Decoupling crop production from water consumption at some irrigation schemes in southern Africa
Michael Wellington, Petra Kuhnert, Roger Lawes, Luigi J. Renzullo, Jamie Pittock, Peter Ramshaw, Martin Moyo, Emmanuel Kimaro, Miguel Tafula, André van Rooyen
Abstract
Improving crop productivity is crucial to food security and rural livelihoods in southern Africa. However, agricultural intensification at irrigation schemes may place greater demands on water resources, even where water use efficiency (WUE) is improved, due to the paradox of irrigation efficiency. We analysed trends in water use efficiency (WUE), Gross Primary Productivity (GPP), evapotranspiration (ET), evaporation (E), and transpiration (T) at six irrigation schemes which received technological and social interventions. GPP was decoupled from ET at some schemes. For example, at the Landela sub-block of the Silalatshani irrigation scheme in Zimbabwe, GPP and T increased at 4.8% and 4.6% per year, respectively. Conversely, E decreased at 13.5% per year, giving a 3.6% decrease in ET per year from 2013 to 2021. This suggests that crop production can be decoupled from water consumption at southern African irrigation schemes, meaning it is possible to produce more food with less water.