Zengwen Reservoir Expected to Gain 30 Million Cubic Meters in 5 Days, Runoff Coefficient is Key

Continuous rainfall in the upstream area of Taiwan's Zengwen Reservoir has significantly boosted water inflow, with the potential to add 30 million cubic meters. The key factor is the "runoff coefficient," which measures how much rainfall becomes surface runoff. During dry periods, dry soil absorbs much of the rain, lowering this coefficient and reducing water entering the reservoir. However, with continuous rain, the ground becomes saturated, increasing the proportion of rainfall that flows into the reservoir. The South Region Water Resources Branch of the Water Resources Agency stated that the current soil saturation suggests inflow could double. Since last Thursday, the Zengwen Reservoir catchment area has received over 172 millimeters of rain, adding approximately 15 million cubic meters of water. With a runoff coefficient of 0.4, the recent rainfall could contribute about 340,000 cubic meters. As of Monday morning, the reservoir's water level reached 196.36 meters, with a storage rate of 12.86%. Combined with the Wushantou Reservoir, the total effective storage capacity is 69.71 million cubic meters.