Abstract
Land use/land cover (LULC) changes have been observed in the Gaborone dam catchment since the 1980s. A comprehensive analysis of future LULC changes is therefore necessary for the purposes of future land use and water resource planning and management. Recent advances in geospatial modelling techniques and the availability of remotely sensed data have become central to the monitoring and assessment of both past and future environmental changes. This study employed the cellular automata and Markov chain (CA-Markov) model combinations to simulate future LULC changes in the Gaborone dam catchment. Classified Landsat images from 1984, 1995, 2005 and 2015 were used to simulate the likely LULCs in 2015 and 2035. Model validation compared the simulated and observed LULCs of 2015 and showed a high level of agreement with Kappa variation estimates of Kno (0.82), Kloc (0.82) and Kstandard (0.76). Simulation results indicated a projected increase of 26.09%, 65.65% and 55.78% in cropland, built-up and bare land categories between 2015 and 2035, respectively. Reductions of 16.03%, 28.76% and 21.89% in areal coverage are expected for shrubland, tree savanna and water body categories, respectively. An increase in built-up and cropland areas is anticipated in order to meet the population’s demand for residential, industry and food production, which should be taken into consideration in future plans for the sustainability of the catchment. In addition, this may lead to water quality and quantity (both surface and groundwater) deterioration in the catchment. Moreover, water body reductions may contribute to water shortages and exacerbate droughts in an already water-stressed catchment. The loss of vegetal cover and an increase in built-up areas may result in increased runoff incidents, leading to flash floods. The output of the study provides useful information for land use planners and water resource managers to make better decisions in improving future land use policies and formulating catchment management strategies within the framework of sustainable land use planning and water resource management.
Highlights
It revealed a slight overestimation of the tree savanna and water body categories, whereas builtup and cropland categories were shown to be marginally under simulated
This study attempted to simulate future Land use/land cover (LULC) changes in the Gaborone dam catchment, Botswana, from 2015 to 2035 using the cellular automata (CA)-Markov model, which assisted in giving a better understanding of possible LULC changes within the study area
Urbanisation and population growth stemming from rural-urban migrations to the city of Gaborone are expected to result in built-up expansions, whereas agricultural subsidy schemes will lead to expansions in croplands in the catchment
Summary
Land use/land cover (LULC) changes are a crucial driver of environmental change, and are increasingly becoming a global concern due to their impact on the local, regional and global environments [1,2]. Anthropogenic activities such as increasing population, urbanisation, deforestation, etc., are known to largely drive these changes [3,4]. In semi-arid areas in particular, the effects of LULC changes on water resources are of great concern, as these areas are known to be more vulnerable to both natural and human-induced changes [6] This often results in modifications in the hydrological cycle [7,8,9] by disrupting hydrological processes such as the interception of water
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