Hydrodynamic Evaluation of Climate Change and the Effects of Coastal Effluent on the Long-Term Circulation ofthe 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 30 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 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) database of twenty CMIP3/AR4 models re-gridded to 2.5 2.5 degrees latitude/longitude, and globally observed databases within a common 20-year reference period (I 980-1999) 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 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 (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.