Remote sensing-based identification and mapping of salinised irrigated land between Upington and Keimoes along the lower Orange River, South Africa

dc.contributor.advisorZietsman, H. L.
dc.contributor.authorMashimbye, Zama Ericen_ZA
dc.contributor.otherUniversity of Stellenbosch. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies.
dc.descriptionThesis (MA (Geography and Environmental Studies))--University of Stellenbosch, 2005.
dc.description.abstractSalinisation is a major environmental hazard that reduces agricultural yields and degrades arable land. Two main categories of salinisation are: primary and secondary soil salinisation. While primary soil salinisation is caused by natural processes, secondary soil salinisation is caused by human factors. Incorrect irrigation practices are the major contributor to secondary soil salinisation. Because of low costs and less time that is associated with the use of remote sensing techniques, remote sensing data is used in this study to identify and map salinised irrigated land between Upington and Keimoes, Northern Cape Province, in South Africa. The aim of this study is to evaluate the potential of digital aerial imagery in identifying salinised cultivated land. Two methods were used to realize this aim. The first method involved visually identifying salinised areas on NIR, and NDVI images and then digitizing them onscreen. In the second method, digital RGB mosaicked, stacked, and NDVI images were subjected to unsupervised image classification to identify salinised land. Soil samples randomly selected and analyzed for salinity were used to validate the results obtained from the analysis of aerial photographs. Both techniques had difficulties in identifying salinised land because of their inability to differentiate salt induced stress from other forms of stress. Visual image analysis was relatively successful in identifying salinised land than unsupervised image classification. Visual image analysis correctly identified about 55% of salinised land while only about 25% was identified by unsupervised classification. The two techniques predict that an average of about 10% of irrigated land is affected by salinisation in the study area. This study found that although visual analysis was time consuming and cannot differentiate salt induced stress from other forms; it is fairly possible to identify areas of crop stress using digital aerial imagery. Unsupervised classification was not successful in identifying areas of crop stress.en_ZA
dc.publisherStellenbosch : University of Stellenbosch
dc.subjectRemote sensingen_ZA
dc.subjectNormalized difference vegetation index (NDVI)en_ZA
dc.subjectImage classificationen_ZA
dc.subjectPlant stressen_ZA
dc.subjectDissertations -- Geography and environmental studiesen
dc.subjectTheses -- Geography and environmental studiesen
dc.titleRemote sensing-based identification and mapping of salinised irrigated land between Upington and Keimoes along the lower Orange River, South Africaen_ZA
dc.rights.holderUniversity of Stellenbosch

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