title: Water Productivity Mapping (WPM) Using Landsat ETM+ Data for the Irrigated Croplands of the Syrdarya River Basin in Central Asia.
abstract: The overarching goal of this paper was to espouse methods and protocols for water productivity mapping (WPM) using high spatial resolution Landsat remote sensing data. In a world where land and water for agriculture are becoming increasingly scarce, growing "more crop per drop" (increasing water productivity) becomes crucial for food security of future generations. The study used time-series Landsat ETM+ data to produce WPMs of irrigated crops, with emphasis on cotton in the Galaba study area in the Syrdarya river basin of Central Asia. The WPM methods and protocols using remote sensing data consisted of: (1) crop productivity (ton/ha) maps (CPMs) involvingcrop type classification, crop yield and biophysical modeling, and extrapolating yield models to larger areas using remotely sensed data; (2) crop water use (m³/ha) maps (WUMs) (or actual seasonal evapotranspiration or actual ET) developed through Simplified Surface Energy Balance (SSEB) model; and (3) water productivity (kg/m³) maps (WPMs) produced by dividing raster layers of CPMs by WUMs. The SSEB model calculated WUMs (actual ET) by multiplying the ET fractionby reference ET. The ETfraction was determined using Landsat thermal imagery by selecting the "hot" pixels (zero ET) and "cold" pixels (maximum ET). The grass reference ET was calculated by FAO Penman-Monteith method using meteorological data. The WPMs for the Galaba study area demonstrated a wide variations (0-0.54 kg/m³) in water productivity of cotton fields with overwhelming proportion (87%) of the area having WP less than 0.30 kg/m³, 11% of the area having WP in range of 0.30-0.36 kg/m³, and only 2% of the area with WP greater than 0.36 kg/m³. These results clearly imply that there are opportunities for significant WP increases in overwhelming proportion of the existing croplands. The areas of low WP are spatially pin-pointed and can be used as focus for WP improvements through better land and water management practices.
authors.affiliation: International Water Management Institute (IWMI), 127, Sunil Mawatha, Colombo, Sri Lanka. a.platonov@cgiar.org.|International Water Management Institute (IWMI), Apt. 123, House 6, Murtazaeva Street, Tashkent 700000, Uzbekistan. a.platonov@cgiar.org.
authors.forename: Alexander
authors.initials: A
authors.lastname: Platonov
authors.affiliation: U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001, USA. pthenkabail@usgs.gov.
authors.forename: Prasad S
authors.initials: PS
authors.lastname: Thenkabail
authors.affiliation: University of Oklahoma, 101 David L. Boren Blvd, Norman, Oklahoma 73019, USA.
authors.forename: Chandrashekhar M
authors.initials: CM
authors.lastname: Biradar
authors.affiliation: International Water Management Institute (IWMI), 127, Sunil Mawatha, Colombo, Sri Lanka.
authors.forename: Xueliang
authors.initials: X
authors.lastname: Cai
authors.affiliation: International Water Management Institute (IWMI), 127, Sunil Mawatha, Colombo, Sri Lanka.
authors.forename: Muralikrishna
authors.initials: M
authors.lastname: Gumma
authors.affiliation: United Nations Joint Logistics Center, Juba, Sudan.
authors.forename: Venkateswarlu
authors.initials: V
authors.lastname: Dheeravath
authors.affiliation: Institute of Agricultural Engineering, ARO, Volcani center, Bet Dagan 50250, Israel.
authors.forename: Yafit
authors.initials: Y
authors.lastname: Cohen
authors.affiliation: Institute of Agricultural Engineering, ARO, Volcani center, Bet Dagan 50250, Israel.
authors.forename: Victor
authors.initials: V
authors.lastname: Alchanatis
authors.affiliation: University of Soil Sciences, ARO, Volcani center, Bet Dagan 50250, Israel.
authors.forename: Naftali
authors.initials: N
authors.lastname: Goldshlager
authors.affiliation: Department of Geography, P.O. B. 39040, Tel-Aviv University 69989, Israel.
authors.forename: Eyal
authors.initials: E
authors.lastname: Ben-Dor
authors.affiliation: International Water Management Institute (IWMI), 127, Sunil Mawatha, Colombo, Sri Lanka.
authors.forename: Jagath
authors.initials: J
authors.lastname: Vithanage
authors.affiliation: International Water Management Institute (IWMI), 127, Sunil Mawatha, Colombo, Sri Lanka.
authors.forename: Herath
authors.initials: H
authors.lastname: Manthrithilake
authors.affiliation: Central Asian Scientific Research Institute of Irrigation, Block 11, Karasu-4, Tashkent, 700187, Uzbekistan.
authors.forename: Shavkat
authors.initials: S
authors.lastname: Kendjabaev
authors.affiliation: Scientific Research Institute for Growing Cotton, Uzbekistan, Tashkent.
authors.forename: Sabirjan
authors.initials: S
authors.lastname: Isaev
keywords: Central Asia; Syrdarya river basin; Water productivity mapping; crop productivity; crop yield modeling; remote sensing; simplified surface energy balance model; water use