Understanding China's water security
A study by the International Institute for Applied Systems Analysis highlights the value and potential of technological strategies to help design targets and incentives for water scarcity mitigation measures.
China’s water security is under threat. Rapid economic growth, accompanied by a rise in food demand, is driving increased water use for agriculture and industry. In the last 100 years, water use has increased by more than twice the rate of the global population, with around 77% of this growth taking place in developing countries.
According to the authors of the study published in the Proceedings of the National Academy of Sciences, a lack of spatially detailed datasets limits our understanding of historical water use trends and its key drivers, which makes future projections unreliable.
With few observation-based studies aimed at understanding the dynamics of historical water use, the authors aimed to create a detailed picture of how water use has been evolving amid socioeconomic, technological and policy impacts, with a particular focus on China.
“The key question we wanted to address was how human water use responds to socioeconomic development, climate change and policy interventions over time and space,” study lead Feng Zhou, an Associate Professor at Peking University, explained.
“We looked at China, not only because the country has transitioned from an underdeveloped country to the second-largest economy in the world, but also because it is home to some of the Earth’s most water-stressed regions.
“Diverse water conservancy measures were developed since the 1980s to avoid a long-term water crisis, but it is not well known how water use is influenced by economic growth, structural transitions and policy interventions.”
The researchers found that although China’s water use doubled between 1965 and 2013, there was a widespread slowdown in the growth rates from 10.66 km3 per year before 1975 to 6.23 km3 per year in 1975 to 1992, and 3.59 km3 per year in the following years. These decelerations were attributed to reduced water use in irrigation and industry, which partly offset the increase driven by pronounced socioeconomic growth.
The adoption of efficient irrigation techniques such as drip or sprinkler irrigation systems and industrial water recycling technologies explained most of the observed reduction in water use intensity across China. Without these technologies, China’s freshwater withdrawals would have been 80% more than the actual water use over the last two decades.
While water-conserving technological adoptions can deliver benefits of decoupling water use from socioeconomic development, studies in other countries have revealed an opposite relationship where technological adoption has led to an increase in intensive farming and thereby an increase in water use. According to the study, the first reason for these inconsistent results could be that intensive farming — such as high planting density and more sequential cropping — had already been developed in many Chinese prefectures. The second reason may relate to land institution in China, where additional intensification requiring a change in irrigation infrastructure has been difficult to adopt due to the high fixed costs of the small fields allocated to farmers.
The authors explain that in China, technological strategies were accompanied by policy interventions including about 40 laws, regulations, programs and action plans. In addition, the growth of China’s water use is likely to slow further as the latest policy interventions provide a more stringent constraint to approach a peak of water withdrawal.
Uncertainties and potential future water scarcity will come from three aspects:
1: China is undergoing a rapid transition towards large-scale farming through the 2014-issued farmland transfer system alongside the adoption of water-conserving irrigation planned to cover 75% of the irrigated area in 2030. These ongoing transitions may lead farmers to expand irrigated areas or shift to water-intensive crops, which could offset the savings due to future improvement of irrigation efficiency.
2: Study findings indicate that the westward development of the industrial sector has worsened water scarcity in many arid and semi-arid regions. High industrial water recycling has already been adopted in almost all of these regions (>88%) except in Xinjiang, so that the potential for further water conservation would be limited. Without a stronger enforcement of capping water withdrawal, the industrial sector may become the most important driver continuing to increase water use.
3: The rate of urbanisation and increasing per-capita income, coupled with generalised tap water accessibility, will likely stimulate more water-intensive lifestyles and thereby increase domestic water use.
The deceleration of water use revealed in this study partly challenges the results from global hydrological models, which commonly suggest an increase of total water use across China over the period 1971 to 2010.
Zhou said that one reason for this bias may be that technological changes were prescribed as constant over space and time without consideration of policy interventions and actual technological adoption. It might also be the case that data on socioeconomic activities in China were disaggregated from national-scale statistics.
The authors recommend that to improve model drivers, survey-based reconstruction datasets of water use — like those presented in this study — are valuable and should be extended to other regions. The link between changes in water use and technological strategies may also be useful in the design of more realistic future water withdrawal scenarios, with the ultimate goal to improve global models used to assess water use targets and water scarcity mitigation.
“Modelling water use is very complex and we need much more regional data and coordination to improve our understanding of people and how they use water,” study co-author and IIASA Acting Water Program Director Yoshihide Wada said.
“The modelling community should work together to achieve this as it is crucial to identify the key drivers and mechanisms behind changing water use patterns across the world that help make future projections more reliable.
“Future policies to underpin water targets, in for example the UN Sustainable Development Goals framework, will be key to addressing the challenge of decoupling water use from socioeconomic development in China and other water-stressed countries,” Wada concluded.
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