Document Type : Research Paper
Authors
1 Assistant Professor, Soil Conservation and Watershed Management Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran
2 Professor, Soil Conservation and Watershed Management Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran
Abstract
Introduction
In the context of climate change and global warming, the comprehensive management and productivity of water resources become increasingly important. Accurate measurement of existing water resources forms a critical foundation for effective water resource management. Precise measurements enable better and more fundamental planning. Surface water, particularly flood-generated water in large and small watersheds, plays a significant role in Iran's water resources. A major challenge in the country's water resource management is the lack of sufficient runoff data, especially for smaller watersheds. The use of hydrometric devices for stable water level measurements can substantially address this issue, improving the collection of surface and groundwater data. Several methods have been developed for water level measurement, which can be categorized as contact or non-contact methods, depending on whether the sensor interacts directly with the water. These methods may record data either automatically or manually. Selecting the appropriate method depends on specific conditions, such as the range of liquid level changes, the physical properties of the liquid (e.g., density, cleanliness, vapor or particle content, corrosiveness), process temperature and pressure, chemical composition, and environmental factors like moisture.
Materials and methods
Non-contact methods offer significant advantages, including independence from fluid type and non-interaction with the fluid itself. Among these methods are image processing using cameras, ultrasonic sensors, infrared sensors, and laser-based techniques. This research investigates the efficiency of the Sharp infrared module model GP2Y0A02YK0F in measuring water level changes in both laboratory and natural environments. The module includes a distance measurement sensor consisting of a Position Sensitive Detector (PSD), Infrared Emitting Diode (IRED), and a signal processing circuit. It operates within a voltage range of 4.5 to 5 volts and a temperature range of -10 to +60 °C. The analog output of this module corresponds to the measured distance, producing values between 0 and 1023. When an object moves closer to the sensor, the output approaches 0, and as the object moves farther away, the output increases toward 1023. Data calibration is required to relate sensor readings to actual values. The sensor's measurement range is 20–150 cm, utilizing infrared light for distance detection. To evaluate its performance, a low-power data logger suitable for watershed environments was employed. Since the method requires a non-reflective surface, it was combined with a traditional float-based method. The mechanical setup includes a polyethylene tube housing the sensor, enclosed within a metal body to resist flood conditions. Laboratory experiments involved measuring water level changes across 10 stages, where sensor data (independent variable) and actual water level values (dependent variable) were collected. Polynomial fitting (first to fourth degree) was applied to establish relationships between variables. Additionally, 30% of the data was reserved for model validation.
Results and discussion
An inverse relationship between sensor readings and actual distances was evident: sensor output values decreased as distance increased. The correlation coefficients (R) for one- to four-term polynomial fits were close to one, indicating a strong alignment between sensor data and actual measurements. The RMSE ranged from 2.16 to 1.89 cm, improving with higher-degree polynomials. In laboratory conditions, the sensor estimated water level changes with a 2 cm error, which was reduced to 1.34 cm by increasing the minimum measurement range to 30 cm. Given its affordability, this sensor is suitable for applications where high precision is unnecessary. For higher accuracy, alternative sensors should be considered. However, in flood environments, issues such as the obstruction and adhesion of floating materials in the tube pose challenges, making this method unsuitable for flood channel measurements. Incorporating additional sensors, such as pressure or ultrasonic sensors, could enhance the device's capabilities.
Conclusions
Various methods have been developed for measuring water level changes. The selection of a method depends on environmental conditions, accuracy requirements, and cost considerations. Given the lack of extensive water level and flow measurement networks in Iran's watersheds, the approach proposed in this research can significantly contribute to water resource management. However, the reliance on floating components within the tube is a critical limitation, as flood-induced sediment can hinder float movement over time. Future research should focus on methods that eliminate the need for floating parts, thereby overcoming these limitations. Additionally, the results of other measurement techniques will be explored in subsequent studies.
Keywords
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