Establishing and Operating a Regional Network for Field Measurement of Actual Crop Water Consumption (Evapotranspiration)

The increasing availability of high-resolution satellite imagery at affordable prices, or even free of charge, has made water flux information derived from remote sensing (RS), specially evapotranspiration (ET), a reliable source for water accounting of agricultural water use over large areas (e.g. sub-national, national or basin level). In fact, remotely-sensed water-accounting products are currently getting implemented in various Ministries of the focus countries of the NENA Water Scarcity Initiative (WSI) and at the same time beneficiaries of the Sida Project on "Implementing the 2030 Agenda for the water efficiency/productivity and water sustainability in NENA countries" (GCP/RNE/009/SWE). Some databases of ET at operational, spatial and temporal scales are being made publicly available for several regions of the world, including NENA. Examples are WaPOR (FAO), ET Ensemble (IHE-Delft), GloDET (Water for Food, Daugherty Global Institute, Nebraska) and OpenET (under preparation by Google with support of the World Bank). Some local institutions generate their own databases using models like SEBAL (Surface Energy Balance Algorithm for Land) or METRIC (Mapping Evapo-Transpiration at high Resolution with Internalized Calibration). However, the weak point of all these databases is that they suffer from a general limited and scattered field validation and, more specifically, virtually no validation at all in the NENA region. If water accounting has to provide the evidence base for strategic planning of water resources, if large-scale crop water-productivity gaps need to be benchmarked and monitored, if water conservation strategies have to be developed based on water consumptive limits, then RS ET determinations need to vary over an acceptable degree of accuracy. In order to define the accuracy of RS ET data, a comparison with field actual ET measurement is required. This comparison will not only serve to define the accuracy of RS ET data but also provide the opportunity to calibrate and validate RS algorithms calculating ET.

ICARDA, through its water unit, has to establish and operate the regional network. The main activities to be carried out are: - A capacity development program in the use of advanced equipment and the adoption of updated methodologies; - Seasonal field measurement; - Share of experience between the network; - Development of standards in the measurement techniques.

The creation of the regional network is expected to be an additional achievement of the FAO water scarcity initiative. Thanks to the validation process, and the development of an updated work methodology, the project will provide the bond between the top-down approach of water accounting and remote sensing (already ongoing) and the bottom-up approach of farm-field determinations (still missing).

UPDATES

In 2021, ICARDA and FAO produced a popular six-part webinar series on state-of-the-art evapotranspiration measurement methods, which attracted over 1,700 international and regional participants. The series coincided with a new regional network, initiated by ICARDA and FAO, to improve evapotranspiration field measurements and enhance adaptation to climate change and freshwater scarcity in the five target countries.

In 2022, FAO extended the evapotranspiration network to field measurement of actual crop-water consumption in Algeria, Egypt, Jordan, Lebanon, Morocco, Palestine and Tunisia. The network compared the measured field data and remote sensing data of evapotranspiration to implement distance coaching for the regional network, and to organize a regional virtual symposium on evapotranspiration measurement. In the same year, ICARDA introduced interventions in Madhya Pradesh, India, including weather-based crop-growth analytics and disease-outbreak alerts, soil moisture-based irrigation, motion-activated, camera-based pest detection and remedial advice, satellite and drone-based remote sensing for early warning on pests, disease, and crop abiotic stresses, as well as soil testing-based fertilizer advice.