On the Global Water Productivity Distribution for Major Cereal Crops: some First Results from Satellite Measurements

Feeding the world requires 70 percent more food for an additional 2.3 billion people by 2050. The increasing competition for water resources prompts the modern consumer society to become more efficient with scarce water resources. The water footprint of agriculture is hundred times more than the footprint for domestic water use, yet we do not fully know how much water is used in relation to the amount of food being produced. Water Productivity describes the crop yield per unit of water consumed and is the ultimate indicator for the efficiency of water use in agriculture. Our basic understanding of actual and benchmark values for Water Productivity is limited, partially because operational measurements and guidelines for Water Productivity do not currently exist.

Remote sensing algorithms have been developed over the last 20 years to compute crop yield Y and evapotranspiration ET, often in an independent manner. The new WatPro and GlobWat algorithms are based on directly solving the Y/ET ratio. Several biophysical parameter and processes such as solar radiation, Leaf Area Index, stomatal aperture and soil moisture affect biomass production and crop transpiration simultaneously, and this enabled us to simplify the schematization of a Y/ET model. Global maps of wheat, rice and maize were prepared from various open-access data sources, and Y/ET was computed across a period of 10 years.

The global distribution demonstrates that 66 percent of the world’s agricultural land cultivated with wheat, rice and corn performs below average. Furthermore, Water Productivity in most countries exhibits a significant spatial variability. Therefore, there is significant scope to produce the same food - or more food - from less water resources if packages with good practices are locally implemented. The global maps of water productivity will be demonstrated, along with some country examples.