Abstract
The scarcity of water and the growing global food demand has fevered the debate on how to increase agricultural production without further depleting water resources. Crop water productivity (CWP) is a performance indicator to monitor and evaluate water use efficiency in agriculture. Often in remote sensing datasets of CWP and its components, i.e. crop yield or above ground biomass production (AGBP) and evapotranspiration (ETa), the end-users and developers are different actors. The accuracy of the datasets should therefore be clear to both users and developers. We assess the accuracy of remotely sensed CWP against the accuracy of estimated in-situ CWP. First, the accuracy of CWP based on in-situ methods, which are assumed to be the user's benchmark for CWP accuracy, is reviewed. Then, the accuracy of current remote sensing products is described to determine if the accuracy benchmark, as set by in-situ methods, can be met with current algorithms. The percentage error of CWP from in-situ methods ranges from 7% to 67%, depending on method and scale. The error of CWP from remote sensing ranges from 7% to 22%, based on the highest reported performing remote sensing products. However, when considering the entire breadth of reported crop yield and ETa accuracy, the achievable errors propagate to CWP ranges of 74% to 108%. Although the remote sensing CWP appears comparable to the accuracy of in-situ methods in many cases, users should determine whether it is suitable for their specific application of CWP.
Highlights
Over the past decades, the use of crop water productivity (CWP) as an agricultural performance indicator has increased
The use of crop water productivity (CWP) as an agricultural performance indicator has increased. This indicator is specified in the United Nations (UN) Sustainable Development Goals (SDGs), which stipulate that agricultural productivity should be doubled by 2030 (SGD2.3) and that water use efficiency must substantially increase (SDG6.4) (UN, 2016)
CWP provides a way to benchmark and define goals, objectives or gaps for management and decision making (Hellegers et al, 2009)
Summary
The use of crop water productivity (CWP) as an agricultural performance indicator has increased. This indicator is specified in the United Nations (UN) Sustainable Development Goals (SDGs), which stipulate that agricultural productivity should be doubled by 2030 (SGD2.3) and that water use efficiency must substantially increase (SDG6.4) (UN, 2016). CWP, as an indicator, is a measurable property that allows users to monitor and evaluate agricultural water productivity. The application of remote sensing in estimating agricultural performance indicators is increasing as it offers a cost effective reproducible method for measurement that can cover larger physical areas as compared to in-situ methods, such as field water balances or ground measurements (Sadras et al, 2015)
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