Plastic waste increasingly accumulates in the marine environment, but data on the distribution and quantification of riverine sources, required for development of effective mitigation, are limited. Our new model approach includes geographical distributed data on plastic waste, landuse, wind, precipitation and rivers and calculates the probability for plastic waste to reach a river and subsequently the ocean. This probabilistic approach highlights regions which are likely to emit plastic into the ocean. We calibrated our model using recent field observations and show that emissions are distributed over up to two orders of magnitude more rivers than previously thought. We estimate that over 1,000 rivers are accountable for 80% of global annual emissions which range between 0.8 – 2.7 million metric tons per year, with small urban rivers amongst the most polluting. This high-resolution data allows for focused development of mitigation strategies and technologies to reduce riverine plastic emissions.

Atmospheric water vapour residence time (WVRT) is an essential indicator of how atmospheric dynamics and thermodynamics mediate hydrological cycle responses to climate change. WVRT is also important in estimating moisture sources and sinks, linking evaporation and precipitation across spatial scales. In this Review, we outline how WVRT is shaped by the interaction between evaporation and precipitation, and, thus, reflects anthropogenic changes in the hydrological cycle. Estimates of WVRT differ owing to contrasting definitions, but these differences can be reconciled by framing WVRT as a probability density function with a mean of 8-10 days and a median of 4-5 days. WVRT varies spatially and temporally in response to regional, seasonal and synoptic-scale differences in evaporation, precipitation, long-range moisture transport and atmospheric mixing. Theory predicts, and observations confirm, that in most (but not all) regions, anthropogenic warming is increasing atmospheric humidity faster than it is speeding up rates of evaporation and precipitation. Warming is, thus, projected to increase global WVRT by 3-6% K −1 , lengthening the distance travelled between evaporation sources and precipitation sinks. Future efforts should focus on data integration, joint measurement initiatives and intercomparisons, and dynamic simulations to provide a formal resolution of WVRT from both Lagrangian and Eulerian perspectives.

Climate change and deforestation reduces the resilience of rainforest ecosystems (Hirota et al., 2011;van Nes et al., 2016), and thus compromise their capacity to remain forests despite various perturbations (Davidson et al., 2012;Malhi et al., 2008). Resilience is quantified and analysed by constructing a 'stability landscape', in which valleys ('basins of attraction') represent 'stable states' and hilltops represent 'unstable states' under transition (Figure 1). Resilience is then measured as the width of the basin of attraction around a

Abstract. Deforestation can considerably affect transpiration dynamics and magnitudes at the catchment-scale and thereby alter the partitioning between drainage and evaporative water fluxes released from terrestrial hydrological systems. However, it has so far remained problematic to directly link reductions in transpiration to changes in the physical properties of the system and to quantify these changes of system properties at the catchment-scale. As a consequence, it is difficult to quantify the effect of deforestation on parameters of catchment-scale hydrological models. This in turn leads to substantial uncertainties in predictions of the hydrological response after deforestation but also to a poor understanding of how deforestation affects principal descriptors of catchment-scale transport, such as travel time distributions and young water fractions. The objectives of this study are therefore to quantify the effects of deforestation in the Wüstebach experimental catchment on the partitioning of water fluxes and to directly associate these changes to changes in parameters of a hydrological model with integrated tracer routine based on the concept of storage age selection functions. Simultaneously modelling stream flow and stable water isotope dynamics using meaningfully adjusted model parameters both for the pre- and post-deforestation periods, respectively, the model is used to track fluxes through the system and to estimate the effects of deforestation on catchment travel time distributions and young water fractions Fyw. It was found that deforestation led to a significant increase of stream flow, accompanied by corresponding reductions of evaporative fluxes. This is reflected by an increase of the runoff ratio from CR = 0.55 to 0.68 in the post-deforestation period despite similar climatic conditions. This reduction of evaporative fluxes could be linked to a reduction of the catchment-scale water storage volume in the unsaturated soil (SU,max) that is within the reach of active roots and thus accessible for vegetation transpiration from ~ 225 mm in the pre-deforestation period to ~ 90 mm in the post-deforestations period. The hydrological model, reflecting the changes in the parameter SU,max indicated that in the post-deforestation period stream water was characterized by slightly higher mean fractions of young water (Fyw ~ 0.13) than in the pre-deforestation period (Fyw ~ 0.11). In spite of these limited effects on the overall Fyw, considerable changes were found for wet periods, during which post-deforestation fractions of young water increased to values Fyw ~ 0.40 for individual storms. Deforestation also caused a significantly increased sensitivity of young water fractions to discharge under wet conditions from dFyw/dQ = 0.25 to 0.43. Overall, this study demonstrates that deforestation has not only the potential to affect the partitioning between drainage and evaporation as well as the vegetation-accessible storage volumes SU,max, and thus the fundamental hydrological response characteristics of catchments, but also catchment-scale tracer circulation dynamics. In particular for wet conditions, deforestation caused higher proportions of younger water to reach the stream, implying faster routing of stable isotopes and plausibly also solutes through the subsurface.

<p>Plastic waste increasingly accumulates in the marine environment, but data on the distribution and quantification of riverine sources, required for development of effective mitigation, are limited. Our new model approach includes geographical distributed data on plastic waste, landuse, wind, precipitation and rivers and calculates the probability for plastic waste to reach a river and subsequently the ocean. This probabilistic approach highlights regions which are likely to emit plastic into the ocean. We calibrated our model using recent field observations and show that emissions are distributed over up to two orders of magnitude more rivers than previously thought. We estimate that over 1,000 rivers are accountable for 80% of global annual emissions which range between 0.8 – 2.7 million metric tons per year, with small urban rivers amongst the most polluting. This high-resolution data allows for focused development of mitigation strategies and technologies to reduce riverine plastic emissions.</p>

Human actions compromise the many life-supporting functions of the global freshwater cycle. Yet, an encompassing analysis of humanity’s aggregate impact on the freshwater cycle is still missing. We compare the current state of the freshwater cycle against a stable reference state by estimating the global area experiencing streamflow and soil moisture deviations beyond pre-industrial variability range. We propose replacing the current freshwater use planetary boundary (PB) with our thus-defined freshwater change PB. Our analysis indicates unprecedented change: locally, the impacts of e.g. climate change, land use, and dams, are clearly visible. Globally, we find 70% and 44% increases in areas experiencing streamflow and soil moisture deviations. This suggests a transgression of the PB, calling for urgent actions to reduce human disturbance of the freshwater cycle.

<p><span>Various studies investigated the fate of evaporation and the origin of precipitation. The more recent studies among them were often carried out with the help of numerical moisture tracking. Many research questions could be answered within this context such as dependencies of atmospheric moisture transfers between different regions, impacts of land cover changes on the hydrological cycle, sustainability related questions as well as questions regarding the seasonal and inter-annual variability of precipitation. In order to facilitate future applications, global datasets on the fate of evaporation and the sources of precipitation are needed. Since most studies are on a regional level and focus more on the sources of precipitation, the goal of this study is to provide a readily available global dataset on the fate of evaporation for a fine-meshed grid of source and receptor cells. The dataset was created through a global run of the numerical moisture tracking model WAM-2layers and focused on the fate of land evaporation. The tracking was conducted on a 1.5° × 1.5° grid and was based on reanalysis data from the ERA-Interim database. Climatic input data were incorporated in 3- respectively 6-hourly time steps and represent the time period from 2001 to 2018. Atmospheric moisture was tracked forward in time and the geographical borders of the model were located at +/- 79.5° latitude. As a result of the model run, the annual and monthly average as well as the inter-annual average fate of evaporation was determined for 8684 land grid cells (all land cells except those located within Greenland and Antarctica) and provided via source-receptor matrices. The gained dataset was complemented via an aggregation to country and basin scales in order to highlight possible usages for areas of interest larger than grid cells. This resulted in data for 265 countries and 8223 basins. Finally, five types of source-receptor matrices for average moisture transfers were chosen to build the core of the dataset: land grid cell to grid cell, country to grid cell, basin to grid cell, country to country, basin to basin. The dataset is, to our knowledge, the first ready-to-download dataset providing the overall fate of evaporation for land cells of a global fine-meshed grid in monthly resolution. At the same time, information on the sources of precipitation can be extracted from it. It could be used for investigations into average annual, seasonal and inter-annual sink and source regions of atmospheric moisture from land masses for most of the regions in the world and shows various application possibilities for studying interactions between people and water such as land cover changes or human water consumption patterns. The dataset is accessible under <a href="https://doi.pangaea.de/10.1594/PANGAEA.908705%20">https://doi.pangaea.de/10.1594/PANGAEA.908705</a></span><span>  and comes along with example scripts for reading and plotting.   </span></p>

Water consumption along value chains of goods and services has increased globally and led to increased attention on water footprinting. Most global water consumption is accounted for by evaporation (E), which is connected via bridges of atmospheric moisture transport to other regions on Earth. However, the resultant source−receptor relationships between different drainage basins have not yet been considered in water footprinting. Based on a previously developed data set on the fate of land evaporation, we aim to close this gap by using comprehensive information on evaporation recycling in water footprinting for the first time. By considering both basin internal evaporation recycling (BIER; >5% in 2% of the world's basins) and basin external evaporation recycling (BEER; >50% in 37% of the world's basins), we were able to use three types of water inventories (basin internal, basin external, and transboundary inventories), which imply different evaluation perspectives in water footprinting. Drawing on recently developed impact assessment methods, we produced characterization models for assessing the impacts of blue and green water evaporation on blue water availability for all evaluation perspectives. The results show that the negative effects of evaporation in the originating basins are counteracted (and partly overcompensated) by the positive effects of reprecipitation in receiving basins. By aggregating them, combined net impacts can be determined. While we argue that these offset results should not be used as a standalone evaluation, the water footprint community should consider atmospheric moisture recycling in future standards and guidelines.