@article{22539,
  abstract     = {Urbanization is projected to add 2.5 billion more urban residents by 2050. The resulting increases in impervious surfaces leads to altered hydrologic processes through greater runoff and reduced transpiration. Urban landscapes, characterized by heterogeneous land covers and infiltration rates, complicates the modeling of the urban water cycle. Existing models tend to focus on event-scale floods and thereby overlooking long-term hydrological alterations, as they often oversimplify hydrological processes such as soil moisture dynamics or evapotranspiration.
Accurately projecting the long-term hydrological budget over cities is essential to better understand water resources availability for water sensitive urban design and to guide urban greening initiatives with the purpose of improving urban water management. Using Singapore —a densely populated tropical city-state committed to water harvesting— as a testbed, this study compares two modeling approaches to resolve the long-term urban hydrological budget. The Urban Tethys & Chloris (UT&C) model offers realistic representations of urban features, microclimate and hydrology, although it is computationally intensive. In contrast, the Tethys & Chloris (T&C) model, originally developed for natural environments, modified here to incorporate simplified urban features, is simpler and faster allowing fully distributed simulations.
Findings suggest that while UT&C results may offer a more reliable representation at local scales, accounting for microclimatic feedback and two-dimensional urban geometries, both models yield similar hydrological budget insights when integrated at the city scale – at least in the wet climate of Singapore. Vegetation fraction emerges as the primary control on total evapotranspiration. T&C’s reduced computational demand, and native support for distributed hydrological modeling make it well-suited for city-wide simulations. The overall study underscores the complexities and feasibility of modeling long-term hydrological processes in urban environments.},
  author       = {Lin Xu, Yexia and Meili, Naika and Fatichi, Simone},
  issn         = {1879-2707},
  journal      = {Journal of Hydrology},
  publisher    = {Elsevier},
  title        = {{Long-term hydrological budget over urban areas: approaches and challenges}},
  doi          = {10.1016/j.jhydrol.2025.134000},
  volume       = {662, Part B},
  year         = {2025},
}

@article{22487,
  abstract     = {As an important part of global semi-arid grassland, adequately understanding how eco-hydrological processes in the Temperate Semi-Arid Grassland of China (TSGC) respond to environmental change over a century-long time scale is of critical importance to environmental change adaptation and mitigation policy in the semi-arid region. We investigated the dynamics and driving forces of key eco-hydrological variables (leaf area index (LAI), gross primary production (GPP), evapotranspiration (ET), water yield (WY), and water use efficiency (WUE)) of 8 typical locations within the TSGC during the period 1901–2016, using a well-tested mechanistic eco-hydrological model, seamlessly integrating land-surface energy balance, hydrological and carbon cycle, vegetation dynamics, and soil biogeochemistry. Results show that dominated by the elevated CO2, the annual LAI, GPP, and WUE increased significantly during 1901–2016, indicating that the environmental conditions were conducive to vegetation growth. Warming conditions were a promoter of vegetation growth in sandy grassland but a suppressant in typical steppe due to water stress increase. For the same reason, ET of sandy grassland exhibited a significant increasing trend, in response to warming, while that of typical steppe had an insignificant decreasing trend, controlled by the precipitation decline. Warming and the vegetation growth acceleration due to the elevated CO2 negatively influenced WY, which showed a decreasing trend, especially in the sandy grassland, suggesting the reduction of available water resources. Overall, our results revealed that this region, especially sandy grassland, exhibited an “enhanced vegetation but decreased water yield” trend under environmental changes occurred in the past century.},
  author       = {Pang, Xinxin and Fatichi, Simone and Lei, Huimin and Cong, Zhentao and Yang, Hanbo and Duan, Limin},
  issn         = {1879-2707},
  journal      = {Journal of Hydrology},
  publisher    = {Elsevier},
  title        = {{Environmental changes promoted vegetation growth and reduced water yield over the temperate semi-arid grassland of China during 1901–2016}},
  doi          = {10.1016/j.jhydrol.2023.129235},
  volume       = {618},
  year         = {2023},
}

@article{22529,
  abstract     = {Mountainous catchments cover a broad range of elevations and their response to a warming climate is expected to vary significantly in space. Nevertheless, studies on climate change impacts typically examine the changes in flow statistics only at the catchment outlet. In this study, we instead demonstrate the high variability of the hydrological response to climate change at the sub-catchment scale, investigating in detail the contribution of all components of the hydrological cycle in two mountainous catchments (Thur and Kleine Emme) in the Swiss Alps. The analysis was conducted with a two-dimensional weather generator model that simulated gridded climate variables at an hourly and 2-km resolution until the end of the 21st century for the RCP8.5 emission scenario. The climate ensemble was used as input into a distributed hydrological model to estimate the changes in hydrological processes at 100-m and hourly resolutions. Climate models show that precipitation intensifies during winter but weakens during summer in the order of ± 5–10% toward the end of the century. Temperature will rise by up to 4°C, leading to a 50% reduction in snowmelt, 10% increase in evapotranspiration, and shift in precipitation type from snowfall to rainfall. As a result, streamflow is projected to increase by 40% in winter but decrease by 20% to 40% during summer, with winter floods becoming more frequent. The changes to streamflow (mean and extreme low and high flows) at the sub-catchments show a strong dependency with elevation. In contrast to the small changes projected at the outlet of the catchments, streamflow shows a reduction at higher elevations (up to −20% change in mean streamflow for sub-catchments at elevations exceeding 1400 m) and an increase at lower elevations (up to +5% for Kleine Emme and +20% for the Thur at elevations below 600 m). These impacts are tied to the changes in precipitation, as well as changes in snowmelt (at high elevation) and evapotranspiration (at low elevation). The results reveal the causes and diversity of hydrological response to climate change, emphasizing the importance of investigating the distributed impacts of climate change in mountainous environments.},
  author       = {Moraga, Jorge Sebastián and Peleg, Nadav and Fatichi, Simone and Molnar, Peter and Burlando, Paolo},
  issn         = {1879-2707},
  journal      = {Journal of Hydrology},
  keywords     = {Catchment modelling, Climate change impacts, Weather generator, Distributed hydrological model, Streamflow extremes, Hydrological response},
  publisher    = {Elsevier},
  title        = {{Revealing the impacts of climate change on mountainous catchments through high-resolution modelling}},
  doi          = {10.1016/j.jhydrol.2021.126806},
  volume       = {603},
  year         = {2021},
}

@article{22549,
  abstract     = {The time that rainfall takes to reach the outlet of a catchment as discharge (transit time) is a fundamental and
integrated measure of catchment hydrological processes and solute transport mechanisms. As such, many efforts
have been dedicated to its understanding and quantification. However, defining and ranking which factors,
internal and external to the system, control the distributions of transit time is still an open challenge. Here, we
develop a two-stage approach to explore climate and topography controls on transit time, using a fully distributed hydrological model coupled with a transport component. Specifically, we apply the model to two
synthetic topographies under five observed climate regimes. With this setup, water fluxes from two years of daily
rainfall events are singularly tracked across the catchments to then derive the distributions of transit time and
fraction of young water for each combination of topography and climate. Results highlight a considerable
variability of transit times in all climates and a pronounced effect of topography within a given climate. They
further reveal that for wet climates it is possible to define a curve describing water transit time as a function of
cumulative discharge that only depends on topographic properties. On the contrary, in dry climates the variability of transit time and young water fraction is much larger and not amenable to a simple summary. Despite
simplifications, quantitative model-based inferences of transit time distributions are useful to better understand
how climate and topography affect catchment functioning.},
  author       = {Remondi, Federica and Botter, Martina and Burlando, Paolo and Fatichi, Simone},
  issn         = {1879-2707},
  journal      = {Journal of Hydrology},
  keywords     = {Transit time distributions, Young water, Climate, Topography, Distributed hydrological modelling},
  pages        = {37--50},
  publisher    = {Elsevier},
  title        = {{Variability of transit time distributions with climate and topography: A modelling approach}},
  doi          = {10.1016/j.jhydrol.2018.11.011},
  volume       = {569},
  year         = {2019},
}

@article{22551,
  abstract     = {Exploring the effects of climate change on the hydrological response at the local scale requires climate data at high spatial and temporal resolutions. This is best achieved by generating downscaled ensembles of future climate variables derived from climate models. For this purpose we present a methodology to re-parameterize the AWE-GEN-2d model (Advanced WEather GENerator for a two-dimensional grid). The model simulates key meteorological variables needed by hydrological models and is particularly suitable to explore the effects of stochastic (natural) climatic uncertainty, which is fundamental for hydrological applications, especially at sub-kilometer and hourly scales. Factors of change for different climate statistics are calculated from climate model simulations of present and future climates and subsequently applied to the statistics derived from observations to re-parameterize AWE-GEN-2d. The model abilities in generating an ensemble of future climate variables for the transient period 2020–2089 is presented with examples of precipitation and near-surface air temperature fields from hourly to multi-annual scales for a small mountainous region in the Swiss Alps. The stochastic uncertainty is examined for present and future periods and for spatial scales from the RCM scale (12-km, daily) to 2-km demonstrating the potential use of AWE-GEN-2d outputs. At the RCM scale, model results yield a small increase in annual precipitation (4%) which is within the stochastic uncertainty range for present and future periods (7%). At the fine scale of 2-km, the increase in annual precipitation can exceed the stochastic uncertainty, but for less than 10% of the domain area. On the contrary, changes in annual near-surface air temperature exceed stochastic uncertainty both at the RCM and finer scales. Stochastic climate uncertainty was concluded to be very similar when comparing present and future periods and 12-km and 2-km scales. The benefits of using AWE-GEN-2d in hydrological climate change impact assessments are finally discussed.},
  author       = {Peleg, Nadav and Molnar, Peter and Burlando, Paolo and Fatichi, Simone},
  issn         = {1879-2707},
  journal      = {Journal of Hydrology},
  keywords     = {Weather generator, Stochastic downscaling, Climate change, Internal climate variability, Climate uncertainty, High-resolution rainfall model},
  pages        = {627--641},
  publisher    = {Elsevier},
  title        = {{Exploring stochastic climate uncertainty in space and time using a gridded hourly weather generator}},
  doi          = {10.1016/j.jhydrol.2019.02.010},
  volume       = {571},
  year         = {2019},
}

@article{22550,
  abstract     = {Extreme rainfall is quantified in engineering practice using Intensity–Duration–Frequency curves (IDF) that are traditionally derived from rain-gauges and more recently also from remote sensing instruments, such as weather radars. These instruments measure rainfall at different spatial scales: rain-gauge samples rainfall at the point scale while weather radar averages precipitation on a relatively large area, generally around 1 km2. As such, a radar derived IDF curve is representative of the mean areal rainfall over a given radar pixel and neglects the within-pixel rainfall variability. In this study, we quantify subpixel variability of extreme rainfall by using a novel space–time rainfall generator (STREAP model) that downscales in space the rainfall within a given radar pixel. The study was conducted using a unique radar data record (23 years) and a very dense rain-gauge network in the Eastern Mediterranean area (northern Israel). Radar–IDF curves, together with an ensemble of point-based IDF curves representing the radar subpixel extreme rainfall variability, were developed fitting Generalized Extreme Value (GEV) distributions to annual rainfall maxima. It was found that the mean areal extreme rainfall derived from the radar underestimate most of the extreme values computed for point locations within the radar pixel (on average, ∼70%). The subpixel variability of rainfall extreme was found to increase with longer return periods and shorter durations (e.g. from a maximum variability of 10% for a return period of 2 years and a duration of 4 h to 30% for 50 years return period and 20 min duration). For the longer return periods, a considerable enhancement of extreme rainfall variability was found when stochastic (natural) climate variability was taken into account. Bounding the range of the subpixel extreme rainfall derived from radar–IDF can be of major importance for different applications that require very local estimates of rainfall extremes.},
  author       = {Peleg, Nadav and Marra, Francesco and Fatichi, Simone and Paschalis, Athanasios and Molnar, Peter and Burlando, Paolo},
  issn         = {1879-2707},
  journal      = {Journal of Hydrology},
  keywords     = {Extreme rainfall variability, High resolution rainfall modeling, IDF curves, Precipitation downscaling, Subpixel scale, Weather radar},
  pages        = {922--933},
  publisher    = {Elsevier},
  title        = {{Spatial variability of extreme rainfall at radar subpixel scale}},
  doi          = {10.1016/j.jhydrol.2016.05.033},
  volume       = {556},
  year         = {2018},
}

@article{22521,
  abstract     = {A fully distributed hydrological analysis at scales significant for water management for present-day, and
projected future climate conditions is presented for a catchment in the Alps. We selected the upper Rhone
basin (Switzerland) as a test case for understanding anthropogenic impacts including climate change on
water resources and flood risk in the Alpine area. The upper Rhone basin contains reservoirs, river diversions and irrigated areas offering the opportunity to study the interaction between climate change effects
and hydraulic infrastructure. Anthropogenic disturbances of the flow regime were implemented in detail
in the hydrological analysis. We downscaled climate model realizations using a methodology that
accounts for the uncertainty in climate change projections related to the stochastic variability of precipitation and air temperature. We showed how climate change effects on streamflow propagate from high
elevation headwater catchments to the river in the main valley by analyzing changes in several hydrological metrics and at various temporal scales across 297 control sections. Changes in the natural hydrological regime imposed by the existing hydraulic infrastructure are likely larger than climate change
signals expected by the middle of the 21st century in most of the river network. Despite a strong uncertainty induced by stochastic climate variability, we identified an elevational dependence of climate
change impacts with a severe reduction in streamflow due to the missing contribution of water from
ice melt at high-elevation and a dampened effect downstream. Reduced ice cover and ice melt are likely
to have significant implications for hydropower production. The impacts can emerge without any additional climate warming. A decrease of August–September discharge and an increase of hourly and daily
maximum flows appear as plausible projected change for the most part of the catchment. However, it is
unlikely that major changes in total runoff for the entire upper Rhone basin will occur in the next four
decades.},
  author       = {Fatichi, Simone and Rimkus, S. and Burlando, P. and Bordoy, R. and Molnar, P.},
  issn         = {1879-2707},
  journal      = {Journal of Hydrology},
  keywords     = {Climate change, Water resources, Stochastic approaches, Ice melt, Alps, Hydrological modeling},
  pages        = {362--382},
  publisher    = {Elsevier},
  title        = {{High-resolution distributed analysis of climate and anthropogenic changes on the hydrology of an Alpine catchment}},
  doi          = {10.1016/j.jhydrol.2015.03.036},
  volume       = {525},
  year         = {2015},
}