Irrigation in the Earth System: Priorities for Data, Modeling, and Cross-disciplinary Research

Irrigation is a critical component of land and water resource management that facilitates nearly 40% of the world’s food supply and accounts for ~80% of global freshwater consumption. This copious water use has a range of important environmental impacts that must be better understood to improve both projections of regional climate change and water resource sustainability. Process-based climate, water, and crop models are useful tools in this respect, but are inhibited by a range of exogenous and endogenous factors, including limitations in irrigation observations and data. This AGCI workshop on Irrigation in Earth System will aim to identify key gaps in irrigation research, particularly with respect to process-based modeling, and will forge new interdisciplinary and cross-sectoral efforts to bridge these gaps and advance our knowledge of irrigation interactions in human and natural systems.

Irrigation is a critical component of land and water resource management, and facilitates nearly 40% of the world’s food supply. While irrigation occupies a relatively small global extent, it nevertheless accounts for the lion’s share of human water use: water for irrigation accounts for ~70% of freshwater withdrawals and 84-90% of annual global freshwater consumption, largely for agriculture.

Furthermore, irrigation may now also constitute a complex driver of environmental change, including groundwater depletion, enhanced soil salinity, and nutrient leaching in agricultural systems. Copiously applied irrigation water also impacts regional hydroclimates, heat extremes in both agricultural and urban areas, and biogeochemical cycling. Demand for irrigation water, both in agriculture and other sectors, is expected to increase into the 21st century. Such increases, particularly when coupled with climate change-induced water disruptions, tax existing irrigation water supplies and may drive some regions into water scarcity. It is therefore crucial to better understand irrigation impacts and interactions across natural and human systems to aid in improving projections of regional environmental/climate change and sustainable water resource management.

However, irrigation remains largely underrepresented or nascent in process-based models of the climate system, crop growth, hydrology, and biogeochemical cycling. This severely impedes our ability to capture important irrigation-Earth system interactions, with major implications for projecting regional environmental change, climate change adaptation and mitigation, and sustainable water resource planning. Inadequate representations of irrigation in process-based models are due to a large assortment of issues, including (but not limited to): gaps in the availability of high quality irrigation data and observations, limitations in the representation of key biophysical processes in models, and uncertainties in characterizing human decision-making within process-based modeling frameworks.

Addressing these issues requires an interdisciplinary and cross-sectoral approach, bridging multiple scientific communities and disciplines. This AGCI workshop will advance a common dialogue for exploring irrigation-Earth system interactions, with an emphasis on the needs and demands for process-based modeling approaches.

The broad goals of this workshop include:

• Building a cross-disciplinary irrigation research community
• Summarizing the “state of the field”: what is known about spatiotemporal water use for irrigation, and its interactions with other Earth system components?
• Identifying important and urgent irrigation research questions, particularly with respect to global environmental change and water sustainability
• Identifying entry points for process-based modeling and ways to integrate evolving irrigation observations and other data and knowledge products

A key advantage of this workshop is the convening of experts across the (irrigation) model and observations/data scientific communities, spanning climate, agriculture, and hydrology, who have much to gain by interacting but for whom funding is rarely available to do so. Forging new scientific dialogues related to irrigation in the Earth System and cross-disciplinary discussion will be a major outcome of the proposed workshop and project activities.

Other expected outcomes of this workshop include (but are not limited to):

• Perspective paper(s) with participants from workshop on the needs and demands for irrigation research and modeling. A special collection of papers on irrigation-climate interactions will also be discussed
• A census and quality assessment criteria for irrigation observational and data products, including those that can aid modeling activities
• A census and characterization of process-based models that do or will include irrigation, from cropping system models to Earth System Models
• The identification of “common domains” for which high-quality data does (or will) exist and which multiple models (climate, crop, hydrologic) can simulate
• The creation of standardized simulation and evaluation protocols for a novel irrigation-specific, multi-disciplinary model intercomparison(s) for potential inclusion into CMIP8 and other coordinated modeling efforts
• Scoping a comprehensive uncertainty assessment in irrigation research, including both data and models
• Scoping research priorities for future irrigation inclusion and development in process-based models, and integration with existing efforts (e.g. World Climate Research Programme’s (WCRP) Grand Challenges “Water for the Food Baskets of the World” endorsed by the Global Energy and Water cycle Exchanges (GEWEX) Project)