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Climate-driven change in circulation of nitrogen and irrigation water: Multi-model projections for Central Asia
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Department of Physical Geography and Geoecology, Charles University in Prague.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Agricultural intensification in semi-arid regions comes at a cost of relatively high water losses through evapotranspiration and can contribute to releases of nutrients and pesticides that affect downstream water quality. In addition, highly managed river basins may be particularly sensitive to future climate change. However, effects on attenuation and transformation of nutrients are difficult to quantify due to the complexity and variability of relevant processes. We here use the example case of the large (covering 1.3% of the earth’s land surface) and extensively irrigated Aral Sea Drainage Basin (ASDB) in Central Asia, together with 65 GCM projection results and field-data driven nitrogen attenuation modeling, to investigate to which extent projected future climate change (for years 2025, 2050 and 2100) can influence nitrogen cycling and attenuation. Results show that water and nitrogen circulation are sensitive to climate-driven changes in discharge of the principal Amu Darya River in the ASDB. This is likely the case also for other highly managed river basins across the world. Specifically, we show that riverine concentrations of nitrogen may decrease considerably throughout the coming century. This is due to projected climate-related decreases in river flow at the basin outlet, which increases internal nitrogen recirculation ratios, average transport distances, and attenuation.

Keyword [en]
Climate change, irrigation, nitrogen attenuation, land-use change, GCM, DIN, water quality, river flow
National Category
Oceanography, Hydrology, Water Resources
URN: urn:nbn:se:su:diva-93213OAI: diva2:645536
Available from: 2013-09-04 Created: 2013-09-04 Last updated: 2013-09-05Bibliographically approved
In thesis
1. Basin-scale change in water availability and water quality under intensified irrigated agriculture
Open this publication in new window or tab >>Basin-scale change in water availability and water quality under intensified irrigated agriculture
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Changes in land use and water use can greatly impact the cycling of water and water-borne substances. Increased redistribution of river water to irrigated fields can cause enhanced evapotranspiration and decreased river discharge. Additionally, the water quality can be affected by the external input of fertilisers and pesticides, and by changed pollutant transport pathways in expansive irrigation canal systems. This thesis examines basin-scale changes in water use, river discharge, water quality and nitrogen (N) loading under conditions of intensified irrigated agriculture, using the Aral Sea drainage basin (ASDB) with its two large rivers Syr Darya and Amu Darya in Central Asia as study area. Results show that more efficient irrigation techniques could reduce outtake of river water to the cotton fields in the ASDB by about 10 km3/year, while the corresponding river water saving at the outlet would be 60% lower. The result illustrates the importance of accounting for return flows of irrigation water in basin-scale water saving assessments. Moreover, a decrease in riverine N concentrations at the outlet of the Amu Darya River Basin (ADRB) was observed during a 40-year period of increasing N fertiliser input. The decrease was identified to be primarily caused by increased recirculation of river water in the irrigation system, leading to increased flow-path lengths and enhanced N attenuation. Decreasing N loads were shown to be primarily related to reduced discharge. N export from the basin may further decrease due to projected discharge reductions related to climate change. Furthermore, nutrients and metals were occasionally found at concentrations above drinking water guideline values in surface waters in the ADRB. However, metal concentrations in groundwater in the lower ADRB were subject to orders of magnitude higher health hazards. Projected decrease in downstream surface water availability would thus imply decreased access to water suitable for drinking.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2013. 34 p.
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 38
Irrigation, Hydrology, Land-use change, Basin-scale, Central Asia, Aral Sea, Semi-arid, Return flow, Water saving, Health risk, Water quality, Surface water, Groundwater, Nitrogen, Attenuation, Recirculation, Climate change
National Category
Oceanography, Hydrology, Water Resources
Research subject
Physical Geography
urn:nbn:se:su:diva-93214 (URN)978-91-7447-724-5 (ISBN)
Public defence
2013-10-18, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Manuscript.

Available from: 2013-09-26 Created: 2013-09-04 Last updated: 2013-09-25Bibliographically approved

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Jarsjö, JerkerTörnqvist, Rebecka
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