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Basin-scale change in water availability and water quality under intensified irrigated agriculture
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
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.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 38
Keyword [en]
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
Identifiers
URN: urn:nbn:se:su:diva-93214ISBN: 978-91-7447-724-5 (print)OAI: oai:DiVA.org:su-93214DiVA: diva2:645547
Public defence
2013-10-18, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

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
List of papers
1. Reduction of Water Losses by Use of Alternative Irrigation Techniques in the Aral Sea Drainage Basin
Open this publication in new window or tab >>Reduction of Water Losses by Use of Alternative Irrigation Techniques in the Aral Sea Drainage Basin
2011 (English)In: Sustainable agricultural development: Recent approaches in resources management and environmentally-balanced production enhancement / [ed] Mohamed Behnassi; Shabbir A Shahid; Joyce D'Silva, Springer Netherlands, 2011, 157-168 p.Chapter in book (Refereed)
Abstract [en]

The Aral Sea drainage basin (ASDB) in Central Asia is a region under severe water stress. Its population depends to a large extent economically on irrigated agriculture, which consumes over 90% of the withdrawn freshwater in the drainage basin. There is thus a strong need to increase the water productivity, i.e. the ratio between crop production and water use. We analyse impacts on water use of possible large-scale implementations of alternative irrigation techniques, replacing traditional furrow irrigation on cotton fields in the ASDB. We base our quantifications on experimental field comparisons of yield and water use between traditional furrow irrigation and alternative irrigation techniques (drip irrigation, alternate furrow irrigation, surge flow irrigation and surge flow irrigation on alternate furrows). All alternative methods, except drip irrigation, are associated with lower cotton yields than the traditional furrow irrigation. In order to keep the cotton production unchanged when yields are lower, extended irrigation areas are needed, over which non-negligible additional water volumes will be lost. We show that despite such negative feedback effects, the irrigation water use on cotton fields in the ASDB could decrease by as much as 10 km3/year, if the traditional furrow irrigation were to be replaced by one of the investigated alternative methods. Such decreases in water use can considerably influence the hydrological conditions in the entire basin. In particular, by reducing the severe water stress in the lower ASDB, which suffers from elevated groundwater tables, and high soil and groundwater salinity.

Place, publisher, year, edition, pages
Springer Netherlands, 2011
National Category
Environmental Sciences Oceanography, Hydrology, Water Resources
Identifiers
urn:nbn:se:su:diva-67753 (URN)10.1007/978-94-007-0519-7_11 (DOI)978-94-007-0518-0 (ISBN)
Available from: 2012-01-01 Created: 2012-01-01 Last updated: 2013-09-05Bibliographically approved
2. Water Savings Through Improved Irrigation Techniques: Basin-Scale Quantification in Semi-Arid Environments
Open this publication in new window or tab >>Water Savings Through Improved Irrigation Techniques: Basin-Scale Quantification in Semi-Arid Environments
2012 (English)In: Water resources management, ISSN 0920-4741, E-ISSN 1573-1650, Vol. 26, no 4, 949-962 p.Article in journal (Refereed) Published
Abstract [en]

In many semi-arid and arid regions of the world, water saving strategies need to be implemented in the agricultural sector in order to increase the resilience to water scarcity. We investigate basin-scale hydrological impacts of possible irrigation technique improvements, considering extensive cotton fields in the Aral Sea drainage basin (ASDB), Central Asia. We use a distributed hydrologic model that combines basin-scale, calibrated discharge and evapotranspiration quantifications with experimental results of (on-farm) water application needs for different irrigation techniques. This allows for quantification of how return flows contribute to river discharge through coupled groundwater-surface water-systems at the basin scale, under different regional climatic conditions. Results show that an implementation of improved irrigation techniques can yield water savings that increase the discharge to the Aral Sea by between 1 and 6 km3/year. Such water savings could contribute to mitigation of the acute water scarcity in the lower ASDB. The basin-scale water savings are about 60% lower than corresponding on-farm reductions in irrigation water application, since water is re-used and, hence, return flows decrease when less water is applied. Spatial analysis of regional differences in climatic conditions shows that implementation of more efficient irrigation systems would result in much larger (up to a factor 4) water savings in the more arid downstream regions than in the colder, upstream mountainous regions.

Keyword
Irrigation, Return flows, Semi-arid, Basin-scale modelling, Central Asia
National Category
Oceanography, Hydrology, Water Resources
Identifiers
urn:nbn:se:su:diva-67752 (URN)10.1007/s11269-011-9819-9 (DOI)000301748200007 ()
Note

2

Available from: 2012-01-01 Created: 2012-01-01 Last updated: 2017-12-08Bibliographically approved
3. Health risks from large-scale water pollution: Trends in Central Asia
Open this publication in new window or tab >>Health risks from large-scale water pollution: Trends in Central Asia
2011 (English)In: Environment International, ISSN 0160-4120, E-ISSN 1873-6750, Vol. 37, no 2, 435-442 p.Article in journal (Refereed) Published
Abstract [en]

Limited data on the pollution status of spatially extensive water systems constrain health-risk assessments at basin-scales. Using a recipient measurement approach in a terminal water body, we show that agricultural and industrial pollutants in groundwaters urface water systems of the Aral Sea Drainage Basin (covering the main part of Central Asia) yield cumulative health hazards above guideline values in downstream surface waters, due to high concentrations of copper, arsenic, nitrite, and to certain extent dichlorodiphenyltrichloroethane (DDT). Considering these high-impact contaminants, we furthermore perform trend analyses of their upstream spatial–temporal distribution, investigating dominant large-scale spreading mechanisms. The ratio between parent DDT and its degradation products showed that discharges into or depositions onto surface waters are likely to be recent or ongoing. In river water, copper concentrations peak during the spring season, after thawing and snow melt. High spatial variability of arsenic concentrations in river water could reflect its local presence in the top soil of nearby agricultural fields. Overall, groundwaters were associated with much higher health risks than surface waters. Health risks can therefore increase considerably, if the downstream population must switch to groundwater-based drinking water supplies during surface water shortage. Arid regions are generally vulnerable to this problem due to ongoing irrigation expansion and climate changes.

Keyword
Aral Sea, Health risk, Pollution, Irrigation, Surface water, Groundwater
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-53291 (URN)10.1016/j.envint.2010.11.006 (DOI)000287620100017 ()
Available from: 2011-01-21 Created: 2011-01-21 Last updated: 2013-09-05Bibliographically approved
4. Mechanisms of basin-scale nitrogen load reductions under intensified irrigated agriculture
Open this publication in new window or tab >>Mechanisms of basin-scale nitrogen load reductions under intensified irrigated agriculture
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Irrigated agriculture can modify the cycling of nitrogen (N), due to associated water diversions, water losses, and changes in transport pathways. We investigate dominant processes behind observed long-term changes in dissolved inorganic nitrogen (DIN) concentrations and loads of the extensive (465,000 km2) semi-arid Amu Darya river basin (ADRB) in Central Asia. We specifically consider a 40-year period (1960-2000) of large irrigation expansion, reduced river water flows, increased fertilizer application and net increase of N input into the soil-water system. Results show that observed decreases in riverine DIN concentration near the Aral Sea outlet of ADRB primarily are due to increased recirculation and reuse of irrigation water, which extends the flow-path lengths and enhances N attenuation-retention. The observed DIN concentrations matched a developed analytical relation between concentration attenuation and recirculation ratio, showing that basin-scale attenuation - retention effects of recirculation may be considerable, which previously only have been observed in laboratory experiments and at agricultural plots. Increased recirculation can furthermore have contributed to observed increases in N attenuation in agriculturally dominated drainage basins in different parts of the world. A six-fold lower DIN export from ADRB during the period 1981-2000, compared to the period 1960-1980, is the combined result of drastic river flow reduction and decreased DIN concentrations at the basin outlet. Several arid and semi-arid regions around the world are projected to undergo similar reductions in discharge as the ADRB due to climate change and agricultural intensification, and may therefore undergo comparable shifts in N export as shown here for the ADRB.

Keyword
Irrigation, Hydrology, Nitrogen, Attenuation, Recirculation, Semi-arid zone, Central Asia
National Category
Oceanography, Hydrology, Water Resources
Identifiers
urn:nbn:se:su:diva-93212 (URN)
Available from: 2013-09-04 Created: 2013-09-04 Last updated: 2013-09-17Bibliographically approved
5. Climate-driven change in circulation of nitrogen and irrigation water: Multi-model projections for Central Asia
Open this publication in new window or tab >>Climate-driven change in circulation of nitrogen and irrigation water: Multi-model projections for Central Asia
(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
Climate change, irrigation, nitrogen attenuation, land-use change, GCM, DIN, water quality, river flow
National Category
Oceanography, Hydrology, Water Resources
Identifiers
urn:nbn:se:su:diva-93213 (URN)
Available from: 2013-09-04 Created: 2013-09-04 Last updated: 2013-09-05Bibliographically approved

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