Although reservoir management units are not directly responsible for water quality management, their long-term operation in the water supply system may be jeopardized in the event of water pollution incidents involving the flow of contaminated water into the reservoir storage range. Establishing an independent monitoring system is therefore crucial to enable proactive, timely countermeasures to be undertaken in conjunction with other relevant units. However, such operational mechanisms have not yet been developed in Taiwan. In addition, many difficulties still hinder catchment monitoring technologies. Through the proposed project, we expected to identify optimal locations for water quality monitoring stations and establish monitoring items based on optimal assessment and analysis results. The content and results of the project are summarized as follows:
Literature review: domestic laws and case studies on automatic water quality monitoring from both Taiwan and abroad were summarized to create a reference for assessing the establishment of monitoring equipment. In addition, interviews were conducted at Fengyuan Water Treatment Plant and Kaohsiung Water Supply Plant to examine water monitoring and contingency management at purification (supply) plants. Finally, the rationality of the locations of the monitoring stations of the Water Resources Agency in the aforementioned four catchment areas was explored.
Investigation and analysis of the items to be monitored: Monitoring items at a conventional station are recommended to include coliform, ammonia, biochemical oxygen demand, pH, dissolved oxygen, suspended solids and phosphorus, and chemical oxygen demand. Monitoring items at an automatic monitoring station are recommended to include ammonia, total organic carbon, pH, dissolved oxygen, turbidity, conductivity, temperature, and oxidation-reduction potential.
Establishment of operational procedures for the monitoring network:
1) Evaluation of the location of water quality monitoring stations: we recommend that apart from complying with the second article of the “Water Quality Monitoring Stations Installation and Monitoring Standards,” simulations of river water quality be performed. The results of the simulations can subsequently be compared with the actual values measured from the rivers to identify the locations where the measured values are abnormally high. In addition, the following locations should be given consideration with respect to establishing water quality monitoring stations: downstream locations of catchments that reflect pollution reduction and governance effectiveness, newly developed areas or locations affected by natural disasters, locations where concentrations of water quality measurements frequently exceed standards during non-rainfall periods, and locations where the water ecological environment frequently sustains pollution for unidentified reasons.
2) Monitoring network planning procedures: for conventional stations, basic information about the target river segments to be monitored is first collected, and the rationality of the existing stations is then examined, followed by field investigations to assess set-up locations. Finally, monitoring items are determined. When available funds permit the establishment of an automatic monitoring station, an early warning value and a strain value must be set.
Rigorous selection of sites for demonstration stations for real-time monitoring: Basic data collection in the projected area involving topography, land use, climate, and historical water quality were collected in catchment areas such as the Shimen Reservoir, the Emerald Reservoir, the Shigang Dam, and the Kaoping River Dam. Then the representativeness, security, feasibility, and demands of various candidate locations in the four catchment areas were assessed before performing field investigations for scoring. Finally, one location in each river basin was selected for location assessment by analytic hierarchy processing. In this study, following evaluation, Chang Geng Bridge on the upstream of Shigang Dam was selected as the demonstration station.
Monitoring items at demonstration stations for real-time monitoring: according to the water quality data sampled at Dongshi Bridge, an early warning value and a strain value were determined in line with requirements of the Taiwan Water Corporation, reservoir management units in the catchment areas, and maintenance units. The early warning and response values were set according to the following principles: 1) the Taiwan Water Corporation company is given the highest priority in allocating the water supply, followed by the upstream catchments and reservoir management units; 2) in consideration of the distance between the station’s location and the water intake, at least two hours should be given to allow the water intake unit to perform repeated analyses and contingency measures; 3) the station maintenance unit should be authorized to set some of the early warning values, to determine the accuracy of the instruments.
Testing and operation of the demonstration station for real-time monitoring: a DS5X multiparameter water quality sonde manufactured by Hydrolab (US) was used. The measured water quality data were transmitted to the main data server via a GPRS wireless network; the monitoring items included turbidity, conductivity, dissolved oxygen, pH, oxidation-reduction potential, temperature, and ammonia. With respect to the monitoring results, turbidity can only be accurately assessed through the follow-up of long-term monitoring data, which are currently unavailable because it is the dry season; regarding conductivity, dissolved oxygen, and pH, no major difference was identified between the values sampled from Dongshi Bridge and those from Chang Geng Bridge; the ammonia data were higher than the peak value sampled from Dongshi Bridge, and consequently the correct unpolluted concentration could not be rendered. Furthermore, the analytical results regarding the quality of manually sampled water reveal that the water quality data collected from Chang Geng Bridge and Shigang Dam were not distinctly different from one another, and consequently, the water data sampled from Chang Geng Bridge can be considered representative of that of the Shigang Dam.
Standard operating manual for contingency-oriented water quality monitoring stations: to establish the locations of water monitoring stations and determine the scope of monitoring items, a manual was compiled as a basis for subsequent development of monitoring station networks.
Keywords: reservoir, water quality monitoring stations, real-time monitoring