# A Real-Time Water Level and Discharge Monitoring Station: A Case Study of the Sakarya River
## 2 Materials and Methods
### River Monitoring Station Laboratory and Field Calibration  
The components and software system of the real-time river monitoring station were integrated and enclosed in a waterproof cabinet to prevent adverse weather effects. Calibration studies were conducted on an open channel at the Hydraulic Laboratory of Sakarya University. During calibration, the distance readings obtained by the sensor were compared directly with manual measurements made using a measuring tape on the water surface. This comparison is crucial for verifying the measurement accuracy of the sensor and making necessary adjustments. Additionally, a web interface designed to monitor and record data from the sensor in real time was utilized. The web interface was integrated to record, access, and analyze calibration data, allowing for real-time evaluation through remote access. Calibration studies conducted on the open channel in the laboratory environment meticulously integrated manual and automatic measurement techniques for the fabricated discharge monitoring station. The calibration study of the ultrasonic distance sensor conducted in the laboratory is shown in Figure 8. The figure illustrates the manual measurement of the distance between the sensor and the water surface using a measuring tape, which is then verified with the sensor readings. The manual measurement is recorded as 106.7 cm, corresponding to the 106.76 cm data automatically recorded by the ultrasonic sensor. Data from the sensor are monitored and recorded in real time on a computer screen, playing a critical role in verifying the sensor's measurements and making necessary calibration adjustments. The consistency between manual measurements and sensor data confirms that the sensor is accurately calibrated and provides reliable data. Figure 8: Laboratory calibration. Figure 7: Arduino–Sensor Connection Flowchart. Following the laboratory calibration of the river monitoring station, fieldwork was conducted to determine its suitability for field conditions and to identify the effects of external factors. The field calibration studies for the river monitoring station, fabricated using an ultrasonic distance sensor for real-time level readings in rivers, were conducted on the Sakarya River at the pipeline bridge connecting Hanl village and the Orencik Bridge, where the station will be installed. These studies are illustrated in Figure 9. During the calibration process, the accuracy and response of the sensors to external factors were thoroughly examined through measurements taken on these two bridges. During the validation phase of the calibration, the distance measurements taken by the sensor at the Orencik Bridge and the bridge connecting Hanl village were monitored via the web interface and compared with laser meter and manual measurements. At the Orencik Bridge, the sensor recorded a distance of 1098 cm, while the laser meter measurement was determined to be 1097 cm; at the Hanl bridge, the sensor measured 1100 cm, and the manual measurement was recorded as 1099 cm. The close proximity of these measurements (with a 0.1% margin of error) indicates that the sensor settings were correctly adjusted and the calibration was successful. Following the field study, the sensor was integrated with a protective apparatus to ensure safe and efficient operation, considering the physical conditions of the Orencik Bridge. This protective apparatus is designed to prevent interference with sensor measurements and can be easily removed when necessary. The real-time river monitoring station was integrated into a compact and waterproof cabinet (30 \(\times\) 25 \(\times\) 15 cm) to ensure the secure operation of components and resistance to environmental conditions. The necessary connections for the sensor and solar panel were optimized to guarantee reliable and uninterrupted functionality. The completed design was installed at the designated location, Orencik Bridge, after obtaining the necessary permissions from the Sakarya Metropolitan Municipality (Figure 10).