Warning device, warning system for detecting water level in drainage well

A warning system for detecting water level in drainage well comprising:

• at least one water level sensor corresponding to at least one preset water level, and the at least one preset water level being set in the drainage well, and each of the at least one water level sensor corresponding to a water level value;
• a transceiver, wherein each of the at least one water level sensor comprises an antenna and a first processing unit, the first processing unit is connected to the antenna, the first processing unit controls the antenna to transmit a communication signal to the transceiver, the transceiver comprises a first communication module and a second processing unit, the first communication module is connected to the second processing unit, the first communication module receives the communication signal sent by the antenna, the second processing unit obtains the communication signal from the first communication module and determines a target water level sensor under water according to a determination result indicating that the communication signal is decaying, and searches a water level relationship table according to the target water level sensor, and determines the water level value corresponding to the target water level sensor, and sends at least one of the water level value and an information of the target water level sensor;
• and
• a terminal device configured to determine the water level value corresponding to the target water level sensor according to the information of the target water level sensor, and send an alarm when determining that the water level value exceeds a warning water level value.