Irrigation in the Earth system: Priorities for data, modeling, and cross-disciplinary research
Irrigation is a critical component of land and water resource management. It is used to grow nearly 40 percent of the world’s food supply and accounts for about 70 percent of freshwater withdrawals and 84 to 90 percent of annual global freshwater consumption, largely for agriculture.
Yet irrigation remains largely underrepresented or nascent in Earth system models that represent different dimensions of the climate system, crop growth, nutrient cycling, or hydrology. 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.
In June 2023, AGCI hosted “Irrigation in the Earth System: Priorities for Data, Modeling, and Cross-disciplinary Research.” Participants included experts across the irrigation modeling and observations/data scientific communities, spanning researchers and practitioners working in climate, agriculture, and hydrology.
The workshop grew out of an earlier 2019 AGCI workshop on land-use modeling, where workshop participant Sonali Shukla McDermid (New York University, NASA GISS) noted that “There’s a lot of people who are looking at irrigation from different perspectives. What would happen if we got all these people in a room talking to each other?” From that question, McDermid went on to develop and co-chair the irrigation workshop with Jonas Jägermeyr (Columbia, NASA GISS), Patricia M. Parker (U Maryland, NASA GSFC), Yadu Pokhrel (Michigan State University), and Wim Thiery (Vrije Universiteit Brussel).
In conjunction with the workshop, AGCI partnered with the Colorado River District to host “Irrigation Re-Imagined: Growing Resilience in Agriculture,” a broad-ranging public conversation on how regenerative irrigation can help solve challenges at the intersection of food, water, and human systems. Attended locally by working landowners and simultaneously live-streamed to a large, global audience, the public panel featured Mallika Nocco (UC Davis), Claudia Ringler (IFPRI), and Perry Cabot, a local Extension scientist from the Colorado State University Western Colorado Research Center.
The main goals of the workshop were to:
- Build a cross-disciplinary irrigation research community;
- Summarize the “state of the field”: what is known about spatiotemporal water use for irrigation and its interactions with other Earth system components?
- Identify urgent irrigation research questions related to global environmental change and water sustainability; and
- Identify entry points for process-based modeling and ways to integrate evolving irrigation observations and other data and knowledge products.
For five days, participants worked to identify actionable steps to forge new interdisciplinary and cross-sectoral efforts that could bridge knowledge gaps and advance understanding of irrigation interactions in human and natural systems.
Reducing model uncertainties
In several sessions, the group grappled with the many dimensions of uncertainty in irrigation models and the limited availability of data that can represent real world decision-making in those models. Representing limited water supplies (especially groundwater), for instance, was repeatedly recognized as a process that needs more attention to reduce model uncertainty. Other uncertainties with wide ranges included irrigation trends and demand, the use efficiency of crop water under changing climate conditions and atmospheric CO2 trends, biogeochemical impacts of irrigation (especially on soils), and how irrigation affects precipitation and heat extremes.
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Participants agreed that some types of uncertainty are “shallow” and may be reduced using new methods (such as data assimilation). They also recognized the immense amount of work done by observation communities (e.g., remote sensing), which could be better leveraged for model development and evaluation. Crop calendars and growing seasons, to take one example, could be gleaned from high resolution remote sensing observations and better represented in regional and global models.
Similarly, while many new tools (such as social science models, coarse scale models, regional scale high resolution weather and climate models, and field scale models and information) have been designed for distinct purposes, unifying some of their processes and leveraging understanding across scales would greatly advance understanding of how irrigation impacts the Earth system. The group also showed an appetite for more systematic intercomparison and improvement of data and models, including collaborating with established model intercomparison (MIP) efforts. Participants also acknowledged the great potential in all the available model data waiting to be mined and analyzed.
While the workshop was largely focused on the biological and physical dimensions of irrigation, vibrant discussions emerged about relevant sociohydrology. Discussions touched on some of the nuances of irrigation’s impact on human health, highlighting the climate justice dimensions of this topic. For example, while irrigation-induced cooling is widely accepted, there are instances in which irrigated lands can actually be more detrimental to the health of field workers than more arid landscapes in extreme weather conditions.
The week of rich dialogue reinforced how inter- and cross-disciplinary collaboration can help address research roadblocks by offering new perspectives, such as applying new ways to represent human decision-making in irrigation models, augmenting more conventional economic cost-benefit analyses. As co-organizer Patricia M. Parker observed, the workshop “made me appreciate how important irrigation is from many different perspectives. For example, I typically only think about how irrigation impacts the weather, water, and climate in the U.S., but irrigation is a global activity, and the practices and reliance on it in other parts of the world are so different than what we typically think about in the U.S. It can be a major factor in the livelihood of some people and ultimately contributes to feeding many of us around the world. Overall, the week really emphasized for me the need to tackle this issue with a multi-pronged approach.”
Yet participants also grappled with the challenges inherent in interdisciplinary collaboration – namely, the need to effectively communicate unfamiliar topics across disciplines while finding common language and avoiding jargon.
Interestingly, one of the challenges voiced by the co-chairs in the wake of the workshop was how the interdisciplinary nature and diverse viewpoints present made it tricky to easily identify actionable “low- hanging fruit” workshop outputs while being inclusive of the full range of participants’ perspectives. Still, the event co-organizers saw this as a sign that they were successful in providing a space where diversity of thought was not only shared, but truly valued. As such, workshop participants are working towards multiple outputs, including research projects, publications, follow-on workshops, and proposals, to capture varying interests and directions.
As co-organizer McDermid reports, “already some folks (including myself) have initiated research projects. This particular group of individuals was so cohesive and supportive and collegial, it made for a highly generative atmosphere. This is my third AGCI workshop and/or session attendance, and, as usual, this is an experience that will last a lifetime and pay dividends well into the future.”