An Assessment of mean and inter-seasonal variation during growing season across Kano region, Nigeria using normalized difference vegetation index derived from SPOT satellite data

Fatima. A. G. Dakata¹ and Sadiq A. Yelwa²*

¹Department of Geography, Kano University of Science and Technology, P.M.B.3244 Wudil, Nigeria

²Department of Geography, Usmanu Danfodiyo University, P.M.B.2346 Sokoto

*Corresponding author E-mail: bubakar9@yahoo.co.uk; Tel: (+234) 8035074239, (+234) 8020616742

Accepted 27 July, 2012

Abstract

Kano Region covers Kano and Jigawa states both located in a semi-arid area of Nigeria that is characterised by large inter-annual variability in precipitation and consequently its vegetation. The aim of this assessment is to highlight changes in the mean and inter-seasonal variation of these variables that affected the general landcover of this area using Remote Sensing and GIS techniques. Fifty four (54) dekadal Normalized Difference vegetation Index (NDVI) images at 1km resolution from SPOT-4 and 5 Satellite System covering the growing season years from 1999 to 2007 were utilised within a GIS environment. Both the mean and a co-efficient of variation (COV) images covering the time series were derived from the assessment. Purposive sampling technique was also used to correlate the 2007 imagery to landcover reality through groundtruthing. The generated COV imagery was classified into seven classes showing percentage changes across the study area. Areas that exhibit highest coefficient of variation were found to be located within Jigawa state with few of such areas in Kano state. Although these changes during the growing season are attributed to anthprogenic factors in this semi-arid area, they are to a certain degree also attributed to climatic affects, particularly the changes on land cover across these two states in Nigeria.

Keywords: Dekadal, NDVI, Inter-seasonal variability, Growing season, Coefficient of Variation.