteristics considered. Analyses of multi-RCM ensemble-averaged projected changes to mean seasonal precipitation and various return levels of RDEs and SDEs show an increase over nearly all the study domain. The changes to seasonal precipitation are not generally found statistically significant at 5 % significance level but those for RDEs and SDEs are found significant more often for return levels of smaller return period (10-year) compared to those of larger return period (50-year). It is expected that changes in seasonal and extreme precipitation characteristics will have important implications for managing regional water security-related issues in the Canadian Prairie Provinces.
Hydrology and Earth System Sciences Discussions, 2017
Over the last decades, the global population has been rapidly increasing and human activities hav... more Over the last decades, the global population has been rapidly increasing and human activities have altered terrestrial water fluxes at an unprecedented scale. 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 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 large-scale 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 are inco...
Hydrology and Earth System Sciences Discussions, 2017
Lakes might be sentinels of climate change, but the uncertainty in their main feedback to the atm... more 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…
Estimating a uniquely best set of values for the parameters of conceptual hydrological models has... more Estimating a uniquely best set of values for the parameters of conceptual hydrological models has long been a problem of considerable concern. More recent interest in using these models to determine the flow paths of water passing through catchments experiencing acidification has sharpened the focus of such concern on the role of tracer observations in model and parameter identifiability. The paper examines the question of a priori identifiability in both deterministic and stochastic frameworks. Working with relatively simple linear and nonlinear two-store models, the deterministic analysis involves merely algebraic manipulation of the model's state space description. It is apparent that, while this form of analysis is of limited applicability (even with the assistance of systems of computer algebra), the availability of tracer observations enhances model identifiability in all the cases examined. More complex model structures, and the effects of model and observation uncertainty, can be explored within a stochastic framework based on filtering theory. It is found that the availability of two tracer signals does not necessarily improve identifiability beyond what is possible with just a single tracer measurement. There is also evidence of a basis for the cross referencing of identifiability results between the deterministic and stochastic frameworks. ß 0.4 0.2
The potential role of rural land use in mitigating flood risk and protecting water supplies conti... more The potential role of rural land use in mitigating flood risk and protecting water supplies continues to be of great interest to regulators and planners. The ability of hydrologists to quantify the impact of rural land use change on the water cycle is however limited and we are not able to provide consistently reliable evidence to support planning and policy decisions. This shortcoming stems mainly from lack of data, but also from lack of modelling methods and tools. Numerous research projects over the last few years have been attempting to address the underlying challenges. This paper describes these challenges, significant areas of progress and modelling innovations, and proposes priorities for further research. The paper is organised into five inter-related subtopics: (1) evidence-based modelling; (2) upscaling to maximise the use of process knowledge and physics-based models; (3) representing hydrological connectivity in models; (4) uncertainty analysis; and (5) integrated catch...
Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences, 2002
Recent floods in the UK have raised public and political awareness of flood risk. There is an inc... more Recent floods in the UK have raised public and political awareness of flood risk. There is an increasing recognition that flood management and land-use planning are linked, and that decision-support modelling tools are required to address issues of climate and land-use change for integrated catchment management. In this paper, the scientific context for fluvial flood modelling is discussed, current modelling capability is considered and research challenges are identified. Priorities include (i) appropriate representation of spatial precipitation, including scenarios of climate change; (ii) development of a national capability for continuous hydrological simulation of ungauged catchments; (iii) improved scientific understanding of impacts of agricultural land-use and land-management change, and the development of new modelling approaches to represent those impacts; (iv) improved representation of urban flooding, at both local and catchment scale; (v) appropriate parametrizations for hydraulic simulation of in-channel and flood-plain flows, assimilating available ground observations and remotely sensed data; and (vi) a flexible decision-support modelling framework, incorporating developments in computing, data availability, data assimilation and uncertainty analysis.
Across Europe, elevated phosphorus (P) concentrations in lowland rivers have made them particular... more Across Europe, elevated phosphorus (P) concentrations in lowland rivers have made them particularly susceptible to eutrophication. This is compounded in southern and central UK by increasing pressures on water resources, which may be further enhanced by the potential effects of climate change. The EU Water Framework Directive requires an integrated approach to water resources management at the catchment scale and highlights the need for modelling tools that can distinguish relative contributions from multiple nutrient sources and are consistent with the information content of the available data. Two such models are introduced and evaluated within a stochastic framework using daily flow and total phosphorus concentrations recorded in a clay catchment typical of many areas of the lowland UK. Both models disaggregate empirical annual load estimates, derived from land use data, as a function of surface/near surface runoff, generated using a simple conceptual rainfall-runoff model. Estimates of the daily load from agricultural land, together with those from baseflow and point sources, feed into an in-stream routing algorithm. The first model assumes constant concentrations in runoff via surface/near surface pathways and incorporates an additional P store in the river-bed sediments, depleted above a critical discharge, to explicitly simulate resuspension. The second model, which is simpler, simulates P concentrations as a function of surface/near surface runoff, thus emphasising the influence of non-point source loads during flow peaks and mixing of baseflow and point sources during low flows. The temporal consistency of parameter estimates and thus the suitability of each approach is assessed dynamically following a new approach based on Monte-Carlo analysis.
System Identification, Environmental Modelling, and Control System Design, 2012
Page 1. Chapter 22 Modelling Environmental Change: Quantification of Impacts of Land Use and Land... more Page 1. Chapter 22 Modelling Environmental Change: Quantification of Impacts of Land Use and Land Management Change on UK Flood Risk HS Wheater, C. Ballard, N. Bulygina, N. McIntyre, and BM Jackson 22.1 Introduction ...
Given the difficulties of ground-based observation in the north of Canada, many researchers rely ... more Given the difficulties of ground-based observation in the north of Canada, many researchers rely heavily on satellite-based, remotely-sensed data sources. The Saskatchewan River Delta (SRD), located on the border of Saskatchewan and Manitoba, is a flat area of low elevation with a complex series of abandoned and active river channels, lakes and wetlands, including the Cumberland Marshes, a bird breeding area of world importance. Tracking hydrological changes over the previous fifty years in this delta and modeling and predicting future change requires data which is currently lacking from conventional ground-based sources. Additionally, existing Digital Elevation Model (DEM) data, which was derived from Radar and extracted from aerial stereo photo images, does not properly represent the water coverage of the area. Radar, including Light Detection and Ranging (LIDAR), does not penetrate water, and also produces “noise” from ground vegetation and trees. Aerial photos show only the wate...
Cold regions provide water resources for half the global population yet face rapid change. Their ... more Cold regions provide water resources for half the global population yet face rapid change. Their hydrology is dominated by snow, ice and frozen soils, and climate warming is having profound effects. Hydrological models have a key role in predicting changing water resources but are challenged in cold regions. Ground‐based data to quantify meteorological forcing and constrain model parameterization are limited, while hydrological processes are complex, often controlled by phase change energetics. River flows are impacted by poorly quantified human activities. This paper discusses the scientific and technical challenges of the large‐scale modelling of cold region systems and reports recent modelling developments, focussing on MESH, the Canadian community hydrological land surface scheme. New cold region process representations include improved blowing snow transport and sublimation, lateral land‐surface flow, prairie pothole pond storage dynamics, frozen ground infiltration and thermod...
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2013
In this paper, we discuss the multiple dimensions of water security and define a set of thematic ... more In this paper, we discuss the multiple dimensions of water security and define a set of thematic challenges for science, policy and governance, based around cross-scale dynamics, complexity and uncertainty. A case study of the Saskatchewan River basin (SRB) in western Canada is presented, which encompasses many of the water-security challenges faced worldwide. A science agenda is defined based on the development of the SRB as a large-scale observatory to develop the underpinning science and social science needed to improve our understanding of water futures under societal and environmental change. We argue that non-stationarity poses profound challenges for existing science and that new integration of the natural sciences, engineering and social sciences is needed to address decision making under deep uncertainty. We suggest that vulnerability analysis can be combined with scenario-based modelling to address issues of water security and that knowledge translation should be coupled w...
Arid and semi-arid regions are defined as areas where water is at its most scarce. The hydrologic... more Arid and semi-arid regions are defined as areas where water is at its most scarce. The hydrological regime in these areas is extreme and highly variable, and they face great pressures to deliver and manage freshwater resources. However, there is no guidance on the decision support tools that are needed to underpin flood and water resource management in arid areas. UNESCO initiated the Global network for Water and Development Information for arid lands (GWADI), and arranged a workshop of the world's leading experts to discuss these issues. This book presents chapters from contributors to the workshop, and includes case studies from the world's major arid regions to demonstrate model applications, and web links to tutorials and state of the art modelling software. This volume is a valuable reference for researchers and engineers working on the water resources of arid and semi-arid regions.
Over the last 50 years there have been significant changes in the rural landscape of the UK as a ... more Over the last 50 years there have been significant changes in the rural landscape of the UK as a result of agricultural intensification. Obvious landscape features include the removal of hedgerows, in-creased field size and changing cropping patterns. In the lowlands, arable ...
Trade-offs between precision of numerical solutions to deterministic models of the environment, a... more Trade-offs between precision of numerical solutions to deterministic models of the environment, and the number of model realizations achievable within a framework of Monte Carlo simulation, are investigated and discussed. A case study of a model of river thermodynamics is employed. It is shown that the tractability of Monte Carlo simulation relies on adaptation of the numerical solution time-step, giving results with a guaranteed error in the time domain as well as near-optimum speed of calibration under any chosen accuracy criteria. Time-step control is implemented using two adaptive Runge-Kutta methods: a second order scheme with first order error estimator, and an embedded fourth-fifth order scheme. In the case study, where the effects of sparse and imprecise data dominate the overall modeling error, both the schemes appear adequate. However, the higher order scheme is concluded to be generally more reliable and efficient, and has wide potential to improve the value of applying the Monte Carlo method to environmental simulation. The problem of reconciling spatial error with the specified temporal error is discussed.
A novel stochastic method for reconstructing daily precipitation timesseries using tree-ring data... more A novel stochastic method for reconstructing daily precipitation timesseries using tree-ring data from the western Canadian Boreal Forest.Dendrochronologia
be larger than that associated with the choice of the driving AOGCM for most of the precipitation... more be larger than that associated with the choice of the driving AOGCM for most of the precipitation characteristics considered. Analyses of multi-RCM ensemble-averaged projected changes to mean seasonal precipitation and various return levels of RDEs and SDEs show an increase over nearly all the study domain. The changes to seasonal precipitation are not generally found statistically significant at 5 % significance level but those for RDEs and SDEs are found significant more often for return levels of smaller return period (10-year) compared to those of larger return period (50-year). It is expected that changes in seasonal and extreme precipitation characteristics will have important implications for managing regional water security-related issues in the Canadian Prairie Provinces.
Hydrology and Earth System Sciences Discussions, 2017
Over the last decades, the global population has been rapidly increasing and human activities hav... more Over the last decades, the global population has been rapidly increasing and human activities have altered terrestrial water fluxes at an unprecedented scale. 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 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 large-scale 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 are inco...
Hydrology and Earth System Sciences Discussions, 2017
Lakes might be sentinels of climate change, but the uncertainty in their main feedback to the atm... more 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…
Estimating a uniquely best set of values for the parameters of conceptual hydrological models has... more Estimating a uniquely best set of values for the parameters of conceptual hydrological models has long been a problem of considerable concern. More recent interest in using these models to determine the flow paths of water passing through catchments experiencing acidification has sharpened the focus of such concern on the role of tracer observations in model and parameter identifiability. The paper examines the question of a priori identifiability in both deterministic and stochastic frameworks. Working with relatively simple linear and nonlinear two-store models, the deterministic analysis involves merely algebraic manipulation of the model's state space description. It is apparent that, while this form of analysis is of limited applicability (even with the assistance of systems of computer algebra), the availability of tracer observations enhances model identifiability in all the cases examined. More complex model structures, and the effects of model and observation uncertainty, can be explored within a stochastic framework based on filtering theory. It is found that the availability of two tracer signals does not necessarily improve identifiability beyond what is possible with just a single tracer measurement. There is also evidence of a basis for the cross referencing of identifiability results between the deterministic and stochastic frameworks. ß 0.4 0.2
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Papers by H. Wheater