Effect of climate change on land suitability for surface irrigation and irrigation potential of the shallow groundwater in Ghana

Despite consistent growth, the country remains a major net importer of agricultural food products due to heavy reliance on rainfed production and drought vulnerability. Less than 2% of the total cultivatable area in Ghana is estimated to be under irrigated production, with the area under small-scale irrigation by individual farmers being about five times that under formal private or public communal irrigation schemes. Agriculture is vulnerable to climate change, which affects food security, human health, livestock production, and marine ecosystems. Climate change will have a significant effect on agriculture production in sub-Saharan countries due to higher seasonal rainfall variability and lower water availability. A temperature increase and rainfall reduction and higher variability will make many agricultural areas less productive or even completely unsuitable for agriculture. Understanding the effect of climate change on land use suitability will help in developing mechanisms to ensure resilience and reduce vulnerability. To address this challenge, a GIS-based Multi-Criteria Evaluation (MCE) technique was applied to identify the spatial distribution of land potentially suitable for shallow groundwater irrigation under both current and future climate conditions. The MCE technique considers multiple factors affecting the suitability of a certain land area for irrigation, including biophysical features such as climate, land use, soil, and slope, and socioeconomic factors such as proximity to roads and population density. These factors were weighted using a pairwise comparison matrix and then reclassified and overlaid on a 30 m grid to estimate the irrigation potential of the country. Groundwater data from the British Geological Survey (BGS) were superimposed onto the land suitability map layer to evaluate the irrigation potential and the accessibility of shallow groundwater with simple water lifting technologies. Downscaled and bias-corrected future climate data from HadGEM2-ES under Representative Concentration Pathways (RCP) 4.5 emission scenario were used to represent the future climate horizon. The study found that approximately 9% of the country is suitable for surface irrigation under the baseline period, with a large portion of the potential land located in the southwestern part of the country. The potential suitable land has an average groundwater access of 12 m from the surface with an average borehole potential yield of 2.5 L/second, making it favorable for utilization of simple water lifting technologies. However, due to climate change, 9.5% of the suitable land will become unfavorable for irrigation in 2050s, and it is expected to reach 17% in 2070s. The study provides valuable information to researchers, decision makers, practitioners, and investors to prioritize irrigated agriculture scaling in Ghana and devise policies to mitigate the impacts of climate change on irrigated agriculture.