In response to the growing need for water in global food production, research has focused on measures such as irrigation practices to improve water usage efficiency, yet environmental change and lack of water availability remains a key concern threatening current and future food security.
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Water scarcity as an emerging challenge facing global agriculture
Across all human activities, agriculture is the largest user of fresh water and accounts for 75% of current human water use on Earth. Despite such considerable water usage, 7% of the world’s human population inhabits areas of water scarcity and this is predicted to rise considerably to 67% by 2050.
Although 2 liters of water on average is typically sufficient for a person to drink every day, it takes around 3,000 liters of water to produce the food a person needs daily. This disparity illustrates the extent to which modern agriculture relies on water, and the challenges agricultural systems face to become less dependent.
The need to improve water usage management has been recognized for over half a century, with agricultural research focusing on key issues surrounding the effects of water in food production. This includes producing more food while using less water, building the resilience of farming communities to cope with floods and drought, and applying clean water technologies that protect the environment.
Of particular significance is the management of water usage, which is predicted to be of particular concern with the increase in global temperatures and the decrease in water availability.
Over the last 30 years, agricultural research has developed many innovative solutions in food production, particularly in cultivation techniques, new crop varieties, and irrigation. However, innovations are primarily technological and were not followed by innovations in the participation of farmers in water and irrigation systems governance.
The mismatch between available technology and lack of governance was echoed in a study by Luis Santos Pereira published in 2017 in the journal for Water Resources Management. The author discusses the challenges and issues relative to water management in the last 30 years, and how the role of active management of the water cycle has gained importance.
Specifically, the author emphasizes the value of correct management to assure water use sustainability, mainly agriculture and natural ecosystems sustainability. Nonetheless, the study also presents how regions face context-specific challenges associated with water scarcity, climate, governance, and population requirements.
The study concludes by addressing what the author identifies as the most fundamental and important challenge to producing enough food for a growing population, which is closely related to challenges of water management, mainly irrigation management.
Strategies to improve irrigation efficiency in agricultural systems and their challenges
Published in the Journal of Agriculture, Ecosystems & Environment by J. Wallace, the author discusses the principal challenge of improving water efficiency in agriculture, which relates to irrigation efficiency.
The study describes how, in recent decades, agricultural science has devised a series of progressive steps to improving water efficiency in irrigation systems that build from computational models to implementing them in practice.
The first step relies on developing computational models using available data on crops, weather, and irrigation itself. Of particular significance is the work from a 1977 study by Doorenbos and Pruitt that provided standardized equations aimed towards improving water usage. The two-step crop coefficient relates to the evapotranspiration of crops to estimate water requirements in a practical way and allows for computational models to be developed across crop types, regions, and systems.
The equations were improved further with later additions incorporating the Penman-Monteith (PM) equation to produce a standardized grass crop reference for comparative analysis. Later additions also added temperature and weather data including solar radiation (Rs) and actual vapor pressure.
The second step to improving water efficiency relies on managing crop water and irrigation requirements based upon evapotranspiration equations. Studies applying these concepts such as the 2011 work by Allen et al, were able to identify key factors affecting evapotranspiration that can be harnessed in practice.
Factors that can improve the accuracy of evapotranspiration equations include measuring changes in soil water, measuring the mass balance over large areas providing for watershed-scale evapotranspiration, lysimetry, including for measuring soil evaporation, eddy covariance, and climatic variations, and a series of measurement tools such as remote sensing and the use of satellite-based vegetation indices.
The final step identified across literature and building upon the initial equations relies on the implementation of irrigation measures developed from the models and factors. Irrigation management is essential to achieve better crop yields, efficient water use, and control the environmental impacts of irrigation.
Irrigation management includes changes in scheduling and timing as well as controlled fertilizer scheduling associated with irrigation scheduling. The effectiveness and variation in management measures may be based on farmers’ knowledge or supported by observations of plant water status and/or soil water monitoring, which can be combined with remote sensing of plant water status.
Implementing successful irrigation measures also depends on smaller scale factors such as the timing, duration, flow rate, and pressure of water supply or delivery schedule. Irrigation systems have diversified greatly, with modern innovations including the use of pressurized distribution systems to better control flow rate.
Altogether the use of models, consideration of factors of variation, and the implementation of measures has allowed large-scale agricultural systems to improve water usage over time.
However, these consecutive approaches rely on the availability of existing data and the ability to monitor data consistently. Whether that is historical food production or climatic data, models and policies rely on information collection, which remains inexistent or limited in certain regions, leading to gaps in knowledge and a substantial challenge to developing global datasets.
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Looking forward – challenges and implications of water usage efficiency in agriculture
Improving water usage in agriculture remains the principal challenge facing modern and future food production. In response, research efforts have focused on standardizing approaches and finding the most efficient ways to improve water usage across regions.
However, many challenges remain. A 2019 bibliometric review by Velasco Muoz et al. of over 6000 articles on water efficiency showed the countries with the highest number of articles on water efficiency were China, the United States of America, and India.
Aside from these countries, data available and research effort decreases drastically. This results in limited data availability, which in turn limits the capacity to design and implement successful practices to better water usage.
This is particularly true for regions that are experiencing burgeoning agricultural systems and lack the funding, support, and awareness, to develop such strategies but remain susceptible to lack of water availability.
The ability to maintain water availability and quality is closely associated with other issues, including food security and environmental sustainability. As such, studies including the 2000 study by J. Wallace, highlight a number of challenges in improving governance and practices related to water efficiency.
Challenges include improving the equity and transparency of water allocation mechanisms, improving the participation of stakeholders in water governance, as well as recognizing and protecting the interests and rights of all users, especially the most vulnerable and marginalized.
In response, research efforts in agricultural science have focused on applicable solutions, focusing on solutions such as irrigation measures to provide standardized and effective strategies. This has proved successful, with recent FAO estimates predicting that by 2030, thanks to improvements in irrigation measures, irrigated land in developing countries will increase by 34% but water quantity used by agriculture will increase by only 14%.
- Jakkula, V S and Wani, S P (2018) Zeolites: Potential soil amendments for improving nutrient and water use efficiency and agriculture productivity. Scientific Reviews & Chemical Communications, 8 (1). pp. 1-15. ISSN 2277-2669
- Cao, Y., Zhang, W., & Ren, J. (2020). Efficiency Analysis of the Input for Water-Saving Agriculture in China. Water, 12(1), 207. DOI: 10.3390/w12010207
- Pereira, L. S. (2017). Water, Agriculture, and Food: Challenges and Issues. Water Resources Management, 31(10), 2985–2999. DOI: 10.1007/s11269-017-1664-z
- Velasco-Muñoz, J., Aznar-Sánchez, J., Belmonte-Ureña, L., & López-Serrano, M. (2018). Advances in Water Use Efficiency in Agriculture: A Bibliometric Analysis. Water, 10(4), 377. doi: 10.3390/w10040377
- Wallace, J. (2000). Increasing agricultural water use efficiency to meet future food production. Agriculture, Ecosystems & Environment, 82(1–3), 105–119. DOI: 10.1016/s0167-8809(00)00220-6