oa Regional hydrodynamic modelling for environmental impact assessment due to desalination plants of Qatar

Desalination of Arabian Gulf is intense. But the environmental issues as not yet addressed on regional scale. Key issues are the concentrate and chemical discharges to the marine environment, the emissions of air pollutants and the energy demand of the processes. For sustainable use of desalination technology, the impacts of each major desalination project should be investigated and mitigated by means of a project- and location-specific environmental impact assessment (EIA) study and long term impact based on the global climate change. In this context, this study is aimed to address the impact of desalination with global climate change on a regional scale. A hydrodynamic model covering the Arabian Gulf driven by Arabian Sea tidal levels was setup to establish the hydrodynamic condition of the Gulf. The model was driven with level and velocity components from the global tidal model TPXO. The results are compared with the predicted tides from ATT (Admiralty Tide Table) of standard ports as well as secondary ports and available tidal streams at the Diamond Points. This is an attempt to make a calibrated working model that drive the coastal Qatar hydrodynamic model which ultimately drive dispersion model with long term climate parameters to assess the impact of climate change on the dispersion of concentrated brine. The model validity compares well with the ATT predicted tides and tidal steams of Admiralty Chart No. 3787. The regional model is shows very good agreement on predicted tides along the regional model and velocity vectors at the admiralty diamonds on chart. Free surface of the model was compared with the ATT predicted tides at ports Mesaieed, Al Wakra, Doh, ras laffan, Jabal Al Fuwarit, mina salman, MINA Saud, Khowr E Musa Bar, Bharder E Shaid Rajai and Port sultan Qaboos. As the bathymetry and coastline near south east part of Qatar were not well resolved, model comparison could not be carried out at this site. The model was run with an updated bathymetry from the navigational charts to resolve the tides of coastal Qatar. Except at Al Wakra, the predicted levels were in good agreement with the model results. Tidal streams on BHO Chart No. 3787 were also compared against the model velocities during spring and neap stages of the tide. The velocity values obtained from Admiralty Diamonds during spring and neap tides are based on very short-term observations. Since the estimates are based on data collected during different periods, it could be used as an estimate of the tidal currents only in the absence of other data. Comparisons between model current speeds and BHO chart values of tidal streams indicate good matching during spring tides while during neap tides the model over-estimates the current speeds at all Diamond points. Variations in tidal current velocities between peak flood and peak ebb at different parts of the gulf convincingly indicate diurnal reversal of the tidal streams.