Micha Werner

• PhD
• Professor (Associate) at IHE Delft Institute for Water Education

Study region: The Guachal River Basin (GRB), a headwater of the Cauca River in Colombia's Tropical Andes. Study focus: Droughts develop gradually, without clear time-space boundaries, affecting extensive geographical areas. When droughts occur, they exacerbate existing water scarcity, aggravating the negative impacts on vulnerable populations and e...

Droughts are often long-lasting phenomena, without a distinct start or end and with impacts cascading across sectors and systems, creating long-term legacies. Nevertheless, our current perceptions and management of droughts and their impacts are often event-based, which can limit the effective assessment of drought risks and reduction of drought im...

Droughts are often long lasting phenomena, without a distinct start or end, and with impacts cascading across sectors and systems, creating long-term legacies. Nevertheless, our current perception and management of droughts and their impacts is often event-based, which can limit the effective assessment of drought risks and reduction of drought imp...

Highlights ➢ A 2D numerical model developed in Delft 3D to study the effects of river bank stabilization ➢ Stabilizing the outer river bends results in a less sinuous and narrower channel with sharper bends. ➢ The river morphological behaviour to bank stabilization should be kept in mind while planning the land use nearby rivers Overview The purpos...

This study examines the effect of different configurations of bank stabilization configurations on river morphology utilizing the advanced modeling capabilities of Delft3D. The investigation encompasses a spectrum of dynamic changes including planform alterations, thalweg deepening, and shifts in curve geometry. Furthermore, the study explores the...

The unprecedented progress in ensemble hydro‐meteorological modelling and forecasting on a range of temporal and spatial scales, raises a variety of new challenges which formed the theme of the Joint Virtual Workshop, ‘Connecting global to local hydrological modelling and forecasting: challenges and scientific advances’. Held from 29 June to 1 July...

(Introducción): Gracias a los recientes datos provistos por los satélites GRACE, es posible, de manera preliminar, estimar los cambios en los almacenamientos de agua subterránea (GWS por sus siglas en inglés), y ofrecer, así, una herramienta novedosa y sin precedentes en el estudio de las dinámicas de los sistemas acuífero-humedal. (Objetivo): A r...

The increasing reliance on global models to address climate and human stresses on hydrology and water resources underlines the necessity for assessing the reliability of these models. In river basins where availability of gauging information from terrestrial networks is poor, models are increasingly proving to be a powerful tool to support hydrolog...

Drought events and their impacts vary spatially and temporally due to diverse pedo-climatic and hydrologic conditions, as well as variations in exposure and vulnerability, such as demographics and response actions. While hazard severity and frequency of past drought events have been studied in detail, little is known about the effect of drought man...

Human activities both aggravate and alleviate streamflow drought. Here we show that aggravation is dominant in contrasting cases around the world analysed with a consistent methodology. Our 28 cases included different combinations of human-water interactions. We found that water abstraction aggravated all drought characteristics, with increases of...

The small spatial and temporal scales at which flash floods occur make predicting events challenging, particularly in data-poor environments where high-resolution weather models may not be available. Additionally, the uptake of warnings may be hampered by difficulties in translating the scientific information to the local context and experiences. H...

Droughts and changing rainfall patterns due to natural climate variability and climate change, threaten the livelihoods of Malawi’s smallholder farmers, who constitute 80% of the population. Provision of seasonal climate forecasts (SCFs) is one means to potentially increase the resilience of rainfed farming to drought by informing farmers in their...

Drought events and their impacts vary spatially and temporally due to diverse pedo-climatic and hydrologic conditions, as well as variations in exposure and vulnerability, such as demographics and response actions. While hazardous severity and frequency of past drought events have been studied in detail, little is known about the effect of drought...

The increasing reliance on global models to address climate and human stresses on hydrology and water resources underlines the necessity for assessing the reliability of these models. In river basins where availability of gauging information from terrestrial networks is poor, models are increasingly proving to be a powerful tool to support hydrolog...

The small spatial and temporal scales at which flash floods occur make predicting events challenging, particularly in data-poor environments where high-resolution weather models may not be available. Additionally, the uptake of warnings may be hampered by difficulties in translating the scientific information to the local context and experiences. H...

Early warning systems trigger early action and enable better disaster preparedness. People-centered dissemination and communication are pivotal for the effective uptake of early warnings. Current research predominantly focuses on sudden-onset hazards, such as floods, ignoring considerable differences with slow-onset hazards, such as droughts. We id...

Dynamics of terrestrial water storage are determinant for many natural and social phenomena, with implications for water security and environmental sustainability. Here we use 2002–2017 data from the Gravity Recovery and Climate Experiment (GRACE) to study these dynamics in the Magdalena-Cauca river basin in northwestern South America. Through comp...

The area to be cropped in irrigation districts needs to be planned according to the allocated water, which in turn is a function of the available water resource. Initially conservative estimates of future (in)flows in rivers and reservoirs may lead to unnecessary reduction of the water allocated. Though water allocations may be revised as the seaso...

Reanalysis and earth observation data have enormous potential to support water resources management, particularly in river basins where data availability is poor or where available stations are unequally distributed. Despite this potential, these datasets continue to be underused around the world. In this article, we combine a recently established...

Hydrological data and information on the availability of water are essential to support water allocation decisions in irrigated agriculture, especially under increasingly water scarce conditions. However, in many agricultural regions hydrological information is scarce, leading to sub-optimal water allocation decisions and crop yield reduction. Here...

The Final Declaration of the High Level Meeting on National Drought Policy (UN HMNDP) that was held in Geneva in March 2013 clearly identified the need to promote greater collaboration to enhance the quality of local/national/regional/global preparedness to drought, identifying drought forecasting and warning as a key strategy to enhance preparedne...

This chapter focuses on the linkages between climate change adaptation and disaster risk reduction, highlighting opportunities to build more resilient systems through a combination of ‘hard’ and ‘soft’ measures.

Abstract. The area to be cropped in irrigation districts needs to be planned according to the allocated water, which in turn is a function of the available water resource. Initially conservative estimates of future (in) flows in rivers and reservoirs may lead to unnecessary reduction of the water allocated. Though water allocations may be revised a...

Previous research has found that users fail to comprehend flood hazard warning messages as well as the possible impacts of the forecast events. A proposed way to improve understanding and uptake is the implementation of impact‐based warning services. However, even though extensive qualitative research has been done on the provision of these impact‐...

This paper presents the developments of a tool for integrated water management (Herramienta para el Manejo Integral del Agua – HERMANA). HERMANA combines: real-time meteorological, hydrological, and water quality data and forecasts; information from an institutional database; surface water and groundwater models; and, drought indicators based on sa...

This guidance document provides direction to effective drought hazard and risk assessments. It is based on a new extensive inventory of drought models and tools, made available through www.droughtcatalogue.com, and a technical evaluation of these models on a set of case studies. The guidance note will hopefully provide the reader with a good overvi...

Reanalysis and earth observation data have enormous potential to support water resources management, particularly in river basins where data availability is poor or where available stations are unequally distributed. Despite this potential, these datasets continue to be underused around the world. In this article, we combine a recently established...

The area to be cropped in irrigation districts needs to be planned according to the available water resources to avoid agricultural production loss. However, the period of record of local hydro-meteorological data may be short, leading to an incomplete understanding of climate variability and consequent uncertainty in estimating surface water avail...

Abstract for EGU presentation in the session HS4.1.3 Flash floods and associated hydro-geomorphic processes: observation, modelling and warning

The area to be cropped in irrigation districts needs to be planned according to the available water resources to avoid agricultural production loss. However, the period of record of local hydro-meteorological data may be short, leading to an incomplete understanding of climate variability and consequent uncertainty in estimating surface water avail...

Drought is a widespread natural hazard and a major issue in the north-western part of Bangladesh. The characterization and identification of drought in the context of drought monitoring and management is challenging. Although several researchers have developed a variety of drought indicators, it is important to assess the effectiveness of these in...

We follow a user-based approach to examine how information supports operational drought management decisions in the Ebro basin and how these can benefit from additional information such as from remote sensing data. First we consulted decision-makers at basin, irrigation district and farmer scale to investigate the drought-related decisions they mak...

La planificación y gestión de los recursos hídricos en Colombia se fundamentan en instrumentos técnicos como el Estudio Nacional del Agua – ENA y las Evaluaciones Regionales del Agua – ERA, cuya fuente de información primaria son los registros de las estaciones hidrometeorológicas del IDEAM. El uso combinado de esta información puntual con datos de...

Hydrological modelling in the Canadian sub-Arctic is hindered by sparse meteorological and snowpack data. The snow water equivalent (SWE) of the winter snowpack is a key predictor and driver of spring flow, but the use of SWE data in hydrological applications is limited due to high uncertainty. Global re-analysis datasets that provide gridded meteo...

Sufficient and accurate hydro-meteorological data are essential to manage water resources. Recently developed global reanalysis datasets have significant potential in providing these data, especially in regions such as Southern Africa that are both vulnerable and data poor. These global reanalysis datasets have, however, not yet been exhaustively v...

We follow a user based approach to examine operational drought management decisions and how the role of information such as from remote sensing can be assessed. First we consulted decision makers at basin, irrigation district and farmer scale in the Ebro basin to investigate the drought related decisions they take and the information they use to su...

Hydrological modelling in the Canadian Sub-Arctic is hindered by sparse meteorological and snowpack data. Snow Water Equivalent (SWE) of the winter snowpack is a key predictor and driver of spring flow, but the use of SWE data in hydrological applications is limited due to high uncertainty. Global re-analysis datasets that provide gridded meteorolo...

Sufficient and accurate hydro-meteorological data are essential to manage water resources. Recently developed global re-analysis datasets have significant potential in providing these data, especially in regions such as Southern Africa that are both vulnerable and data poor. These global re-analysis datasets have, however, not yet been exhaustively...

Global datasets from water resources reanalyses are increasingly becoming available, enabling consistent assessment of water resources availability, variability and trends at the global level. These datasets are often purported to promote better decision making and policy implementation. While these claims are real, and often used to motivate resea...

Numerical weather prediction (NWP) models are fundamental to extend forecast lead times beyond the concentration time of a watershed. Particularly for flash flood forecasting in tropical mountainous watersheds, forecast precipitation is required to provide timely warnings. This paper aims to assess the potential of NWP for flood early warning purpo...

Uncertainty reduces reliability and performance of water system operations. A decision-maker can take action, accepting the present uncertainty and facing its risks, or reduce uncertainty by first obtaining additional information. Information, however, comes at a cost. The decision-maker must therefore efficiently use his/her resources, selecting t...

The implementation of drought management plans contributes to reduce the wide range of adverse impacts caused by water shortage. A crucial element of the development of drought management plans is the selection of appropriate indicators and their associated thresholds to detect drought events and monitor the evolution. Drought indicators should be...

Hydrological information on water availability and demand is vital for sound water allocation decisions in irrigation districts, particularly in times of water scarcity. However, water allocation decisions are often taken based on uncertain hydrological information, which may lead to sub-optimal decisions and agricultural production loss. This stud...

Numerical Weather Prediction (NWP) models are fundamental to extend forecast lead-times beyond the concentration time of a watershed. Particularly for flash flood forecasting in tropical mountainous watersheds, forecast precipitation is required to provide timely warnings. This paper aims to assess the potential of NWP for flood early warning purpo...

The implementation of drought management plans contributes to reduce the wide range of adverse impacts caused by water shortage. A crucial element of the development of drought management plans is the selection of appropriate indicators and their associated thresholds to detect drought events and monitor their evolution. Drought indicators should b...

The Magdalena Cauca Macrobasin (MCMB) in Colombia, with an area of about 257,000 km 2 , is the largest and most important water resources system in the country. With almost 80% of the Colombian population (46 million people) settled in the basin, it is the main source of water for demands including human consumption, agriculture , hydropower genera...

The La Niña event of 2010–11, and the consequent severe floods that affected a large part of the Magdalena-Cauca basin in Colombia, underlined several weaknesses in the approach to managing flood risks in the country. One identified weakness was the absence of advance warning of flood events through flood forecasting and warning systems. Although a...

The Magdalena - Cauca Basin (257,000 km2) - McMC, formed by the two rivers of the same names, is the most important hydrosystem in Colombia. In this watershed the Institute of Hydrology, Meteorology and Environmental Studies in Colombia (IDEAM) is responsible for the hydroclimatological monitoring. IDEAM also formulates, every four years, the Natio...

This poster is presented in EGU General Assembly 2016.

A distributed model (TETIS), a semi-distributed model (TOPMODEL) and a lumped model (HEC HMS soil moisture accounting) were used to simulate the discharge response of a tropical high mountain basin characterized by soils with high water storage capacity and high conductivity. The models were calibrated with the Shuffle Complex Evolution algorithm,...

An analysis of observed trends in African annual-average near-surface temperatures over the last five decades reveals drastic increases, particularly over parts of the subtropics and central tropical Africa. Over these regions, temperatures have been rising at more than twice the global rate of temperature increase. An ensemble of high-resolution d...

A regional analysis of flood risk was carried out in the mountainous area surrounding the city of Bogotá (Colombia). Vulnerability at regional level was assessed on the basis of a principal component analysis carried out with variables recognised in literature to contribute to vulnerability; using watersheds as the unit of analysis. The area expose...

The rainfall in southern Africa has a large inter-annual variability, which can cause rain-fed agriculture to fail. The staple crop maize is especially sensitive to dry spells during the early growing season. An early prediction of the probability of dry spells and below normal precipitation can potentially mitigate damages through water management...

Drought forecasting and warning is increasingly recognised as a key element in a comprehensive drought management strategy. This was clearly underlined in the Final Declara- tion of the High Level Meeting on National Drought Policy (HMNDP) held in Geneva in March 2013. From 2011 through 2013 a consortium of 19 partners collaborated within the con-...

Data and information plays a crucial role in quantifying the abundance of the available water resource and the demand placed on it in water scarce regions, and is central to decision making. This is particularly so for water allocation decisions in large irrigation districts. However, in most irrigation schemes data collection is normally limited d...

Ensemble hydrological predictions are normally obtained by forcing hydrological models with ensembles of atmospheric forecasts produced by numerical weather prediction models. To be of practical value to water users, such forecasts should not only be sufficiently skilful, they should also provide information that is relevant to the decisions end us...

Purpose – The purpose of this study is to provide recommendations for improving the social performance of warnings using mobile services in flash flood prone communities. A warning cannot be considered effective until it is received, understood and responded to by those at risk. This is defined as the social performance of warning communication tec...

Assessing the water supply reliability in river basins is essential for adequate planning and development of irrigated agriculture and urban water systems. In many cases hydrological models are applied to determine the surface water availability in river basins. However, surface water availability and variability is often not appropriately quantifi...

If the future availability of water is uncertain to water managers, dam operators and water users, then an effective allocation among competing uses can be difficult. The difficulties can partly be alleviated by including streamflow forecasting as a tool for informed decision making. The Incomati basin in Southern Africa frequently experiences wate...

A method for assessing regional debris flow susceptibility at the watershed scale, based on an index composed of a morphometric indicator and a land cover indicator, is proposed and applied in 106 peri-urban mountainous watersheds in Bogotá, Colombia. The indicator of debris flow susceptibility is obtained from readily available information common...

Ensemble hydrological predictions are normally obtained by forcing hydrological models with ensembles of atmospheric forecasts produced by Numerical weather prediction models. To be of practical value to water users, such forecasts should not only be sufficiently skilful, they should also provide information that is relevant to the decisions end us...

In order to include the water quality state in the reservoir release policy for long and short term optimization, a forecasting surrogate model was developed using M5 model trees algorithm. This data-driven model is able to recreate the state of the system while reducing the number of input variables from the original numerical model. After testing...

Droughts are widespread natural hazards and in many regions their frequency seems to be increasing. A finer-resolution version (0.05° × 0.05°) of the continental-scale hydrological model PCRaster Global Water Balance (PCR-GLOBWB) was set up for the Limpopo River basin, one of the most water-stressed basins on the African continent. An irrigation mo...

One of the main problems in the water supply system in the city of Cali is related to the water quality of the Cauca River. An important source of pollution upstream of the intake of the Puerto Mallarino Treatment Plant (PMTP) is the south channel, part of the South Drainage System (SDS), which discharges into the Cauca River. The existing Early Wa...

Drought warning provides a potentially efficient approach to mitigation of drought impacts, and should be targeted at areas most vulnerable to being adversely impacted. Assessing drought vulnerability is, however, complex and needs to consider susceptibility to drought impact as well as the capacity to cope with drought. In this paper a Drought Vul...

Subsistence farming in southern Africa is vulnerable to extreme weather conditions. The yield of rain-fed agriculture depends largely on rainfall-related factors such as total seasonal rainfall, anomalous onsets and lengths of the rainy season and the frequency of occurrence of dry spells. Livestock, in turn, may be seriously impacted by climatic s...

Droughts are widespread natural hazards and in many regions their frequency seems to be increasing. A finer resolution version (0.05° x 0.05°) of the continental scale hydrological model PCR-GLOBWB was set up for the Limpopo river basin, one of the most water stressed basins on the African continent. An irrigation module was included to account for...

Evaporation is a key process in the water cycle, with implications ranging from water management, to weather forecast and climate change assessments. The estimation of continental evaporation fluxes is complex and typically relies on continental-scale hydrological or land-surface models. However, it appears that most global or continental-scale hyd...

This paper presents an analysis of uncertainty in hydraulic modelling of floods, focusing on the inaccuracy caused by inflow errors and parameter uncertainty. In particular, the study develops a method to propagate the uncertainty induced by, firstly, application of a stage-discharge rating curve and, secondly, parameterisation of a onedimensional...

Endorheic basins, often found in semi-arid and arid climates, are particularly sensitive to changes in climatological fluxes such as precipitation, evaporation and runoff, resulting in variability of river flows as well as of water levels in end-point lakes that are often present. In this paper we apply the Indicators of Hydrological Alteration (IH...

The rainfall in Southern Africa has a large interannual variability, which can cause rain-fed agriculture to fail. The staple crop maize is especially sensitive to dry spells during the early growing season. An early prediction of the probability of dry spells and below normal precipitation can potentially mitigate damages through water management....

Subsistence farming in Southern Africa is vulnerable to extreme weather conditions. The yield of rain-fed agriculture depends largely on rainfall-related factors such as total seasonal rainfall, anomalous onsets and lengths of the rainy season and the frequency of occurrence of dry spells. Livestock, in turn, may be seriously impacted by climatic s...

A classification of susceptibility to flooding of 106 mountain watersheds was carried out in Bogotá (Colombia) through the use of an index composed of a morphometric indicator and a land cover indicator. Susceptibility was considered to increase with flashiness and the possibility of debris flows. Morphological variables recognised in literature to...

RESUMEN En la ciudad de Cali, Colombia, una de las fuentes más importantes de contaminación aguas arriba de la bocatoma de la Planta de Tratamiento de Puerto Mallarino (PTPM) es el Canal Sur que forma parte del Sistema de Drenaje Sur (SDS). El prototipo desarrollado de Sistema de Alerta Temprana denominado SAT Centinela, permite estimar el nivel de...

The aim of this review is to provide a basis for selecting a suitable hydrological model, or combination of models, for hydrological drought forecasting in Africa at different temporal and spatial scales; for example short and medium range (1–10 days or monthly) forecasts at medium to large river basin scales or seasonal forecasts at the Pan-Africa...