| Abstract |
Surface and groundwater sources are vital to sustainable livelihood. They constitute a key component of human life, and in achieving the Sustainable Development Goals outlined by the United Nations. However, with the rise in industrialisation, population growth and an increase in anthropogenic activities, the quality of the water sources is of great concern when considering its suitability for irrigated agriculture. This study was therefore, aimed at profiling the microbial and physico-chemical characteristics of the water used for irrigation of horticultural crops in alignment with water and food security under climate change in Namibia. Surface and groundwater, and sediment samples were collected from four irrigation schemes and farms in the Grootfontein-Otavi-Tsumeb area. Physico-chemical analysis was conducted at the Namibia University of Science and Technology and the Namibia Water Corporation laboratories using Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES). DNA extraction and sequencing were performed at Inqaba Biotech. To assess the impact of climate change on water availability and its impact on food security, historical data on major staple food crops’ production was obtained from the Namibian Agronomic Board from 2010 to 2024 and, monthly climatic parameter data of precipitation, climatic temperature, relative humidity and evapotranspiration were obtained from CHIRPS’ gridded data, and from NASA Climatology Resource for Agroclimatology for the period of 1972-01-01 to 2023-12-01. Results indicated that the abundance of ions in analysed water samples was in the following order: Na+ > Mg2+ > Ca2+ > K+ and alkalinity > SO42- > Cl- > NO3- > F- > NO2-. The water quality indices showed that all the water samples ranged from being permissible to excellent for Na%, while 48% of the samples were classified as water that could be used safely for irrigation according to the Residual Sodium Carbonate index. The index-based assessment of the irrigation water quality is appropriate in decision-making processes, when it comes to identifying surface and ground water sources that are suitable for irrigation schemes and, in establishing preventive measures against crop damage for enhanced productivity in alignment with SDGs 2, 3, 6, 12, 14, and 15. Furthermore, the profile of the microbial community composition of the water indicated that Pseudomonadota was the most prevalent phylum, dominating 54% of samples, particularly in groundwater sources, where it constituted 93% of microbial communities in Grootfontein. The presence of faecal indicator organisms in the irrigation water, confirmed by the detection of Escherichia coli in Shadikongoro and Ndonga Linena, underscores the necessity of understanding microbial community structure to enhance water management strategies for producing safe horticultural products, thereby protecting human, plant, and environmental health, and advancing sustainable development goals. Lastly, trend analysis of the precipitation versus the production of major crops showed in 2019 when the precipitation was 469mm, white maize, wheat and pearl millet productions were 28887, 4466 and 278 tons respectively, while in 2020 when the precipitation rose to 976mm, the crop production was 66642, 11498 and 4139 tons respectively for white maize, wheat and pearl millet. Therefore, climate change is indeed affecting food production and security. |
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