The Yujiacun NDS has been safeguarding the village’s water security for centuries. As a life support system, it lays a solid foundation for the survival and well-being of generations of villagers; its dual functionality operates effectively and incessantly when the natural pendulum swings between drought and flood. This enduring effectiveness reveals, and indeed results from, two ecologically wise (i.e., ecophronetic) ideas the villagers built the NDS upon.Footnote 13
The ecophronetic idea of working with the duality of stormwater
To the Yujiacun villagers, stormwater is both an asset and a nuisance. As an asset, stormwater is the principal water source they can count on for life, livelihood, and prosperity (see subsection 1.1 of this article); as a nuisance, stormwater’s destructive potential constitutes a very real common threat of flooding to all inhabitants of the village and to their properties.Footnote 14 Every storm event, therefore, is a double-edged sword. On the one hand, it presents the villagers a critical window of opportunity for stormwater harvesting to secure their water supply; on the other hand, it puts huge pressure on the villagers to divert stormwater as quickly as possible to the outside of the village to reduce flood risk.
For the villagers, therefore, working with the duality of stormwater is a must. By “working with”, it means to reach two goals simultaneously during a storm event: taking advantage of the constructive side of stormwater; avoiding or mitigating the destructive side. This time-sensitive, high-stakes, and recurring task entails a delicate exercise of coordinating two opposite water security processes: keeping some portion of stormwater in the village for subsequent use and letting the rest go outside the village to prevent flood.
The phenomenal working of the bifunctional NDS, as we presented in the previous section, is both a manifestation of this idea and a testimony of its powerful efficacy: the drainage system this ecophronetic idea led to has been ably managing the duality of stormwater with an effective and robust dual functionality for centuries.
It is noteworthy that the idea working with the duality of stormwater has its root in the Chinese cultural belief in duality of nature. In a 2009 essay for Encyclopedia of positive psychology, the Chinese-Canadian psychologist Paul PT Wong posits that the belief in duality of nature and five other cultural beliefs and a concomitant set of signature virtues have enabled the Chinese people to survive the myriad vicissitudes of life for more than 5000 years (Wong 2009, p.152, p.155).Footnote 15 Specifically, the belief in duality of nature (1) recognizes the coexistence of opposites (e.g., good and bad) in both nature and human nature as a universal truth; (2) regards the balance between the opposites, however uneasy it is, as the best way toward a good life and better world; (3) values the individual and collective efforts to embrace the opposites in work and life and to maintain a dynamic balance (Ibid., p.153). This strong cultural root helps explain the fact that, throughout China’s 5000-year history, the idea of working with the duality of stormwater has been widely and effectively executed in many areas in China [e.g., the Fushougou (福寿沟) stormwater management system in Ganzhou (赣州), China (1069–present) (Han 2012; La Rosa et al. 2021, p.331)]. Equally noteworthy is the revival of the very idea in the twenty-first century—it has been gaining significant popularity in urban areas in China and around the world and underlies such contemporary movements as “water sensitive city” (Grant 2016), “water sensitive urban design” (Wong et al. 2013, p.11), “modern stormwater management” (Holm et al. 2014, p.2 of 4), and “sponge cities” (Zevenbergen et al. 2018, pp.3–4 of 13).
The ecophronetic idea of building with nature
To the Yujiacun villagers, a bifunctional drainage system is ideally double high and triple low. “Double high” refers to the high effectiveness and high robustness of the system—its built-in dual functionality operates properly and incessantly when the natural pendulum swings between drought and flood; “triple low” means that the system is technologically simple (low-tech); requiring little money, time, or effort to look after (low maintenance); and causing minimum harm to the already fragile environs (low impact). A double-high and triple-low bifunctional drainage system is ideal because it meets the villagers’ water-security needs in a technically feasible, resource-efficient, and affordable fashion (Zhao et al. 2018, pp.41–42, p.44). For the villagers, therefore, building such a system is the right thing to do without doubt.
But then, what would be the right way to do this right thing? In other words, how should a bifunctional drainage system be built that meets the double-high and triple-low criteria? The villagers’ answer was, building with nature, that is, in the design and construction of the drainage system, harnessing the properties, functions, and processes of in situ natural ecosystems as well as using locally available natural materials.
Manifesting this idea, as we presented in Sect. 2, the Yujiacun NDS is built entirely with nature. The sloped permeable streets use moderate inclines and stone pavers to regulate the speed of surface runoff and allow stormwater infiltration; the three-leveled stormwater conveyance network mimics a natural drainage system to divert stormwater by virtue of gravity; the 1000-plus underground cisterns utilize underground space and take advantage of the relatively constant temperature of the Earth to store and supply water year-round; the cisterns are built with stones from the surrounding mountains; the cistern water is treated with quicklime powder whose production from limestone is both economical and low tech. These and other built-with-nature features together make the Yujiacun NDS an extraordinary feat of socio-ecological practice that has been ably safeguarding water security in a double-high and triple-low fashion for its conscientious builders and their posterity for centuries.Footnote 16
It is noteworthy that the idea of building with nature, like that of working with the duality of stormwater, is neither new nor unique. It in fact has a close affinity with design with nature, another perpetual idea which was reemerged in the 1960s in the USA and made prominent by Scottish American landscape planner and educator Ian McHarg through his 1969 book “Design with nature” (McHarg 1969; Lyle 1999, p.45). These two comparable ideas share a common aim to “give expression to the potential harmony of man-nature” (McHarg, 1969, p. 5) and have been found underlying a great many extraordinary feats of socio-ecological practice that provide lasting benefits and stand the test of time. These exemplary engineering feats include, but are definitely not limited to, the Dujiangyan (都江堰) irrigation system in Sichuan, China (256 BC–present) (Needham et al. 1971, p.288; Xiang 2014, pp.65–66); the aforementioned Fushougou (福寿沟) stormwater management system in Ganzhou (赣州), China (1069–present) (Han 2012; La Rosa et al. 2021, p.331); the Red Flag Canal in Henan, China (1969–present) (Chen and Xiang 2020a; b; Li et al. 2021; Xiang 2020b); the Woodlands New Community in Texas, USA (1974–present) (Forman 2002, pp.102–104; Lyle 1999, p.103, p.237; McHarg 1996, pp.256–264; Xiang 2016, pp.56–57; Xiang 2019b, pp.166–167; Yang 2019; Yang and Li 2016, 2019, pp.217–219); afforested woodlands in the Alps (Knott 1991; Mayer and Ott 1991); Škocjanski Zatok Nature Reserve in Koper, Slovenia (Ivajnšič and Kaligarič, 2014; Jurinčič et al. 2011); ancient woodlands and urban parks in many European cities, such as Eilenriede in the heart of Hanover, Germany (Hannover 2016; Oppermann and Thies 2017), and the hitherto best-kept secret—the Yujiacun NDS.
However, unlike most on the above honor roll, little is known about the centuries-long process of building with nature that led to the Yujiacun NDS because much of it is undocumented. Questions that arise and await answers include, inter alia: How and when did the villagers come up with the idea of building with nature? What were some specific challenges they encountered throughout the process of building with nature? What exactly did they do to overcome the challenges? How did they figure out both the right thing to do in the face of these challenges and the right way to do the right thing? Did they choose to pursue the triple-low simply by default because no modern sciences, high technology, high building materials (for example, cement, steel), and funding were available to them? Until this knowledge gap is filled, or at least narrowed substantially, the Yujiacun NDS, as the tangible product of the building-with-nature process, is the researchers’ best friend.