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  • 1.
    Asokan, Shilpa M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Appendix to Paper V: Climate model performance versus basin-scalehydro-climatic dataManuscript (preprint) (Other academic)
  • 2.
    Asokan, Shilpa M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Irrigation effects on hydro-climatic change: Basin-wise water balance-constrained quantification and cross-regional comparison2014In: Surveys in geophysics, ISSN 0169-3298, E-ISSN 1573-0956, Vol. 35, no 3, p. 879-895Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    Asokan, Shilpa M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Dutta, Dushmanta
    Analysis of water resources in the Mahanadi River Basin, India under projected climate conditions2008In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 22, no 18, p. 3589-3603Article in journal (Refereed)
    Abstract [en]

    The paper presents the outcomes of a study conducted to analyse water resources availability and demand in the Mahanadi River Basin in India under climate change conditions. Climate change impact analysis was carried out for the years 2000, 2025, 2050, 2075 and 2100, for the months of September and April (representing wet and dry months), at a sub-catchment level. A physically based distributed hydrologic model (DHM) was used for estimation of the present water availability. For future scenarios under climate change conditions, precipitation output of Canadian Centre for Climate Modelling and Analysis General Circulation Model (CGCM2) was used as the input data for the DHM. The model results show that the highest increase in peak runoff (38%) in the Mahanadi River outlet will occur during September, for the period 2075-2100 and the maximum decrease in average runoff (32·5%) will be in April, for the period 2050-2075. The outcomes indicate that the Mahanadi River Basin is expected to experience progressively increasing intensities of flood in September and drought in April over the considered years. The sectors of domestic, irrigation and industry were considered for water demand estimation. The outcomes of the analysis on present water use indicated a high water abstraction by the irrigation sector. Future water demand shows an increasing trend until 2050, beyond which the demand will decrease owing to the assumed regulation of population explosion. From the simulated future water availability and projected water demand, water stress was computed. Among the six sub-catchments, the sub-catchment six shows the peak water demand. This study hence emphasizes on the need for re-defining water management policies, by incorporating hydrological response of the basin to the long-term climate change, which will help in developing appropriate flood and drought mitigation measures at the basin level.

  • 4.
    Asokan, Shilpa M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Vapor flux by evapotranspiration: effects of changes in climate, land-use and water-use2010In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, no D24Article in journal (Refereed)
    Abstract [en]

    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.

  • 5.
    Asokan, Shilpa M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Rogberg, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Bring, Arvid
    Stockholm University, Faculty of Science, Department of Physical Geography. University of New Hampshire, USA.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Climate model performance and change projection for freshwater fluxes: comparison for irrigated areas in Central and South Asia2016In: Journal of Hydrology Regional Studies, ISSN 1070-9428, E-ISSN 1857-8489, Vol. 5, p. 48-65Article in journal (Refereed)
    Abstract [en]

    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.

  • 6.
    Bring, Arvid
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of New Hampshire, USA.
    Asokan, Shilpa M.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Levi, Lea
    Stockholm University, Faculty of Science, Department of Physical Geography. KTH Royal Institute of Technology, Sweden; University of Split, Croatia.
    Pietroń, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Rogberg, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Implications of freshwater flux data from the CMIP5 multimodel output across a set of Northern Hemisphere drainage basins2015In: Earths Future, ISSN 2328-4277, Vol. 3, no 6, p. 206-217Article in journal (Refereed)
    Abstract [en]

    The multimodel ensemble of the Coupled Model Intercomparison Project, Phase 5 (CMIP5) synthesizes the latest research in global climate modeling. The freshwater system on land, particularly runoff, has so far been of relatively low priority in global climate models, despite the societal and ecosystem importance of freshwater changes, and the science and policy needs for such model output on drainage basin scales. Here we investigate the implications of CMIP5 multimodel ensemble output data for the freshwater system across a set of drainage basins in the Northern Hemisphere. Results of individual models vary widely, with even ensemble mean results differing greatly from observations and implying unrealistic long-term systematic changes in water storage and level within entire basins. The CMIP5 projections of basin-scale freshwater fluxes differ considerably more from observations and among models for the warm temperate study basins than for the Arctic and cold temperate study basins. In general, the results call for concerted research efforts and model developments for improving the understanding and modeling of the freshwater system and its change drivers. Specifically, more attention to basin-scale water flux analyses should be a priority for climate model development, and an important focus for relevant model-based advice for adaptation to climate change.

  • 7.
    Destouni, Georgia
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Asokan, Shilpa M.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Augustsson, Anna
    Balfors, Berit
    Bring, Arvid
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Johansson, Emma
    Stockholm University, Faculty of Science, Department of Physical Geography. Swedish Nuclear Fuel and Waste Management Co, Sweden.
    Juston, John
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Levi, Lea
    Stockholm University, Faculty of Science, Department of Physical Geography. The Royal Institute of Technology, Sweden; University of Split, Croatia.
    Olofsson, Bo
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Quin, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Åström, Mats
    Cvetkovic, Vladimir
    Needs and means to advance science, policy and management understanding of the freshwater system – A synthesis report2015Report (Other academic)
    Abstract [en]

    Fragmented and inconsistent understanding of the freshwater system limits our ability to achieve water security and sustainability under the human-driven changes occurring in the Anthropocene. To advance system-level understanding of freshwater, gaps and inconsistencies in knowledge, data, representations and links of processes and subsystems need to be identified and bridged under consideration of the freshwater system as a continuous whole. 

    Based on such identification, a freshwater system conceptualization is developed in this report, which emphasizes four essential, yet often neglected system aspects:

    i) Distinction of coastal divergent catchments.

    ii) Four main zones (surface, subsurface, coastal, observation) of different types of freshwater change.

    iii) Water pathways as system-coupling agents that link and partition water change among the four change zones.

    iv) Direct interactions with the anthroposphere as integral system pathways across the change zones.

    We explain and exemplify some key implications of these aspects, identifying in the process also distinct patterns of human-driven changes in large-scale water fluxes and nutrient loads.

    The present conceptualization provides a basis for common inter- and trans-disciplinary understanding and systematic characterization of the freshwater system function and its changes, and of approaches to their modeling and monitoring. This can be viewed and used as a unifying checklist that can advance science, policy and management of freshwater and related environmental changes across various scales and world regions.

  • 8.
    Destouni, Georgia
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Asokan, Shilpa M.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Inland hydro-climatic interaction: Effects of human water use on regional climate2010In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 37, no 18, p. L18402-Article in journal (Refereed)
    Abstract [en]

    This study has quantified the regional evaporation and evapotranspiration changes, and the associated latent heat flux and surface temperature changes in the Central Asian region of the Aral Sea drainage basin and the Aral Sea itself from the pre-1950 period of the 20th century to 1983-2002. The human water use for irrigation yielded an average regional cooling effect of -0.6 degrees C due to increased evapotranspiration and latent heat flux from the irrigated land. The runoff water diverted for irrigation was more than 80% of the pre-1950 runoff into the terminal Aral Sea, and was largely lost from the regional water system by the evapotranspiration increase. The Aral Sea shrank due to this water loss, resulting in decreased evaporation and latent heat flux from the pre-1950 Aral Sea area extent, with an average regional warming effect of 0.5 degrees C. In general, the endorheic (land-internal) runoff and relative consumptive use of irrigation water from that runoff determine the relative inland water area shrinkage, its warming effect, and to what extent the warming counteracts the cooling effect of irrigation. Citation: Destouni, G., S. M. Asokan, and J. Jarsjo (2010), Inland hydro-climatic interaction: Effects of human water use on regional climate.

  • 9.
    Jarsjö, Jerker
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Asokan, Shilpa M.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Bring, Arvid
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hydrological responses to climate change conditioned by historic alterations of land use and water use2012In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 16, no 5, p. 1335-1347Article in journal (Refereed)
    Abstract [en]

    This paper quantifies and conditions expected hydrological responses in the Aral Sea Drainage Basin (ASDB; occupying 1.3% of the earth's land surface), Central Asia, to multi-model projections of climate change in the region from 20 general circulation models (GCMs). The aim is to investigate how uncertainties of future climate change interact with the effects of historic human re-distributions of water for land irrigation to influence future water fluxes and water resources. So far, historic irrigation changes have greatly amplified water losses by evapotranspiration (ET) in the ASDB, whereas 20th century climate change has not much affected the regional net water loss to the atmosphere. Results show that errors in temperature (T) and precipitation (P) from single GCMs have large influence on projected change trends (for the period 2010-2039) of river runoff (R), even though the ASDB is spatially well resolved by current GCMs. By contrast, observed biases in GCM ensemble mean results have relatively small influence on projected R change trends. Ensemble mean results show that projected future climate change will considerably increase the net water loss to the atmosphere. Furthermore, the ET response strength to any future T change will be further increased by maintained (or increased) irrigation practices, which shows how climate change and water use change can interact in modifying ET (and R). With maintained irrigation practices, R is likely to decrease to near-total depletion, with risk for cascading ecological regime shifts in aquatic ecosystems downstream of irrigated land areas. Without irrigation, the agricultural areas of the principal Syr Darya river basin could sustain a 50% higher T increase (of 2.3 A degrees C instead of the projected 1.5 A degrees C until 2010-2039) before yielding the same consumptive ET increase and associated R decrease as with the present irrigation practices.

  • 10.
    Jarsjö, Jerker
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Asokan, Shilpa Muliyil
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Shibuo, Yoshihiro
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Water scarcity in the Aral Sea Drainage Basin: Contributions of agricultural irrigation and a changing climate2008In: Environmental Problems of Central Asia and their Economic, Social and Security Impacts. Book Series: Nato Science for Peace and Security Series C: Environmental Security; Qi J, Evered KT (Eds.), ISSN 1874-6519, p. 99-108Article in journal (Refereed)
  • 11.
    Muliyil Asokan, Shilpa
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hydro-climatic changes in irrigated world regions2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Understanding of hydro-climatic changes in the world’s river basins is required to ensure future food security. Different regional basins experience different levels of hydro-climatic change depending on the endorheic or exorheic nature of a hydrological basin, along with the climatic conditions and human land and water-use practices, for instance for irrigation. This thesis has analyzed long-term hydro-climatic changes in two main irrigated regions of the world: the Mahanadi River Basin in India and the Aral region in Central Asia. Thesis applies a basin-wise, data-driven water balance-constrained approach to quantifying the hydro-climatic changes, and to distinguish their main drivers in the past century and for future. Results point at human water-use and re-distribution for irrigation within a basin as a major driver of water balance changes, which also affect surface temperature in the region.

    Cross-regional comparison focused on the climatically important changes of water, vapor and latent heat fluxes at the land surface, and also on the changes to water resource availability in the landscape. Results show that irrigation- driven changes in evapotranspiration, latent heat fluxes and associated temperature changes at land surface may be greater in regions with small relative irrigation impacts on water availability in the landscape than in regions with severe such impacts. This implies that one cannot from the knowledge about only one aspect of hydro-climatic change simply extrapolate the impact importance of those changes for other types of water changes in a region.

    Climate model projections results show lack of consistency in individual GCM performance with regard to temperature and to precipitation, implying difficulties to identify well-performing GCMs with regard to both of these variables in a region. In Aral region, the thesis shows that ensemble mean of different GCM outputs may provide robust projection of future hydro-climate changes.

  • 12.
    Törnqvist, Rebecka
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Pietroń, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Bring, Arvid
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Rogberg, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Asokan, Shilpa M.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Evolution of the hydro-climate system in the Lake Baikal basin2014In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 519, p. 1953-1962Article in journal (Refereed)
    Abstract [en]

    Climatic changes can profoundly alter hydrological conditions in river basins. Lake Baikal is the deepest and largest freshwater reservoir on Earth, and has a unique ecosystem with numerous endemic animal and plant species. We here identify long-term historical (1938-2009) and projected future hydro-climatic trends in the Selenga River Basin, which is the largest sub-basin (>60% inflow) of Lake Baikal. Our analysis is based on long-term river monitoring and historical hydro-climatic observation data, as well as ensemble mean and 22 individual model results of the Coupled Model Intercomparison Project, Phase 5 (CMIP5). Study of the latter considers a historical period (from 1961) and projections for 2010-2039 and 2070-2099. Observations show almost twice as fast warming as the global average during the period 1938-2009. Decreased intra-annual variability of river discharge over this period indicates basin-scale permafrost degradation. CMIP5 ensemble projections show further future warming, implying continued permafrost thaw. Modelling of runoff change, however, is highly uncertain, with many models (64%) and their ensemble mean failing to reproduce historical behaviour, and with indicated future increase being small relative to the large differences among individual model results.

1 - 12 of 12
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