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 international research, forming a holistic approach to catchment hydrology and providing a one-stop resource for hydrologists in both developed and developing countries. Topics include data for runoff regionalisation, the prediction of runoff hydrographs, flow duration curves, flow paths and residence times, annual and seasonal runoff, and floods. Illustrated with many case studies and including a final chapter on recommendations for researchers and practitioners, this book is written by expert authors involved in the prestigious IAHS PUB initiative. It is a key resource for academic researchers and professionals in the fields of hydrology, hydrogeology, ecology, geography, soil science, and environmental and civil engineering.
Summer precipitation totals in the Alpine Region do not exhibit a systematic trend over the last 120 years. However, we find significant low frequency periodicity of interannual variability which ...occurs in synchronization with a dominant two-phase state of the atmospheric circulation over the Alps. Enhanced meridional flow increases precipitation variability through positive soil moisture precipitation feedbacks on the regional scale, whereas enhanced zonal flow results in less variability through constant moisture flow from the Atlantic and suppressed feedbacks with the land surface. The dominant state of the atmospheric circulation over the Alps in these periods appears to be steered by zonal sea surface temperature gradients in the mid-latitude North Atlantic. The strength and the location of the westerlies in the mid-latitude Atlantic play an important role in the physical mechanisms linking atmosphere and oceanic temperature gradients and the meridional/zonal circulation characteristics.
The Sustainable Development Goals (SDGs) of the United Nations Agenda 2030 represent an ambitious blueprint to reduce inequalities globally and achieve a sustainable future for all mankind. Meeting ...the SDGs for water requires an integrated approach to managing and allocating water resources, by involving all actors and stakeholders, and considering how water resources link different sectors of society. To date, water management practice is dominated by technocratic, scenario‐based approaches that may work well in the short term but can result in unintended consequences in the long term due to limited accounting of dynamic feedbacks between the natural, technical, and social dimensions of human‐water systems. The discipline of sociohydrology has an important role to play in informing policy by developing a generalizable understanding of phenomena that arise from interactions between water and human systems. To explain these phenomena, sociohydrology must address several scientific challenges to strengthen the field and broaden its scope. These include engagement with social scientists to accommodate social heterogeneity, power relations, trust, cultural beliefs, and cognitive biases, which strongly influence the way in which people alter, and adapt to, changing hydrological regimes. It also requires development of new methods to formulate and test alternative hypotheses for the explanation of emergent phenomena generated by feedbacks between water and society. Advancing sociohydrology in these ways therefore represents a major contribution toward meeting the targets set by the SDGs, the societal grand challenge of our time.
Plain Language Summary
Water crises that humanity faces are increasingly connected and are growing in complexity. As such, they require a more integrated approach in managing water resources,which involves all actors and stakeholders and considers how water resources link different sectors of society. Yet, water management practice is still dominated by technocratic approaches, which emphasize technical solutions. While these approaches may work in the short‐term, they often result in unintended consequences in the long‐term. Sociohydrology is developing a generalizable understanding of the interactions and feedbacks between natural,technical and social processes, which can improve water management practice. As such, advancing sociohydrology can contribute to address the global water crises and meet the water‐related targets defined by the United Nations' Sustainable Development Goals.
Key Points
The crises that humanity faces over access to a clean water supply are increasingly connected and are growing in complexity
Sociohydrology researchers must address several scientific challenges to strengthen basic knowledge and broaden the range of solvable problems
Advances in sociohydrology research are progress toward meeting the targets defined by the United Nations' Sustainable Development Goals
Recent forest fires potentially intensify flood hazards. However, forest fire amplification of floods is not well understood at a large scale due to the complex compound impacts of forest fires and ...climate variability, while available small‐scale cases may not represent regional changes. Here, we show that the 2019–2020 mega forest fires in southeast Australia, with unprecedented burned areas, significantly (p < 0.05) increased the peak discharges of floods during the 2 years after the fires. Spatially, fire impacts on these floods are much stronger in regions with winter‐dominated and uniform rainfall but insignificant in regions with summer‐dominated rainfall. The regional divergence reveals that burned areas can aggravate floods by exacerbating infiltration‐excess runoff processes but may not exert significant effects where saturation‐excess processes dominate. People may be increasingly exposed to such flood hazards, especially in regions where forest fires have become more frequent under climate change.
Plain Language Summary
Wildfires and floods are both natural hazards that cause damage to lives and properties. Understanding how these two are linked is critical not only for catchment hydrological processes but also for hazard control and water resources management. However, it is unclear whether mega forest fires can influence the subsequent floods on a large scale. This study demonstrates that the recent mega forest fires in southeast Australia have significantly amplified floods for most fire‐impacted catchments. Apart from raising awareness of global fire activities, this study indicates that people living in the fire‐prone area may be also susceptible to more flood hazards after fires in the future.
Key Points
The unprecedented 2019–2020 forest fires intensified subsequent river flood magnitudes in southeast Australia
Forest fire amplification of floods is divergent in different regions
Regional divergence in fire impacts is attributed to different burned areas and dominant flood generating mechanisms
Abstract
Increasing floods and droughts are raising concerns of an accelerating water cycle, however, the relative contributions to streamflow changes from climate and land management have not been ...assessed at the continental scale. We analyze streamflow data in major South American tropical river basins and show that water use and deforestation have amplified climate change effects on streamflow extremes over the past four decades. Drying (fewer floods and more droughts) is aligned with decreasing rainfall and increasing water use in agricultural zones and occurs in 42% of the study area. Acceleration (both more severe floods and droughts) is related to more extreme rainfall and deforestation and occurs in 29% of the study area, including southern Amazonia. The regionally accelerating water cycle may have adverse global impacts on carbon sequestration and food security.
Substantial evidence shows that the frequency of hydrological extremes has been changing and is likely to continue to change in the near future. Non-stationary models for flood frequency analyses are ...one method of accounting for these changes in estimating design values. The objective of the present study is to compare four models in terms of goodness of fit, their uncertainties, the parameter estimation methods and the implications for estimating flood quantiles. Stationary and non-stationary models using the GEV distribution were considered, with parameters dependent on time and on annual precipitation. Furthermore, in order to study the influence of the parameter estimation approach on the results, the maximum likelihood (MLE) and Bayesian Monte Carlo Markov chain (MCMC) methods were compared. The methods were tested for two gauging stations in Slovenia that exhibit significantly increasing trends in annual maximum (AM) discharge series. The comparison of the models suggests that the stationary model tends to underestimate flood quantiles relative to the non-stationary models in recent years. The model with annual precipitation as a covariate exhibits the best goodness-of-fit performance. For a 10% increase in annual precipitation, the 10-year flood increases by 8%. Use of the model for design purposes requires scenarios of future annual precipitation. It is argued that these may be obtained more reliably than scenarios of extreme event precipitation which makes the proposed model more practically useful than alternative models.
We simulate the water balance dynamics of 308 catchments in Austria using a lumped conceptual model involving 11 calibration parameters. We calibrate and verify the model for two non-overlapping ...11-year periods of daily runoff data. A comparison of the calibrated parameter values of the two periods suggests that all parameters are associated with some uncertainty although the degree of uncertainty differs between the parameters. The regional patterns of the calibrated parameters can be interpreted based on hydrological process reasoning indicating that they are able to represent the regional or large-scale differences in the hydrological conditions. Catchment attributes explain some of the spatial parameter variability with coefficients of determination of up to
R
2=0.27, but usually the
R
2 values are lower. Parameter uncertainty does not seem to cloud the relationship between calibrated parameters and catchment attributes to a significant extent as suggested by an optimised correlation analysis. The median Nash–Sutcliffe efficiencies of simulating streamflow decrease from 0.67 to 0.63 when moving from the calibration to the verification period. This is a small decrease, which suggests that problems with over-parameterisation of the model are unlikely. We then compare regionalisation methods for estimating the model parameters in ungauged catchments, in terms of the model performance. The best regionalisation methods are the use of the average parameters of immediate upstream and downstream (nested) neighbours and regionalisation by kriging. For the calibration period, the average decrease in the Nash–Sutcliffe model efficiency, as a result of the regionalisation, is 0.10 which is about twice the decrease of moving from the calibration to the verification period. The methods based on multiple regressions with catchment attributes perform significantly poorer. Apparently, spatial proximity is a better surrogate of unknown controls on runoff dynamics than catchment attributes.
The bacterioplankton diversity in large rivers has thus far been under‐sampled despite the importance of streams and rivers as components of continental landscapes. Here, we present a comprehensive ...dataset detailing the bacterioplankton diversity along the midstream of the Danube River and its tributaries. Using 16S rRNA‐gene amplicon sequencing, our analysis revealed that bacterial richness and evenness gradually declined downriver in both the free‐living and particle‐associated bacterial communities. These shifts were also supported by beta diversity analysis, where the effects of tributaries were negligible in regards to the overall variation. In addition, the river was largely dominated by bacteria that are commonly observed in freshwaters. Dominated by the acI lineage, the freshwater SAR11 (LD12) and the Polynucleobacter group, typical freshwater taxa increased in proportion downriver and were accompanied by a decrease in soil and groundwater‐affiliated bacteria. Based on views of the meta‐community and River Continuum Concept, we interpret the observed taxonomic patterns and accompanying changes in alpha and beta diversity with the intention of laying the foundation for a unified concept for river bacterioplankton diversity.
The flow duration curve (FDC) is effectively the cumulative distribution function of streamflow. For a long time, hydrologists have sought deeper understanding of the process controls on the shape of ...FDC, which has been a challenge due to contrasting processes controlling the fast flow and slow flow components of streamflow and their interactions. In this paper, we outline a new framework for exploring the process controls of the FDC, which involves studying fast and slow flow components of FDC separately and combining them statistically, explicitly accounting for their dependence. We illustrate the potential of the framework by constructing empirical fast flow duration (FFDC) and slow flow duration (SFDC) curves from the flow components obtained by traditional baseflow separation. Streamflow time series data from 245 MOPEX catchments across the continental United States are used. The dependence of FFDC and SFDC components is captured by the Gumbel copula, the strength of which varies regionally. In catchments where FFDC and SFDC are independent, FDC can be approximated by a simple convolution of FFDC and SFDC. The proposed conceptual framework opens the way for future modeling studies to explore process controls of fast and slow components of streamflow separately, their dependence, and their relative contributions to the shape of the FDC.
Key Points
A new framework is proposed for exploring process controls of flow duration curves (FDC), which involves separating total streamflow into its fast and slow components
The FDC of total streamflow can be constructed by combining FDCs of fast flow and slow flow components and a measure of their dependence
The dependence between fast flow and slow flow is captured by a copula model and shows regional patterns
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