New Technology for Affordable and Deployable Direct Evapotranspiration Measurements

Declining water availability is among key global concerns in the modern society manifesting uniquely at different scales, from the farm field to the global food distribution, and requires innovative composite solutions in terms of policy, education, science, and technology. Solutions to water use in agriculture require resource management based upon socioeconomic and scientific understanding.

These important goals are achieved through crucial regulatory, societal, and technical means. Among the latter, monitoring of water flows at multiple scales, from the field to the state and beyond, can help achieve water use reduction, optimization and prediction. Even small water savings, when achieved at scale, can bring about massive benefits. To properly track and document single digit percent improvements, measurement accuracy is especially important, and cannot ordinarily be achieved with indirect evapotranspiration (ET) estimations such as potential, reference or equilibrium ET models based on weather data. A fundamental component of a dense, coordinated grid for effective water monitoring is therefore the accurate, real-time, high spatio-temporal resolution measurement of direct water use and transport.

In this work we present the main features and specifications of the very latest technology specifically developed for affordable yet accurate, direct, unattended, and automated field-scale ET measurements. We discuss laboratory performance evaluations as well as field testing against reference methods, with a focus on the scientific and technological trade-offs underlying the innovative design. Representing the synthesis of three decades of expertise in the design and development of research-grade systems for the quantification of in-situ gas and energy flux, this new technology is specifically intended to enable and encourage the creation of new, denser networks of unmanned ET measurements.