پژوهشنامه مدیریت حوزه آبخیز (Jul 2024)
Design and Construction of an Automatic Discharge and Sediment Load Monitoring Equipment
Abstract
Extended Abstract Background: Large-scale and regional planning requires observed data on environmental variables, such as runoff and suspended sediment load from watersheds. Data is fundamental for generating information and knowledge, and scientific management of a system is impossible without a monitoring and measurement plan. Management of watershed systems and water resources is no exception to this axiom. With ongoing trends in socioeconomic development, climate change, increasing pressure on natural resources and watersheds, and, consequently, an increase in floods and sediment yield, there will be a greater need for more accurate information about sediment and runoff processes in the near future. Many tools and instruments for measuring runoff and sediment components have been produced and marketed by a number of foreign companies. However, their cost is very high in Iran, on the one hand, and a device that measures both components at once is very rare, on the other hand. To carry out simulations that are both accurate and efficient, it is essential to have access to sufficient and reliable data and information for verification and validation purposes. In the field of water resources and watershed management, data and information are considered to be crucial tools. By providing important insights into the management of water resources, the availability of data and information can help enhance the efficiency and optimization of water usage, prevent natural hazards (such as floods and droughts), manage water quality, and improve the management of water supply and demand. Therefore, this study aimed to design and construct an automated flood and sediment load-monitoring device with the ability to record the runoff height of watersheds and a planned sampling of runoff for measuring suspended sediment using cheap sensors and tools. Methods: This study presents an innovative device designed to monitor runoff discharge and suspended sediment sampling. The device has been constructed and installed at the outlet of the sub-basin under study. A regular cross-section was constructed at the outlet to facilitate the installation of the device, which enabled the monitoring of the runoff hydrograph of the sub-basin outlet and suspended sediment load sampling. In this research, analog hygrometer sensors were used to measure the height of runoff with 3 cm intervals (measurement accuracy of 3 cm). DC pumps with valves were used to collect the sediment sample, which created a vacuum in the sampling container and caused the runoff sample to be transferred into the container. To evaluate the device's capabilities in real and natural conditions, it was installed at the outlet of a sub-watershed in the eastern loess lands of Golestan province, located upstream of Qapan Oliya village in the Kalaleh district for two years to record the hydrograph of likely flood events and take runoff samples at the user-defined depths of flood (two samples at depths of 20 and 60 cm in rising limb and one sample at a depth of 20 cm in recession limb of hydrographs). The samples were stored in 0.5 liter containers, and the user was informed by sending an SMS to replace the filled containers with empty ones. It is noteworthy that the device under consideration facilitates the collection of runoff samples at any frequency and at any height for research requirements. The device boasts a remarkable advantage in the form of its SMS notification feature, which keeps the user informed about the monitoring site and equipment status, including runoff sampling, power outages, and battery status. The device incorporates a built-in battery that remains active during power outages in the electricity network to record flood events. Additionally, the user can communicate with the device via a mobile phone at any time and receive SMS updates on the device's operating status, such as power, battery, memory level, and event registration. Furthermore, to ensure accurate rainfall data recording, a WatchDog tipping bucket rain gauge has been installed within the studied sub-basin. Results: During these two years, only three rainfall events leading to runoff and flooding occurred in this sub-watershed, and the designed device successfully recorded the hydrograph of all three events and informed the user. In each of these recorded flood events, at least two runoff samples (one sample in the rising limb and one sample in the recession limb of the hydrograph) were collected and stored by the device to be transferred to the laboratory to determine the suspended load. The present study has demonstrated that the automated runoff and sediment monitoring device, which has been specifically designed to measure a range of parameters such as flow rate, water level, and suspended sediment load, represents a valuable and practical tool for those seeking to monitor runoff and sediment at the outlet of watersheds. Conclusion: Data and information play a vital role in water resources and watershed management. The availability of such data and information in the management of watersheds and water resources helps enhance water use optimization and efficiency, prevent natural disasters such as floods and droughts, manage water quality, and improve water supply and demand management. Therefore, the prototype of the designed device shows that this device has a good capability for the industrial production of an inexpensive runoff and sediment monitoring tool to scientifically manage small-scale watersheds.
