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Data-driven analysis of water and nutrient flows: Case of the Sava River Catchment and comparison with other regions
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. Department of Physical Geography and the Bolin Center for Climate Research, Stockholm University, Stockholm, Sweden; Department of Applied Hydraulics, Faculty of Civil Engineering, Architecture and Geodesy, University of Split, Split, Croatia.ORCID iD: 0000-0003-1225-3526
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A growing human population and demands for food, freshwater and energy are causing extensive changes in the water and biogeochemical cycles of river catchments around the world. Addressing and investigating such changes is particularly important for transboundary river catchments, where they impose additional risk to a region’s stability. This thesis investigates and develops data-driven methodologies for detecting hydro-climatic and nutrient load changes and their drivers with limited available data and on different catchment scales. As a specific case study, we analyze the Sava River Catchment (SRC) and compare its results with other world regions. A past–present to future evaluation of hydro-climatic data is done on the basis of a water balance approach including analysis of historic developments of land use and hydropower development data and projections of the Coupled Model Intercomparison Project, Phase 5 (CMIP5) output. Using observed water discharge and nutrient concentration data, we propose a novel conceptual model for estimating and spatially resolving total nitrogen (TN) and total phosphorus (TP) input and delivery-retention properties for a river catchment and its nested subcatchments, as well as detection of nutrient hotspots. The thesis identifies hydroclimatic change signals of hydropower-related drivers and finds consistency with other world regions. The proposed nutrient screening methodology provides a good distinction between human-related nutrient inputs and landscape-related transport influences on nutrient loading at subcatchment to catchment scale. A cross-regional comparison of the SRC data with the Baltic region shows similarity between nutrient-relevant indicators and driving socio-economic and hydro-climatic conditions. The study highlights a number of complexities with regard to CMIP5 model representation of water fluxes. The large intermodel range of CMIP5 future projections of fluxes calls for caution when using individual model results for assessing ongoing and future water and nutrient changes.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , 30 p.
Series
TRITA-LWR. PHD, ISSN 1650-8602 ; 2017:03
Keyword [en]
River catchment, Transboundary, Hydro-climatic change, Total nitrogen, Total phosphorus, CMIP5
National Category
Water Engineering
Research subject
Land and Water Resources Engineering
Identifiers
URN: urn:nbn:se:kth:diva-207102ISBN: 978-91-7729-415-3 (print)OAI: oai:DiVA.org:kth-207102DiVA: diva2:1095755
Public defence
2017-06-08, Sal F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
VR 2009-3221FORMAS 2014-43
Note

QC 20170516

Available from: 2017-05-16 Created: 2017-05-15 Last updated: 2017-05-17Bibliographically approved
List of papers
1. Hydroclimatic changes and drivers in the Sava River Catchment and comparison with Swedish catchments
Open this publication in new window or tab >>Hydroclimatic changes and drivers in the Sava River Catchment and comparison with Swedish catchments
2015 (English)In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, no 7, 624-634 p.Article in journal (Refereed) Published
Abstract [en]

In this study, we investigate long-term hydroclimatic changes and their possible relation to regional changes in climate, land-use and water-use over the twentieth century in the transboundary Sava River Catchment (SRC) in South Eastern Europe. In a hydropower dominated part of the SRC, unlike in an unregulated part, we find increase in average annual evapotranspiration and decrease in temporal runoff variability, which are not readily explainable by observed concurrent climate change in temperature and precipitation and may be more related to landscape-internal change drivers. Among the latter investigated here, results indicate hydropower developments as most closely related to the found hydroclimatic shifts, consistent with previous such indications in studies of Swedish hydropower catchments. Overall, the present results have quantitatively framed the recent history and present state of hydroclimate in the SRC, of relevance for water resources in several countries and for a majority of their populations. This provides a useful basis for further assessment of possible future hydroclimatic changes, under different scenarios of climate change and land/water-use developments in the region.

Keyword
Hydroclimatic change, Evapotranspiration, Runoff variability, Land-use, Hydropower, Sava River
National Category
Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-175901 (URN)10.1007/s13280-015-0641-0 (DOI)000362290300003 ()25753574 (PubMedID)2-s2.0-84942983490 (Scopus ID)
Funder
Swedish Research Council, 2009-3221
Note

QC 20151104

Available from: 2015-11-04 Created: 2015-10-26 Last updated: 2017-05-15Bibliographically approved
2. Data-driven analysis of nutrient inputs and transfer through nested catchments
Open this publication in new window or tab >>Data-driven analysis of nutrient inputs and transfer through nested catchments
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A data-driven screening methodology is developed for estimating nutrient inputs, deliveries and retentions in catchments with measured water discharges and nutrient concentrations along the river network. The methodology is also specifically applied to the Sava River Catchment (SRC), a major transboundary catchment in the Southeast Europe. A characteristic regional value emerges for nutrient input per unit area of around 30 T/yr/km2 for dissolved inorganic nitrogen (DIN) and 2 T/yr/km2 for total phosphorus (TP) in the relatively large nested catchments (>40 000 km2) of the SRC; fluctuating values are obtained for smaller nested catchments (of around 10 000 km2). The applied methodology also identifies hotspot catchments for nutrient input per unit area, in the range of 158 T/yr/km2 for DIN and 13 T/yr/km2 for TP, within the SRC. Furthermore, relative nutrient delivery is found to be scale-dependent, exhibiting power-law decay with increasing catchment area, with exponents of around 1.4-1.7 for both DIN and TP. At the largest catchment scale with available data within the SRC the relative delivery is around 0.08 for DIN and 0.03 for TP. Overall, the SRC nutrient data show similar nutrient relations to driving hydro-climatic conditions (runoff for nutrient loads) and socio-economic conditions (population density and farmland share for nutrient concentrations) as in the compared Baltic region.

Keyword
Total nitrogen, Total phosphorus, Input, Delivery, Loads, Methodology, (Sub)catchments
National Category
Other Environmental Engineering
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-207097 (URN)
Projects
VR 2009-3221FORMAS 2014-43
Note

QC 20170522

Available from: 2017-05-15 Created: 2017-05-15 Last updated: 2017-05-22Bibliographically approved
3. Implications of freshwater flux data from the CMIP5 multimodel output across a set of Northern Hemisphere drainage basins
Open this publication in new window or tab >>Implications of freshwater flux data from the CMIP5 multimodel output across a set of Northern Hemisphere drainage basins
Show others...
2015 (English)In: EARTHS FUTURE, ISSN 2328-4277, Vol. 3, no 6, 206-217 p.Article in journal (Refereed) Published
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.

Keyword
Freshwater system, Water fluxes, Water budget, Water change and variability, Land-atmosphere interactions, Hydro-climate
National Category
Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-171903 (URN)10.1002/2014EF000296 (DOI)000358142500003 ()2-s2.0-85000347807 (Scopus ID)
Funder
Swedish Research Council, 2009-3221
Note

QC 20150811

Available from: 2015-08-11 Created: 2015-08-10 Last updated: 2017-05-15Bibliographically approved
4. Multi-model projections of future hydro-climatic and nutrient-load evolution in the Sava River Catchment
Open this publication in new window or tab >>Multi-model projections of future hydro-climatic and nutrient-load evolution in the Sava River Catchment
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The direct output of the multi-model ensemble of the Coupled Model Intercompariosn Project, Phase 5 (CMIP5) for the Sava River Catchment shows high uncertainty of hydro-climatic changes for the two future scenarios but exhibits overall agreement with the direction of the changes with results of some previous studies conducted for the SRC. Of particular importance are runoff changes induced by climate change as they might influence nutrient pollution in the catchment and as such cause water quality issues on a subcatchment to catchment scale. Such changes might have impact not only for the waters of the SRC but also the Danube River Catchment and the Black Sea. As none of the models shows to out-perfom any other model in reproducing observed temperature and water fluxes or their changes, nutrient yield calculation based on the ensemble mean and particular models show wide range of results and make any possible conclusions challenging and potentially misleading.

Keyword
Sava River Catchment, Subcatchment, CMIP5, climate models, Hydro-climatic change, Dissolved inorganic nitrogen, Total phosphorus
National Category
Other Environmental Engineering
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-207099 (URN)
Projects
VR 2009-3221
Note

QC 20170522

Available from: 2017-05-15 Created: 2017-05-15 Last updated: 2017-05-22Bibliographically approved

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