Jamie Hannaford

UK Centre for Ecology & Hydrology | CEH · UK Centre for Ecology and Hydrology Wallingford

There is a burgeoning international literature on hydro-climatic trend detection, motivated by the need to detect and interpret any emerging changes in river flows associated with anthropogenic climate change. The UK has a particularly strong evidence base in this area thanks to a well-developed monitoring programme and a wealth of studies publishe...

This paper outlines the hydrological aspects of the 2013/2014 winter flooding in the UK, as well as the impacts. The episode is considered in a long-term historical context and wider issues raised by the flood events are discussed briefly.

Hydrological classification systems seek to provide information about the dominant processes in the catchment to enable information to be transferred between catchments. Currently there is no widely agreed-upon system for classifying river catchments. This paper develops a novel approach to classifying catchments based on the temporal dependence st...

Drought monitoring and early warning (M & EW) systems are a crucial component of drought preparedness. M & EW systems typically make use of drought indicators such as the Standardised Precipitation Index (SPI), but such indicators are not widely used in the UK. More generally, such tools have not been well developed for hydrological (i.e. streamflo...

Drought indicators are proliferating, but with little consideration of which are most meaningful for describing drought impacts. A number of recent reviews compare different drought indicators, but none assess which indicators are actually used in the many operational drought monitoring and early warning efforts, why they were selected, or whether...

When extreme hydrological events (floods and droughts) occur, there is inevitably speculation that such events are a manifestation of anthropogenic global warming. The UK is generally held as a wet country, but recent drought events in the UK have led to growing concerns around droughts becoming more severe – for sound scientific reasons, given phy...

Meteorological and hydrological hazards present challenges to people and ecosystems worldwide, but the limited length of observational data means that the possible extreme range is not fully understood. Here, a large ensemble of climate model data is combined with a simple grid-based hydrological model to assess unprecedented but plausible hydrolog...

Flash droughts have been the subject of a great deal of scientific attention in the last decade, but the greatest emphasis has been on relatively dry climates. Here, we characterised the occurrence of this type of rapid-onset drought events in a more humid setting, the United Kingdom (UK), for the period 1969–2021. Our results show that flash droug...

This study evaluates the efficacy of bias-correction (BC) and data assimilation (DA) techniques in refining hydrological model predictions. Both approaches are routinely used to enhance hydrological forecasts, yet there have been no studies that have systematically compared their utility. We focus on the application of these techniques to improve o...

Understanding temporal trends in low streamflows is important for water management and ecosystems. This work focuses on trends in the occurrence rate of extreme low‐flow events (5‐ to 100‐year return periods) for pooled groups of stations. We use data from 1,184 minimally altered catchments in Europe, North and South America, and Australia to disce...

Meteorological and hydrological hazards present challenges to people and ecosystems worldwide, but the limited length of observational data means that the possible extreme range is not fully understood. Here, a large ensemble of climate model data is combined with a simple grid-based hydrological model, to assess unprecedented but plausible hydrolo...

The summer of 2022 was particularly notable for the prolonged and extensive hot and dry conditions experienced across the UK. The resultant 2022 drought had widespread impacts and prompted much discussion about the continuing vulnerability of the UK to drought, particularly in the context of anthropogenic warming. Here, we briefly describe the evol...

Hydrological drought is a serious issue globally, which is likely to be amplified by 21st century climate change. In the UK, the impacts of changes in river flow and groundwater drought severity in a future of climate change and higher water demand are potentially severe. Recent publication of a new nationally consistent set of river flow and groun...

Hydrological data are the foundation of hydrological research, as well as effective water management. Hydrological data are therefore of pivotal importance to any drought or low flow study. While there have been significant advances in hydrological data acquisition, analysis and dissemination in recent decades, it is still crucially important to en...

Droughts in Thailand are becoming more severe due to climate change. Developing a reliable drought monitoring and early warning system (DMEWS) is essential to strengthen a country's resilience to droughts. However, for a DMEWS to be valuable, the drought indicators provided to stakeholders must have relevance to tangible impacts on the ground. Here...

How climate change will affect spatial coherence of droughts is a key question that water managers must answer in order to adopt strategies to mitigate impacts on water resources. Water transfers from regions with excess to those in deficit are fundamental to such strategies, but only possible if both regions are not simultaneously under drought co...

Droughts in Thailand are becoming more severe due to climate change. Developing a reliable Drought Monitoring and Early Warning System (DMEWS) is essential to strengthen a country’s resilience to droughts. However, for a DMEWS to be valuable, the drought indicators it provides stakeholders must have relevance to tangible impacts on the ground. Here...

Understanding the current hydro-meteorological situation is critical to manage extreme events and water resources. The United Kingdom Water Resources Portal (UKWRP) has been developed to enable dynamic, interactive access to hydro-meteorological data across the United Kingdom, including catchment daily rainfall (near), real-time daily mean river fl...

This study presents a new data set of gauged streamflow (N = 3,224) for Europe spanning the period 1962–2017. The Monthly Streamflow of Europe Dataset (MSED) is freely available at http://msed.csic.es/. Based on this data set, changes in the characteristics of hydrological drought (i.e., frequency, duration, and severity) were assessed for differen...

This study identifies significant periodicities in streamflow dynamics across western Europe using a hydrological database encompassing 1874 monthly series from catchments in Ireland, the United Kingdom, France, Spain and Portugal, spanning the years 1962 to 2012. Significant and synchronous periodicities with the main atmospheric mechanisms over t...

This paper combines evidence from the analyses of large sets of newspaper material and long-term rainfall records to gain insights into representations of drought events in the United Kingdom, between 1800 and 2014. More specifically, we bring together two different, though complementary, approaches to trace longitudinal patterns in the ways drough...

This paper presents an ‘enhanced future FLows and Groundwater’ (eFLaG) dataset of nationally consistent hydrological projections for the UK, based on the latest UK Climate Projections (UKCP18). The hydrological projections are derived from a range of river flow models (Grid-to-Grid, PDM, GR4J and GR6J), to provide an indication of hydrological mode...

Soil moisture is an important component of the Earth system and plays a key role in land-atmosphere interactions. Remote sensing of soil moisture is of great scientific interest and the scientific community has made significant progress in soil moisture estimation using Earth observations. Currently, several satellite-based coarse spatial resolutio...

Between 2016 and 2019, the UK was in a period of prolonged dry conditions with varying spatial and temporal foci. We look at the rainfall, river flows, soil moisture and drought impacts leading up to and including the heatwave of 2018, and the following year, placing the events into historical context. Using incident data from the UK regulators, we...

Between June 2019 and February 2020 the UK saw a succession of severe flood events. Many river flows in northern England, the Midlands and on both sides of the English/Welsh border exceeded their highest on record, and some defences were overwhelmed. The impact of widespread, prolonged and in places, repeated flooding reinforces the importance of d...

A cluster of recent floods in the UK has prompted significant interest in the question of whether floods are becoming more frequent or severe over time. Many trend assessments have addressed this in recent decades, typically concluding that there is evidence for positive trends in flood magnitude at the national scale. However, trend testing is a c...

Despite being one of the most damaging natural hazards, droughts and their spatiotemporal dynamics are typically not well understood. Great Britain, which is the focus of this work, has experienced many major drought episodes in the past, causing a range of socioeconomic and environmental impacts. Here, we apply a recently developed technique to id...

We present the first large-sample catchment hydrology dataset for Great Britain, CAMELS-GB (Catchment Attributes and MEteorology for Large-sample Studies). CAMELS-GB collates river flows, catchment attributes and catchment boundaries from the UK National River Flow Archive together with a suite of new meteorological time series and catchment attrib...

Numerous indices exist for the description of hydrological drought. The EURO FRIEND-Water Low flow and Drought Group has repeatedly discussed changing paradigms in the perception and use of existing and emerging new indices for hydrological drought identification and characterization. Group members have also tested the communication of different in...

Geographic and socio-economic factors combined make China particularly vulnerable to droughts. Here we review academic literature to assess publication trends on the topics of drought monitoring and early warning in China, exploring the common themes and recent advances presented. Literature searches for the 1970–2017 period were made for a range o...

Drought is an inherent meteorological characteristic of any given region, but is particularly important in China due to its monsoon climate and the “three ladder” landform system. The Chinese government has constructed large-scale water conservation projects since 1949, and developed drought and water scarcity relief frameworks. However, drought st...

We analysed long‐term variability and trends in meteorological droughts across Western Europe using the Standardized Precipitation Index (SPI). Precipitation data from 199 stations spanning the period 1851–2018 were employed, following homogenisation, to derive SPI‐3 and SPI‐12 series for each station, together with indices on drought duration and...

Drought risk assessment is a vital part of drought risk management, which plays an important role in drought mitigation. Due to its complexity, drought risk is difficult to define and challenging to quantitatively assess, as the drought impacts associate with many social sectors. This contribution method the issue by quantitatively evaluating the y...

Abstract. We present the first large-sample catchment hydrology dataset for Great Britain, CAMELS-GB (Catchment Attributes and MEteorology for Large-sample Studies). CAMELS-GB collates river flows, catchment attributes and catchment boundaries from the UK National River Flow Archive together with a suite of new meteorological timeseries and catchme...

Drought is a ubiquitous and recurring hazard that has wide-ranging impacts on society, agriculture and the environment. Drought indices are vital for characterising the nature and severity of drought hazards, and there have been extensive efforts to identify the most suitable drought indices for drought monitoring and risk assessment. However, to d...

Historical precipitation records are fundamental for the management of water resources, yet rainfall observations typically span 100–150 years at most, with considerable uncertainties surrounding earlier records. Here, we analyse some of the longest available precipitation records globally, for England and Wales, Scotland and Ireland. To assess the...

Hydrological droughts occur in all climate zones and can have severe impacts on society and the environment. Understanding historical drought occurrence and quantifying severity is crucial for underpinning drought risk assessments and developing drought management plans. However, hydrometric records are often short and capture only a limited range...

Attribution of trends in streamflow is complex, but essential, in identifying optimal management options for water resources. Disagreement remains on the relative role of climate change and human factors, including water abstractions and land cover change, in driving change in annual streamflow. We construct a very dense network of gauging stations...

Drought is a ubiquitous and reoccurring hazard that has wide ranging impacts on society, agriculture and the environment. Drought indices are vital for characterizing the nature and severity of drought hazards, and there have been extensive efforts to identify the most suitable drought indices for drought monitoring and risk assessments. However, t...

Persistent atmospheric high pressures can lead to long-lasting droughts and heatwaves with severe societal and environmental impacts, as evident in summer 2018 in Europe. It is known that oceanic and atmospheric features connected with the tropical Pacific influence the atmospheric circulation regimes over the North Atlantic/European sector leading...

Climate change has led to concerns about increasing river floods resulting from the greater water-holding capacity of a warmer atmosphere¹. These concerns are reinforced by evidence of increasing economic losses associated with flooding in many parts of the world, including Europe². Any changes in river floods would have lasting implications for th...

Hydrological models can provide estimates of streamflow pre- and post-observations, which enable greater understanding of past hydrological behaviour, and potential futures. In this paper, a new multi-objective calibration method was derived and tested for 303 catchments in the UK, and the calibrations were used to reconstruct river flows back to 1...

Hydrological droughts occur in all climate zones and can have severe impacts on society and the environment. Understanding historical drought occurrence and quantifying severity is crucial for underpinning drought risk assessments and the developing drought management plans. However, hydrometric records are often short and capture only a limited ra...

Long-term planning of water resources has been a key requirement of the providers of water supplies, and this is extremely important nowadays. There are multiple competing demands on public water supplies due to increasing populations, climate change and the need to protect the environment. In the UK, public water supply is provided by around 25 w...

This article presents an analysis of the response of the annual crop yield in five main dryland cultivations in the United States to different time-scales of drought, and explores the environmental and climatic characteristics that determine the response. For this purpose we analysed barley, winter wheat, soybean, corn and cotton. Drought was quant...

We analyzed the relationships between meteorological drought and hydrological drought using very dense and diverse network of gauged natural drainage basins across the conterminous U.S. Specifically, this work utilized a dataset of 289 gauging stations, covering the period 1940–2013. Drainage basins were obtained for each gauging station using a di...

A thorough understanding of the recurrence intervals of peak river flows (typically annual maximum, AMAX, flows) is of crucial importance for designing engineering solutions that will effectively mitigate the negative consequences of flooding for people and the environment. However, flood risk assessments are typically based on an assumption of sta...

Drought is widely written about as a complex, multifaceted phenomenon, with complexity arising not just from biophysical drivers, but also human understanding and experiences of drought and its impacts. This has led to a proliferation of different drought definitions and indicators, creating a challenge for the design of drought monitoring and earl...

Studies on past trends in drought indices and, in particular, those of hydrological drought have revealed complex patterns of variability and provided some emerging signals that could facilitate early detection of potential future changes in drought hazard. This chapter reviews studies from European projects that span a range of countries and scale...

In North America, the occurrence of extreme drought events has increased significantly in number and severity over the last decades. Past droughts have contributed to lower agricultural productivity in major farming and ranching areas across the US.We evaluated the relationship between drought indices and crop yields across the US for the period 19...

Potential evapotranspiration (PET) is a necessary input data for most hydrological models and is often needed at a daily time step. An accurate estimation of PET requires many input climate variables which are, in most cases, not available prior to the 1960s for the UK, nor indeed most parts of the world. Therefore, when applying hydrological model...

Observational trend analysis is fundamental for tracking emerging changes in river flows and placing extreme events in their longer-term historical context, particularly as climate change is expected to intensify the hydrological cycle. However, human disturbance within catchments can introduce artificial changes and confound any underlying climate...

This dataset is model output from the GR4J lumped catchment hydrology model. It provides 500 model realisations of daily river flow, in cubic metres per second (cumecs, m3/s), for 303 UK catchments for the period between 1891-2015. The modelled catchments are part of the National River Flow Archive (NRFA) (https://nrfa.ceh.ac.uk/) and provide good...

This dataset contains the Standardised Streamflow Index (SSI) data for 303 catchments across the United Kingdom from 1891 to 2015. The SSI is a drought index based on the cumulative probability of a given monthly mean streamflow occurring for a given catchment. Here, the SSI is calculated for the following accumulation periods: 1, 3, 6, 9, 12, 18 a...

Drought monitoring and early warning (M&EW) systems are an important component of agriculture/silviculture drought risk assessment. Many operational information systems rely mostly on meteorological indicators, and a few incorporate vegetation state information. However, the relationships between meteorological drought indicators and agricultural/s...

Human influences can affect streamflow drought characteristics and propagation. The question is where, when and why? To answer these questions, the impact of different human influences on streamflow droughts were assessed in England and Wales, across a broad range of climate and catchments conditions. We used a dataset consisting of catchments with...

Potential Evapotranspiration (PET) is a necessary input data for most hydrological models and is usually needed at a daily or shorter time-step. An accurate estimation of PET requires many input climate variables which are in most cases not available prior to the 1960s for the UK, nor indeed most parts of the world. Therefore, when applying hydrolo...

This paper describes the development of the first operational seasonal hydrological forecasting service for the UK, the Hydrological Outlook UK (HOUK). Since June 2013, this service has delivered monthly forecasts of streamflow and groundwater levels, with an emphasis on forecasting hydrological conditions over the next three months, accompanied by...