Irrigation Potential Mapping Using Gis-Based Parametric Evaluation Approach In Upper Blue Nile River Basin, Ethiopia
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Date
2018-06-03
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Addis Ababa University
Abstract
In Ethiopia, irrigation potential of many rivers has not been studied in depth, and the current extent of irrigated areas is not known, as the source of information for local level irrigated areas are official reports rather than actual areas that deviate from the real irrigated areas. The ability of GIS to manipulate various types of data helps to perform complex analysis extracting information about spatially distributed phenomena in greater efficiency, which enables suitability analysis for large areas. Similarly, remote sensing can deliver useful spatial information on exact locations of irrigated lands rather than mere totals within arbitrary political units due to their synoptic coverage and high revisiting frequency. The present study was aimed to assess land suitability for different types of irrigation systems including surface, drip, and sprinkler methods by parametric approach, and mapping irrigated areas using OBIA of upper Blue Nile basin. The study also evaluated surface water irrigation potential of selected rivers in Choke mountain watersheds. The study used soil texture, soil depth, Calcium Carbonate (CaCO3) content, electrical conductivity, drainage and slope for suitability analysis. Multi-resolution segmentation and assign class algorithm to identify irrigated areas using spectral indices and mask features prepared for non-irrigable areas, using Sentinel 2A images. The analysis revealed that, 639,554.05 ha of the land was suitable for surface irrigation, 3,037,849.43 ha for sprinkler irrigation, and 5,506,189.33 ha for drip irrigation. The results show that the highest irrigation potential obtained on plain areas of Gojjam, Northern Shewa and lowlands of the basin. The main limiting factors were physical limitations of high slope and clay dominated soil texture. The total irrigated area is 310,707 ha for the year 2016/2017with overall accuracy of 91.04% was obtained. Major irrigated areas were identified in the north-eastern highlands of the basin mainly plain areas of Gojjam, while Abay valley and the western part of the basin are less irrigated. Validation was also done by comparing the final classified map of irrigated areas with official irrigation area statistics. The official statistics lacks spatial distribution and is a merely total of feasibility studies not the current status of irrigation schemes. It can there be concluded that satellite image processing using OBIA is a robust method for irrigated land mapping. Additional land of 2,398,295.38ha and 4,882,097.32 ha can be irrigated using sprinkler and drip irrigation, respectively. About 1800 ha of land can be irrigated at the gauge location of the rivers in Choke mountain watersheds without further development on the downstream.
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Blue Nile Basin, Irrigation, Land suitability evaluation, OBIA, Parametric method, Sentinel 2