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Discharge measurement at the river "Große Roeder" in Saxony - Germany

Due to the seasonally strong weed growth and low flow during low water periods the relation level/flow at the measurement site "„Kleinraschuetz“ was rather distorted and had to be corrected by putting in additional manpower for manual measurements. Therefore it was decided to modernize the station completely and to install a stationary discharge measuring system. The challenge of the measurent situation was to find a solution that measures reliably at all water levels  from low level 29 cm to high level at flood events with 310 cm.

OTT SLD

Système Doppler de mesure d'écoulement stationnaire

OTT SLD est un système de mesure autonome à effet Doppler pour enregistrer en continu la vitesse d’écoulement et le niveau d’eau des cours d’eau naturels et semi-naturels.

  • Installation à poste fixe
  • Acoustique
  • Vitesse d'écoulement
  • Appareil à ultrasons horizontal fonctionnant selon le principe Doppler pour la mesure de débit en continu dans les rivières et les canaux. Calcul de débit selon la méthode d'indice de vitesses. Filtre de bateau intégré, interface Modbus pour les systèmes d
  • ± 10 m/s
  • ± 1 % de la valeur mesurée ± 0.5 cm/s

The river Große Roeder is a tributary of the river Schwarze Elster. It has a length of 105 km, rises northeastern from Dresden and is flowing into the river Schwarze Elster near the town Elsterwerda. At the measuring station „Kleinraschuetz“ the Große Roeder is a typical man-induced lowland river.

This measure was ordered by the BfUL (Staatliche Betriebsgesellschaft für Umwelt und Landwirtschaft) who is also the operator of the Saxonian water measurement network.

The measurement task was: online measurement of velocity of flow and subsequent calculation of discharge per velocity – index method in water levels from 29 cm to 310 cm

Storage and management of all data for the Saxonian authority for environment, agriculture and geology (LfULG) with remote data transfer and remote maintenance of the measuring systems

This was realized by:

  • OTT SonicFlow travel time system (one-level cross path)
  • OTT SLD 2.0 MHz Side-Looking-Doppler-Sensor for measurement of local velocity of flow (index velocity)
  • OTT SE 200 shaft encoder water level sensor
  • Datalogger OTT LogoSens2 for monitoring and storing measured data, for discharge calculation and for  remote data transfer

The measurement profile was designed as double-trapeze and paved with armour stone. Two independently installed empty conduits DN 50 which are protected by a galvanized steel tube at the river bed (mainly during the pavement works) are crossing the water body. For easier access to the cables a cable duct has been installed.

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