Hydrodynamic Evaluation of Climate Change and the Effects of Coastal Effluent on the Long-Term Circulation of the Arabian Gulf and its Impact on Desalination
Abstract
The prime objectives of this dissertation are to develop, validate, and use a
state of the art 3D Hydrodynamic Model (HD) to evaluate the long term salinity and
seawater temperature variations in the Gulf subject to climate change and coastal
effluent; and to develop a quantification tool that can assess the impact of projected
ambient conditions upon the cost of desalination. Both objectives were realized.
Evaluating the long-term variability of seawater salinity and temperature due
to climate change and coastal effluent is a growing concern. It may represent an
economic and operational limiting factor in desalination process given the clear trend
for constructing new plants and/or expanding existing ones to meet the growing
demand for fresh water. This is also significant for the research and development of
sustainable desalination technologies in the Gulf and beyond. The hydrodynamic
model (HD) developed here was rigorously validated against short term and long
term field observations. It proved to be reliable in evaluating long term basin-wide
response to climate change and coastal effluent loading in the Gulf.
An Atmospheric Ocean General Circulation Model (AOGCM) data base of
twenty CMIP3/AR4 models re-gridded to 2.5 x 2.5 degrees latitude/longitude, and
globally observed data bases within a common 20-year reference period (1980-1999)
were used to obtain data for air temperature, precipitation and sea level rises in the
Gulf for long term evaluation. Including the contribution of coastal discharge from
desalination plants, refineries and power generation plants, the HD was used to
simulate a total of 17 scenarios, each with a duration of 90 years to appraise the
future condition of the Gulf. These scenarios include realistic, optimistic and extreme
case scenarios for fresh water demand in Gulf countries. The results ascertained the
long term increase in salinity and seawater temperature in every scenario. The
responses were found to vary spatially based on several factors such as season, water
depth, degree of flow restriction, vertical mixing and flushing. Coastal effluent
impact was localized to within 10 to 20 km offshore from the discharge location, but
did not show a serious trend for massive alongshore phenomena. Salinity and
temperature were found to be steadily increasing over time near desalination plants.
Based on a conceptual understanding of the cost of desalination a mathematical
assessment tool was developed to map the projected changes in salinity and seawater
temperature into operational costs, particularly chemical and electrical costs.
Accordingly, desalination technologies were ranked by time for each desalination
plant (a total of 34 plants) to advice on the most appropriate planning approaches at
each location until 2080. The main finding of this study indicated insignificant
impact of future ambient conditions in the Gulf on the operational cost of the
considered desalination technologies and that the Multi Effect Distillation (MED)
technology is expected to be the least affected