Dam Safety management for 45 Dams

INTRODUCTION

The Ebro Hydrographic Confederation (CHE) has set up an integral dam safety management programme so as to effectively maintain and increase safety of the 45 dams. Below we list the tasks related to the auscultation that OFITECO is undertaking for CHE.

In general this deals with the following tasks that interact among themselves:

• Implementation, maintenance and updating of computer tools
• Continuous monitoring of dam behaviour
• Installation and maintenance of the auscultation and automated systems
• Visual inspection of the dams and carrying out manual readings
• Assessment of  behaviour and determining the safety level

The tasks require a high level of coordination, on the one hand due to the geographic distribution of the dams (the basin has a surface area of 85,362 km2) and on the other hand through the incorporation of a multidisciplinary team with specialists in dams, geology, electrical  installations and computers.

Implementation, maintenance and updating of LA computer tools

So as to manage the information and the auscultation data efficiently, we have opted to implement the DAMDATA computer tool. All the dams have been included into a centralised database and the configuration of each dam has been customised according to their characteristics and the auscultation system installed.

As the dams have been built over more than 100 years, there are a large variety of types of sensors and data readings. All the available information has been compiled and the sensors with their historical data, formulas and constants have been included. More than 5000 sensors have been included, some of them with data of more than 30 years.

Example of the sensor configuration

Thanks to a clear and programmable calculations motor we have been able to include any sensor with their specific formulas and data. Some dams have data spanning several decades and the  auscultation system of all the dams has been continuously improving which has meant including some changes in readings of origin and recalibration.

Example of the formula configuration

Continuous monitoring of dam behaviour

So as to know the current status of the dams we carry out a continuous control of all the auscultation data. Taking into account the large quantity of data provided in all the dams, it has been necessary on the one hand to include an automatic control and on the other, to display the data clearly and in a structured way to help in their manual review.

From the automated sensors we  automatically store a daily value on the database and the other data is added according to how often they are manually read. Through the DAMDATA SCADA option we see the last value available for each sensor on a map. For this, we have prepared different customised visits for each dam to display the sensors with their reading according to  their location.

SCADA example

The thresholds established in the Exploitation Regulations and Emergency Plans are also included and are automatically compared with the data readings. The thresholds are for constant and variable types, according to the time, reservoir level and temperature. Through the use of different colours we indicate the alarm state of the data obtained and functioning of the sensor on the SCADA screens.

All the information gathered in the DAMDATA is subject to an automatic and manual debugging, which is carried out by engineering experts in dam safety, after a rigorous analysis.

Installation and maintenance of the auscultation and automated systems

To guarantee that data is gathered reliably and continuously with the required precision, it is essential to ensure that the auscultation system functions properly. This is achieved through a preventative and corrective maintenance programme for all its elements such as sensors and automated and communication systems. In the following chart we display the different tasks that are being carried out:

Monitoring visits are carried out to inspect, calibrate and start up the auscultation systems, reporting on their status and proposing possible improvements to solve problems that may have been detected. Likewise, the opportunity is taken to show the staff in charge of the dam, the main maintenance jobs they should carry out regularly. These jobs are carried out by specialists in electrical systems and installations who work closely with the experts in auscultation and dams so as to meet the safety requirements of each dam.

Visual inspection of dams

Visual inspection is one of the most important jobs in the auscultation of dams. Besides the daily inspections by those in charge of the dam, the dam specialists should carry out more comprehensive visual inspections, not only on the civil works, but also on everything relating to the auscultation systems, the manual ones as well as the automatic ones for gathering data. The observations made are used to confirm and complete the information obtained through the auscultation system.

The observations made are reflected in descriptive reports with a large amount of photographs. To clarify details on position and size, special photos of interest are displayed on maps.

Visual inspection map of the parameter of waters downstream at the Santolea Dam

Manual readings

Those in charge of the dams carry out manual readings according to the specifications in the Exploitation Regulations. These are also reflected in the configuration of the DAMDATA in such a way that they are included in the Field Sheets customised according to the manual reading (daily, weekly, monthly, etc.). They list all the sensors that have to be read in order of their route and ordered by type, according to the technician’s preferences. They also always include the last reading value which allows an immediate check in the value field taken.

Example of a field sheet created by Damdata

Example for the planning of the readings

After the readings have been carried out, those in charge load the data from the computer at the dam directly onto the database through the Internet. For this, DAMDATA has a personalised menu for each dam that automatically converts the reading data into engineering data.

Assessment of  behaviour and determining the safety level

Besides the daily monitoring of the auscultation data, a comprehensive assessment of all the data and observations obtained during the visual inspection is carried out periodically. The main aim is to display all the information clearly and descriptively so as to help in assessing the behaviour of each dam. The result consists of determining the safety level and in creating responses for actions to be undertaken.

Methodology applied to assess  behaviour and determine the safety level

A key element for interpreting the auscultation data involves its graphic representation. For this we use the DAMDATA layout function, which allows us to compare the different variables among themselves on a sheet with different boxes and images. This way sensors that are installed on the same level or section can be grouped together and compared directly with the external variables. Images are also included with the agreement of signs and information on the location of the sensors.

Example of the provisional progress of a pendulum compared to the external variables

Plans are also prepared which indicate  the values obtained with key sensors such as sub-pressures, isotherms or crowning movements.

Presentation of the isotherms and pendulum movements on a map

Conclusion

The tasks carried out in the auscultation field have allowed us to considerable increase our knowledge on the current state of each of the 45 dams and extend the auscultation utility.

By including the data into a new DAMDATA database we have been able to debug the old data and review the configurations of the sensors. This way we have been able to improve the quality of the data, not only the historic but also the current data. Continuous maintenance of the auscultation system has improved its functioning and helped increase the amount of reliable data.

Thanks to the use of the DAMDATA tool, this has helped in the process of interpreting data, from its reading to preparing the behaviour report and follow-up in real time. As it is a platform in a web environment, experts from different offices are able to have access to the same updated information at the same time.

As we have data in real time we have been able to link the auscultation with the Exploitation Regulations and the Emergency Plans and this way develop an integral solution for safety management of dams.