In the memory of Chen Lianghua, a weather forecaster at the Three Gorges Cascade Dispatch & Communication Center, the forecast office of the 1980s was always filled with the rustle of pencils gliding across paper. Back then, forecasters had to plot telegraphic messages—coded by hand—stroke by stroke onto giant weather charts. "It took an hour to receive and plot a single upper-air chart," he recalled. The charts spread across the walls were their "screens" for watching the skies.

Echoing Chen Lianghua's purely hand-drawn original was another "manuscript" from the field of hydrological forecasting—a piece of graph paper used for manually calculating the flow of the lower Jinsha River. Across it wound a flow curve, traced by the hand of a hydrological forecaster.

In an era when forecasting relied solely on pencils and paper, "reading" a river depended on a devotion bordering on reverence. Chen Lianghua admitted that back then, "the thing we feared most was sudden, short-duration heavy rainfall during the flood period, because the location, intensity, and movement of localized torrential rains were extremely difficult to forecast accurately, and during floods, we had to continuously adjust the dispatch plans." Without advanced tools, they raced against time and weather with nothing but their hands and their minds. The forecasters kept watch over chattering fax machines, scanning for critical meteorological and hydrological clues across charts that covered entire walls. This was work that yielded no immediate glory—yet it produced tangible results, recording every effort the forecasters made to ensure the steady operation of the power stations and safeguard the safety of the Yangtze River.

Following the era of "hand-drawn charts" in the 1990s, the industry entered a critical period of technological transformation. Wired communications and computers began to replace radio and manual operations, and plotters took over from pencils, automatically rendering data into charts. These machine-plotted charts became important tokens of the technological iteration in hydrometeorological forecasting—marking the first leap from "hand-drawn charts" to "automated plotting". The meticulous lines on these charts encapsulate the rigorous craftsmanship and technical precision of that transitional era. Today, one such chart—a witness to the passing of the manual calculation age—is preserved in the archives of the Three Gorges Cascade Dispatch & Communication Center.

After the Three Gorges Project began impounding water, there were higher requirements for forecasting. "Back then, we had to calculate flood travel times on graph paper," said Zhou Xiaoqian, a hydrological forecaster. But reality was already sending a clear signal: the traditional method of calculating flows based on upstream reports alone could no longer fully leverage the primary function of the Three Gorges Project—flood control.

Necessity drove change; technology powered upgrade. The reach of forecasting had to extend further upstream—all the way to the river's headwaters. Forecasters at the Three Gorges Cascade Dispatch & Communication Center began to join forces with research institutions. The Xin'anjiang Model and the Kalman Filter algorithm were introduced, as they sought to use mathematical language to more precisely describe how rainfall infiltrates the soil and converges into floodwaters. Forecasting began to evolve into a science grounded in physical processes and data. In 2006, the Three Gorges Reservoir inflow forecasting and consultation system was completed, significantly expanding the forecast coverage upstream and transitioning the forecasting paradigm from "empirical deduction" to "model-based display". From then on, "science-based decision-making" became the unshakable cornerstone of dispatch.

After the world's largest clean energy corridor was fully completed, the six large hydropower stations along the main stream of the Yangtze River came under coordinated, unified dispatch. The forecasting network had to cover nearly 80% of the upper Yangtze River Basin, with a forecast period of up to ten days and unprecedented accuracy requirements.

A "fine-grid" revolution emerged in response. In meteorology, the Three Gorges Cascade Dispatch & Communication Center increased the spatial resolution of weather forecasts for the Yangtze River Basin to 5 km × 5 km leveraging its own and jointly developed technologies, providing critical support for scientific dispatch and proactive response. For hydrological data collection, the center established the Hydrological Forecasting System for Upper Yangtze River Basin, dividing the vast basin into 377 hydrological units. Leveraging nearly 900 self-built telemetry stations, contracted flood-reporting stations, and data from nearly 20,000 basin-wide meteorological stations obtained through information sharing, the system covers 80% of the upper Yangtze River Basin in terms of data collection and can complete the acquisition and compilation of hydrological and rainfall information from the upper Yangtze River within ten minutes. This information is transmitted in real time via radar, BeiDou satellites, and ground-based information transmission networks, ultimately realizing "space-air-ground" integrated information monitoring and transmission. Sitting before their screens, forecasters can now, with a light tap of their fingers, summon their "clairvoyance" to survey the clouds and rain, and activate their "clairaudience" to listen to the rivers.

In 2020, as the Three Gorges Reservoir braced for its record-high flood peak since impoundment, this system detected the flood-inducing heavy rainfall ten days in advance and accurately predicted the peak discharge two days ahead, buying precious time for the Three Gorges Project to respond with composure.

In September 2025, when the strongest autumn rains in western China since 1961 struck, the system had already accurately captured their "pulse" ten days before the flood peak formed. The Three Gorges Reservoir lowered its water level to 162.6 meters in advance, reserving ample storage capacity for the incoming flood. As the flood peak passed, the outflow was precisely regulated, ensuring safety downstream while leaving sufficient room for subsequent impoundment.

Now, the 2026 flood period has arrived. On the giant screens at the Three Gorges Cascade Dispatch & Communication Center, data from satellites, radar, and hydrological stations pulse in real time. The craftsmanship and dedication of the "hand-drawn chart" era have been infused into every precise beat of the digital river, transformed into the wisdom and composure at the fingertips of today's forecasters.

The evolution of charts bears witness to the journey of the forecasting enterprise for a great river from "touch" to "perception", from "empirical calculation" to "intelligent simulation".

While the manuscripts of the past have been archived, the spirit they embody—the quest for truth and pragmatism, the pursuit of excellence, the courage to experiment and innovate while staying true to foundational principles, and the unwavering commitment to serving the nation and safeguarding the people—has been passed down through generations. This is the power of a "token": it bridges the past and the present, embodying what it means to "press forward with resolve" and what constitutes true "tangible achievement".