The net exchange of water between the surface and atmosphere is mainly determined by the freshwater flux: the difference between evaporation (E) and precipitation (P), or E−P. Although there is consensus among modelers that with a warming climate E−P will increase, evidence from satellite data is still not conclusive, mainly due to sensor calibration issues. We here investigate the degree of correspondence among six recent
satellite-based climate data records and ERA5 reanalysis E−P data.
We combine systematic, historical, and paleo information to obtain flood information from the last 10 300 years for the Glomma River in Norway. We identify periods with increased flood activity (4000–2000 years ago and the recent 1000 years) that correspond broadly to periods with low summer temperatures and glacier growth. The design floods in Glomma were more than 20 % higher during the 18th century than today. We suggest that trends in flood variability are linked to snow in late spring.
Streams and groundwaters often show daily cycles in response to snowmelt and evapotranspiration. These typically have a roughly 6 h time lag, which is often interpreted as a travel-time lag. Here we show that it is instead primarily a phase lag that arises because aquifers integrate their inputs over time. We further show how these cycles shift seasonally, mirroring the springtime retreat of snow cover to higher elevations and the seasonal advance and retreat of photosynthetic activity.
Wild salmon numbers in Nova Scotia, Canada, have been plummeting in recent decades. In 2014, we launched an ionic aluminium monitoring program in Nova Scotia to see if this toxic element was a threat to salmon populations. We found that all 10 monitored rivers had ionic aluminium concentrations that exceeded the threshold for aquatic health. Our results demonstrate that elevated aluminium still threatens aquatic ecosystems and that delays in recovery from acid rain remains a critical issue.
Like in all ancient civilisations, the need to manage water propelled the growth of hydrological science in ancient India also. In this paper, we provide some fascinating glimpses into the hydrological, hydraulic, and related engineering knowledge that existed in ancient India, as discussed in contemporary literature and recent explorations and findings. Many interesting dimensions of early scientific endeavours emerge as we investigate deeper into ancient texts, including Indian mythology.
Water isotopes are a scientific tool that can be used to identify sources of water and answer questions such as From which soil depths do plants take up water?, which are highly relevant under changing climatic conditions. In the past, the measurement of water isotopes required tremendous effort. In the last decade methods have advanced and can now be applied in the field. Herein, we review the current status of direct field measurements of water isotopes and discuss future applications.
We overview and retrieve a great amount of global hydroclimatic data sets. We improve the quantification of the global hydrological cycle, its variability and its uncertainties through the surge of newly available data sets. We test (but do not confirm) established climatological hypotheses, according to which the hydrological cycle should be intensifying due to global warming. We outline a stochastic view of hydroclimate, which provides a reliable means of dealing with its variability.
During the Pliocene, the Qaidam Basin on the Tibetan Plateau contained a mega-lake system. During the Pleistocene, it disappeared almost completely. Today, hyperarid climates prevail in the low-altitude parts of the basin. This study reveals that today's mean water balance of the Qaidam Basin is nearly zero and is positive during warmer, less dry years. The results explain how the mega-lake system could survive for a long time in the past and could eventually be restored in the future.
We investigate why a conceptual hydrological model failed to correctly predict observed discharge changes in response to increasing precipitation and air temperature in 156 Austrian catchments. Simulations indicate that poor model performance is related to two problems, namely a model structure that neglects changes in vegetation dynamics and inhomogeneities in precipitation data caused by changes in stations density with time. Other hypotheses did not improve simulated discharge changes.
Previous studies on water saving through food trade focussed either on comparing water productivities among countries or on analysing food trade in relation to national water endowments. Here, we consider, for the first time, both differences in water productivities and water endowments to analyse national comparative advantages. Our study reveals that blue water scarcity can be reduced to sustainable levels by changing cropping patterns while maintaining current levels of global production.
Many previous studies using offline drought indices report that future warming will increase worldwide drought. However, this contradicts observations/projections of vegetation greening and increased runoff. We resolved this paradox by re-calculating the same drought indices using direct climate model outputs and find no increase in future drought as the climate warms. We also find that accounting for the impact of CO2 on plant transpiration avoids the previous overestimation of drought.
We describe a socio-hydrologic model that couples an agent-based model (ABM) of human decision-making with a hydrologic model. We establish this model for a typical agricultural watershed in Iowa, USA, and simulate the evolution of large discharge events over a 47-year period under changing land use. Using this modeling approach, relationships between seemingly unrelated variables such as crop markets or crop yields and local peak flow trends are quantified.
Wetropolis is a table-top demonstration model with extreme rainfall and flooding, including random rainfall, river flow, flood plains, an upland reservoir, a porous moor, and a city which can flood. It lets the viewer experience extreme rainfall and flood events in a physical model on reduced spatial and temporal scales with an event return period of 6.06 min rather than, say, 200 years. We disseminate its mathematical design and how it has been shown most prominently to over 500 flood victims.
We present a blueprint for a unified modelling framework to quantify chemical transport in both surface water and groundwater systems. There has been extensive debate over recent decades, particularly in the surface water literature, about how to explain and account for long travel times of chemical species that are distinct from water flow (rainfall-runoff) travel times. We suggest a powerful modelling framework known to be robust and effective from the field of groundwater hydrology.
Between 1992 and 2012, concentrations of suspended sediment decreased at about 60 % of 137 US stream sites, with increases at only 17 % of sites. Sediment trends were primarily attributed to changes in land management, but streamflow changes also contributed to these trends at > 50 % of sites. At many sites, decreases in sediment occurred despite small-to-moderate increases in the amount of anthropogenic land use, suggesting sediment reduction activities across the US may be seeing some success.
Lateral carbon fluxes from terrestrial to aquatic systems remain central uncertainties in determining ecosystem carbon balance. This work explores how temperature and hydrology control production and export of dissolved organic carbon (DOC) at the catchment scale. Results illustrate the asynchrony of DOC production, controlled by temperature, and export, governed by flow paths; concentration–discharge relationships are determined by the relative contribution of shallow versus groundwater flow.
We revisit and shed light on the textbook The Extraction of Hidden Waters by the Persian mathematician and engineer Abubakr Mohammad Karaji. Ground-breaking ideas and descriptions of hydrological and hydrogeological perceptions such as components of the hydrological cycle, groundwater quality and driving factors for groundwater flow were presented in the book. We speculate that Karaji's book is the first of its kind to provide a construction and maintenance manual for an engineering project.
Secondary dryland salinity is a global land degradation issue. Our understanding of causal processes is adapted from wet and hydrologically connected landscapes and concludes that low end-of-catchment runoff indicates land clearing alters water balance in favour of increased infiltration and rising groundwater that bring salts to the surface causing salinity. This study shows surface flows play an important role in causing valley floor recharge and dryland salinity in low-gradient landscapes.
How far can we reach in predicting river flow globally, using integrated catchment modelling and open global data? For the first time, a catchment model was applied world-wide, covering the entire globe with a relatively high resolution. The results show that stepwise calibration provided better performance than traditional modelling of the globe. The study highlights that open data and models are crucial to advance hydrological sciences by sharing knowledge and enabling transparent evaluation.
Perhaps the oldest question in hydrology is Where does water go when it rains?. Here we present a new way to measure how the terrestrial water cycle partitions precipitation into its two ultimate fates: green water that is evaporated or transpired back to the atmosphere and blue water that is discharged to stream channels. Our analysis may help in gauging the vulnerability of both water resources and terrestrial ecosystems to changes in rainfall patterns.
This paper examines the influence of the subsurface structure on water routing, water residence times, and the hydrologic response of distinct groundwater stores and further investigates their contribution to streamflow. We conclude that deep groundwater from the fractured aquifer system, rather than shallow groundwater, is the dominant source of streamflow, which highlights the need to better characterize the deep subsurface of mountain systems using interdisciplinary studies such as this one.
We evaluated four hydrological model structures and their parameters on over 1100 catchments across Great Britain, considering modelling uncertainties. Models performed well for most catchments but failed in parts of Scotland and south-eastern England. Failures were often linked to inconsistencies in the water balance. This research shows what conceptual lumped models can achieve, gives insights into where and why these models may fail, and provides a benchmark of national modelling capability.
A simple and effective index for the quantitative estimation of the evolution of human pressure on rivers at global scale is proposed. This index, based on nightlights and river discharge data, shows a significant increase from 1992 to 2013 worldwide. The most notable changes are found in river basins across Africa and Asia, where human pressure on rivers is growing markedly. This index identifies priority areas that can be targeted for the implementation of mitigation strategies and plans.
Over the past decades, changes in land use and climate over Europe have impacted the average flow of water flowing through rivers and reservoirs (the so-called water yield). We quantify these changes using a simple but widely tested modelling approach constrained by observations of lysimeters across Europe. Results show that the contribution of land use to changes in water yield are of the same order as changes in climate, showing that impacts of land use changes cannot be neglected.
Ronald E. Stewart, Kit K. Szeto, Barrie R. Bonsal, John M. Hanesiak, Bohdan Kochtubajda, Yanping Li, Julie M. Thériault, Chris M. DeBeer, Benita Y. Tam, Zhenhua Li, Zhuo Liu, Jennifer A. Bruneau, Patrick Duplessis, Sébastien Marinier, and Dominic Matte
This article examines future atmospheric-related phenomena across the interior of western Canada associated with a business-as-usual climate scenario. Changes in large-scale atmospheric circulation and extent of warming vary with season, and these generally lead to increases, especially after mid-century, in factors associated with winter snowstorms, freezing rain, drought, forest fires, as well as atmospheric forcing of spring floods, although not necessarily summer convection.
Salinity is one of the most common water quality threats in river basins and irrigated regions worldwide. Available watershed models, however, do not simulate the fate and transport of salt species. This paper presents a modified version of the popular SWAT watershed model that simulates the transport of major salt ions in a watershed system. Salt is transported via surface runoff, soil percolation, groundwater flow, and streamflow. The model can be used in salt-affected watersheds worldwide.
Flooding can arise from multiple sources, including waves, extreme sea levels, rivers, and severe rainfall. When two or more sources combine, the consequences can be greatly multiplied. We find the potential for the joint occurrence of extreme sea levels and river discharge to be greater on the western coast of the UK compared to the eastern coast. This is due to the weather conditions generating each flood source around the UK. These results will help increase our flood forecasting ability.
Most commercial automatic rain samplers are costly and do not prevent evaporation from the collection bottles. Hence, we have developed a microcontroller-based collector enabling timer-actuated integral rain sampling. The simple, low-cost device is robust and effectively minimizes post-sampling evaporation. The excellent performance of the collector during an evaporation experiment in a lab oven suggests that even multi-week field deployments in warm climates are feasible.
This study applies a two-way coupled agent-based model (ABM) with a river-reservoir management model (RiverWare) to analyze the role of risk perception in water management decisions using the Bayesian inference mapping joined with the cost–loss model. The calibration results capture the dynamics of historical irrigated area and streamflow changes and suggest that the proposed framework improves the representation of human decision-making processes compared to conventional rule-based ABMs.
Hydrometric and geochemical dynamics are controlled by interplay of meteorological conditions, topography and geological heterogeneity. Nivo-meteorological indicators (such as global solar radiation, temperature and decreasing snow depth) explain monthly conductivity and isotopic dynamics best. These insights are important for better understanding hydrochemical responses of glacierized catchments under a changing cryosphere.
Many variables, e.g., in hydrology, geology, and social sciences, are only observed at a few distinct measurement locations, and their actual distribution in the entire space remains unknown. We introduce the new geostatistical interpolation method of quantile kriging, providing an improved estimator and associated uncertainty. It can also host variables, which would not fulfill the implicit presumptions of the traditional geostatistical interpolation methods.
Sjoukje Philip, Sarah Sparrow, Sarah F. Kew, Karin van der Wiel, Niko Wanders, Roop Singh, Ahmadul Hassan, Khaled Mohammed, Hammad Javid, Karsten Haustein, Friederike E. L. Otto, Feyera Hirpa, Ruksana H. Rimi, A. K. M. Saiful Islam, David C. H. Wallom, and Geert Jan van Oldenborgh
In August 2017 Bangladesh faced one of its worst river flooding events in recent history. For the large Brahmaputra basin, using precipitation alone as a proxy for flooding might not be appropriate. In this paper we explicitly test this assumption by performing an attribution of both precipitation and discharge as a flooding-related measure to climate change. We find the change in risk to be of similar order of magnitude (between 1 and 2) for both the meteorological and hydrological approach.
Several multivariate bias correction methods have been developed recently, but only a few studies have tested the effect of multivariate bias correction on hydrological impact projections. This study shows that incorporating or ignoring inter-variable relations between air temperature and precipitation can have a notable effect on the projected snowfall fraction. The effect translated to considerable consequences for the glacio-hydrological responses and streamflow components of the catchments.
A new derivation of the equations for one-dimensional open-channel flow in rivers and storm drainage systems has been developed. The new approach solves some long-standing problems for obtaining well-behaved solutions with conservation forms of the equations. This research was motivated by the need for highly accurate models of large-scale river networks and the storm drainage systems in megacities. Such models are difficult to create with existing equation forms.
We used stable isotopes of xylem water to study differences in the seasonal origin of water in more than 900 individual trees from three dominant species in 182 Swiss forested sites. We discovered that midsummer transpiration was mostly supplied by winter precipitation across diverse humid climates. Our findings provide new insights into tree vulnerability to droughts, transport of water (and thus solutes) in soils, and the climatic information conveyed by plant-tissue isotopes.
Supported by large-sample ecological observations, a novel, simple and topography-driven runoff generation module (HSC-MCT) was created. The HSC-MCT is calibration-free, and therefore it can be used to predict in ungauged basins, and has great potential to be generalized at the global scale. Also, it allows us to reproduce the variation of saturation areas, which has great potential to be used for broader hydrological, ecological, climatological, and biogeochemical studies.
Our study shows that there is declining coupling between sediment concentration and discharge from daily to annual scales for gauges across the Yellow River basin (YRB). Not only the coupling, but also the magnitude of sediment response to discharge variation decreases with long-term mean discharge. This emergent stationarity can be related to sediment retardation by vegetation, suggesting the shift of dominance from water to vegetation as mean annual discharge increases.
How long does it take for raindrops to become streamflow? Here I propose a new approach to this old problem. I show how we can use time series of isotope data to measure the average fraction of same-day rainfall appearing in streamflow, even if this fraction varies greatly from rainstorm to rainstorm. I show that we can quantify how this fraction changes from small rainstorms to big ones, and from high flows to low flows, and how it changes with the lag time between rainfall and streamflow.
In this study, we explore the use of an underground superconducting gravimeter as a new source of in situ observations for the evaluation of radar-based precipitation estimates. The comparison of radar and gravity time series over 15 years shows that short-duration intense rainfall events cause a rapid decrease in the measured gravity. Rainfall amounts can be derived from this decrease. The gravimeter allows capture of rainfall at a much larger spatial scale than a traditional rain gauge.
Phosphorus (P) is important to global food security. Thus it is concerning that natural P reserves are predicted to deplete within the century. Here we explore the potential of P recovery from wastewater (WW) at global scale. We identify high production and demand sites to determine optimal market prices and trade flows. We show that 20 % of the agricultural demand can be met, yet only 4 % can be met economically. Nonetheless, this recovery stimulates circular economic development in WW treatment.
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 lake precipitation and evaporation, inflow from rivers and lake outflow, controlled by two hydropower dams. Here, we present a water balance model for Lake Victoria, which closely represents the observed lake levels. The model results highlight the sensitivity of the lake level to human operations at the dam.
Lake Victoria is the second largest freshwater lake in the world and one of the major sources of the Nile River, which is controlled by two hydropower dams. In this paper we estimate the potential consequences of climate change for future water level fluctuations of Lake Victoria. Our results reveal that the operating strategies at the dam are the main controlling factors of future lake levels and that regional climate simulations used in the projections encompass large uncertainties.
Artificial water bodies are a major source of methane and an important contributor to flooded land greenhouse gas emissions. Past studies focussed on large water supply or hydropower reservoirs with small artificial water bodies (ponds) almost completely ignored. This regional study demonstrated ponds accounted for one-third of flooded land surface area and emitted over 1.6 million t CO2 eq. yr−1 (10 % of land use sector emissions). Ponds should be included in regional GHG inventories.
We analyze changes in catchment evaporation estimated from the water balances of 156 catchments in Austria over 1977–2014, as well as the possible causes of these changes. Our results show that catchment evaporation increased on average by 29 ± 14 mm yr−1 decade−1. We attribute this increase to changes in atmospheric demand (based on reference and pan evaporation), changes in vegetation (quantified by a satellite-based vegetation index), and changes in precipitation.
Evaporation from wetlands, lakes and irrigation areas needs to be measured to understand water scarcity. So far, this has only been possible for small regions. Here, we develop a solution that can be applied at a very high resolution globally by making use of satellite observations. Our results show that 16% of global water resources evaporate before reaching the ocean, mostly from surface water. Irrigation water use is less than 1% globally but is a very large water user in several dry basins.
Groundwater is a significant water resource for humans and for groundwater-dependent vegetation. Several challenges to managing both groundwater resources and dependent vegetation include defining the location of dependent vegetation, the rate of groundwater use, and the depth of roots accessing groundwater. In this study we demonstrate a novel application of measurements of stable isotopes of carbon that can be used to identify the location, the rooting depth, and the rate of groundwater use.
Satellite soil moisture products can provide critical information on incipient droughts and the interplay between vegetation and water availability. However, time-variant systematic errors in the soil moisture products may impede their usefulness. Using a novel statistical approach, we detect such errors (associated with changing vegetation) in the SMAP soil moisture product. The vegetation-associated biases impede drought detection and the quantification of vegetation–water interactions.
In this study we explore the role of spatially distributed information on hydrological modeling. For that, we develop and test an approach which draws upon information theory and thermodynamic reasoning. We show that the proposed set of methods provide a powerful framework for understanding and diagnosing how and when process organization and functional similarity of hydrological systems emerge in time and, hence, when which landscape characteristic is important in a model application.
Natalie Orlowski, Lutz Breuer, Nicolas Angeli, Pascal Boeckx, Christophe Brumbt, Craig S. Cook, Maren Dubbert, Jens Dyckmans, Barbora Gallagher, Benjamin Gralher, Barbara Herbstritt, Pedro Hervé-Fernández, Christophe Hissler, Paul Koeniger, Arnaud Legout, Chandelle Joan Macdonald, Carlos Oyarzún, Regine Redelstein, Christof Seidler, Rolf Siegwolf, Christine Stumpp, Simon Thomsen, Markus Weiler, Christiane Werner, and Jeffrey J. McDonnell
To extract water from soils for isotopic analysis, cryogenic water extraction is the most widely used removal technique. This work presents results from a worldwide laboratory intercomparison test of cryogenic extraction systems. Our results showed large differences in retrieved isotopic signatures among participating laboratories linked to interactions between soil type and properties, system setup, extraction efficiency, extraction system leaks, and each lab’s internal accuracy.
Stefanie R. Lutz, Andrea Popp, Tim van Emmerik, Tom Gleeson, Liz Kalaugher, Karsten Möbius, Tonie Mudde, Brett Walton, Rolf Hut, Hubert Savenije, Louise J. Slater, Anna Solcerova, Cathelijne R. Stoof, and Matthias Zink
Media play a key role in the communication between scientists and the general public. However, the interaction between scientists and journalists is not always straightforward. In this opinion paper, we present insights from hydrologists and journalists into the benefits, aftermath and potential pitfalls of science–media interaction. We aim to encourage scientists to participate in the diverse and evolving media landscape, and we call on the scientific community to support scientists who do so.
Evaporation causes the isotopic composition of soil water to become different from that of the original precipitation source. If multiple samples originating from the same source are available, they can be used to reconstruct the original source composition. However, soil water is influenced by seasonal variability in both precipitation sources and evaporation patterns. We show that this variability, if not accounted for, can lead to biased estimates of the precipitation source water.
Flooding is a significant hazard and extreme events in recent years have focused attention on effective means of reducing its risk. An approach known as natural flood management (NFM) seeks to increase flood resilience by a range of measures that work with natural processes. The paper develops a modelling approach to assess one type NFM of intervention – distributed additional hillslope storage features – and demonstrates that more strategic placement is required than has hitherto been applied.
We report the first ever regional-scale implementation of the Surface Temperature Initiated Closure (STIC1.2) model for mapping evapotranspiration (ET) using MODIS land surface and gridded climate datasets to overcome the existing uncertainties in aerodynamic temperature and conductance estimation in global ET models. Validation and intercomparison with SEBS and MOD16 products across an aridity gradient in the US manifested better ET mapping potential of STIC1.2 in different climates and biomes.
This study used a portable 56-sensor, 3-D temperature array with three heat pulse sources to measure the flow direction and magnitude below the water–sediment interface. Breakthrough curves from each of the sensors were analyzed using a heat transport equation. The use of short-duration heat pulses provided a rapid, accurate assessment technique for determining dynamic and multi-directional flow patterns in the hyporheic zone and is a basis for improved understanding of biogeochemical processes.
The paper presents major milestones in the transformation of hydrologic science over the last 50 years from engineering hydrology to Earth system science. This transformation has involved a transition from a focus on time (empirical) to space (Newtonian mechanics), and to time (Darwinian co-evolution). Hydrology is now well positioned to again return to a focus on space or space–time and a move towards regional process hydrology.
This article tackles the problem of finding the origin of groundwater in basin aquifers adjacent to mountains. In particular, we aim to determine whether the recharge occurs predominantly through stream infiltration along the mountain front or through subsurface flow from the mountain. To this end, we discuss the use of routinely measured variables: hydraulic head, chloride and electrical conductivity. A case study from Australia demonstrates the approach.
Understanding water infiltration in karst regions is crucial as the aquifers they host provide drinkable water for a quarter of the world's population. We present a non-invasive tool to image hydrological processes in karst systems. At our field site, the injection of electrical current in the ground, repeated daily over a 3-year period, allowed imaging changes in the groundwater content. We show that specific geological layers control seasonal to rainfall-triggered water infiltration dynamics.
Citizens can contribute to science by providing data, analysing them and as such contributing to decision-making processes. For example, citizens have collected water levels from gauges, which are important when simulating/forecasting floods, where data are usually scarce. This study reviewed such contributions and concluded that integration of citizen data may not be easy due to their spatio-temporal characteristics but that citizen data still proved valuable and can be used in flood modelling.
This study is the first to describe the quantitative association between forest and plantation areas and the flow indicators (surface runoff and baseflow) in a watershed; this understanding is required by spatial planners if they are to balance the ecology and socioeconomic functions of a landscape with the rapid expansion of plantation crops. In addition, our study provides data regarding how SWAT input parameters related to tropical plantations such as oil palm and rubber should be adjusted.
In eastern Austria, where air temperature rise is double that recorded globally, stream temperatures of a human-impacted river were simulated during heat waves, as calculated by regional climate models until 2100. An increase of up to 3 °C was predicted – thus exceeding thresholds of resident cold-adapted species. Vegetation management scenarios showed that adding vegetation can reduce both absolute temperatures and its rate of increase but is not able to fully mitigate the expected rise.
We present a new prototype lab in the field named River Lab (RL) designed for water quality monitoring to perform a complete analysis at sub-hourly frequency of major dissolved species in river water.
The article is an analytical paper to present the proof of concept, its performances and improvements. Our tests reveal a significant improvement of reproducibility compared to conventional analysis in the laboratory. First results are promising for understanding the critical zone.
We introduce a data set describing the landscape of 671 catchments in the contiguous USA: we synthesized various data sources to characterize the topography, climate, streamflow, land cover, soil, and geology of each catchment. This extends the daily time series of meteorological forcing and discharge provided by an earlier study. The diversity of these catchments will help to improve our understanding and modeling of how the interplay between catchment attributes shapes hydrological processes.
Martin Schrön, Markus Köhli, Lena Scheiffele, Joost Iwema, Heye R. Bogena, Ling Lv, Edoardo Martini, Gabriele Baroni, Rafael Rosolem, Jannis Weimar, Juliane Mai, Matthias Cuntz, Corinna Rebmann, Sascha E. Oswald, Peter Dietrich, Ulrich Schmidt, and Steffen Zacharias
A field-scale average of near-surface water content can be sensed by cosmic-ray neutron detectors. To interpret, calibrate, and validate the integral signal, it is important to account for its sensitivity to heterogeneous patterns like dry or wet spots. We show how point samples contribute to the neutron signal based on their depth and distance from the detector. This approach robustly improves the sensor performance and data consistency, and even reveals otherwise hidden hydrological features.
This study investigates the relationship between skill and value of ensemble seasonal streamflow forecasts. Using data from a modern forecasting system, we show that skilled forecasts are more likely to provide benefits for reservoirs operated to maintain a target water level rather than reservoirs operated to satisfy a target demand. We identify the primary causes for this behaviour and provide specific recommendations for assessing the value of forecasts for reservoirs with supply objectives.
The research presented here provides the first evaluation of the skill of a seasonal hydrological forecast for the UK. The forecast scheme combines rainfall forecasts from the Met Office GloSea5 forecast system with a national-scale hydrological model to provide estimates of river flows 1 to 3 months ahead. The skill in the combined model is assessed for different seasons and regions of Britain, and the analysis indicates that Autumn/Winter flows can be forecast with reasonable confidence.
In this study we provide a numerical quantification of changes in flood hazard in the Vietnamese Mekong Delta as a result of dyke development. Other important drivers to the alteration of delta flood hazard are also investigated, e.g. tidal level. The findings of our study are substantial valuable for the decision makers in Vietnam to develop holistic and harmonized floods and flood-related issues management plan for the whole delta.
Water supply forecasts are critical to support water resources operations and planning. The skill of such forecasts depends on our knowledge of (i) future meteorological conditions and (ii) the amount of water stored in a basin. We address this problem by testing several approaches that make use of these sources of predictability, either separately or in a combined fashion. The main goal is to understand the marginal benefits of both information and methodological complexity in forecast skill.
Fruits take up soil water as they grow, and thus the fruit water is related to the rain or irrigation the crop receives. We used a novel sampling system to measure the stable isotopes of H and O in the fruit water to determine its geographic origin by comparing it to maps of isotopes in rain. We used this approach to teach an audience of science students and teachers about water cycle concepts and how humans may modify the water cycle through agriculture and irrigation water diversions.
John Kochendorfer, Rodica Nitu, Mareile Wolff, Eva Mekis, Roy Rasmussen, Bruce Baker, Michael E. Earle, Audrey Reverdin, Kai Wong, Craig D. Smith, Daqing Yang, Yves-Alain Roulet, Samuel Buisan, Timo Laine, Gyuwon Lee, Jose Luis C. Aceituno, Javier Alastrué, Ketil Isaksen, Tilden Meyers, Ragnar Brækkan, Scott Landolt, Al Jachcik, and Antti Poikonen
Precipitation measurements were combined from eight separate precipitation testbeds to create multi-site transfer functions for the correction of unshielded and single-Alter-shielded precipitation gauge measurements. Site-specific errors and more universally applicable corrections were created from these WMO-SPICE measurements. The importance and magnitude of such wind speed corrections were demonstrated.
In 2009, the "planetary boundaries" were introduced. They consist of nine global control variables and corresponding "thresholds which, if crossed, could generate unacceptable environmental change". The idea has been very successful, but also controversial. This paper picks up the debate with regard to the boundary on "global freshwater use": it argues that such a boundary is based on mere speculation, and that any exercise of assigning actual numbers is arbitrary, premature, and misleading.
Gregor Laaha, Tobias Gauster, Lena M. Tallaksen, Jean-Philippe Vidal, Kerstin Stahl, Christel Prudhomme, Benedikt Heudorfer, Radek Vlnas, Monica Ionita, Henny A. J. Van Lanen, Mary-Jeanne Adler, Laurie Caillouet, Claire Delus, Miriam Fendekova, Sebastien Gailliez, Jamie Hannaford, Daniel Kingston, Anne F. Van Loon, Luis Mediero, Marzena Osuch, Renata Romanowicz, Eric Sauquet, James H. Stagge, and Wai K. Wong
In 2015 large parts of Europe were affected by a drought. In terms of low flow magnitude, a region around the Czech Republic was most affected, with return periods > 100 yr. In terms of deficit volumes, the drought was particularly severe around S. Germany where the event lasted notably long. Meteorological and hydrological events developed differently in space and time. For an assessment of drought impacts on water resources, hydrological data are required in addition to meteorological indices.
During August 2016, heavy precipitation led to devastating floods in south Louisiana, USA. Here, we analyze the climatological statistics of the precipitation event, as defined by its 3-day total over 12–14 August. Using observational data and high-resolution global coupled model experiments, we find for a comparable event on the central US Gulf Coast an average return period of about 30 years and the odds being increased by at least 1.4 since 1900 due to anthropogenic climate change.
In this study a comprehensive model was developed that combines numerical schemes with high-order accuracy for solution of the advection–dispersion equation considering transient storage zones term in rivers. In developing the subjected model (TOASTS), for achieving better accuracy and applicability, irregular-cross sections and unsteady flow regime were considered. For this purpose the QUICK scheme due to its high stability and low approximation error has been used for spatial discretization.
The remaining populations of the endangered dwarf wedgemussel (DWM) (Alasmidonta heterodon) in the upper Delaware River, northeastern USA, were thought to be located in areas of substantial groundwater discharge to the river. Physical, thermal, and geophysical methods applied at several spatial scales indicate that DWM are located within or directly downstream of areas of substantial groundwater discharge to the river. DWM may depend on groundwater discharge for their survival.
While the assessment of "vertical" (magnitude) errors of streamflow simulations is standard practice, "horizontal" (timing) errors are rarely considered. To assess their role, we propose a method to quantify both errors simultaneously which closely resembles visual hydrograph comparison. Our results reveal differences in time–magnitude error statistics for different flow conditions. The proposed method thus offers novel perspectives for model diagnostics and evaluation.
This theoretical paper describes the energy fluxes and dissipation along the flow paths involved in root water uptake, an approach that is rarely taken. We show that this provides useful additional insights for understanding the biotic and abiotic impediments to root water uptake. This approach shall be applied to explore efficient water uptake strategies and help locate the limiting processes in the complex soil–plant–atmosphere system.
Geomorphometry, the science of quantitative terrain characterization, has traditionally focused on the investigation of terrestrial landscapes. More recently, a suite of geomorphometric techniques have been applied to characterize the seafloor. The dynamic, four-dimensional nature of the marine environment and differences in data collection methods cause issues for geomorphometry that are specific to marine applications. This article offers the first review of marine geomorphometry to date.
We assessed if nitrogen stable isotopes in mussels are a suitable indicator, capable of resolving spatial and temporal variability of nutrient pollution in an urban estuary. Our results highlight the value of using stable isotope analysis as an integrative tool to establish an understanding of local processes and pollution levels in theses urban aquatic systems. We suggest that mussels can become a robust tool for the detection of emerging anthropogenic pollutants of concern in urban water systems.
We statistically modeled surface water extent (SWE) and inundation dynamics from a unique Landsat-based time series (1986–2011) for Australia's Murray–Darling Basin as a function of river flow and spatially explicit time series of rainfall, evapotranspiration and soil moisture. We present a data-driven and transferable approach that allowed us to model SWE through periods of flooding and drying for 363 floodplain units and to identify local combinations of variables that drive SWE dynamics.
Regional climate model (RegCM4) simulations demonstrate that part of the observed decrease in moderate rainfall events during the summer monsoon season over central India from 1951 to 2005 is attributed to anthropogenically induced land-use land-cover change (LULCC). LULCC also partly explains the observed warming trend in the daily mean and maximum temperatures over India. This study demonstrates the importance of LULCC in the context of regional climate change over India.
We derived indices of landscape properties as well as hydrological response and examined their relation with catchment age and climate. We found significant correlation between drainage density and baseflow index with age, but not with climate. We compared our data with data from volcanic catchments in Oregon and could confirm that baseflow index decreases with time, but also discovered that drainage density seems to stabilize after 2M years, after an initial increase due to landscape incision.
We derived mathematical formulations of relations between relative wetness and gradients driving run-off and evaporation for a one-box model such that, when conductances are optimized with the maximum power principle, the model leads exactly to a point on the Budyko curve.
With dry spells and dynamics in actual evaporation added, the model compared well with catchment observations without calibrating any parameter.
The maximum-power principle may thus be used to derive the Budyko curve.
Catchment mean transit times have been widely inferred from seasonal cycles of environmental tracers in precipitation and streamflow. Here I show that these cycles yield strongly biased estimates of mean transit times in spatially heterogeneous catchments (and, by implication, in real-world catchments). However, I also show that these cycles can be used to reliably estimate the fraction of "young" water in streamflow, meaning water that fell as precipitation less than roughly 2–3 months ago.
Here I show that seasonal tracer cycles yield strongly biased estimates of mean transit times in nonstationary catchments (and, by implication, in real-world catchments). However, they can be used to reliably estimate the fraction of "young" water in streamflow, meaning water that fell as precipitation less than roughly 2–3 months ago. This young water fraction varies systematically between high and low flows and may help in characterizing controls on stream chemistry.
– A strategy to diagnose hydrological limitations of a Land Surface Model
– Land Surface Model adaptation for hydrological applications
– Highlights challenges faced while moving towards high resolution modelling
To improve the design of drought monitoring networks and water resource management during episodes of drought, there is a need for a better understanding of spatial variations in the response of aquifers to major meteorological droughts. This paper is the first to describe a suite of methods to quantify such variations. Using an analysis of groundwater level data for a case study from the UK, the influence of catchment characteristics on the varied response of groundwater to droughts is explored
Water storages and fluxes on land are key variables in the Earth system. To provide context for local investigations and to understand phenomena that emerge at large spatial scales, information on continental freshwater dynamics is needed. This paper presents a methodology to estimate continental-scale runoff on a 0.5° spatial grid, which combines the advantages of in situ observations with the power of machine learning regression. The resulting runoff estimates compare well with observations.
Our paper is one of very few studies where the influence of stochastic internal atmospheric variability (IAV) on the hydrological response is analyzed. On the basis of ensemble experiments with GCM and hydrological models, we found, e.g., that averaging over ensemble members filters the stochastic term related to IAV, and that a considerable portion of the simulated trend in annual Lena R. runoff can be explained by the externally forced signal (global SST and SIC changes in our experiments).
We present an empirical study of the rates of increase in precipitation intensity with air temperature using high-resolution 10 min precipitation records in Switzerland. We estimated the scaling rates for lightning (convective) and non-lightning event subsets and show that scaling rates are between 7 and 14%/C for convective rain and that mixing of storm types exaggerates the relations to air temperature. Doubled CC rates reported by other studies are an exception in our data set.
In this study, we analyze a set of high-resolution, surface-based, 2-D ground-penetrating radar (GPR) observations of artificially induced subsurface water dynamics. In particular, we place close scrutiny on the evolution of the capillary fringe in a highly dynamic regime with surface-based time-lapse GPR. We thoroughly explain all observed phenomena based on theoretical soil physical considerations and numerical simulations of both subsurface water flow and the expected GPR response.
We present a systematic comparison of changes in historical extreme precipitation in station observations (HadEX2) and 15 climate models from the CMIP5 (as the largest and most recent sets of available observational and modeled data sets), on global and continental scales for 1901-2010, using both parametric (linear regression) and non-parametric (the Mann-Kendall as well as Sen’s slope estimator) methods, taking care to sample observations and models spatially and temporally in comparable ways.
In this paper we present a high-resolution global-scale groundwater model of an upper aquifer. An equilibrium water table at its natural state is constructed. Aquifer parameterization is based on available global datasets on lithology and conductivity combined with estimated aquifer thickness. The results showed groundwater levels are well simulated for many regions of the world. Simulated flow paths showed the relevance of including lateral groundwater flows in global scale hydrological models.
ERA-Interim/Land is a global land surface reanalysis covering the period 1979–2010. It describes the evolution of soil moisture, soil temperature and snowpack. ERA-Interim/Land includes a number of parameterization improvements in the land surface scheme with respect to the original ERA-Interim and a precipitation bias correction based on GPCP. A selection of verification results show the added value in representing the terrestrial water cycle and its main land surface storages and fluxes.
The focus of this paper is to (1) present a community data set of daily forcing and hydrologic response data for 671 unimpaired basins across the contiguous United States that spans a very wide range of hydroclimatic conditions, and (2) provide a calibrated model performance benchmark using a common conceptual snow and hydrologic modeling system. This benchmark provides a reference level of model performance across a very large basin sample and highlights regional variations in performance.
This study demonstrates the processes by which instantaneous longitudinal water temperature gradients may be generated in a stream reach that transitions from moorland to semi-natural forest in the absence of substantial groundwater inflows. Water did not cool as it flowed downstream. Instead, temperature gradients were generated by a combination of reduced rates of heating in the forested reach and advection of cooler (overnight and early morning) water from the upstream moorland catchment.
Hydrological modeling and assessment tools were used to provide evidence of the expected hydrological alterations that hydropower development in the lower Mekong tributaries could bring to the Tonle Sap. The most significant alterations are in terms of water levels during the dry season and rates of water level rise/drop which are crucial for tree seed germination and fish migrations, and therefore major ecological disruptions are likely to follow.
In this paper, we propose a new method for estimating the snowmelt degree-day factor (DDFS) directly from MODIS snow covered area (SCA) and ground-based snow depth data without calibration. Snow density is estimated as the ratio between observed precipitation and changes in the snow volume for days with snow accumulation. DDFS values are estimated as the ratio between changes in the snow water equivalent and difference between the daily temperature and a threshold value for days with snowmelt.
This study introduces the theory of networks, and in particular complex networks, to examine connections in streamflow dynamics. Monthly streamflow data from a network of 639 stations in the United States are studied. The connections are examined primarily using the concept of clustering coefficient, which quantifies the network’s tendency to cluster. The clustering coefficient analysis is performed with several different threshold levels based on correlations in streamflow between the stations.
Natural patterns of water levels in the Mekong are changing as a result of hydropower and irrigation development. Since 1991, significant changes in water level fluctuations and rising and falling rates have occurred along the lower Mekong. The changes were linked to temporal and spatial trends in water infrastructure development and can lead to impacts on ecosystem productivity. Climatic change is also important, but it has not been the main cause of the key water level alternations.