Remote sensing based hydrological modelling for irrigation performance assessment in the lower reaches of the Amu Darya River in Central Asia

C Conrad, SW Dech, MM Hafeez, J. Lamers, B. Tischbein

Research output: Book chapter/Published conference paperConference paperpeer-review

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Abstract

According to FAO standards underperforming irrigation systems are reported from Central Asia, especially for the downstream parts of Amu Daryaand Syr Darya. A lack of reliable and consistent data for various reasons, is the major bottleneck to analyse the system functioning and irrigation performance in detail. To overcome these limitations is an important step towards integrated water resource management aiming improved environmental conditions in the Aral Sea Basin. Remote sensing may be a technical advance to contribute reliable and consistent data for a better understanding and assessment of the irrigation complexes at different spatial scales. This study utilizes satellite images for water balancing and irrigation performance assessments in Khorezm, a 275.000 ha sized hydrological unity, within the lower reaches of the Amu Darya. Agricultural land use was derived from 250 mMODIS NDVI time series. To calculate seasonal actual evapotranspiration (ETact) the widely used SEBAL model was applied to 1 km MODIS data for 63 days of the vegetation period 2005. Discharge measurements were recorded continuously in the irrigation and drainage channel system throughout the vegetation period 2005, covering 82 % of the irrigated land. Relative evapotranspiration (ETrel), depleted fraction (DF) and drainage ratio (DR) were calculated to disclose the functioning of the irrigation system at the scale of major distribution channels. A decreasing tendency of ET act towards the distal parts of the irrigation system demonstrated decreasing water availability at field complex level. In the downstream parts, crop water demand was not met whereas ETrel indicated water saving potentials in the upstream locations. But this upstream-downstream gradient of irrigation water supply was not found at the higher distribution level. 24.000 m3 water per ha agricultural land revealed very high water availability in 2005. DR of about 55 % indicated a functioning drainage; however, considerin drainage problems observed at field level and given the fact, that capillary rise contributes significantly to irrigation, it could be concluded that the drainage system empties the groundwater body at large scale, which was filled up by percolation losses in the irrigation system. Equally, low DF emphasized the risk of groundwater and soil salinity especially in the distant parts of the irrigation system. The case study underlined the under-performing irrigation system in the Khorezm region representing the lower reaches of the Amu Daryain Uzbekistan. Adequate water distribution, increased irrigation efficiency, and sustainable water use were identified as major challenges.
Original languageEnglish
Title of host publicationLand, Water and Environmental Management
Subtitle of host publicationIntegrated Systems for Sustainability
EditorsLes Oxley, Don Kulasiri
Place of PublicationChristchurch, New Zealand
PublisherModelling and Simulation Society of Australia and New Zealand
Pages2597-2603
Number of pages7
ISBN (Electronic)9780975840047
Publication statusPublished - 2007
EventInternational Congress on Modelling and Simulation (MODSIM) - Christchurch, New Zealand
Duration: 10 Dec 200713 Dec 2007

Conference

ConferenceInternational Congress on Modelling and Simulation (MODSIM)
CountryNew Zealand
CityChristchurch
Period10/12/0713/12/07

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