Monitoring of Water Resources in arid/semi-arid regions by Mr. Kai Vogel / Dr. Issa Hansen (SEBA Hydrometrie)

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1 Monitoring of Water Resources in arid/semi-arid regions by Mr. Kai Vogel / Dr. Issa Hansen (SEBA Hydrometrie) The newest innovative product, a camera-based discharge measurement system, called DISCHARGE KEEPER including reference projects. Following an invitation from Mr. Samer Shouman, Director at Saudi Geological Survey Zamzam Studies and Research Centre, Mr. Kai Vogel (MSc. Hydrogeologist), Key Account Manager for Middle East & Africa from SEBA-Hydrometrie GmbH & Co. KG was holding a lecture on Monitoring of Water Resources in arid/semi-arid regions. The talk focused on the challenges, methods and solutions for sustainable water resources monitoring networks including the introduction of newest technical innovations. Founded in 1967 in Germany, SEBA Hydrometrie is one of the world s leading manufacturers of environmental monitoring equipment. With over 50 years of monitoring experience in the fields of groundwater, surface water, water quality, meteorology and flow/discharge in over 140 countries, the sensors, loggers and operating / data management software have proven their reliability and excellence in all climate conditions worldwide. Within the Kingdom of Saudi Arabia, SEBA Hydrometrie is working very closely together for almost 20 years through Kenaaz United with the department of Zamzam Studies and Research Centre as well as other departments of SGS. For the Ministry of Water and Electricity (MoWE) Riyadh as well as Saudi ARAMCO, SEBA supplied fully telemetric hydrometrical networks covering more than 250 stations for groundwater/surface-water/meteorology. The DischargeKeeper is a completely new method for the continuous acquisition and storage of flow velocity profiles, water levels and flow rates in natural water streams, irrigation furrows and waste water channels. The DischargeKeeper consists of an IP-camera, an infrared beamer, and a measuring transducer with remote data transmission. The surface velocity profile is measured by means of an optical method (based on the cross correlation technique) for capturing the flow velocity. The water level detection is carried out simultaneously by an image processing technique. The vertical velocity profile is obtained employing a mixing length model. Subsequently, the discharge is calculated directly on site. After a very short time the user receives the measurement results of the average flow velocity, the water level, and the discharge. In general, a measurement process takes only 40 seconds. In addition to the digitized measured values, proof images are stored and can be transmitted to an FTP server via GPRS. The equipment was tested at several sites and under different weather and light conditions. The validation of the DischargeKeeper was carried out by comparing the flow determined by the newly developed gauge, against the flow measured by a reference gauge. The correlation between the measurements carried out by the camera-based system and by the reference gauge was highly satisfactory.

2 The calibration of the DischargeKeeper requires some input parameters. These are: the crosssection of the river/channel, the positions of at least four reference points on the far shore of the river/channel and the current position of the water line, which is equivalent to the initial water level (see figure 1). This position of the water line and the reference points are only needed when setting up a site. Figure 1 Schematic overview of the geometrical input parameters required for the calibration of the DischargeKeeper The reference points can be placed anywhere, as long as they are in the camera field of vision. The x, y, z coodinates of such reference points have to be given to the DischargeKeeper. The hydraulic input parameters (velocity and water level) can be optically detected. Subsequently, the discharge is calculated directly on site (Q = v Am 3 s -1 ). The surface velocity profile is measured by means of an optical method (based on the cross correlation technique) for capturing the flow velocity. The applied optical method for velocity measurements is based on the well-established Particle Image Velocimetry (PIV) technique, which is also known of being successfully applied to large scale free surface flows of flumes or open channels, also known as Large Scale PIV (LSPIV). The water level detection is carried out simultaneously by an image processing technique. For the estimation of the water level several optical methods are available. A new approach (patent pending) for water level detection was developed to separate the moving water from the rest of the image using a sequence of images. The vertical velocity profile is obtained employing a roughness dependent mixing length model. Some special features and benefits of the DischargeKeeper Flexible positioning of the measuring equipment: The weatherproof IP-camera and the sensor controlled infrared beamer can be mounted easily on e.g. a water gauge station, a mast, concrete constructions or a bridge. The process unit can be housed in a water gauge station or in a protective case. Elaborate and expensive installations in the water are no longer required. No flow tracers required: A special feature of the developed measuring system is that no flow tracers need to be added for flow velocity detection. The DischargeKeeper operates

3 on visible moving surface structures. Nevertheless, naturally occurring floating objects on the water surface (e.g. leaves) enhance the measurement signal. Representative measurement: Unlike other non-intrusive sensor types (such as radar), the DischargeKeeper delivers a flow rate measurement (profiling) on the entire surface of the image section. This provides a representative and spatially resolved flow velocity detection. Non-intrusive: The optical measuring system DischargeKeeper does not come into contact with the measured medium. A damage of the equipment as a result of siltation, vegetation growth etc. is excluded. Therefore the technology is practically maintenance-free. On-site evaluation: All DischargeKeeper measurement parameters (water level, velocity profile, and discharge) are collected and processed locally on the measuring site almost in real time. Robust, weather insensitive, precise: The DischargeKeeper can also be used under a wide variety of environmental, weather, and lighting conditions. More than just a sensor: The DischargeKeeper provideos both, the required measurement values and proof images from the measuring site in HD quality. In case of doubt, the parameters, such as the water level, can be verified using the present image information. Time-consuming service missions to the measuring site can be reduced or even avoided. Saxony/Germany Some Reference Projects of DischargeKeeper Installations The site is a river with about 10 m width and 0.6 m depth. Infrared-Illuminator DischargeKeeper-Camera Figure 2. DischargeKeeper installation, Wesenitz river

4 Figure 3. Hydrographs of the measured parameters water level, mean velocity and discharge DischargeKeeper vs rating curve 6 Q DischargeKeeper [m3/s] 5 Q Rating curve [m3/s] Discharge [m3/s] Waterlevel [cm] Figure 4 Comparison between the DischargeKeeper and the rating curve values 70 80

5 Figure 5. Result images with the optically detected velocity vectors and water level line (day and night measurements)

6 Lower Saxony/Germany Outflow of a waste water plant. Figure 6 DischargeKeeper installation in the outflow of a waste water plant Figure 7 Result image with the optically detected velocity vectors and water level line (day measurement)

7 Figure8. Result image with the optically detected velocity vectors and water level line (flood event, day measurement) Bavaria/ Germany Figure 9 DischargeKeeper installations hardware components, Wertach river

8 Figure10. Result image with the optically detected velocity vectors and water level line (day measurements at different water levels) C o r r e la t io n c a m e r a - b a s e d s y s t e m ( D is c h a r g e K e e p e r ) v s. A D C P D is c h a rg e K e e p e r Q [ m 3 /s ] R ² = A D C P Q [ m 3 /s ] Figure 11. Correlation between the camera-based system (DischargeKeeper) the ADCP comparative measurements Luxembourg Inflow of a waste water plant.

9 Figure 12. DischargeKeeper installation on a waste water site, Luxembourg Figure 13 Result image with the optically detected velocity vectors and water level line (day measurement)

10 Figure 14 Result image with the optically detected velocity vectors and water level line (night measurement) Some images of further DischargeKeeper installations