Geospatial modelling of land use/land cover dynamics in the Gongola basin for water resource applications through CA-Markov

摘要

The Gongola basin has witnessed tremendous environmental changes over the last three decades as a direct consequence of urban growth, deforestation (including encroachment of existing forest reserves), agricultural expansion, overgrazing, bush burning, drought and recurrent flooding episodes. The impact of these changes is influential on the basin’s hydrology, water resource and ecological process, yet, future land cover information to evaluate possible implications on its hydrology and the overall ecosystem is non-existence. Consequently, this study attempts to simulate future land cover demands of 2028 and 2038 for the basin, based on land cover images of 1988, 2003 and 2018 to develop land use/landcover (LU/LC) scenarios for possible hydrologic impact assessments. The method of the research therefore, premised on the use of cellular automata and Markov chain (CA-Markov) model, driven by a number of factors and constraints. Results indicate the land cover change to be mainly driven by rapid growth in urban and agricultural lands, contrary to the vegetation cover, which had been the dominant land cover type in the past. Besides, during the 30 years period, there were noticeable 37.05, 20.21 and 11.55 % increase in urban built-up, bare surface and agricultural land respectively, at the detriment of natural vegetation, which has itself decreased by 18.78 % over the period, with an estimated annual loss of approximately 330 km2 of natural vegetation. The decrease in the coverage area of water body was significant (3.55 %) for the same period. Findings from future simulations of LU/LC trends in the basin, show that urban area would have increased by 39 % and agriculture by 34 % by 2028 relative to the baseline period of 2003. Conversely, the natural vegetation trailed a declining trend (39 %) higher in magnitude than the preceding years. The developed LU/LC scenarios for the basin can provide an opportunity for water resource managers and experts to understand the trends in changing land use for effective planning and management.