Water security requires not only sufficient availability of and access to safe and acceptable quality for domestic uses, but also fair distribution within and across populations. However, a key research gap remains in understanding water security inequality and its dynamics, which in turn creates an impediment to tracking progress towards sustainable development. Therefore, we analyse the inequality of water security using data from 7603 households across 28 sites in 22 low- and middle-income countries, measured using the Household Water Insecurity Experiences Scale. Here we show an inverted-U shaped relationship between site water security and inequality of household water security. This Kuznets-like curve suggests a process that as water security grows, the inequality of water security first increases then decreases. This research extends the Kuznets curve applications and introduces the Development Kuznets Curve concept. Its practical implications support building water security and achieving more fair, inclusive, and sustainable development.

水安全不仅需要足够的可用性和获得安全和可接受的质量供家庭使用，还需要在人群内部和人群之间公平分配。然而，在理解水安全不平等及其动态方面仍然存在一个关键的研究差距，这反过来又阻碍了追踪可持续发展的进展。因此，我们使用来自 22 个低收入和中等收入国家 28 个地点的 7603 个家庭的数据分析水安全的不平等，这些数据使用家庭水不安全体验量表进行衡量。在这里，我们展示了场地用水安全与家庭用水安全不平等之间的倒 U 形关系。这条库兹涅茨曲线表明了一个过程，即随着水安全的增长，水安全的不平等程度先增加后减少。本研究扩展了库兹涅茨曲线的应用，引入了发展库兹涅茨曲线的概念。它的实际意义支持建立水安全和实现更公平、包容和可持续的发展。