By Keyvan Malek, Civil and Environmental Engineering at Cornell University
In an earlier AgClimate.net article I discussed studies that have looked into the effects of investments in efficient irrigation technology on other water-related sectors. I argued that many studies have concluded that such investments might have negative implications for other water users, such as farmers or energy producers. I also mentioned that we were studying this issue, and promised to report our findings. This article and our soon-to-be-published paper deliver on that promise.
Why we did what we did
Among agro-hydrologists—people who study the dynamics of water in agricultural systems—it is a widely accepted fact that one farmer’s investment in new, irrigation efficiency technologies negatively affects other farmers and sectors. However, questions remain, as past studies have not explicitly quantified the impacts of new irrigation systems on other sectors. What is the implication for overall agricultural productivity? How do efficient systems impact the ecological condition of the basin? How do energy production and demand change as people switch to more efficient systems? Are there any social implications? And do these productivity, ecological, and social implications change as the climate changes?
Most modeling frameworks used in other studies tend to simplify significantly the complicated nature of interactions between agricultural and physical processes, water rights, and the operation of dams and other water infrastructure (note that the italics on the word “significantly” do not adequately emphasize this issue), and do not evaluate the compound impacts of climate change and irrigation technology improvements. For over a decade we have been developing coupled physically-based modeling frameworks that mechanistically capture key water, agricultural, and human decision-making processes. We used our coupled modeling frameworks to quantify the impacts of investing in efficient irrigation technology on different aspects of the connected food-energy-water system in the Yakima River Basin.
Climate change and irrigation efficiency scenarios
We considered eleven different climate scenarios: one is historical and ten are future scenarios. We also have three irrigation efficiency investment scenarios:
- No action: Everyone maintains their existing irrigation technologies.
- All switched: Everybody uses efficient irrigation systems.
- Market-driven: Individual farmers switch to more efficient irrigation technologies if the calculated benefits are greater than the costs (for details on the cost-benefit analyses we carried out to map costs and benefits across the Yakima River Basin see Malek et al. 2018).
When we compared a variety of metrics of agricultural productivity, ecological processes, and socio-economic factors across the three irrigation efficiency scenarios, under historical and projected future climates, we found that:
- More efficient irrigation increases consumptive use and evaporative loss, and reduces return flow, which is very important in the Yakima Basin (the U.S. Bureau of Reclamation estimates that return flow constitutes 40% of total water supply during the summer).
- Irrigation demand and diversion for irrigation declines, which offsets some of the negative consequences of a reduction in return flow.
- Overall impacts of new irrigation systems for basin-wide water availability is negative. That is, less water is available with more efficient irrigation systems.
- Streamflows increase, especially during the spring, and deteriorate during the summer (Figure 2). In general, the effects of climate change on streamflow is stronger than that of new irrigation technologies.
- Hydropower generation declines in the Yakima Basin, as a result of the changing streamflow profile.
- Basin-wide energy demand in the agricultural sector falls due to lower water demand and expansion of energy-efficient systems (e.g., LEPA and drip irrigation).
- The economy of the agricultural sector improves (Figure 3), while for fishing and hydropower generation there are adverse effects. Also, the number of workers employed in the agriculture sector declines, which might have socioeconomic consequences. Therefore, we expect there will be winners and losers, which further socioeconomic analyses should explore.
Three points I’d like to add. First, I want to be clear that it is almost impossible to generalize our findings, simply because they are controlled by factors, such as the structure of water rights and reservoir systems, that are only applicable to the Yakima River Basin. If you are a decision-maker in a different basin, and you want to know what would happen if you supported a farm-level water conservation initiative, you really need to look for region-specific studies that consider all the key details of your area; studies from other places might be really misleading. Ironically, this “lack of universality” is our universal and transferable take-home message.
Second, don’t forget other sectors. Impacts may extend beyond agriculture, as we saw in the Yakima River Basin. And third, although we are confident that this study is a significant step towards a better understanding of interactions between agricultural systems, water resources, and other water-dependent sectors, there are many scenarios that we did not take into account. For example, we only consider status quo water rights, but what if water regulations change in future? What if the way that water rights are enforced changes? Stay tuned: the WSU team is currently tackling these questions too.
Malek, Keyvan, Jennifer Adam, Claudio Stockle, Michael Brady, and Kirti Rajagopalan. “When Should Irrigators Invest in More Water‐Efficient Technologies as an Adaptation to Climate Change?” Water Resources Research 54, no. 11 (2018): 8999-9032.
This article is modified slightly from Malek, K., Adam, J.C. 2019. Are Efficient Irrigation Technologies a Winning Solution in the Yakima River Basin? in Hall, S.A., Yorgey, G.G., Padowski, J.C., Adam, J.C. Food-Energy-Water: Innovations in Storage for Resilience in the Columbia River Basin. Progress Report for the Columbia River FEW Project. This Report will be available online at www.fewstorage.wsu.edu in November 2019.
The work described in this article was supported jointly by the National Science Foundation under EAR grant #1639458 and the U.S. Department of Agriculture’s National Institute of Food and Agriculture under grant #2017- 67004-26131, as well as the Washington State University Graduate School.
What about Carbon? How do the various ways of irrigating affect soil C sequestration?
Thanks for the question Dominique. Though the effects on carbon sequestration were outside the scope of this project, we can comment generally on what we know about carbon sequestration in irrigated systems. If irrigation systems simply delivered water to existing crops in a more efficient manner (but did not fundamentally changing the rotations or crop biomass in these systems), we would not expect any impact on carbon sequestration. If it is of interest to you, there is a white paper posted on the CSANR website (http://s3-us-west-2.amazonaws.com/wp2.cahnrs.wsu.edu/wp-content/uploads/sites/32/2019/04/CarbonSeqPNW-for-CSANR-website-FINAL.pdf) that reviews the literature on carbon sequestration in both dryland and irrigated systems in the Pacific Northwest.