scholarly journals Exploratory studies into seasonal flow forecasting potential for large lakes

2018 ◽  
Vol 22 (1) ◽  
pp. 127-141 ◽  
Author(s):  
Kevin Sene ◽  
Wlodek Tych ◽  
Keith Beven
Keyword(s):  
Water Balance ◽  
Lake Victoria ◽  
Spatial Scales ◽  
Data Availability ◽  
Climate Indices ◽  
Test Case ◽  
Large Lakes ◽  
Analytical Approximations ◽  
Seasonal Flow ◽  
The Individual

Abstract. In seasonal flow forecasting applications, one factor which can help predictability is a significant hydrological response time between rainfall and flows. On account of storage influences, large lakes therefore provide a useful test case although, due to the spatial scales involved, there are a number of modelling challenges related to data availability and understanding the individual components in the water balance. Here some possible model structures are investigated using a range of stochastic regression and transfer function techniques with additional insights gained from simple analytical approximations. The methods were evaluated using records for two of the largest lakes in the world – Lake Malawi and Lake Victoria – with forecast skill demonstrated several months ahead using water balance models formulated in terms of net inflows. In both cases slight improvements were obtained for lead times up to 4–5 months from including climate indices in the data assimilation component. The paper concludes with a discussion of the relevance of the results to operational flow forecasting systems for other large lakes.

scholarly journals Exploratory studies into seasonal flow forecasting potential for large lakes

2017 ◽  
Author(s):  
Kevin Sene ◽  
Wlodek Tych ◽  
Keith Beven
Keyword(s):  
Water Balance ◽  
Lake Victoria ◽  
Spatial Scales ◽  
Data Availability ◽  
Climate Indices ◽  
Test Case ◽  
Large Lakes ◽  
Analytical Approximations ◽  
Seasonal Flow ◽  
The Individual

Abstract. In seasonal flow forecasting applications, one factor which can help predictability is a significant hydrological response time between rainfall and flows. On account of storage influences, large lakes therefore provide a useful test case although, due to the spatial scales involved, there are a number of modelling challenges related to data availability and understanding the individual components in the water balance. Here some possible model structures are investigated using a 10 range of stochastic regression and transfer function techniques with additional insights gained from simple analytical approximations. The methods were evaluated using records for two of the largest lakes in the world – Lake Malawi and Lake Victoria – with forecast skill demonstrated several months ahead using water balance models formulated in terms of net inflows. In both cases slight improvements were obtained for lead times up to 4–5 months from including climate indices in the data assimilation component. The paper concludes with a discussion of the relevance of the results to operational flow 15 forecasting systems for other large lakes.

scholarly journals Reflections on almost a century of hydrological studies on Africa's largest lake

2021 ◽  
Vol 384 ◽  
pp. 141-147
Author(s):  
Kevin Sene ◽  
Helen Houghton Carr ◽  
Wlodek Tych
Keyword(s):  
Water Balance ◽  
Lake Victoria ◽  
Research Priorities ◽  
Future Research ◽  
Monitoring Networks ◽  
Local Climate ◽  
Seasonal Flow ◽  
Research Programmes ◽  
Sub Saharan ◽  
White Nile

Abstract. Lake Victoria is the largest lake in Africa and its outflows strongly influence flows in the White Nile, including the availability of water for hydropower generation, irrigation and water supply. Understanding the water balance is a major challenge since the lake is large enough to influence the local climate and its catchment spans several countries. Hydrometeorological monitoring networks are also sparse in some parts of the basin. In this paper, we consider the history of water balance estimates for the lake and how the science has developed as new information and techniques have become available, including in areas such as seasonal flow forecasting and estimating the potential impacts of dam operations and climate change. These findings are placed into a wider context including the challenges arising from a changing climate and evolving ideas from international research programmes, which lead to some suggestions for future research priorities for Lake Victoria and other sub-Saharan/Rift Valley lakes.

scholarly journals Seasonal flow forecasting in Africa; exploratory studies for large lakes

2021 ◽  
Vol 384 ◽  
pp. 289-293
Author(s):  
Kevin Sene ◽  
Wlodek Tych
Keyword(s):  
Performance Metrics ◽  
Response Times ◽  
Lake Victoria ◽  
Lessons Learned ◽  
Data Driven ◽  
Hydrological Response ◽  
Large Lakes ◽  
Seasonal Flow ◽  
Data Driven Approach ◽  
The Indian Ocean

Abstract. For many applications, it would be extremely useful to have insights into river flows at timescales of a few weeks to months ahead. However, seasonal predictions of this type are necessarily probabilistic which raises challenges both in generating forecasts and their interpretation. Despite this, an increasing number of studies have shown promising results and this is an active area for research. In this paper, we discuss insights gained from previous studies using a novel combined water balance and data-driven approach for two of Africa's largest lakes, Lake Victoria and Lake Malawi. Factors which increased predictability included the unusually long hydrological response times and statistically significant links to ocean-atmosphere processes such as the Indian Ocean Dipole. Other lessons learned included the benefits of data assimilation and the need for care in the choice of performance metrics.

scholarly journals Modelling the water balance of Lake Victoria (East Africa) – Part 1: Observational analysis

2018 ◽  
Vol 22 (10) ◽  
pp. 5509-5525 ◽  
Author(s):  
Inne Vanderkelen ◽  
Nicole P. M. van Lipzig ◽  
Wim Thiery
Keyword(s):  
Water Balance ◽  
Lake Level ◽  
Lake Victoria ◽  
Balance Model ◽  
Lake Victoria Basin ◽  
Lake Level Fluctuations ◽  
Lake Evaporation ◽  
In Situ Observations ◽  
The Individual

Abstract. Lake Victoria is the largest lake in Africa and one of the two major sources of the Nile river. The water level of Lake Victoria is determined by its water balance, consisting of precipitation on the lake, evaporation from the lake, inflow from tributary rivers and lake outflow, controlled by two hydropower dams. Due to a scarcity of in situ observations, previous estimates of individual water balance terms are characterized by substantial uncertainties, which means that the water balance is often not closed independently. In this first part of a two-paper series, we present a water balance model for Lake Victoria, using state-of-the-art remote sensing observations, high-resolution reanalysis downscaling and outflow values recorded at the dam. The uncalibrated computation of the individual water balance terms yields lake level fluctuations that closely match the levels retrieved from satellite altimetry. Precipitation is the main cause of seasonal and interannual lake level fluctuations, and on average causes the lake level to rise from May to July and to fall from August to December. Finally, our results indicate that the 2004–2005 drop in lake level can be about half attributed to a drought in the Lake Victoria Basin and about half to an enhanced outflow, highlighting the sensitivity of the lake level to human operations at the outflow dam.

scholarly journals Modelling the water balance of Lake Victoria (East Africa) – Part 1: Observational analysis

2018 ◽  
Author(s):  
Inne Vanderkelen ◽  
Nicole P. M. van Lipzig ◽  
Wim Thiery
Keyword(s):  
Water Balance ◽  
Lake Level ◽  
Lake Victoria ◽  
Balance Model ◽  
Lake Victoria Basin ◽  
Lake Level Fluctuations ◽  
Lake Evaporation ◽  
In Situ Observations ◽  
The Individual

Abstract. Lake Victoria is the largest lake in Africa and one of the two major sources of the Nile River. The water level of Lake Victoria is determined by its water balance, consisting of precipitation on the lake, evaporation from the lake, inflow from tributary rivers and lake outflow, controlled by two hydropower dams. Due to scarcity of in-situ observations, previous estimates of individual water balance terms are characterised by substantial uncertainties, which makes that the water balance is often not closed independently. Here we present a water balance model for Lake Victoria, using state-of-the-art remote sensing observations, high resolution reanalysis downscaling and outflow values recorded at the dam. The uncalibrated computation of the individual water balance terms yield lake level fluctuations that closely match the levels retrieved from satellite altimetry. Precipitation is the main cause of seasonal and inter-annual lake level fluctuations, and on average causes the lake level to rise from May to July and to fall from August to December. Finally, our results indicate that the 2004–2005 drop in lake level can be attributed about half to a drought in the Lake Victoria Basin and about half to an enhanced outflow, highlighting the sensitivity of the lake level to human operations at the outflow dam.

scholarly journals Results from the Ice Thickness Models Intercomparison eXperiment Phase 2 (ITMIX2)

2021 ◽  
Vol 8 ◽  
Author(s):  
Daniel Farinotti ◽  
Douglas J. Brinkerhoff ◽  
Johannes J. Fürst ◽  
Prateek Gantayat ◽  
Fabien Gillet-Chaulet ◽  
...  
Keyword(s):  
Spatial Information ◽  
Numerical Models ◽  
Spatial Scales ◽  
Thickness Distribution ◽  
Data Availability ◽  
Added Value ◽  
Ice Thickness ◽  
Test Case ◽  
Glacier Surface ◽  
The Mean

Knowing the ice thickness distribution of a glacier is of fundamental importance for a number of applications, ranging from the planning of glaciological fieldwork to the assessments of future sea-level change. Across spatial scales, however, this knowledge is limited by the paucity and discrete character of available thickness observations. To obtain a spatially coherent distribution of the glacier ice thickness, interpolation or numerical models have to be used. Whilst the first phase of the Ice Thickness Models Intercomparison eXperiment (ITMIX) focused on approaches that estimate such spatial information from characteristics of the glacier surface alone, ITMIX2 sought insights for the capability of the models to extract information from a limited number of thickness observations. The analyses were designed around 23 test cases comprising both real-world and synthetic glaciers, with each test case comprising a set of 16 different experiments mimicking possible scenarios of data availability. A total of 13 models participated in the experiments. The results show that the inter-model variability in the calculated local thickness is high, and that for unmeasured locations, deviations of 16% of the mean glacier thickness are typical (median estimate, three-quarters of the deviations within 37% of the mean glacier thickness). This notwithstanding, limited sets of ice thickness observations are shown to be effective in constraining the mean glacier thickness, demonstrating the value of even partial surveys. Whilst the results are only weakly affected by the spatial distribution of the observations, surveys that preferentially sample the lowest glacier elevations are found to cause a systematic underestimation of the thickness in several models. Conversely, a preferential sampling of the thickest glacier parts proves effective in reducing the deviations. The response to the availability of ice thickness observations is characteristic to each approach and varies across models. On average across models, the deviation between modeled and observed thickness increase by 8.5% of the mean ice thickness every time the distance to the closest observation increases by a factor of 10. No single best model emerges from the analyses, confirming the added value of using model ensembles.

Error Management in Audit Firms: Error Climate, Type, and Originator

2013 ◽  
Vol 89 (1) ◽  
pp. 303-330 ◽  
Author(s):  
Anna Gold ◽  
Ulfert Gronewold ◽  
Steven E. Salterio
Keyword(s):  
Impression Management ◽  
Data Availability ◽  
Error Management ◽  
Organizational Life ◽  
Climate Type ◽  
Error Type ◽  
Audit Firms ◽  
The Individual ◽  
Post Hoc ◽  
Willingness To Report

ABSTRACT This paper examines how the treatment of audit staff who discover errors in audit files by superiors affects their willingness to report these errors. The way staff are treated by superiors is labelled as the audit office error management climate. In a “blame-oriented” climate errors are not tolerated and those committing errors are punished. In contrast, an “open” climate characterizes error commitment as a normal, albeit unfortunate aspect of organizational life that offers opportunities for learning without sanctions on the originator. We examine error management climate in the context of audit-specific factors that might affect the decision to report errors: audit error type (conceptual or mechanical) and who committed the error (the individual who discovered it or a peer). An open climate results in an increase in the reporting of mechanical (but not conceptual) errors and all peer errors versus a blame climate. Post hoc findings suggest that one obstacle to reporting conceptual errors stems from an auditor's own impression management concerns. We discuss how auditing standards and regulatory inspections may impact audit firm error management climates. Data Availability: Experimental data are available from the second author subject to data confidentiality restrictions issued by the participating firms.

scholarly journals Fluxes and Metabolic Pools as Model Traits for Quantitative Genetics. I. The L-Shaped Distribution of Gene Effects

Genetics ◽  
1999 ◽  
Vol 153 (4) ◽  
pp. 2001-2012 ◽  
Author(s):  
Bruno Bost ◽  
Christine Dillmann ◽  
Dominique de Vienne
Keyword(s):  
Enzyme Activity ◽  
Metabolic Pathways ◽  
Quantitative Traits ◽  
Intrinsic Property ◽  
Gene Effects ◽  
Analytical Approximations ◽  
Mean And Variance ◽  
The Individual ◽  
Metabolic Control Theory ◽  
Control Coefficients

Abstract The fluxes through metabolic pathways can be considered as model quantitative traits, whose QTL are the polymorphic loci controlling the activity or quantity of the enzymes. Relying on metabolic control theory, we investigated the relationships between the variations of enzyme activity along metabolic pathways and the variations of the flux in a population with biallelic QTL. Two kinds of variations were taken into account, the variation of the average enzyme activity across the loci, and the variation of the activity of each enzyme of the pathway among the individuals of the population. We proposed analytical approximations for the flux mean and variance in the population as well as for the additive and dominance variances of the individual QTL. Monte Carlo simulations based on these approximations showed that an L-shaped distribution of the contributions of individual QTL to the flux variance (R2) is consistently expected in an F2 progeny. This result could partly account for the classically observed L-shaped distribution of QTL effects for quantitative traits. The high correlation we found between R2 value and flux control coefficients variance suggests that such a distribution is an intrinsic property of metabolic pathways due to the summation property of control coefficients.

scholarly journals Using a Groundwater Adjusted Water Balance Approach and Copulas to Evaluate Spatial Patterns and Dependence Structures in Remote Sensing Derived Evapotranspiration Products

2021 ◽  
Vol 13 (5) ◽  
pp. 853
Author(s):  
Mohsen Soltani ◽  
Julian Koch ◽  
Simon Stisen
Keyword(s):  
Remote Sensing ◽  
Water Balance ◽  
Spatial Pattern ◽  
Spatial Patterns ◽  
Principal Component ◽  
Small Scale ◽  
Dependence Structure ◽  
Test Case ◽  
Catchment Scale ◽  
Balance Approach

This study aims to improve the standard water balance evapotranspiration (WB ET) estimate, which is typically used as benchmark data for catchment-scale ET estimation, by accounting for net intercatchment groundwater flow in the ET calculation. Using the modified WB ET approach, we examine errors and shortcomings associated with the long-term annual mean (2002–2014) spatial patterns of three remote-sensing (RS) MODIS-based ET products from MODIS16, PML_V2, and TSEB algorithms at 1 km spatial resolution over Denmark, as a test case for small-scale, energy-limited regions. Our results indicate that the novel approach of adding groundwater net in water balance ET calculation results in a more trustworthy ET spatial pattern. This is especially relevant for smaller catchments where groundwater net can be a significant component of the catchment water balance. Nevertheless, large discrepancies are observed both amongst RS ET datasets and compared to modified water balance ET spatial pattern at the national scale; however, catchment-scale analysis highlights that difference in RS ET and WB ET decreases with increasing catchment size and that 90%, 87%, and 93% of all catchments have ∆ET < ±150 mm/year for MODIS16, PML_V2, and TSEB, respectively. In addition, Copula approach captures a nonlinear structure of the joint relationship with multiple densities amongst the RS/WB ET products, showing a complex dependence structure (correlation); however, among the three RS ET datasets, MODIS16 ET shows a closer spatial pattern to the modified WB ET, as identified by a principal component analysis also. This study will help improve the water balance approach by the addition of groundwater net in the ET estimation and contribute to better understand the true correlations amongst RS/WB ET products especially over energy-limited environments.

Impacts cumulatifs du développement hydro-électrique sur le bilan d'eau douce de la baie d'Hudson

1994 ◽  
Vol 21 (2) ◽  
pp. 297-306 ◽  
Author(s):  
François Anctil ◽  
Richard Couture
Keyword(s):  
Water Balance ◽  
Fresh Water ◽  
Marine Environment ◽  
Mass Exchange ◽  
Spatial Scales ◽  
Ice Cover ◽  
Hudson Bay ◽  
Freezing And Thawing ◽  
Runoff Water ◽  
Hydroelectric Development

This paper discusses the consequences on the marine environment, more specifically on the fresh water balance, of the hydroelectric development of several tributaries of Hudson Bay, including James Bay and Foxe Basin. The fresh water balance is determined by identifying, at different scales, the modifications caused by each complex. The main inputs are the freezing and thawing of the ice cover, runoff water, and mass exchange at the air–water interface. Three spatial scales were used to obtain the resolution required to document the cumulative effects of fresh water balance modifications on the water surface layer: the Hudson Bay, the Hudson Strait, and the Labrador Sea. Finally, the addition of the proposed Grande-Baleine hydroelectric complex is examined from the available information and forecasts. Key words: hydroelectric development, impact, marine environment, fresh water balance, ice cover, runoff water, mass exchange.[Journal translation]

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