To maintain a satisfactory water quality level, after a marina development in Lazaretto Creek/Manoel Island, the circulation of the water may have to be improved by widening the channel at Gzira Bridge.

To evaluate the present current patterns, CTD observations are carried out at various locations in Marsamxett Bay. Also currents under the Gzira Bridge and simultaneous water level measurements on various locations in the creeks have been carried out.

The following surveys were carried out:

• Temperature and salinity profiles.
  For the profile measurements the VALEPORT 108 MKIII CTD instrument was used. CTD profiles were sampled at 17 locations around Marsamxett Bay, see figure below.
• Current measurements.
  The same VALEPORT 108 MKIII instrument has been used for current measurements below the Gzira Bridge. The instrument was fixed ± 0.4 m below the water level by means of a rope from the underside of the bridge and an elastic band to a stone on the bottom. The current meter was placed at the deepest location of the trench.
• Water level measurement.
  On various locations water level measurements have been carried out in the surroundings of Sliema creek and Lazaretto Creek. For these measurements an ORPHEUS pressure probe with integral data logger has been used.