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Urban green–blue infrastructure (GBI) can provide important benefits to urban residents but may also affect mosquito abundance, with associated negative nuisance and infection transmission impacts. This study addresses important knowledge and quantification gaps for the relationships between mosquito prevalence and GBI features within cities. This is done for the city of Uppsala in Sweden as an urban case example, where mosquitos were captured and ambient air temperature and humidity were observed at seven different locations in the summer of 2022. A weighted multi-critera analysis (WMCA) model was developed based on relevant open data and open tools for resolving the mosquito (Culex pipiens) variations based on geographical variables, such as land cover/use, leaf area index, and building and green (vegetation) area fractions, within the city. The results show a clear relationship between mosquito prevalence and green-area fraction (of grass and trees), indicating that urban GBI extension can enhance mosquito prevalence, with possible associated negative impacts. This relationship is supported directly by data, showing significantly higher mosquito prevalence with higher ambient humidity, which in turn is related to larger green-area fraction. The developed WMCA model emerges as a promising tool, e.g., for urban development planning that needs to account for and seek relevant trade-off balances between positive and negative effects of urban GBI changes. [ABSTRACT FROM AUTHOR]

Hydrology plays a crucial role in understanding Earth's intricate water system and addressing water‐related problems, including against the backdrop of ongoing climate change. A retrospective review of the evolution of hydrology up to the current state of research is of great importance for understanding this role. While there have been some quantitative reviews of large numbers of hydrological publications, there still remains a lack of overarching hydrological research assessment, particularly with the focus on hydrological basins as fundamental spatial‐geographic units of hydrological analysis. Large language models, represented by OpenAI's ChatGPT, have demonstrated powerful textual understanding capabilities, making it possible to extract such overarching and basin information from hydrological publications. Here, we considered publications related to hydrology from Web of Science spanning January 1980 to October 2023, and parsed the information from this extensive body of literature by integrating a large language model and geocoding. These techniques enable quantitative analysis of research characteristics across different spatio‐temporal scales, focusing on hotspot topics, collaboration networks, and various basins worldwide. Our study revealed an increase in hydrological research since the 1990 s, with shifts in research priorities from groundwater and nutrients to climate change and ecohydrology. Some basins in North America and Europe have consistently been hotspots for hydrological research. Since the 2010s, there has been a noteworthy increase in interest toward basins in China and South Asia, but attention to many regions with frequent extreme rainfall remains insufficient. Geographical patterns show different preferred research topics for different basins, but climate change has emerged as the most prominent topic across all regions in the last decade. In conclusion, our study provides an effective approach to quantitative analysis of research trends, offering a fresh view on the evolution of hydrology as a research field, its focus on various hydrological basins around the world, and the emergence of overarching and basin‐specific hot topics over time. Key Points: We explore the literature review capability of a large language model combined with geocoding over the whole field of hydrological researchWe quantify the evolution of hydrological research, hotspot topics, collaboration networks, and basins in focus, worldwide over timeHydrological research publication exhibits major and accelerating growth with WRR emerging as the top influential journal over time [ABSTRACT FROM AUTHOR]

The article titled "Thank You to Our 2023 Reviewers" expresses gratitude to the individuals who reviewed manuscripts for the journal Water Resources Research (WRR) in 2023. The efforts of these reviewers have contributed to the high quality and impact of the journal's papers and the overall research in the field of water science. In total, 2,809 individuals provided 4,453 peer reviews, with 354 individuals reviewing three or more papers. The editors, associate editors, and authors of WRR sincerely thank all the reviewers and anticipate the publication of exciting advances in 2024. [Extracted from the article]

The out‐of‐sight groundwater and visible but much less extensive surface waters on land constitute a linked terrestrial water system around the planet. Research is crucial for our understanding of these terrestrial water system links and interactions with other geosystems and key challenges of Earth System change. This study uses a scoping review approach to discuss and identify topical, methodological and geographical gaps and priorities for research on these links and interactions of the coupled ground‐ and surface water (GSW) system at scales of whole‐catchments or greater. Results show that the large‐scale GSW system is considered in just a small part (0.4%–0.8%) of all studies (order of 105 for each topic) of either groundwater or surface water flow, storage, or quality at any scale. While relatively many of the large‐scale GSW studies consider links with the atmosphere or climate (8%–43%), considerably fewer address links with: (a) the cryosphere or coastal ocean as additional interacting geosystems (5%–9%); (b) change drivers/pressures of land‐use, water use, or the energy or food nexus (2%–12%); (c) change impacts related to health, biodiversity or ecosystem services (1%–4%). Methodologically, use of remote sensing data and participatory methods is small, while South America and Africa emerge as the least studied geographic regions. The paper discusses why these topical, methodological and geographical findings indicate important research gaps and priorities for the large‐scale coupled terrestrial GSW system and its roles in the future of the Earth System. Plain Language Summary: The water on the land surface (surface water) and that beneath it (groundwater), along with the water that is continuously and increasingly used and managed in human societies, are connected and constitute a coherent natural‐social water system around the world. Many unknowns and open questions remain for how the small‐scale variations add up to large‐scale variability and change of this water system on land, as an integral part of the whole Earth System. Relevant research is crucial for reducing the unknowns and answering the questions, and this study's scoping review aims to assess how they have been addressed in published research so far. The aim is to identify key research gaps and priorities for further research on how the integrated water system on land functions and evolves on large scales, from whole hydrological catchments and in multiple catchments around the world up to global scale. The scoping review results show key research gaps and priorities to be the coupling of surface water and groundwater on land, and the interactions of this coupled water system with other parts and major challenges of the Earth System. Geographically, the gaps and priorities emerge as particularly large and urgent for South America and Africa. Key Points: Coupling of the ground‐surface water system is a key gap in terrestrial water research, particularly at large scalesResearch on terrestrial water interactions with other geospheres and key challenges of Earth System change is rare but impactfulMajor geographic gaps in research on the large‐scale coupled terrestrial water system emerge for South America and Africa [ABSTRACT FROM AUTHOR]

Flooding is one of the most serious and frequent natural hazards affecting human life, property, and the environment. This study develops and tests a deep learning approach for large‐scale spatial flood modeling, using Convolutional Neural Network (CNN) and optimized versions combined with the Gray Wolf Optimizer (GWO) or the Imperialist Competitive Algorithm (ICA). With Sweden as an application case for nation‐wide flood susceptibility mapping, this modeling approach considers ten geo‐environmental input factors (slope, elevation, aspect, plan curvature, length of slope, topographic wetness index, distance from river, distance from wetland, rainfall, and land use). The GWO and ICA optimization improves model prediction by 12% and 8%, respectively, compared with the standalone CNN model performance. The results show 40% of the land area, 45% of the railroad, and 43% of the road network of Sweden to have high or very high flood susceptibility. They also show the aspect to have the highest input factor impact on flood susceptibility prediction while, for example, rainfall ranks only seven of the total 10 considered geo‐environmental input factors. In general, accurate nation‐wide flood susceptibility prediction is essential for guiding flood management and mitigation efforts. This study's approach to such prediction has emerged as well‐performing and cost‐effective for the case of Sweden, calling for further application and testing in other world regions. Plain Language Summary: Floods have the potential to negatively affect human wellbeing, infrastructures and the natural environment. Identifying regions prone to flooding is essential in avoiding such catastrophes. In the current study, standard and optimized convolutional neural network models are used to generate maps identifying the regions of Sweden with highest probability of flooding. Various topographic, hydrological, and anthropogenic factors are taken into account for the modeling. The analysis reveals numerous areas in Sweden prone to flooding, especially in the northern, central, and southeastern parts of the country. Malmo (the third largest city in Sweden) and some areas of Stockholm (capital) are the cities most susceptible to flooding. Additionally, considerable extensions of Sweden's roadways and railways might be impacted by floods. Accurate flood susceptibility mapping is required to assist policymakers and urban planners in implementing measures aimed at mitigating flood vulnerability. Furthermore, the findings show the ability of deep learning models for detecting flood‐susceptible areas, which can be implemented worldwide to improve flood management strategies and protect lives. Key Points: Deep learning model of convolutional neural network (CNN) was optimized and improved with gray wolf optimizer (GWO) and imperialist competitive algorithm (ICA) to detect flood‐prone areasDuring both the training and testing phases, the CNN‐GWO model demonstrated superior performance compared to CNN‐ICA and the standalone CNN modelThe results show 40% of the land area, 45% of the railroad, and 43% of the road network of Sweden to have high or very high flood susceptibility [ABSTRACT FROM AUTHOR]

The emergence of large language models (LLMs), such as ChatGPT, has garnered significant attention, particularly in academic and scientific circles. Researchers, scientists, and instructors hold varying perspectives on the advantages and disadvantages of using ChatGPT for research and teaching purposes. ChatGPT will be used by many scientists going forward for creating content and driving scientific progress. This commentary offers a brief explanation of the fundamental principles behind ChatGPT and how it can be applied in the fields of hydrology and other Earth sciences. The article examines the primary applications of this open artificial intelligence tool within these fields, specifically its ability to assist with writing and coding tasks, and highlights both the advantages and concerns associated with using such a model. Moreover, the study brings up some other limitations of the model, and the dangers of potential miss‐uses. Finally, we suggest that the academic community adapts its regulations and policies to harness the potential benefits of LLMs while mitigating its pitfalls, including establishing a structure for utilizing LLMs and presenting clear regulations for their implementation. We also outline some specific steps on how to accomplish this structure. Key Points: Large language models (LLMs) such as ChatGPT, are new technological tools that might fundamentally change academiaChatGPT can assist in academic writing but should not be relied on as the only source of information in hydrology and Earth Science studiesAuthors should exhibit transparency in their utilization of LLMs and uphold ethical responsibility [ABSTRACT FROM AUTHOR]

Drought's intensity and duration have increased in many regions over the last decades. However, the propagation of drought‐induced water deficits through the terrestrial water cycle is not fully understood at a global scale. Here we study responses of monthly evaporation (ET) and runoff to soil moisture droughts occurring between 2001 and 2015 using independent gridded datasets based on machine learning‐assisted upscaling of satellite and in‐situ observations. We find that runoff and ET show generally contrasting drought responses across climate regimes. In wet regions, runoff is strongly reduced while ET is decoupled from soil moisture decreases and enhanced by sunny and warm weather typically accompanying soil moisture droughts. In drier regions, ET is reduced during droughts due to vegetation water stress, while runoff is largely unchanged as precipitation deficits are typically low in these regions and ET decreases are buffering runoff reductions. While these water flux drought responses are controlled by the large‐scale climate regimes, they are additionally modulated by local vegetation characteristics. Land surface models capture the observed water cycle responses to drought in the case of runoff, but not for ET where the ET deficit (surplus) is overestimated (underestimated), related to a misrepresentation of the general soil moisture‐evaporation interplay. In summary, our study illustrates how the joint analysis of machine learning‐enhanced Earth observations can advance the understanding of global eco‐hydrological processes, as well as the validation of land surface models. Key Points: Contrasting drought response for both evaporation (ET) and runoff between wet and dry regionsET increases during drought in tree‐covered and wet regions, which in turn enhances runoff deficitsLand surface models capture runoff deficits but overestimate ET deficits due to misrepresented soil moisture‐evaporation interplay [ABSTRACT FROM AUTHOR]

Translational research (TR) represents a promising systematic process for going from scientific discoveries to practical applications. Through conversations with academics, practitioners, decision‐makers and users, there has emerged a broad level of water science community support for including TR in Water Resources Research (WRR) publications. Based on this, we now open a continuing special collection of TR papers in WRR. The aim is to facilitate a community within hydrology and water science that seeks to provide actionable knowledge for societal benefit across disciplines, scales and contexts, with a focus on water as a key societal resource or a risk (e.g., of floods, droughts, or as pollutant carrier). This Editorial discusses what the multi‐faceted nature of TR may include in the context of WRR, why it is important to encourage TR papers in WRR, and how the opening of a continuing special collection of translational water research papers initiates a process to include such articles in the journal. Key Points: Opening a continuing special collection for translational research (TR) papers in the context of Water Resources Research (WRR)Explaining the multi‐faceted nature of TR and Initiating a process to encourage and include such papers in WRRAiming to facilitate a community within hydrology and water science that seeks to provide actionable knowledge for societal benefit [ABSTRACT FROM AUTHOR]

On‐going climatic changes and land‐use changes may impact water storage dynamics within wetlandscapes (defined as the entire hydrological catchments of interconnected wetland systems). These dynamics are closely linked to many wetland ecosystem services including flood buffering, nutrient retention and biodiversity support. Here, we investigate if and how current water storage dynamics can differ between wetlands within the same wetlandscape. Based on continuous monitoring of water levels in multiple wetlands throughout a growing season (spring, summer, autumn) in Vattholma, Sweden, we show that there are two distinct storage behaviours depending on the position of the wetland within the landscape. Headwater wetland regions were active in temporary storage of surplus water from regular summer rains while water levels of downstream wetlands dropped to seasonal low values without responding to individual summer precipitation events. Thereby, the downstream wetlands maintained capacity to buffer extreme floods. We also found that headwater wetlands were associated with complex and patchy inundation, which causes habitat conditions to vary over short time scales both within and among these wetlands, in contrast to the prolonged low‐water state of the downstream wetlands. These differences between headwater‐downstream wetlands imply that the functionality of an entire wetlandscape cannot be assessed by simple extrapolation of data from monitoring stations that typically are located downstream of headwater regions. Increased understanding of these differences can support wetland management practices that target location‐specific nature‐based solutions and ecosystem services. [ABSTRACT FROM AUTHOR]

Population growth is increasing the pressure on water resource availability. For useful assessment and planning for societal water availability impacts, it is imperative to disentangle the direct influences of human activities in the landscape from external climate‐driven influences on water flows and their variation and change. In this study we used the water balance model, a gridded global hydrological model, to quantify and distinguish human‐driven change components, modified by interventions such as dams, reservoirs, and water withdrawals for irrigation, industry, and households, from climate‐driven change components on four key water balance variables in the terrestrial hydrological system (evapotranspiration, runoff, soil moisture, storage change). We also analyzed emergent effect patterns in and across different parts of the world, facilitating exploration of spatial variability and regional patterns on multiple spatial scales, from pixel to global, including previously uninvestigated parts of the world. Our results show that human activities drive changes in all hydrological variables, with different magnitudes and directions depending on geographical location. The differences between model scenarios with and without human activities were largest in regions with the highest population densities. In such regions, which also have relatively large numbers of dams for irrigation, water largely tends to be removed from storage and go to feed increased runoff and evapotranspiration fluxes. Our analysis considers a more complete set of hydrological variables than previous studies and can guide further research and management planning for future hydrological and water availability trends, including in relatively data‐poor parts of the world. Plain Language Summary: The global population is growing, increasing demands for water use. Knowledge of how human activities affect water resources is available for some areas and water cycle components, but more data are needed for solid scientific understanding of climate and human‐driven effects on water resources in the past and present, and to underpin management approaches to future trends in hydrology and water availability. This study examined human activity effects on different components of the terrestrial water cycle, distinct from the effects of climate change. Results showed that human activities alter movements of water worldwide, with changes, magnitudes, and directions depending on world region. The greatest human‐driven changes emerged in regions with the highest population density, which also have relatively large numbers of dams providing water for agricultural use. Overall, the water changes in these regions tend to include water removal from storage going to feed increased evapotranspiration and/or runoff. Regions with such change trends will require solutions to overcome future negative impacts on society and ecosystems. This study showed how different water cycle components and land regions have been affected by changes in human activities, and findings can guide research and management planning for hydrological and water availability in future years. Key Points: Human activities affected all four hydrological variables studied (runoff, evapotranspiration, soil moisture, and storage change)Human‐driven hydrological effects emerged as considerable over the northern tropical to temperate latitudes, where most people liveHigher runoff was seen in areas with dams of various types, with additional hydrological effects depending on dam type [ABSTRACT FROM AUTHOR]

On behalf of the editorial board of Water Resources Research (WRR) and the entire water science community, we want to express our most heartfelt gratitude to all who reviewed manuscripts for the journal in 2021. Your great efforts have ensured and improved the high quality and impact of the WRR papers and generally of research in our field. In 2021, the 2,960 individuals listed below have contributed 4,788 peer reviews with the 432 people indicated in italics, reviewing three or more papers for the journal. The editors, associate editors, and authors of WRR sincerely thank all our reviewers and look forward to the exciting advances that will be published in WRR in 2022. [ABSTRACT FROM AUTHOR]

Urban growth alters environmental conditions with major consequences for climate regulation and the exposure of population to heat. Nature-based solutions may be used to alleviate the increasing urban climate pressures, but the climate regulation services that these solutions can supply for and across different urban conditions remains understudied. We comparatively investigate the urban ecosystem service realization (considering the ecosystem service supply and demand spatial interactions) of local climate regulation by vegetated (green) and water-covered (blue) areas across 660 European cities. Results show relatively robust power-law relationships with city population density (average R2 of 0.34) of main indicators of ecosystem service realization. Country-wise fitting for city-average indicators strengthens these relationships, in particular for western European cities (average R2 of 0.66). Cross-city results also show strong power-law relationship of effectiveness in ecosystem service realization with socio-economic measures like Human Development Index and GPD per capita, in particular for the area fraction of city parts with high ecosystem service realization (R2 of 0.77). The quantified relationships are useful for comparative understanding of differences in ecosystem services realization between cities and city parts, and quantitative projection of possible change trends under different types of city growth so that relevant measures can be taken to counteract undesirable trends. [ABSTRACT FROM AUTHOR]

Recognition of climate-sensitive infectious diseases is crucial for mitigating health threats from climate change. Recent studies have reasoned about potential climate sensitivity of diseases in the Northern/Arctic Region, where climate change is particularly pronounced. By linking disease and climate data for this region, we here comprehensively quantify empirical climate-disease relationships. Results show significant relationships of borreliosis, leptospirosis, tick-borne encephalitis (TBE), Puumala virus infection, cryptosporidiosis, and Q fever with climate variables related to temperature and freshwater conditions. These data-driven results are consistent with previous reasoning-based propositions of climate-sensitive infections as increasing threats for humans, with notable exceptions for TBE and leptospirosis. For the latter, the data imply decrease with increasing temperature and precipitation experienced in, and projected for, the Northern/Arctic Region. This study provides significant data-based underpinning for simplified empirical assessments of the risks of several infectious diseases under future climate change. [ABSTRACT FROM AUTHOR]

Large‐scale covariations of freshwater fluxes and storages on land can critically regulate the balance of green (evapotranspiration) and blue (runoff) water fluxes, and related land‐atmosphere interactions and hydroclimatic hazards. Such large‐scale covariation patterns are not evident from smaller‐scale hydrological studies that have been most common so far, and remain largely unknown for various regions and climates around the world. To contribute to bridging the large‐scale knowledge gaps, we synthesize and decipher hydroclimatic data time series over the period 1980–2010 for 6,405 catchments around the world. From observation‐based data, we identify dominant large‐scale linear covariation patterns between monthly freshwater fluxes and soil moisture (SM) for different world parts and climates. These covariation patterns are also compared with those obtained from reanalysis products and Earth System Models (ESMs). The observation‐based data sets robustly show the strongest large‐scale hydrological relationship to be that between SM and runoff (R), consistently across the study catchments and their different climate characteristics. This predominantly strongest covariation between monthly SM and R is also the most misrepresented by ESMs and reanalysis products, followed by that between monthly precipitation and R. Comparison of observation‐based and ESM results also shows that an ESM may perform well for individual monthly variables, but fail in representing the patterns of large‐scale linear covariations between them. Observation‐based quantification of these patterns, and ESM and reanalysis improvements for their representation are essential for fundamental understanding, and more accurate and reliable modeling and projection of large‐scale hydrological conditions and changes under ongoing global and regional change. Key Points: The closest large‐scale monthly covariations across different regions and worldwide are between soil moisture and runoffMonthly covariations in blue‐water precipitation‐runoff and green‐water precipitation‐evapotranspiration are mostly weakerSoil moisture‐runoff and precipitation‐runoff relationships are the most misrepresented by studied reanalysis products and Earth System Models [ABSTRACT FROM AUTHOR]

Warming and hydrological changes have already affected and shifted environments in the Arctic. Arctic wetlands are complex systems of coupled hydrological, ecological, and permafrost‐related processes, vulnerable to such environmental changes. This review uses a systems perspective approach to synthesize and elucidate the various interlinked responses and feedbacks of Arctic wetlands to hydroclimatic changes. Starting from increased air temperatures, subsequent permafrost thaw and concurrent hydrological changes are identified as key factors for both shrinkage and expansion of wetland area. Other diverse factors further interact with warming, hydrological changes, and permafrost thaw in altering the Arctic wetland systems. Surface albedo shifts driven by land cover alterations are powerful in reinforcing Arctic warming, while vegetation‐related factors can balance and decelerate permafrost thaw, causing negative feedback loops. With the vast amounts of carbon stored in Arctic wetlands, their changes in turn affect the global carbon cycle. Overall, the systems perspectives outlined and highlighted in this review can be useful in structuring and elucidating the interactions of wetlands with climate, hydrological, and other environmental changes in the Arctic, including the essential permafrost‐carbon feedback. This article is categorized under:Water and Life > Nature of Freshwater EcosystemsWater and Life > Stresses and Pressures on EcosystemsScience of Water > Water and Environmental Change [ABSTRACT FROM AUTHOR]

Hydrochemical constituents in streams may originate from currently active sources at the surface and/or legacy sources from earlier surface inputs, waste deposits and land contamination. Distinction and quantification of these source contributions are needed for improved interpretation of tracer data and effective reduction of waterborne environmental pollutants. This article develops a methodology that recognizes and quantifies some general mechanistic differences in stream concentration and load behavior versus discharge between such source contributions. The methodology is applied to comparative analysis of stream concentration data for chloride (Cl−), copper (Cu), lead (Pb), and zinc (Zn), and corresponding data for water discharge, measured over the period 1990–2018 in multiple hydrological catchments (19 for Cl−, 11 for Cu and Zn, 10 for Pb) around the major Lake Mälaren in Sweden. For Cl−, the average load fraction of active sources is quantified to be 19%, and the average active and legacy concentration contributions as 2.9 and 11 mg/L, respectively. For the metals, the average active load fractions at outlets are 1%–3% over all catchments and 9%–14% in the relatively few catchments with mixed metal sources. Average active and legacy concentration contributions are 0.14 and 3.2 μg/L for Cu, 0.05 and 1.5 μg/L for Pb, and 1.4 and 12 μg/L for Zn, respectively. This multi‐catchment analysis thus indicates a widespread prevalence of legacy sources, with greater legacy than active concentration contributions for both Cl− and the metals, and active contributions playing a greater role for chloride than for the metals. The relatively simple first‐order methodology developed and applied in the study can be used to screen commonly available stream monitoring data for possible distinction of active and legacy contributions of any hydrochemical constituent in and across various hydrological catchment settings. [ABSTRACT FROM AUTHOR]

Distinction between active and legacy sources of nutrients is needed for effective reduction of waterborne nutrient loads and associated eutrophication. This study quantifies main typological differences in nutrient load behaviour versus water discharge for active and legacy sources. This quantitative typology is used for source attribution based on monitoring data for water discharge and concentrations of total nitrogen (TN) and total phosphorous (TP) from 37 catchments draining into the Baltic Sea along the coastline of Sweden over the period 2003–2013. Results indicate dominant legacy source contributions to the monitored loads of TN and TP in most (33 of the total 37) study catchments. Dominant active sources are indicated in 1 catchment for TN, and mixed sources are indicated in 3 catchments for TN, and 4 catchments for TP. The TN and TP concentration contributions are quantified to be overall higher from the legacy than the active sources. Legacy concentrations also correlate well with key indicators of human activity in the catchments, agricultural land share for TN (R2 = 0.65) and population density for TP (R2 = 0.56). Legacy‐dominated nutrient concentrations also change more slowly than in catchments with dominant active or mixed sources. Various data‐based results and indications converge in indicating legacy source contributions as largely dominant, mainly anthropogenic, and with near‐zero average change trends in the present study of catchments draining into the Baltic Sea along the coastline of Sweden, as in other parts of the world. These convergent indications emphasize needs to identify and map the different types of sources in each catchment, and differentiate strategies and measures to target each source type for possible achievement of shorter‐ and longer‐term goals of water quality improvement. [ABSTRACT FROM AUTHOR]

Wetlands provide multiple ecosystem services of local and global importance, but currently there exists no comprehensive, high‐quality wetland map for the Arctic region. Improved information about Arctic wetland extents and their vulnerability to climate change is essential for adaptation and mitigation efforts, including for indigenous people dependent on the ecosystem services that wetlands provide, as inadequate planning could result in dire consequences for societies and ecosystems alike. Synthesizing high‐resolution wetland databases and datasets on soil wetness and soil types from multiple sources, we created the first high‐resolution map with full coverage of Arctic wetlands. We assess the vulnerability of Arctic wetlands for the years 2050, 2075, and 2100, using datasets on permafrost extent, soil types, and projected mean annual air temperature from the HadGEM2‐ES climate model for three change scenarios (RCP2.6, RCP4.5, and RCP8.5). Our mapping shows that wetlands cover approximately 3.5 million km2 or roughly 25% of Arctic landmass and 99% of these wetlands are in permafrost areas, indicating considerable vulnerability to future climate change. Unless global warming is limited to scenario RCP2.6, robust results show that large areas of Arctic wetlands are vulnerable to ecosystem regime shifts. If scenario RCP8.5 becomes a reality, at least 50% of the Arctic wetland area would be highly vulnerable to regime shifts with considerable adverse impacts on human health, infrastructure, economics, ecosystems, and biodiversity. The developed wetland and vulnerability maps can aid planning and prioritization of the most vulnerable areas for protection and mitigation of change. Plain Language Summary: Wetlands play an important role in the Arctic; they cool the global climate, hold freshwater for animals and plants, regulate water, carbon, and nutrient cycling, and are biologically diverse and of great importance for indigenous human activities. Large areas lie on frozen ground (permafrost), but this could thaw out under expected future global and regional warming. Permafrost thaw can lead to wetland change leading to ecosystem as well as societal problems since the permafrost also acts as the foundation for roads and buildings in the Arctic. Through combined multi‐variable mapping, we estimate that wetlands cover 25% of land in the Arctic region, almost entirely on permafrost areas. Air temperatures above −2 degrees Celsius may lead to permafrost thaw and associated wetlands drainage, and this is enhanced by higher temperatures and longer durations of temperature elevation. If global temperatures increase by more than 2 degrees Celsius from preindustrial levels to year 2100, 30%–50% of Arctic wetlands are vulnerable to change. Limiting global warming is critical for preserving Arctic wetlands and reducing societal and ecosystem impacts of their changes. Key Points: Multi‐data synthesis shows that wetlands cover 25% of the Arctic landmassAround 50% of Arctic wetlands are vulnerable to permafrost thaw by the year 2100 in climate scenario RCP8.5Much of the permafrost underlying Arctic wetland areas can remain stable up until the year 2100 under climate scenario RCP2.6 [ABSTRACT FROM AUTHOR]

Key Points: The editors thank the 2020 peer reviewers [ABSTRACT FROM AUTHOR]

Freshwater ecosystems provide irreplaceable services for both nature and society. The quality and quantity of freshwater affect biogeochemical processes and ecological dynamics that determine biodiversity, ecosystem productivity, and human health and welfare at local, regional and global scales. Freshwater ecosystems and their associated riparian habitats are amongst the most biologically diverse on Earth, and have inestimable economic, health, cultural, scientific and educational values. Yet human impacts to lakes, rivers, streams, wetlands and groundwater are dramatically reducing biodiversity and robbing critical natural resources and services from current and future generations. Freshwater biodiversity is declining rapidly on every continent and in every major river basin on Earth, and this degradation is occurring more rapidly than in terrestrial ecosystems. Currently, about one third of all global freshwater discharges pass through human agricultural, industrial or urban infrastructure. About one fifth of the Earth's arable land is now already equipped for irrigation, including all the most productive lands, and this proportion is projected to surpass one third by midcentury to feed the rapidly expanding populations of humans and commensal species, especially poultry and ruminant livestock. Less than one fifth of the world's preindustrial freshwater wetlands remain, and this proportion is projected to decline to under one tenth by midcentury, with imminent threats from water transfer megaprojects in Brazil and India, and coastal wetland drainage megaprojects in China. The Living Planet Index for freshwater vertebrate populations has declined to just one third that of 1970, and is projected to sink below one fifth by midcentury. A linear model of global economic expansion yields the chilling prediction that human utilization of critical freshwater resources will approach one half of the Earth's total capacity by midcentury. Although the magnitude and growth of the human freshwater footprint are greater than is generally understood by policy makers, the news media, or the general public, slowing and reversing dramatic losses of freshwater species and ecosystems is still possible. We recommend a set of urgent policy actions that promote clean water, conserve watershed services, and restore freshwater ecosystems and their vital services. Effective management of freshwater resources and ecosystems must be ranked amongst humanity's highest priorities. [ABSTRACT FROM AUTHOR]

Human-induced urban growth and sprawl have implications for greenhouse gas (GHG) emissions that may not be included in conventional GHG accounting methods. Improved understanding of this issue requires use of interactive, spatial-explicit social–ecological systems modeling. This paper develops a comprehensive approach to modeling GHG emissions from urban developments, considering Stockholm County, Sweden as a case study. GHG projections to 2040 with a social–ecological system model yield overall greater emissions than simple extrapolations in official climate action planning. The most pronounced difference in emissions (39% higher) from energy use single-residence buildings resulting from urban sprawl. And this difference is not accounted for in the simple extrapolations. Scenario results indicate that a zoning policy, restricting urban development in certain areas, can mitigate 72% of the total emission effects of the model-projected urban sprawl. The study outcomes include a decision support interface for communicating results and policy implications with policymakers. [ABSTRACT FROM AUTHOR]

Coastal wetlands and lagoons are under pressure due to competing demands for freshwater resources and climatic changes, which may increase salinity and cause a loss of ecological functions. These pressures are particularly high in Mediterranean regions with high evaporative demand compared to precipitation. To manage such wetlands and maximize their provision of ecosystem services, their hydrologic balance must be quantified. However, multiple channels, diffuse surface water exchanges, and diverse groundwater pathways complicate the quantification of different water balance components. To overcome this difficulty, we developed a mass balance approach based on coupled water and salt balance equations to estimate currently unknown water exchange fluxes through the Gialova lagoon, southwestern Peloponnese, Greece. Our approach facilitates quantification of both saline and freshwater exchange fluxes, using measured precipitation, water depth and salinity, and estimated evaporation rates over a study period of 2 years (2016–2017). While water exchanges were dominated by evaporation and saline water inputs from the sea during the summer, precipitation and freshwater inputs were more important during the winter. About 40 % and 60 % of the freshwater inputs were from precipitation and lateral freshwater flows, respectively. Approximately 70 % of the outputs was due to evaporation, with the remaining 30 % being water flow from the lagoon to the sea. Under future drier and warmer conditions, salinity in the lagoon is expected to increase, unless freshwater inputs are enhanced by restoring hydrologic connectivity between the lagoon and the surrounding freshwater bodies. This restoration strategy would be fundamental to stabilizing the current wide seasonal fluctuations in salinity and maintain ecosystem functionality but could be challenging to implement due to expected reductions in water availability in the freshwater bodies supporting the lagoon. [ABSTRACT FROM AUTHOR]

Comprehensive assessment of hydro-climatic variations and change trends is essential for understanding, mitigating, and adapting to key water resource changes in different parts of the world. We performed such an assessment on Iran, as representative of an arid/semi-arid and geopolitically important world region. We acquired and calculated data time series of surface temperature (T), precipitation (P), runoff (R), evapotranspiration (ET), and water storage change (DS), to determine their status and changes in and among the 30 main hydrological basins in Iran over the period 1986–2016. From 1986–2000 to 2001–2016, the country warmed, P mostly decreased and R even more so, while water storage was depleted (DS < 0) and ET increased in some basins. Overall, the extra water provided from primarily groundwater depletion has fed and kept ET at levels beyond those sustained by the annually renewable water input from P. This indicates unsustainable use of water for maintaining and expanding human activities, such as irrigated agriculture, in this part of the world. [ABSTRACT FROM AUTHOR]

Soil moisture droughts have comprehensive implications for terrestrial ecosystems. Here we study time-accumulated impacts of the strongest observed droughts on vegetation. The results show that drought duration, the time during which surface soil moisture is below seasonal average, is a key diagnostic variable for predicting drought-integrated changes in (i) gross primary productivity, (ii) evapotranspiration, (iii) vegetation greenness, and (iv) crop yields. Drought-integrated anomalies in these vegetation-related variables scale linearly with drought duration with a slope depending on climate. In arid regions, the slope is steep such that vegetation drought response intensifies with drought duration, whereas in humid regions, it is small such that drought impacts on vegetation are weak even for long droughts. These emergent large-scale linearities are not well captured by state-of-the-art hydrological, land surface, and vegetation models. Overall, the linear relationship of drought duration versus vegetation response and crop yield reductions can serve as a model benchmark and support drought impact interpretation and prediction. [ABSTRACT FROM AUTHOR]

Geography and associated hydrological, hydroclimate and land-use conditions and their changes determine the states and dynamics of wetlands and their ecosystem services. The influences of these controls are not limited to just the local scale of each individual wetland but extend over larger landscape areas that integrate multiple wetlands and their total hydrological catchment – the wetlandscape. However, the data and knowledge of conditions and changes over entire wetlandscapes are still scarce, limiting the capacity to accurately understand and manage critical wetland ecosystems and their services under global change. We present a new Wetlandscape Change Information Database (WetCID), consisting of geographic, hydrological, hydroclimate and land-use information and data for 27 wetlandscapes around the world. This combines survey-based local information with geographic shapefiles and gridded datasets of large-scale hydroclimate and land-use conditions and their changes over whole wetlandscapes. Temporally, WetCID contains 30-year time series of data for mean monthly precipitation and temperature and annual land-use conditions. The survey-based site information includes local knowledge on the wetlands, hydrology, hydroclimate and land uses within each wetlandscape and on the availability and accessibility of associated local data. This novel database (available through PANGAEA 10.1594/PANGAEA.907398; Ghajarnia et al., 2019) can support site assessments; cross-regional comparisons; and scenario analyses of the roles and impacts of land use, hydroclimatic and wetland conditions, and changes in whole-wetlandscape functions and ecosystem services. [ABSTRACT FROM AUTHOR]

Soil moisture is an important variable for land-climate and hydrological interactions. To investigate emergent large-scale, long-term interactions between soil moisture and other key hydro-climatic variables (precipitation, actual evapotranspiration, runoff, temperature), we analyze monthly values and anomalies of these variables in 1378 hydrological catchments across Europe over the period 1980–2010. The study distinguishes results for the main European climate regions, and tests how sensitive or robust they are to the use of three alternative observational and re-analysis datasets. Robustly across the European climates and datasets, monthly soil moisture anomalies correlate well with runoff anomalies, and extreme soil moisture and runoff values also largely co-occur. For precipitation, evapotranspiration, and temperature, anomaly correlation and extreme value co-occurrence with soil moisture are overall lower than for runoff. The runoff results indicate a possible new approach to assessing variability and change of large-scale soil moisture conditions by use of long-term time series of monitored catchment-integrating stream discharges. [ABSTRACT FROM AUTHOR]

Surface water bodies and their changes in the landscape are critical for societies and ecosystems. However, the global change in surface water area over the last decades remains unclear, as recent studies using the same satellite data disagree on its direction. Here, we reanalyze reported maps of global water classification based on that data in order to estimate the changes in long‐term average surface water area from the first (1985–2000) to the second (2001–2015) half of the recent 30‐year period (1985–2015). We find a net gain in global surface water area by 100,454 km2, primarily due to seasonal water gains (83,329 km2). Over the world, we identify net wetting in 187 and net drying in 57 regional hydrological catchments, with the greatest water gain in Sabarmati (India) and loss in Amu Darya (Uzbekistan). We provide an interactive map to further explore the highly heterogeneous local changes around the world. Plain Language Summary: The surface water resources over the world's continental area are critical for water security, ecosystem functioning, hydroclimatic regulation, and related societal functions. To resolve contrasting reports on how global surface water area has changed over the last decades, we have reanalyzed the underlying data from satellite observations over the period 1985–2015. We find that the world's surface water area has increased from the first to the second half of that period, and this net global wetting has been mainly due to seasonal water gains. Permanent surface water area has also increased but considerably less than the seasonal gains, and there are also some major local drying exceptions, like the Aral Sea in Central Asia and Lake Urmia in Iran. Most commonly, the local surface water changes have been heterogeneous, with relatively small distances between wetting and drying occurrences, and we provide an interactive map for further exploration and visualization of these changes around the world. Our results are important for freshwater resource and ecosystem management, planning, and adaptation and call for further research on the drivers and processes that determine seasonal and permanent water changes and their distributions in and among different world regions. Key Points: Contrasting findings are reported for changes in global surface water area over the last decadesThis study finds a net gain in global surface water area from 1985–2000 to 2001–2015Most of the world's regional hydrological catchments have gained surface water area, primarily by increased seasonal water cover [ABSTRACT FROM AUTHOR]

Soil moisture droughts have comprehensive implications for terrestrial ecosystems. Here we study accumulated impacts of the strongest observed droughts on vegetation. The results show that drought duration, the time during which surface soil moisture is below seasonal average, is a key diagnostic variable for predicting drought-integrated changes in (i) gross primary productivity, (ii) evapotranspiration, (iii) vegetation greenness, and (iv) crop yields. Drought-integrated anomalies in these vegetation-related variables scale linearly with drought duration with a slope depending on climate. In arid regions, the slope is steep such that vegetation drought response intensifies with drought duration, whereas in humid regions, it is small such that drought impacts on vegetation are weak even for long droughts. These emergent large-scale linearities are not well captured by state- of-the-art hydrological, land surface and vegetation models. Overall, the linear relationship of drought duration versus vegetation response and crop yield reductions can serve as model benchmark, and support drought impact interpretation and prediction. [ABSTRACT FROM AUTHOR]

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come. [ABSTRACT FROM AUTHOR]

Coastal wetlands and lagoons are under pressure due to competing demands for freshwater resources and climatic changes, which may increase salinity and cause loss of ecological functions. These pressures are particularly high in Mediterranean regions with high evaporative demand compared to precipitation. To manage such wetlands and maximize their provision of ecosystem services, their hydrologic balance must be quantified. However, multiple channels, diffuse surface water exchanges, and diverse groundwater pathways complicate the quantification of different water balance components. To overcome this difficulty, we developed a mass balance approach based on coupled water and salt balance equations to estimate currently unknown water exchange fluxes through the Gialova lagoon, SW Peloponnese, Greece. Our approach facilitates quantification of both saline and freshwater exchange fluxes, using measured precipitation, water depth and salinity, and estimated evaporation rates over a study period of two years (2016-2017). While water exchanges were dominated by evaporation and saline water inputs from the sea during the summer, precipitation and freshwater inputs were more important during the winter. About 40 % and 60 % of the freshwater inputs were from precipitation and lateral freshwater flows, respectively. Approximately 70 % of the outputs was due to evaporation, with the remaining 30 % being water flow from the lagoon to the sea. Under future drier and warmer conditions, salinity in the lagoon is expected to increase, unless freshwater inputs are enhanced by restoring hydrologic connectivity between the lagoon and the surrounding freshwater bodies. This restoration strategy would be fundamental to stabilize the current wide seasonal fluctuations in salinity and maintain ecosystem functionality, but could be challenging to implement due to expected reductions in water availability in the freshwater bodies supporting the lagoon. [ABSTRACT FROM AUTHOR]

Geography and associated hydrological, hydroclimate and land use conditions and their changes determine the states and dynamics of wetlands and their ecosystem services. The influences of these controls are not limited to just the local scale of each individual wetland, but extend over larger landscape areas that integrate multiple wetlands and their total hydrological catchment – the wetlandscape. However, the data and knowledge of conditions and changes over entire wetlandscapes are still scarce, limiting the capacity to accurately understand and manage critical wetland ecosystems and their services under global change. We present a new database, consisting of geographic, hydrological, hydroclimate and land use information and data for 27 wetlandscapes around the world. This combines survey-based local information with geographic shapefiles and gridded datasets of large-scale hydroclimate and land use conditions and their changes over whole wetlandscapes. Temporally, the database contains 30-year time series of data for mean monthly precipitation and temperature, and annual land use conditions. The survey-based site information includes local knowledge on the wetlands, hydrology, hydroclimate and land uses within each wetlandscape, and on the availability and accessibility of associated local data. [ABSTRACT FROM AUTHOR]

Hydrological connectivity describes the water‐mediated transfer of mass, energy, and organisms between landscape elements and is the foundation for understanding how individual elements such as wetlands and streams integrate to support ecosystem services and nature‐based solutions in the landscape. Hydrological connectivity of geographically isolated wetlands (GIWs)—that is, wetlands without persistent surface water connections—is particularly poorly understood. To better understand GIW hydrological connectivity, we use a novel chloride mass‐balance approach to quantify the local runoff generation (defined as precipitation minus evapotranspiration, assuming negligible long‐term water storage) for 260 GIW subcatchments across North America. To evaluate hydrological connectivity, we compare the estimated local runoff from GIW subcatchments with the catchment‐average runoff. These comparisons provide three novel insights regarding the magnitude and variability of GIW hydrological connectivity. First, across 10 study regions, GIW subcatchments generate runoff at 120% of the mean catchment rate, implying they are well‐connected elements of the larger hydrologic landscape. Second, there is substantial heterogeneity in runoff generation among GIW subcatchments, which may enable support for a wide array of ecosystem functions and services. Finally, observed heterogeneity in runoff generation was largely uncorrelated to simple linear geographic predictors, indicating that GIW landscape position cannot reliably predict hydrological connectivity. In stark contrast to a priori legal assumptions that GIWs exhibit low or no hydrological connectivity, our results suggest that GIW subcatchments are active landscape features in runoff generation. [ABSTRACT FROM AUTHOR]

In an increasingly urban world, developing sustainable cities is crucial for global sustainability. Urban nature‐based solutions (NBS), such as green infrastructure, are often promoted for their potential to provide several urban services. These include stormwater mitigation, improving energy efficiency of buildings, and carbon emissions mitigation, but few studies have compared the multifunctionality of NBS to conventional urban solutions providing similar services. Fewer yet have acknowledged the indirect resource (specifically climate, land, energy, water [CLEW] nexus) impacts that these solutions may have. This paper analyzes these aspects, employing a simple CLEW nexus accounting framework, and attempts a consistent comparison across different resource systems. The comparison includes direct and indirect impacts of a set of stylized—and diverse—solutions, each with different primary objectives: green roofs, representing a multifunctional urban NBS; permeable pavements targeting mitigation of stormwater flows; window retrofits targeting energy efficiency; and rooftop PV installations targeting CO2 emissions mitigation. The results highlight both the direct and total (CLEW nexus) impacts of green roofs on stormwater retention, energy use, and CO2 emissions. However, also for the studied conventional solutions with primarily a single direct function, CLEW nexus impacts spread across all measured dimensions (energy, water, and CO2) to varying degrees. Although the numerical results are indicative and uncertainty needs to be further assessed, we suggest that the development of this type of multifunctional, multisystem assessment can assist urban sustainability planning, with comprehensive and consistent comparison of diverse (NBS and conventional) solutions. [ABSTRACT FROM AUTHOR]

This paper argues that a systems' thinking and explicit modeling approach is needed to address noted weaknesses (in terms of practicality and usefulness) in integrated water resource management. A process of coupling complex regional land use, economy, and water system interactions in integrated modeling is demonstrated with proof‐of‐concept applications to two urban cases (Chicago and Stockholm). In this uniquely coupled systems model, urban land use scenarios are considered a complex urban system represented by dynamic systems models of land use, economics, and water with a focus on urban environments that include drivers and system feedbacks with implications focused on urban water systems. The integrated model results reveal that the physical availability of land for economic activities (forecasted via a bottom‐up land use change model) and their locations differ sharply from top‐down sectoral‐based economic forecasts. This shows that both human systems (economic and land use planning) and natural systems (land use limitations and associated water implications) need to be considered in order to accurately account for system(s) impacts. For example, flood zone regulations divert land use to other locations, whereas land cover changes can greatly affect the water infiltration characteristics of land surfaces and thereby alter hydrological outcomes. Our results indicate that modeling social and natural processes using a systems approach can provide a more comprehensive understanding of coupled causal mechanisms, impacts, and feedbacks in applications of integrated water resource management. [ABSTRACT FROM AUTHOR]

Considering the potential of wetlands to dampen temporal variability of water flow through the landscape, they are increasingly considered as possible nature‐based solutions to mitigate risks of flooding and drought. In this study, we investigate flow variability by means of a flow dampening factor and use observation data from 1984 to 2013 for 82 Swedish catchments to statistically and comparatively analyze the large‐scale effects on this factor of multiple wetlands and lakes in the landscape. The results show good correlation between large‐scale flow dampening and relative area of lakes and floodplain wetlands within a catchment. An increase in relative area up to around 15% for lakes and 0.5% for floodplain wetlands lowers the temporal standard deviation of runoff (R) to around 10%–15% of that for precipitation (P), compared with a common flow‐variability dampening of around 35% for catchments with lake‐wetland area close to zero. Further increase in these relative areas, or in those of wetland types other than floodplain wetlands, has little or no flow dampening effect. The results indicate that the large‐scale flow dampening effect of lakes and floodplain wetlands is mainly due to their water‐storage capacity and less due to their possible effects on the partitioning of P between R and evapotranspiration. Overall, the results emphasize the importance of accounting for the problem scale and relative water‐storage capacity of wetlands when considering their large‐scale efficiency as possible nature‐based solutions for large‐scale flow‐variability regulation in whole catchments. [ABSTRACT FROM AUTHOR]

Numerous cities in the world have to handle and support increasing populations, with questions remaining concerning good planning strategies for their growth and development. Among these questions, access to nature for urban residents has been the subject of increased scrutiny in recent years. We here propose and apply a generally applicable new approach to quantitatively investigate the role of close access to natural or nature‐based green–blue areas for the well‐being of urban populations. A key novel aspect of this approach is to use income level as a measure of people's ability to choose their nearby living environment such that it provides them with the highest affordable level of well‐being. Based on this measure, we concretely investigate possible trends in local green–blue area access with increasing local income level in the case‐study example of the Stockholm Metropolitan region in Sweden. For this regional case, we find clear relationships between income level (and related degree of nationality homogeneity) and share of natural/nature‐based green–blue areas and man‐made grey areas within walksheds of different population segments. The results point at the importance of maintaining and restoring nearby natural and nature‐based green–blue areas as key solutions for increased well‐being of urban populations and call for further testing and comparative investigations of local‐scale associations between socio‐economic descriptors and physical environment in other parts of the world. [ABSTRACT FROM AUTHOR]

Drought comprehensively affects different interlinked aspects of the terrestrial water cycle, which have so far been mostly investigated without direct comparison. Resolving the partitioning of water deficit during drought into blue-water runoff and green-water evapotranspiration fluxes is critical, as anomalies in these fluxes threaten different associated societal sectors and ecosystems. Here, we analyze the propagation of drought-inducing precipitation deficits through soil moisture reductions to their impacts on blue and greenwater fluxes by use of comprehensive multi-decadal data from > 400 near-natural catchments along a steep climate gradient across Europe. We show that soil-moisture drought reduces runoff stronger and faster than it reduces evapotranspiration over the entire continent. While runoff responds within weeks, evapotranspiration can be unaffected for months. Understanding these drought-impact pathways across blue and green-water fluxes and geospheres is essential for ensuring food and water security, and developing early-warning and adaptation systems in support of society and ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: In response to increasing pressures on water resources, watershed services management programs are implemented throughout the tropics. These programs aim to promote land management activities that enhance the quantity and quality of water available to local communities. The success of these programs hinges on our ability to (a) understand the impacts of watershed interventions on ecohydrology; (b) model these impacts and design efficient management programs; and (c) develop strategies to overcome barriers to practical policy development, including resource limitations or the absence of baseline data. In this paper, we review opportunities in ecohydrological science that will help address these three challenges. The opportunities are grouped into measurement techniques, modelling approaches, and access to resources in our hyperconnected world. We then assess management implications of both the knowledge gaps and the new research developments related to the effect of land management. Overall, we stress the importance of policy‐relevant knowledge for implementing efficient and equitable watershed services programs in the tropics. [ABSTRACT FROM AUTHOR]

Relatively few studies have so far investigated the hydrological impacts of urbanization in Mediterranean catchments, and particularly in peri-urban catchments experiencing relatively rapid and large changes in their land-use mosaic. This study uses data-based model simulations to investigate such impacts, with the Ribeira dos Covões catchment in Portugal as a concrete Mediterranean peri-urban catchment example. We distinguish the impacts of urbanization from those of climatic change on the water flux partitioning and connectivity in the catchment over the period 1958-2013. Decrease in precipitation over this period has primarily driven decreases in annual runoff and actual evapotranspiration, while the urbanization development has primarily changed the relative flux partitioning and connectivity pattern in the catchment. The relative contribution of overland flow to annual and seasonal runoff has increased, keeping the absolute overland flow more or less intact, while the baseflow contribution to the stream network has decreased. Methodologically, the present simulation approach provides a relevant means for distinguishing main drivers of change in hydrological flux partitioning and connectivity under concurrent urbanization and climatic changes. © 2017 The Authors. Land Degradation & Development Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

This study investigates nutrient-related water quality conditions and change trends in the first management periods of the EU Water Framework Directive (WFD; since 2009) and Baltic Sea Action Plan (BASP; since 2007). With mitigation of nutrients in inland waters and their discharges to the Baltic Sea being a common WFD and BSAP target, we use Sweden as a case study of observable effects, by compiling and analyzing all openly available water and nutrient monitoring data across Sweden since 2003. The data compilation reveals that nutrient monitoring covers only around 1% (down to 0.2% for nutrient loads) of the total number of WFD-classified stream and lake water bodies in Sweden. The data analysis further shows that the hydro-climatically driven water discharge dominates the determination of waterborne loads of both total phosphorus and total nitrogen across Sweden. Both water discharge and the related nutrient loads are in turn well correlated with the ecosystem status classification of Swedish water bodies. Nutrient concentrations do not exhibit such correlation and their changes over the study period are on average small, but concentration increases are found for moderate-to-bad status waters, for which both the WFD and the BSAP have instead targeted concentration decreases. In general, these results indicate insufficient distinction and mitigation of human-driven nutrient components in inland waters and their discharges to the sea by the internationally harmonized applications of the WFD and the BSAP. The results call for further comparative investigations of observable large-scale effects of such regulatory/management frameworks in different parts of the world. [ABSTRACT FROM AUTHOR]

This paper investigates a novel simulation-optimization (S-O) framework for identifying optimal treatment levels and treatment processes for multiple wastewater dischargers to rivers. A commonly used water quality simulation model, Qual2K, was linked to a Genetic Algorithm optimization model for exploration of relevant fuzzy objective-function formulations for addressing imprecision and conflicting goals of pollution control agencies and various dischargers. Results showed a dynamic flow dependence of optimal wastewater loading with good convergence to near global optimum. Explicit considerations of real-world technological limitations, which were developed here in a new S-O framework, led to better compromise solutions between conflicting goals than those identified within traditional S-O frameworks. The newly developed framework, in addition to being more technologically realistic, is also less complicated and converges on solutions more rapidly than traditional frameworks. This technique marks a significant step forward for development of holistic, riverscape-based approaches that balance the conflicting needs of the stakeholders. [ABSTRACT FROM AUTHOR]

Previous studies have identified relationships between nutrient exports and upstream conditions, but have often disconnected interpretations from hydrological flows and changes. Here, we investigated basic relationships between largely flow-independent nutrient concentrations and two key descriptors of upstream landscape and human activity: population density and arable land cover. Consistent data were gathered from previous studies of the Baltic Sea and Mississippi River basins. These data span wide ranges of subcatchment scales, hydroclimatic conditions, and landscape characteristics. In general, investigated relationships were stronger in the Baltic than in the Mississippi region and stronger for total nitrogen (TN) than total phosphorous (TP) concentrations. However, TN concentration was both highly and consistently correlated to arable land cover across all scales and both regions. These findings support that TN export from catchments is dictated principally by retention and slow release from subsurface legacy stores while export TP concentrations appear to be dictated more by faster particulate surface transport. [ABSTRACT FROM AUTHOR]

Soil moisture is a key variable in hydrology, ecology, and climate change science. It is also of primary importance for the agricultural and water resource sectors of society. This paper investigates how hydro-climatic changes, projected by 14 CMIP5 models and for different radiative forcing (RCP) scenarios to occur from 2006-2025 to 2080-2099, may affect different soil moisture aspects in 81 large catchments worldwide. Overall, for investigated changes in dry/wet event occurrence and in average value and inter-annual variability of seasonal water content, different RCP scenarios imply opposite directions of change in around half or more of the study catchments. Regardless of RCP scenario, the greatest projected changes are found for the inter-annual variability of seasonal soil water content. Especially for the dry-season water content, large increases in inter-annual variability emerge for several large catchments over the world; the considered RCP scenario determines precisely which these catchments are. [ABSTRACT FROM AUTHOR]

Our possibility to appropriately detect, interpret and respond to climate-driven phenological changes depends on our ability to model and predict the changes. This ability may be hampered by non-linearity in climate-phenological relations, and by spatiotemporal variability and scale mismatches of climate and phenological data. A modeling methodology capable of handling such complexities can be a powerful tool for phenological change projection. Here we develop such a methodology using citizen scientists’ observations of first flight dates for orange tip butterflies (Anthocharis cardamines) in three areas extending along a steep climate gradient. The developed methodology links point data of first flight observations to calculated cumulative degree-days until first flight based on gridded temperature data. Using this methodology we identify and quantify a first flight model that is consistent across different regions, data support scales and assumptions of subgrid variability and observation bias. Model application to observed warming over the past 60 years demonstrates the model usefulness for assessment of climate-driven first flight change. The cross-regional consistency of the model implies predictive capability for future changes, and calls for further application and testing of analogous modeling approaches to other species, phenological variables and parts of the world. [ABSTRACT FROM AUTHOR]