A new study that looks at the water competition between cities and agriculture has found that urban water demand in 482 of the world’s largest cities will increase by 80% by 2050, leading to an acute urban surface-water deficit.
READ Land: SA’s real watershed moment Recent studies have estimated that between 3,5 billion and 4,4 billion people are expected to live with water scarcity in 2050 because of climate change and increasing water demand for human activities.
More than one billion urban residents may face water shortage in the future due to urbanisation and climate change.
Urban-rural comparison A new study, ‘Water competition between cities and agriculture driven by climate change and urban growth’, has assessed urban water provision amid climate change impacts and socioeconomic changes by 2050.
The study also provides estimates of the urban surface-water deficit, highlighting the competition between urban water provision, agricultural water demand and environmental flow requirements.
The study quantifies the urban surface-water deficit as well as additional withdrawals from groundwater resources (urban groundwater footprint) in the future by testing two scenarios.
Globally, under the urban-first priority scenario, about 14 000km2 of irrigated area will be at risk of crop-water deficit in transfer of water, showing that urban surface-water withdrawals decrease water security for people who live far from the city centre.
Reducing urban water deficit Altogether, 40% of the cities (409 million people) are vulnerable to urban surface-water deficits under the last-priority scenario because of competition with water abstractions for irrigation.
Urban water demand could be met in these basins by improving water-use efficiency of the agricultural sector as a soft-path measure to reduce irrigation-water withdrawals.
A moderate increase of 10% in irrigation water-use efficiency (0,3%/year over a 50-year period), could reduce the urban surface-water deficit by about 2,62 billion cubic metres and therefore help 78% of the vulnerable cities and their 236 million urbanites to overcome water deficits in the future.