Assessment of irrigation expansion and implications for water resources by using RS and GIS techniques in the Lake Tana
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Assessment of irrigation expansion and implications for water resources by using RS and GIS techniques in the Lake Tana Basin of Ethiopia Abebech Abera & Niko E. C. Verhoest & Seifu Tilahun & Hilary Inyang & Jan Nyssen
Received: 20 December 2019 / Accepted: 25 November 2020 # The Author(s), under exclusive licence to Springer Nature Switzerland AG part of Springer Nature 2020
Abstract Understanding irrigation expansion and its implications on water availability is critical for development of decision support tools for sustainable water resources planning. Irrigation expansion in the Lake Tana Basin of Ethiopia from 1986 to 2016 was examined using image classification from thematic maps and remote sensing imagery (Landsat5-8 TM/ETM+, OLI). The soil-adjusted vegetation index (SAVI) imagery was used to identify irrigated cropland based on greenness. Irrigation water consumption was determined by calculating irrigation water requirements of the major crops grown with irrigation and using the estimated irrigated land size of the basin. Irrigated croplands have increased in area from 55 to 65 % in the last past 30 years (from 1986 to 2016). The classification obtained is accurate to the level of 89.6% and Kappa coefficient of 0.83. The Landsat imagery is useful in tracking of the spatiotemporal patterns of irrigated croplands for water management purposes, especially in data deficient areas dotted sparsely by small holder irrigated A. Abera (*) : S. Tilahun : H. Inyang Civil and Water Resources Engineering Faculty, Bahir Dar University, 239 Bahir Dar, Ethiopia e-mail: [email protected] A. Abera Blue Nile Water Institute, Bahir Dar University, Bahir Dar, Ethiopia N. E. C. Verhoest Laboratory of Hydrology and Water Management, Ghent University, Ghent, Belgium J. Nyssen Department of Geography, Ghent University, Ghent, Belgium
farms. The results indicated that irrigation consumption in the basin increased from 0.380 km3 year-1 in 1986 to 0.798 km3 year-1 in 2016. It is found that the available water cannot sustain the projected irrigation expansion unless alternative water sources are found. Also, more precise irrigation technologies have to be implemented to minimize water losses. Keywords Irrigation consumption . Abay Basin . Land use . Irrigated lands . Satellite imagery . SAVI
Introduction Availability of water is a critical factor in agricultural decision-making and economic outcomes (Chance et al. 2018). Among competitive fresh water user sectors, irrigated agriculture is the leading fresh water consumer (Burton 2010; Zwart and Bastiaanssen 2004), and it plays a significant role in efforts to meet the projected food demand (Ambika et al. 2016). Agricultural water resources planning and management need spatially explicit irrigated area information (Ambika et al. 2016; Thenkabail et al. 2009). Irrigated area refers to areas that receive full or partial application of water by artificial means, at least, once annually to meet its water requirements during the growing period (Ambika et al. 2016; Ozdogan et al. 2010;
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