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From August 11 to 15, affected by both Typhoon Lekima and cold air from the north, heavy rainfall will occur successively in eastern Jianghuai, eastern Huanghuai, eastern North China, and southern eastern Northeast China. The cumulative rainfall amount will be around 70–150 millimeters; in some areas of northern Shandong, eastern Hebei, southern Liaoning, and eastern Jilin, it will reach 200–300 millimeters, with the highest local rainfall amounts exceeding 500 millimeters. Typhoon Lekima is moving northward, bringing floods to areas such as Shandong, Hebei, and Jilin. According to statistics from the Ministry of Water Resources, since the 9th, affected by both Typhoon Lekima and cold air, regions including Zhejiang, Shanghai, Jiangsu, Anhui, Shandong, Hebei, and Liaoning have experienced heavy to extremely heavy rainfall, with localized areas seeing torrential rains. The highest peak rainfall was recorded at Fuxi Reservoir in Wenzhou, Zhejiang (732 mm), Paifang in Xuancheng, Anhui (390 mm), and Changle in Weifang, Shandong (367 mm). Affected by heavy rainfall, the water levels (flows) of 73 rivers in Zhejiang, Jiangsu, Shanghai, Anhui, Shandong and other regions exceeded the warning levels (flows); among them, floods exceeding the guaranteed levels (flows) occurred in 38 rivers, and record-breaking floods occurred in three rivers in Shandong – the Mi River and Sha River – as well as the Wusong River in Shanghai. On the 11th, **E Jingping, deputy commander of the National Flood Control and Drought Relief Headquarters and minister of water resources, said that this typhoon brought heavy rainfall in concentrated periods, causing severe damage; all regions must make every effort to prepare for such intense rainfall. At the same time, the safety of reservoirs must be given top priority; 24/7 monitoring of these reservoirs is necessary, and strict control must be exercised over their water levels during flood seasons. It is strictly prohibited to allow reservoirs to operate above their designated flood levels due to concerns about water scarcity or a desire to conserve water. The Ministry of Water Resources requires areas prone to flash floods to strengthen monitoring and early warning, information dissemination, and evacuation efforts, to ensure that actions are taken in the right direction and swiftly, thus safeguarding the lives of the people. It is reported that on the afternoon of the 10th, news of floods caused by the super typhoon \"Lekima\" that trapped people in Linhai, Zhejiang, spread rapidly, sparking widespread concern. The impact of this flood represents a significant challenge for the various municipal departments to improve their flood disaster monitoring systems. To address this, sensor technology can be fully utilized to monitor water levels in real time, helping smart cities establish effective flood warning systems that safeguard the safety of urban buildings and citizens during heavy rainfall. Applications of various sensor technologies in flood warning systems: Nowadays, water level monitors are relatively common monitoring devices in the flood control and monitoring systems of many cities in China. Common roadside water level monitors can be divided into two main parts: the sensors located inside the well, and the receivers mounted on street lamp posts. These two components are used to monitor the water level in the well in real time, with the data being sent to the mobile apps of flood control personnel so that maintenance staff can be dispatched promptly to handle the situation. As for how to monitor water levels, common IoT water level sensors include ultrasonic level sensors, pressure sensors, radar level sensors, and so on. ①Ultrasonic level gauges typically emit sound waves to determine the liquid level. Whether used to monitor chemicals in storage tanks or to measure river levels on bridges, ultrasonic level gauges can determine the liquid level based on the time it takes for the sound waves to reach the target (such as water) and return to the sensor. Based on these high-frequency sound waves, ultrasonic level gauges output sensor readings, typically in an industrial standard sensor format such as 4-20mA. An ultrasonic level gauge is installed above the liquid that needs to be monitored, and is known as a non-contact sensor. ②Pressure transmitters can, in a sense, measure the pressure or weight exerted by the liquid located above a device. They are considered passive sensors, as opposed to active sensors such as ultrasonic and radar sensors, which actively generate signals for level measurement. Pressure transmitters convert pressure into output signals in a sensor standard protocol (such as 4-20 mA). It should be noted that the pressure transmitter will come into contact with the water body being monitored, and more accurate measurements are required at the bottom. For certain monitoring scenarios, this can be a challenge, as the liquid may contain sediment or floating debris that could damage the sensors; in other cases, such as monitoring water level and well depth in wells, pressure transmitters are usually the most effective water level sensors. ③Radar level gauge: A radar level gauge uses a probe to direct high-frequency radar and electromagnetic waves from the sensor toward the water level being monitored. Based on the time it takes for the radar pulses to return, the gauge outputs a reading of the water level. Typically, radar level gauges are more expensive than other types of level sensors. However, the waves and pulses emitted by radar level gauges can usually penetrate things that may interfere with the accurate measurement of the level, such as foam or vapor. For this reason, it is necessary to carefully consider which combination of level sensors or level sensor technologies will be effective in specific scenarios. Source: Changhui Instruments http://yunrun.com.cn/