| 1. |
- Blösch, Günter, et al.
(författare)
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Twenty-three unsolved problems in hydrology (UPH) - a community perspective
- 2019
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 64:10, s. 1141-1158
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Albert, James S., et al.
(författare)
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Scientists' warning to humanity on the freshwater biodiversity crisis
- 2021
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 50, s. 85-94
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Alekseeva, I., et al.
(författare)
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Reconstruction of historic changes of the Aral Sea water budget and sea-groundwater interactions by a coupled 3D sea-ice-groundwater model
- 2007
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Ingår i: Geophysical Research Abstracts, Vol. 9, 10629, 2007.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A 3D coupled sea-ice-groundwater model has been developed and applied for an estimation of the water balance and groundwater-seawater interactions in the shrinking Aral Sea. The model developed combines the complete 3D sea-ice hydrodynamics model ECOSMO, including a mass and energy conserving wetting and drying scheme, and a simple groundwater model based on changes in hydraulic gradient in response to the sea surface variability. During the simulation period 1979-1993, the model successfully reproduced the rapid Aral Sea level drop, surface area decrease, coastline position changes and salinization. Model predictions of evaporation and groundwater inflow were also consistent with independent estimations. Model results indicated that within the 15 years period of simulations the net groundwater inflow to the Aral Sea might have increased by 10% or more as a direct effect of the sea level lowering.Furthermore, model scenario tests were carried out to examine effects of salinity on sea hydrodynamics and to estimate non-linear feedbacks of the sea thermo- and hydrodynamics, air-sea turbulent fluxes and the sea water balance. It was shown that a neglect of salinity in the sea hydro- and thermo dynamics resulted in considerable differences in the Aral Sea winter thermal conditions, which in turn influenced the air-sea exchange in the following spring and summer. As a result, the zero salinity scenario predicted higher evaporation rates and an considerably accelerated sea level lowering by up to 2 cm/yr, in comparison with the basic model run. An indirect influence of the fresh groundwater inflow in terms of water balance has been identified as less significant, however it was shown that the fresh groundwater input could influence the Aral Sea salinity distribution considerably since 1990’s.
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| 4. |
- Alekseeva, Irina, et al.
(författare)
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Reproducing the Aral Sea water budget and sea-groundwater dynamics between 1979 and 1993 using a coupled 3-D sea-ice-groundwater model
- 2009
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Ingår i: Journal of Marine Systems. - : Elsevier. - 0924-7963. ; 76:3, s. 296-309
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Tidskriftsartikel (refereegranskat)abstract
- We have developed the 3-D sea-ice model, ECOSMO, into a coupled sea-ice–groundwater model and investigated the factors that may have influenced the groundwater–seawater interactions and the water balance of the shrinking Aral Sea. During the simulation period, 1979–1993, the model successfully reproduced the rapid Aral Sea level drop, surface area decrease, coastline position changes and increasing salinization of the Aral Sea. Model predictions of evaporation and groundwater inflow were also consistent with independent estimations. Model results indicated that the net groundwater inflow to the Aral Sea may have increased by 10% or more as a direct effect of the sea level lowering. Furthermore, model scenario tests showed that in comparison with a basic scenario, in which salinity effects were accounted for, not accounting for such effects resulted in considerable changes in ice formation and winter thermal conditions, which in turn influenced the thermo- and hydrodynamics and fresh water air-sea fluxes in the Aral Sea. As a result, the zero-salinity scenario predicted higher evaporation rates and an accelerated sea level lowering by up to 2 cm/yr, in comparison with the basic scenario. Model results showed that increased groundwater inflow to the sea may have influenced the Aral Sea salinity distribution since the 1990's. Our results emphasise the importance of taking into account both baroclinic hydrodynamics, sea-ice dynamics and as well as potentially increased future groundwater-related salinity effects in order to accurately estimate the Aral Sea water balance. More generally, models that can handle such highly dynamic systems may have a realistic potential for making detailed assessments of sea characteristics under the influence of climate and hydrological cycle changes.
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| 5. |
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| 6. |
- Althoff, Daniel, 1991-, et al.
(författare)
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Global patterns in water flux partitioning : Irrigated and rainfed agriculture drives asymmetrical flux to vegetation over runoff
- 2023
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Ingår i: One Earth. - 2590-3330 .- 2590-3322. ; 6:9, s. 1246-1257
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Tidskriftsartikel (refereegranskat)abstract
- The partitioning of precipitation water input on land between green (evapotranspiration) and blue (runoff) water fluxes distributes the annually renewable freshwater resource among sectors and ecosystems. The patterns and main drivers of this partitioning are not fully understood around the global land area. We decipher the worldwide patterns and key determinants of this water flux partitioning and investigate its predictability based on a global machine learning model. Available data for 3,614 hydrological catchments and model application to the global land area agree in showing mostly larger green than blue water flux. Possible expansion/intensification of irrigated and/or rainfed agriculture to feed a growing human population, along with climate warming, will tend to increase this flux partitioning asymmetry, jeopardizing blue water security. The developed machine learning model presents a promising predictive tool for future blue and green water availability under various forthcoming climate and land-use change scenarios around the world.
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| 7. |
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| 8. |
- Asokan, Shilpa M., et al.
(författare)
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Climate model performance and change projection for freshwater fluxes : comparison for irrigated areas in Central and South Asia
- 2016
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 2214-5818. ; 5, s. 48-65
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Tidskriftsartikel (refereegranskat)abstract
- Study region: The large semi-arid Aral Region in Central Asia and the smaller tropical Mahanadi River Basin (MRB) in India. Study focus: Few studies have so far evaluated the performance of the latest generation ofglobal climate models on hydrological basin scales. We here investigate the performanceand projections of the global climate models in the Coupled Model Intercomparison Project, Phase 5 (CMIP5) for freshwater fluxes and their changes in two regional hydrological basins, which are both irrigated but of different scale and with different climate. New hydrological insights for the region: For precipitation in both regions, model accuracy relative to observations has remained the same or decreased in successive climate model generations until and including CMIP5. No single climate model out-performs other models across all key freshwater variables in any of the investigated basins. Scale effects are not evident from global model application directly to freshwater assessment for the two basins of widely different size. Overall, model results are less accurate and more uncertain for freshwater fluxes than for temperature, and particularly so for model-implied water storage changes. Also, the monsoon-driven runoff seasonality in MRB is not accurately reproduced. Model projections agree on evapotranspiration increase in both regions until the climatic period 2070–2099. This increase is fed by precipitation increase in MRB and by runoff water (thereby decreasing runoff) in the Aral Region.
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| 9. |
- Asokan, Shilpa M., 1979-, et al.
(författare)
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Irrigation effects on hydro-climatic change : Basin-wise water balance-constrained quantification and cross-regional comparison
- 2014
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Ingår i: Surveys in geophysics. - : Springer Science and Business Media LLC. - 0169-3298 .- 1573-0956. ; 35:3, s. 879-895
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Forskningsöversikt (refereegranskat)abstract
- Hydro-climatic changes driven by human land and water use, including water use for irrigation, may be difficult to distinguish fromthe effects of global, natural and anthropogenic climate change. This paper quantifies and compares the hydro-climatic change effects ofirrigation using a data-driven, basin-wise quantification approach in two different irrigated world regions: the Aral Sea drainage basinin Central Asia, and the Indian Mahanadi River Basin draining into the Bay of Bengal. Results show that irrigation-driven changesin evapotranspiration and latent heat fluxes and associated temperature changes at the land surface may be greater in regions withsmall relative irrigation impacts on water availability in the landscape (here represented by the MRB) than in regions with severe suchimpacts (here represented by the Aral region). Different perspectives on the continental part of Earth’s hydrological cycle may thus implydifferent importance assessment of various drivers and impacts of hydro-climatic change. Regardless of perspective, however, actualbasin-wise water balance constraints should be accounted to realistically understand and accurately quantify continental water change.
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| 10. |
- Asokan, Shilpa M., 1979-, et al.
(författare)
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Vapor flux by evapotranspiration : effects of changes in climate, land-use and water-use
- 2010
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 115:D24
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Tidskriftsartikel (refereegranskat)abstract
- Enhanced evapotranspiration (ET) over irrigated land and associated latent heat flux change can modify the climate. Model studies of such climate change effects of irrigation are commonly based on land use parameterizations, in terms of irrigated land area, or land area equipped for irrigation. Actual ET change, however, may also be driven by water use change in addition to land use change. This study quantifies and compares ET changes due to changes in climate, land use, and water use from the preirrigation period 1901–1955 to the recent period 1990–2000 (with irrigation) for the example case of Mahanadi River Basin (MRB) in India. The results show that actual water use per unit area of irrigated land may vary greatly over a hydrological drainage basin. In MRB, much higher water use per irrigated land unit in the downstream humid basin parts leads to higher vapor flux by ET, and irrigation‐induced ET flux change, than in the upstream, water‐stressed basin parts. This is consistent with water supply limitations in water‐stressed basins. In contrast, the assumption in land use−based models that irrigation maintains high soil moisture contents can imply higher modeled water use and therefore also higher modeled ET fluxes under dry conditions than under humid conditions. The present results indicate water use as an important driver of regional climate change, in addition to land use and greenhouse gas‐driven changes.
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