When the canals in Rotterdam shimmered in the morning mist, Xi'an, thousands of miles away, was surrounded by the dried up Loess Plateau. This ancient capital of thirteen dynasties has an annual precipitation of only 500-700 millimeters, and its per capita water resources are only 1/6 of the Chinese average. In addition, excessive excavation of canals in history, modern industrial expansion, and overexploitation of groundwater have caused the groundwater level to drop by more than 30 meters compared to the 1970s, leading the city into a sand trap of water scarcity.

On this land that carries the civilization of thirteen dynasties, a silent water revolution is reshaping the harmonious coexistence logic between cities and drought. The water scarce Xi'an and the abundant Rotterdam, as well as the water-saving wisdom of arid areas and the water management experience of ocean cities, reflect the same wisdom of coexisting with water.

In the practice of solving the water resource dilemma in Xi'an, the three core technology modules have built a path of "sewage regeneration - spatiotemporal water storage - intelligent water control" to reconcile with drought.

According to the latest bulletin from the Xi'an Municipal Ecology and Environment Bureau, the total amount of industrial wastewater discharged in Xi'an in 2020 was approximately 2.9982 million cubic meters, accounting for about 5.6% of the city's total sewage discharge. However, the recycling water plant uses a combination of "biological treatment+membrane separation" technology to convert industrial wastewater into high-purity recycled water. For example, the "Xi'an Fourth Recycling Water Plant" processes 200000 cubic meters of industrial wastewater per day and uses a triple purification process of "anoxic aerobic membrane filtration" to reduce the effluent COD to below 20mg/L, increasing the industrial wastewater reuse rate to 65%. It is directly reused in Samsung Semiconductor's cooling system. At the same time, the sludge is fermented at high temperatures to produce biochar for soil remediation, and the annual replacement of clean water in China's water pipeline network reaches 120 million cubic meters.

From July to September each year, Xi'an experiences short-term heavy rainfall that releases 70% of the annual precipitation. This spatially and temporally mismatched precipitation pattern, coupled with the traditional "flood discharge and fast discharge" model in the past, can result in a significant loss of rainwater resources. Nowadays, the Dayu underground reservoir has a storage capacity of 12 million cubic meters constructed through a 30 meter thick sand and gravel layer, and uses clay core wall anti-seepage technology to achieve strategic underground water reserve. Its intelligent regulation and storage system can automatically switch to the "water storage water supply" mode according to meteorological forecasts. During the precipitation period, 32 injection wells inject water at a rate of 2000 cubic meters per hour, and during the drought period, 18 mining wells replenish water at a rate of 1500 cubic meters per hour. The fluctuation of groundwater level is precisely controlled within 0.5 meters.

Xi'an has further proposed the concept of intelligent water control, which forms a three in one water resource management system with sewage regeneration and spatiotemporal water storage technology. The three achieve full lifecycle management of water resources through data-driven and engineering innovation. Smart water control, as the top-level design concept, constructs a full chain intelligent control system covering "water source pipe network user drainage" through a digital twin platform and an Internet of Things perception network.

Xi'an has deployed 30000 intelligent sensors in the 3000 kilometer main pipeline network to monitor real-time pressure changes at 0.01MPa level and leakage at 0.1L/s level, with a positioning accuracy of 3 meters. The sensor monitoring data is fed back to the digital twin platform in real time, driving the optimization of treatment processes in the regeneration water plant and the adjustment of storage and leakage strategies in the underground reservoir, achieving a "monitoring decision-making execution" response in seconds. Smart water control reduces pipeline leakage by 15%, sewage regeneration provides stable regeneration water sources, and spatiotemporal water storage improves the utilization rate of rainwater and flood resources. The combination of the three increases the city's water resource utilization efficiency by 40%.

These three technological breakthroughs are like precision gears, transforming sewage, rainwater, and groundwater into the source of life that supports the sustainable development of cities, interpreting the modern water management wisdom of "making every drop of water valuable".

From Rotterdam's "Coexistence with Water" to Xi'an's "Reconciliation with Drought", the wisdom of water use in the two cities leads to the same goal, and their resilience practices reveal a truth: true urban resilience does not lie in resisting the arrogance of nature, but in establishing a dynamic and balanced symbiotic system. The director of Xi'an Water Bureau sighed, "If Rotterdam taught us how to coexist with floods, Xi'an is teaching the world how to reconcile with drought

The flood control gates on the banks of the Thames River echo the water diversion projects on the banks of the Wei River, while the tidal turbine generators in Rotterdam and the recycled water pipelines in Xi'an weave a new civilization map together. In this land shaped and constantly reshaped by water, the water deficient use technology to tame drought, the abundant accept tides with humility, and humanity finally understands that the essence of dancing with water is to sign a sustainable contract with nature. The answer sheets of Rotterdam and Xi'an may be the passport for humanity to the future.