D. A. Hughes

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Verified

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• PhD
• Professor Emeritus at Rhodes University

Riparian zones are vital regulators of ecosystems, serving as dynamic sources and sinks for energy, solutes, and clastic sediments. There are increasing concerns about African riparian zones since only a little information is available in the literature compared to the developed world. This chapter attempts to underscore the significance of riparia...

In this article, we examine the scientific and sustainable research capacity outcomes of the ‘Congo River: user Hydraulics and Morphology’ or CRuHM project, a six-year effort supported by the Royal Society’s Africa Capacity Building Initiative. This project brought together a consortium of African and UK universities to undertake the first large-sc...

The proliferation and extent of small dams is a significant issue for water resources management. South Africa has an extensive spatial database of farm dams; however, uncertainties remain when estimating the water volume held, although satellite-based techniques offer some means of measurement. This chapter compares various datasets on the occurre...

The Kwando (Cuando) River and the western headwaters of the Zambezi River, which are data-scarce basins of southern Africa. Study Focus: A comparative analysis of the performance of two fundamentally different hydrological modelling approaches (a conceptual model and a theory guided machine learning model) in a data-sparse region. New Hydrological...

Managing water resources and preventing water-related disasters requires investing in tools that aid knowledge-based group decision-making at local levels. We contribute to this toolbox by demonstrating the utility of the Analytic Hierarchical Process (AHP) for establishing an expressed equity-based allocation criteria (called community weighting i...

Introduction High erosion and sediment yield rates continue to pose a significant threat to the environment globally. Information on erosion and sediment rates is key for supporting effective and sustainable mitigation measures. Models that estimate sediment yield are vital in providing information about erosion and sediment yield rates, as empiric...

The Ecological Reserve (environmental flows) as defined under the South African National Water Act 36 of 1998 was designed to equitably manage water for river sustainability while maximizing economic and social welfare. We investigated the climate change impacts on the Ecological Reserve targets for a seasonal river in an agricultural catchment in...

Southern Africa could experience major hydrological changes in coming decades, bringing drastic changes to hydropower. Focusing on four large hydropower dams in the Kafue and Zambezi Rivers (Itezhi‐Tezhi, Kafue Gorge Upper, Kariba, and Cahora Bassa), accounting for over 90% of the installed capacity in the basin, this study analyzed how these dams...

The Congo River provides a huge potential for socio‐economic growth at the regional scale, but with limited information on the river dynamics it is difficult for basin countries to benefit from this potential, and to invest in the development of water resources. Accurate information is needed to support adequate management strategies such as predic...

The need for a catchment classification framework for the Congo Basin is obvious given the basin's inherent heterogeneities, the ungauged nature of the basin, and the pressing needs for water resources management that include the quantification of current and future supplies and demands, which also encompass the impacts of future changes associated...

The Congo River is navigable along much of its length and plays a crucial role in the economies of nine basin countries. River users rely on river transport for access to markets, resources, and key services. These users range from millions of small‐scale informal users, to industrial‐scale users such as mining and logging companies. Without a func...

La nécessité de mettre en place un cadre de classification des unités hydrologiques est évidente dans le Bassin du Congo à cause de ses hétérogénéités, de sa nature non jaugée et des besoins pressants d'utilisation des ressources en eau. Ces besoins comprennent la quantification des approvisionnements et des demandes actuels et futures, qui incluen...

Le fleuve Congo offre un potentiel important pour la croissance économique à l’échelle régionale, mais avec des informations limitées sur la dynamique des cours d'eau, il est difficile pour les pays riverains de tirer profit de ce potentiel et d'investir dans le développement des ressources en eau. Des informations précises sont nécessaires pour so...

Le fleuve Congo est navigable sur une grande partie de sa longueur et il joue un rôle crucial dans les économies de neuf pays du bassin. Les usagers du fleuve dépendent du transport fluvial pour accéder aux marchés, aux ressources et aux services essentiels. Ces utilisateurs vont des millions de petits utilisateurs informels aux utilisateurs indust...

Soil erosion-associated sedimentation has become a significant global threat to sustainable land and water resources management. Semi-arid regions that characterise much of southern Africa are particularly at risk due to extreme hydrological regimes and sparse vegetative cover. This study aims to address the need for an erosion and sediment deliver...

The characteristics of a sub-basin's long-term hydrological behaviour are used as multiple constraint filters for constraining hydrological model simulations in the Congo Basin using the monthly time step Pitman model. The results suggest that the constraints are appropriate in many sub-basins (≥20 gauging stations), but not all. Detailed examinati...

Wetlands are important components of many large river systems. Some basin scale hydrological models do include explicit sub-models to deal with wetland impacts, but one of the key challenges is to estimate appropriate parameter values to represent the channel-wetland exchange processes. A combined modelling approach is applied in this study and inv...

Vegetation cover is an important factor controlling erosion and sediment yield. Therefore, its effect is accounted for in both experimental and modelling studies of erosion and sediment yield. Numerous studies have been conducted to account for the effects of vegetation cover on erosion across spatial scales; however, little has been conducted acro...

Africa is severely affected by floods, with an increasing vulnerability to these events in the most recent decades. Our improved preparation against and response to this hazard would benefit from an enhanced understanding of the physical processes at play. Here, a database of 399 African stream gauges is used to analyze the seasonality of observed...

The African continent is probably the one with the lowest density of hydrometric stations currently measuring river discharge despite the fact that the number of operating stations was quite important until the 1970s. This new African Database of Hydrometric Indices (ADHI) provides a wide range of hydrometric indices and hydrological signatures com...

The main objective of this study was to use an uncertainty version of a widely used monthly time step, semi‐distributed model (the Pitman model) to explore the equifinalities in the way in which the main hydrological processes are simulated and any identifiable linkages with uncertainties in the available observational data. The study area is the Z...

Study region : The Zambezi River basin, a transboundary basin supplying vital resources to vast human and environmental systems and subject to radical changes linked to climate and infrastructural development. Study focus : Application of a hydrological model (Pitman) established for 76 sub-basins covering the total basin area of about 1 350 000 k...

Study region : The Zambezi River basin, one of the most important water resources in sub-Saharan Africa from both a water supply and hydro-power generation perspective. Study focus : Calibration of two hydrological models (Pitman and WEAP) that have been established for 76 sub-basins covering the total basin area of about 1 350 000 km². The longer...

The African continent is probably the one with the lowest density of hydrometric stations currently measuring river discharge, despite the fact that the number of operating stations was quite important until the 70s. This new African Database of Hydrometric Indices (ADHI) is compiling data from different sources carefully checked for quality contro...

The proposed site for the construction of a new dam (Laleni Dam) on the Tsitsa River in the Eastern Cape, South Africa falls within a high soil erosion zone, which is expected to affect the lifespan of the dam. Estimating the sediment yield of the catchment is important from a management perspective, and thus we designed this study to assess the ap...

The main objective of this study was to use an uncertainty version of a widely used monthly time step, semi-distributed model (the Pitman model) to explore the equifinalities in the way in which the main hydrological processes are simulated and any identifiable linkages with uncertainties in the available observational data. The study area is the Z...

Study region The five drainage systems of the Congo River Basin in central Africa. Study focus This study aims to establish uncertainty ranges of hydrologic indices and to provide a basis for transferring hydrologic indices from gauged to ungauged sub-basins by identifying the most influential climate and physiographic attributes. New insights fo...

Seven years ago, Elsevier’s Journal of Hydrology: Regional Studies (EJRH) started its life as a companion title to the highly-respected Journal of Hydrology. EJRH publishes original research papers enhancing the science of hydrology and aiming at region-specific problems, past and future conditions, analysis, review and solutions. The journal parti...

Study region: South Africa, Lesotho and Swaziland. Study focus: The focus of this study is on the development of simple transmission loss functions that can account for channel evaporation and alluvial storage losses from upstream flows in the downstream sub-basins of large river systems. New hydrological insights for this region: The importance of...

Satellite imagery has been widely used to delineate, map and monitor different wetland types. However, the influence of clouds and spectral confusion between wetlands and other land cover types has a negative effect on classification accuracies across nearly all methods. Most wetlands are topographic lowlands surrounded by uplands, and this study e...

Study region Sub-Saharan Africa. Study focus Water resources availability assessments are highly uncertain due to inadequate observation networks, and this is expected to get worse into the future. This uncertainty is expected to increase in the future due to climate, environmental, population and other socio-economic development changes. New hyd...

The MUSLE is used within hydrological models to estimate sediment yields from catchments of various sizes, but the spatial scale dependency issues associated with estimating the MUSLE parameters has not been adequately addressed. In the absence of detailed observed data on both hydrological response and sediment yield, some analytical approaches an...

The level of complexity, and the number of parameters, to include in a hydrological model is a relatively contentious issue in hydrological modelling. However, it can be argued that explicitly representing important runoff generation processes can improve the practical value of a model's outputs. This paper explores the benefits of including a new...

Understanding the impact of key hydrological processes on the availability of water resources is an integral component of equitable and sustainable integrated water resource management. Previous hydrological studies conducted in the Limpopo River Basin have revealed a gap in the understanding of surface water-groundwater interactions, particularly...

Water availability is one of the major societal issues facing the world. The ability to understand and quantify the impact of key hydrological processes, on the availability of water resources, is therefore integral to ensuring equitable and sustainable resource management. Channel transmission losses are an under-researched hydrological process th...

The demand for water resources is rapidly growing, placing more strain on access to water and its management. In order to appropriately manage water resources, there is a need to accurately quantify available water resources. Unfortunately, the data required for such assessment are frequently far from sufficient in terms of availability and quality...

The aim of hydrological research has always been, and should still be to improve our understanding of hydrologic processes. Catchment hydrological response has the potential to enhance understanding of these processes. Regionalisation of hydrological response is important in identifying watersheds with similar catchment hydrological response, thus...

The estimation of soil loss and sediment transport is important for effective management of catchments. A model for semi-arid catchments in southern Africa has been developed; however, simplification of the model parameters and further testing are required. Soil loss is calculated through the Modified Universal Soil Loss Equation (MUSLE). The aims...

Sustainable management of water resources and associated freshwater ecosystems fundamentally requires datasets that describe water availability within a catchment. However, the required level of hydrological monitoring data (e.g. long term river gauging) is rarely available, in particular in developing countries, making the application of good wate...

In the absence of historical observed data, models are generally used to describe the different hydrological processes and generate data and information that will inform management and policy decision making. Ideally, any hydrological model should be based on a sound conceptual understanding of the processes in the basin and be backed by quantitati...

Due to the degeneration of water quality globally, water quality models could increasingly be utilised within water resource management. However, a lack of observed data as well as financial resources often constrain the number of potential water quality models that could practically be utilised. This study presents the Water Quality Systems Assess...

The focus of this study is on bias correcting semi-distributed rainfall inputs into a hydrological model applied in the Okavango River basin in southern Africa where there are very few local observations and heavy reliance is placed on global rainfall datasets. While the hydrological model, before rainfall bias correction, is able to represent the...

Study region: The 5 river basins that flow through or within Swaziland in southern Africa. Study focus: A regional water resource assessment using an uncertainty version of the Pitman monthly rainfall-runoff model whose outputs are constrained by six indices of natural hydrological response (mean monthly runoff, mean monthly groundwater recharge, Q...

Water resources allocation decisions have always been subject to uncertainty, but it has rarely been explicitly included. Greater competition for scarce resources and future uncertainties in supply suggest that risk estimates are required for different management decisions. Models are often used to generate information that can be used in decision...

Desktop approaches to setting environmental flow requirements (EFRs) have the potential to be useful in situations where resources (time, expertise, and information) are limited, but they will almost always provide estimates with lower confidence, or higher uncertainty, than more comprehensive assessments. There is a continuum between desktop appro...

A model designed to disaggregate the water balance components of a monthly water resources system model to daily time series is presented. The objective of the model is to add value to existing monthly model setups and to provide daily water balance data for a water quality model. The model components include the disaggregation of incremental catch...

Editors of several journals in the field of hydrology met during the Assembly of the International Association of Hydrological Sciences—IAHS (within the Assembly of the International Union of Geodesy and Geophysics—IUGG) in Prague in June 2015. This event was a follow-up of a similar meeting held in July 2013 in Gothenburg (as reported by Blöschl e...

Editors of several journals in the field of hydrology met during the Assembly of the International Association of Hydrological Sciences—IAHS (within the Assembly of the International Union of Geodesy and Geophysics—IUGG) in Prague in June 2015. This event was a follow-up of a similar meeting held in July 2013 in Gothenburg (as reported by Blöschl e...

The present study assessed rainwater quantity and quality in the Grahamstown area of Makana Local Municipality in the Eastern Cape Province of South Africa. Rainwater samples from 9 sampling sites were taken opportunistically and analysed for the concentration of Escherichia coli, pH and turbidity in February and April 2013. A simple rainwater harv...

During the four decades of Keith Beven's career there have been many developments in the science of hydrological modelling. Some have focused on the links between hydrological process understanding and the structure and complexity of hydrological models, others on the related issues of modelling uncertainty. The southern Africa region continues to...

Study region: Selected countries in southern Africa. Study focus: The study uses a combination of a monthly rainfall-runoff model and a daily rainfall based disaggregation method to simulate daily flows. The two models were forced with different rainfall data (local and global) and the results examined to determine the major reasons for modelling s...

This review assesses the potential of the African continent to contribute to the three main targets of the new science decade of IAHS (Panta Rhei): understanding, estimation and prediction, and science in practice. The continent has an extremely diverse climate and physical environment, and is faced with many problems in the interaction between hyd...

Editor D. Koutsoyiannis; Guest editor G. Mahé Interactions between surface water and groundwater systems in fractured rock environments, covering large parts of southern Africa, are poorly understood, such that modelling the different water balance components is highly uncertain. Some of these uncertainties are highlighted and attempts are made to...

Future flow regimes will be different to today and imperfect knowledge of present and future climate variations, rainfall–runoff processes and anthropogenic impacts make them highly uncertain. Future water resources decisions will rely on practical and appropriate simulation tools that are sensitive to changes, can assimilate different types of cha...

Modelling uncertainty under future climate change and socio-economic development is essential for adaptive planning and sustainable management of water resources. This is the first study in South Africa incorporating uncertainty within climate and development scenario modelling for understanding the implications on water availability through compar...

A monthly to daily streamflow disaggregation method is presented as part of an emerging water quality model designed to link with established monthly hydrology and yield models. The daily time step is assumed necessary for simulating water quality dynamics. The method is tested on two catchments in South Africa where observed daily flow data are av...

Uncertainty analysis has become the standard approach to hydrological modelling, but has yet to be effectively used in practical water resources assessment. This study of the Great Ruaha River basin in Tanzania is based on the use of regional estimates of mean runoff, groundwater recharge and three flow points on flow duration curves (FDCs) to cons...

Temporal variability can result from shifts in climate, or from changes in the runoff response due to land- or water-use changes, and represents a potential source of uncertainty in calibrating hydrological models. Parameter values were determined using Monte Carlo parameter sampling methods for a monthly rainfall-runoff model (Pitman model) for di...

The increasing level of competition in scientific publishing arguably has a greater negative impact on hydrologists from developing countries and specifically young scientists. This paper discusses the constraints they face and offers suggestions to authors and the hydrological community about how these may be mitigated. These include a lack of acc...

An approach is presented for desktop-level environmental flow requirement (EFR) determination that is aligned with the Habitat Flow–Stressor Response (HFSR) method which evolved in South Africa over recent years. The HFSR method integrates hydrological, hydraulic and ecological habitat data, involves ecological and hydraulic specialists and is data...

This study combines the application of a hydrological model with the use of field data derived from short period measurement campaigns at two sites, one a low topography forested area and the other a steep grassland catchment. The main objective was to determine if the structure of the widely used Pitman model could be considered appropriate for si...

The processes that occur in wetlands and natural lakes are often overlooked and not fully incorporated in the conceptual development of many hydrological models of basin runoff. These processes can exert a considerable influence on downstream flow regimes and are critical in understanding the general patterns of runoff generation at the basin scale...

in hydrological information of the Congo Basin increase uncertainties in understanding hydroclimatic processes in the basin, and consequently the risks associated with decision making for major water resources development plans. There is also uncertainty about the predictions of future climate and land use change. These challenges make it essential...

Uncertainties associated with General Circulation Models (GCMs) and the downscaling methods used for regional or local scale hydrological modelling can result in substantial differences in estimates of future water resources availability. This paper assesses the skill of nine statistically downscaled GCMs in reproducing historical climate for 15 ca...

The development of watershed models with minimal quantified uncertainty under nonstationary conditions is a major challenge in the field of hydrology. This is especially problematic in data-poor areas where values for model inputs are lacking or measured on temporally and/or spatially sparse scales. The objective of this work is to conduct a global...

The 40th anniversary of the initial development of the Pitman rainfall-runoff (developed in South Africa and widely applied throughout southern Africa) approximately coincides with the end of the IAHS PUB programme and the start of a new decade focussing on hydrological change (Panta Rhei) and society. The paper reviews the developments and applica...

Africa's water challenges calls for the continent to develop its own skilled body of expertise. The students at SSAWRN are conducting projects that are aligned to applied research, and that address the solutions to identified socioeconomic problems affecting various countries, thus creating a bridge between academia and society. The SSAWRN has enco...

In semi-arid, groundwater-dependent regions of South Africa, allocation of additional water resources can become problematic in the absence of quantified regional groundwater recharge values. In this study in the northern Sandveld, remote-sensing-data products for precipitation (P) and evapotranspiration (ET) are used to quantify groundwater rechar...

The new Scientific Decade 2013–2022 of IAHS, entitled “Panta Rhei—Everything Flows”, is dedicated to research activities on change in hydrology and society. The purpose of Panta Rhei is to reach an improved interpretation of the processes governing the water cycle by focusing on their changing dynamics in connection with rapidly changing human syst...

The Prediction in Ungauged Basins (PUB) initiative of the International Association of Hydrological Sciences (IAHS), launched in 2003 and concluded by the PUB Symposium 2012 held in Delft (23–25 October 2012), set out to shift the scientific culture of hydrology towards improved scientific understanding of hydrological processes, as well as associa...

A simple model has been developed to simulate the relationships between stream flow and point and diffuse nutrient concentrations. The point source component is based on a mechanistic approach (including uncertainty), while the diffuse component relies on a statistical regression model. The model is explained and its application illustrated using f...

The most appropriate scale to use for hydrological modelling depends on the model structure, the purpose of the results and the resolution of available data used to quantify parameter values and provide the climatic forcing. There is little consensus amongst the community of model users on the appropriate model complexity and number of model parame...

Predicting water runoff in ungauged water catchment areas is vital to practical applications such as the design of drainage infrastructure and flooding defences, runoff forecasting, and for catchment management tasks such as water allocation and climate impact analysis. This full colour book offers an impressive synthesis of decades of internationa...

The Russian ECOMAG model has been suggested as a possible candidate for use in South Africa, and this aims to evaluate its suitability for use under South African conditions. In the abscence of the software code, the ECOMAG Model was evaluated qualitatively (without setting up and running it) against the South African equivalent models such as the...

The practical application of hydrological uncertainty models that are designed to generate multiple ensembles can be severely restricted by the available computer processing power and thus, the time taken to generate the results. CPU clusters can help in this regard, but are often costly to use continuously and maintain, causing scientists to look...

This study assesses the hydrological response of the Congo Basin’s runoff to future changes of climatic conditions. The study is carried out at the sub-basin scale in the northern part of the Congo Basin for which downscaled GCM data have been obtained. In order to assess the impacts of climate change scenarios on water resources availability of th...

Multiple linear regression equations are derived for the estimation of rainfall variables, specifically mean annual rainfall, from three physiographic variables, namely, altitude, longitude and exposure. The relationships can be used to estimate mean annual catchment rainfal1s which can then provide a weighting factor to correct daily or monthly st...

The increasing demand for water in southern Africa necessitates adequate quantification of current freshwater resources. Watershed models are the standard tool used to generate continuous estimates of streamflow and other hydrological variables. However, the accuracy of the results is often not quantified, and model assessment is hindered by a scar...

This paper represents a perspective on the education and training needs related to hydrology and water resources science within the sub-Saharan Africa region and discusses the requirements of the region, some of the relatively recent developments and initiatives and some of the constraints that exist and remain difficult to surmount. The requiremen...

A monthly time step hydrological model was applied with the aim to address the challenge of water resources estimation in the Congo basin. This paper presents the results of an initial calibration of the model in the basin. In the absence of adequate local input rainfall data for the model, global datasets (CRU TS 2.1 and GHCN-v1) were explored as...

Analyses of long records of rainfall data indicate that the African climate has always been variable both intra-seasonally and inter-seasonally. Associated with this variability are extreme flood and drought events that have impacted negatively on the availability and use of water resources. It is necessary to put into perspective the historical va...

One might be tempted to assume that joint projects between partners in developed and developing countries follow a one-way path in which scientific knowledge is passed on from developed to less developed regions of the world. However, experience shows that projects of this type are generally neither successful nor sustainable unless a strong two-wa...

This paper represents a perspective on the education and training needs related to hydrology and water resources science within the sub-Saharan Africa region and discusses the requirements of the region, some of the relatively recent developments and initiatives and some of the constraints that exist and remain difficult to surmount. The requiremen...

Abstract Low flows play an important role in the eco-hydrology of any natural system and within South Africa are mainly derived from near-surface interflow or deeper ground water processes. In South Africa there is much uncertainty about the dominant source of low flows in any specific basin. Understanding surface-ground water interactions and dete...

Many large basins of the world are located in developing countries where the hydrometric networks are limited and where hydrological models have the potential to contribute to water resources management. However, it is difficult to ensure that models adequately represent the dominant hydrological processes, a problem further exacerbated by spatial...

This special edition is a compilation of papers delivered orally at the workshop on regionalization of models for operational purposes in developing countries held during the joint International Association of Hydrological Sciences (IAHS) and International Association of Hydrogeologists (IAH) International Convention in Hyderabad, India during Sept...