| 1. |
- Blösch, Günter, et al.
(author)
-
Twenty-three unsolved problems in hydrology (UPH) - a community perspective
- 2019
-
In: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 64:10, s. 1141-1158
-
Journal article (peer-reviewed)abstract
- This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.
|
|
| 2. |
- Freer, J., et al.
(author)
-
Flood risk and uncertainty
- 2013
-
In: Risk and Uncertainty Assessment for Natural Hazards. - : Cambridge University Press. - 9781139047562 - 9781107006195 ; , s. 190-233
-
Book chapter (other academic/artistic)abstract
- IntroductionExtreme floods are among the most destructive forces of nature. Flooding accounts for a significant proportion of the total number of reported natural disasters occurring in the world (Figure 7.1a) and over the last 30 years this proportion has been increasing (Figure 7.1b). Reasons for this trend may not be clear; for each hazard there is a need to quantify whether this is an increase in the hazard itself, an increase in exposure to the hazard internationally or a change in the reporting of what constitutes a natural disaster. Internationally, the costs and scale of flooding are enormous but differ depending on the types of impact that are analysed and the databases used. Globally in 2007 it was estimated that annually 520 million people are affected by floods and that the death toll is approximately 25 000 people in any one year. Jonkman (2005) found for a study using data from 1974 to 2003 (from data maintained by the Centre for Research on the Epidemiology of Disasters in Brussels) that floods are the most significant natural disaster type in terms of the number of people affected – some 51% of the total of that period of approximately five billion people affected by natural disaster (droughts are second with 36%, and earthquakes third at 2%). However, in terms of overall estimated deaths flooding accounts for 10% of the approximately two million reported deaths associated with natural disasters over the 1974–2003 period (droughts 44% and earthquakes 27%). In monetary terms an assessment by Munich RE for the period 1980–2010 determined that at 2010 prices the losses totalled US$3000 billion from ~19 400 events with 2.275 million fatalities. Of these, hydrological catastrophes (flooding and mass movement, i.e. landslips and debris flow in this case) accounted for 24% of these monetary losses, from 35% of the total events, and 11% of the fatalities. Other categories of natural disasters included in these totals were geophysical, meteorological and climatological (NatCatSERVICE, 2011).
|
|
| 3. |
- McDonnell, J.J., et al.
(author)
-
How old is streamwater? : Open questions in catchment transit time conceptualization, modelling and analysis
- 2010
-
In: Hydrological Processes. - : John Wiley & Sons. - 0885-6087 .- 1099-1085. ; 24:12, s. 1745-1754
-
Journal article (peer-reviewed)abstract
- The time water spends travelling subsurface through a catchment to the stream network (i.e. the catchment water transit time) fundamentally describes the storage, flow pathway heterogeneity and sources of water in a catchment. The distribution of transit times reflects how catchments retain and release water and solutes that in turn set biogeochemical conditions and affect contamination release or persistence. Thus, quan- tifying the transit time distribution provides an important constraint on biogeochemical processes and catchment sensitivity to anthropogenic inputs, contamination and land-use change. Although the assumptions and limitations of past and present transit time modelling approaches have been recently reviewed (McGuire and McDonnell, 2006), there remain many fundamental research challenges for understanding how transit time can be used to quantify catchment flow processes and aid in the development and testing of rainfall–runoff models. In this Commen- tary study, we summarize what we think are the open research questions in transit time research. These thoughts come from a 3-day workshop in January 2009 at the International Atomic Energy Agency in Vienna. We attempt to lay out a roadmap for this work for the hydrological commu- nity over the next 10 years. We do this by first defining what we mean (qualitatively and quantitatively) by transit time and then organize our vision around needs in transit time theory, needs in field studies of tran- sit time and needs in rainfall – runoff modelling. Our goal in presenting this material is to encourage widespread use of transit time information in process studies to provide new insights to catchment function and to inform the structural development and testing of hydrologic models.
|
|
| 4. |
- Kulasova, A., et al.
(author)
-
A method of computing uncertain nitrogen and phosphorus loads in a small stream from an agricultural catchment using continuous monitoring data
- 2012
-
In: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 458-459, s. 1-8
-
Journal article (peer-reviewed)abstract
- A method for computing loads of total phosphorus and nitrate from a small catchment in the Czech Republic has been presented, given continuous measurements of water levels, turbidity and an ion-specific NO3--N probe together with a limited number of discharge measurements and analyses of grab samples. Given the observed variability in the observations, log-log regressions are used to convert water levels to discharge and to derive continuous estimates of total phosphorus and nitrate. Integrations to estimate loads using predicted values of the true discharges and concentrations are then carried out by a Monte Carlo method to avoid strong assumptions of independence and distribution. Coefficients of variation for the estimated monthly loads range from 5% to 23% for TP and 12-36% for NO3--N. At the annual time scales, coefficients of variation are of the order of 5% for both TP and NO3--N. The variability in the estimated annual loads between the years was, however, significantly larger than the uncertainties estimated within each year.
|
|
| 5. |
- Beven, Keith J, et al.
(author)
-
Comment on “Hydrological forecasting uncertainty assessment: Incoherence of the GLUE methodology” by Pietro Mantovan and Ezio Todini
- 2007
-
In: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 338:3-4, s. 315-318
-
Journal article (peer-reviewed)abstract
- This comment is a response to the criticisms of the GLUE methodology by [Mantovan, P., Todini, E., 2006. Hydrological forecasting uncertainty assessment: Incoherence of the GLUE methodology, J. Hydrology, 2006]. In this comment it is shown that the formal Bayesian identification of models is a special case of GLUE that can be used where the modeller is prepared to make very strong assumptions about the nature of the modelling errors. For the hypothetical study of Mantovan and Todini, exact assumptions were assumed known for the formal Bayesian identification, but were then ignored in the application of GLUE to the same data. We show that a more reasonable application of GLUE to this problem using similar prior knowledge shows that gives equally coherent results to the formal Bayes identification. In real applications, subject to input and model structural error it is suggested that the coherency condition of MT06 cannot hold at the single observation level and that the choice of a formal Bayesian likelihood function may then be incoherent. In these (more interesting) cases, GLUE can be coherent in the application of likelihood measures based on blocks of data, but different choices of measures and blocks effectively represent different beliefs about the information content of data in real applications with input and model structural errors.
|
|
| 6. |
- Beven, Keith J., et al.
(author)
-
Struggling with Epistemic Uncertainties in Environmental Modelling of Natural Hazards
- 2014
-
In: Vulnerability, Uncertainty, and Risk. - Reston, VA : American Society of Civil Engineers. - 9780784413609 ; , s. 13-22
-
Conference paper (peer-reviewed)abstract
- Epistemic uncertainties create difficulties for the quantitative estimation of uncertainties associated with environmental models. The nature of the issues involved is discussed, particularly in how to assign likelihood values to models when the forcing data and evaluation data might both be subject to epistemic uncertainties. A case study of a rainfall-runoff model of the River Brue catchment is developed with the Generalised Likelihood Uncertainty Estimation (GLUE) methodology. Model evaluation is carried out using limits of acceptability set from considerations of the available data prior to running a model, while the errors associated with a model are treated non-parametrically for different parts of the hydrograph.
|
|
| 7. |
- Davies, J., et al.
(author)
-
Comparison of a Multiple Interacting Pathways model with a classical kinematic wave subsurface flow solution
- 2012
-
In: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 57:2, s. 203-216
-
Journal article (peer-reviewed)abstract
- A discrete random particle representation of flow processes on shallow hillslopes is compared with solutions of the classical kinematic wave representation. The discrete Multiple Interacting Pathways (MIPs) model has the potential to represent the effects of complex heterogeneities and preferential flow pathways. It is shown that, under shared assumptions, the MIPs model can produce equivalent flow predictions to a standard kinematic wave realization. The MIPs model is then used to further explore the relationship between celerity and water velocity by introducing a velocity distribution, which represents the range of possible flow pathways, and therefore is representative of the nature of heterogeneity (or lack of it within a homogeneous case) within the subsurface. It is shown that, whilst flux constraints can be satisfied with a distribution of flow velocities, it can result in changes to the hydrograph. Multiple pathways also have an influence on the residence times for input increments, output increments and storage in the system.
|
|
| 8. |
- Delsman, Joost R., et al.
(author)
-
Uncertainty estimation of end-member mixing using generalized likelihood uncertainty estimation (GLUE), applied in a lowland catchment
- 2013
-
In: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 49:8, s. 4792-4806
-
Journal article (peer-reviewed)abstract
- End-member mixing models have been widely used to separate the different components of a hydrograph, but their effectiveness suffers from uncertainty in both the identification of end-members and spatiotemporal variation in end-member concentrations. In this paper, we outline a procedure, based on the generalized likelihood uncertainty estimation (GLUE) framework, to more inclusively evaluate uncertainty in mixing models than existing approaches. We apply this procedure, referred to as G-EMMA, to a yearlong chemical data set from the heavily impacted agricultural Lissertocht catchment, Netherlands, and compare its results to the traditional end-member mixing analysis (EMMA). While the traditional approach appears unable to adequately deal with the large spatial variation in one of the end-members, the G-EMMA procedure successfully identified, with varying uncertainty, contributions of five different end-members to the stream. Our results suggest that the concentration distribution of effective end-members, that is, the flux-weighted input of an end-member to the stream, can differ markedly from that inferred from sampling of water stored in the catchment. Results also show that the uncertainty arising from identifying the correct end-members may alter calculated end-member contributions by up to 30%, stressing the importance of including the identification of end-members in the uncertainty assessment.
|
|
| 9. |
- Ellerbæk Nielsen, J., et al.
(author)
-
GLUE based marine X-band weather radar data calibration and uncertainty estimation
- 2015
-
In: Urban Water Journal. - 1573-062X. ; 12:4, s. 283-294
-
Journal article (peer-reviewed)abstract
- The Generalized Likelihood Uncertainty Estimation methodology (GLUE) is investigated for radar rainfall calibration and uncertainty assessment. The method is used to calibrate radar data collected by a Local Area Weather Radar (LAWR).In contrast to other LAWR data calibrations, the method combines calibration with uncertainty estimation. Instead of searching for a single set of calibration parameters, the method uses the observations to construct distributions of the calibration parameters. These parameter sets provide valuable knowledge of parameter sensitivity and the uncertainty.Two approaches are analyzed; the static calibration approach, where the LAWR is calibrated once for a long period and the dynamic approach, where the estimate is continuously adjusted based on ground observations.The analysis illustrates that the static calibration performs insufficiently, whereas the dynamic adjustment improves the performance significantly.It is found that even if the dynamic adjustment method is used the uncertainty of rainfall estimates can still be significant.
|
|
| 10. |
- Gallart, F., et al.
(author)
-
Using internal catchment information to reduce the uncertainty of discharge and baseflow prediction
- 2007
-
In: Advances in Water Resources. - : Elsevier BV. - 0309-1708 .- 1872-9657. ; 30:4, s. 808-823
-
Journal article (peer-reviewed)abstract
- The semi-distributed hydrological model TOPMODEL was tested with data from the Can Vila research basin (Vallcebre) in order to verify its adequacy for simulating runoff and the relative contributions from saturated overland flow and groundwater flow. After a test of the overall performance of the model, only data from a wet period were selected for this work. The test was performed using the GLUE method. The model was conditioned on continuous discharge and water table records. Furthermore, point measurements of recession flow simultaneous with water table depth and the extent of saturated areas were used to condition the distributions of the more relevant parameters, using new or updated evaluation measures. A wide range of parameter sets provided acceptable results for flow simulation when the model was conditioned on flow data alone, and the uncertainty of prediction of the contribution from groundwater was extremely large. However, conditioning on water table records and the distribution of parameters obtained from point observations strongly reduced the uncertainty of predictions for both stream flow and groundwater contribution.
|
|
