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The impact of desalination and climate change on salinity in the Arabian Gulf

Dols, F.L. (2019) The impact of desalination and climate change on salinity in the Arabian Gulf.

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Abstract:In the Arabian Gulf region, growth in population size and water use per capita causes a growing trend in water demand over the last decades. The trend of increasing fresh water demand is projected to continue, while groundwater resources are projected to be depleted by 2050. Desalination is currently the only viable solution to fresh water deficiency and new desalination plants are installed at an increasing rate, together adding up to a significant capacity of fresh water extraction from the Arabian Gulf. Another trend of increased fresh water extraction is the rate of evaporation, which is projected to increase as a result of global climate change induced air temperature rise. Salt is conserved during water extraction by desalination or evaporation, causing salt accumulation in the Arabian Gulf. The Gulf is more saline than the ocean and that density gradient drives lateral exchange. Year round, an equilibrium is reached in which the amount of salt in the Gulf is stable. Little is known about the future impact on the development of salinity in the Arabian Gulf of large scale desalination capacity increase and air temperature rise is. This research provides a gross combined impact assessment of desalination and climate change on salinities in the Arabian Gulf. The main objective is to identify the significance of the impact of the desalination industry combined with and relative to the impact of climate change on salinity in the Arabian Gulf. Increased salinities affect ecology and the efficiency of desalination plants. The most vital ecology and desalination is concentrated in and at the shallow coastal area, which is the reason the focus of the research is on this region. Impact is measured in year averages, seasonal variations and weekly variations of salinity. The software package of Delft3D FM is used to conduct numerical experiments that simulate hydrodynamic flow and salt distribution for a reference case and numerous alternative forcings on the Arabian Gulf. The numerical model accurately represents water temperatures and processes of importance, like geostrophic circulation, seasonal stratification and meso-scale eddies. Salinities seem to be overestimated compared to the available field data. The research focusses on salinities of alternative conditions relative to the reference case, for which absolute values are of lesser relevance. Climate change, in this research defined as increase in atmospheric and oceanic water temperature, drives the evaporation rates. Increased evaporation rates did not cause increased Gulf wide salinity. Due to climate change the temperature of the oceanic inflow increases more than the temperature of the bottom outflow. The resulting increase in density gradient through the Strait stimulates lateral exchange, which dampens the salinity increase due to increased rate of evaporation. Combined, desalination capacity increase and climate change barely influence the Gulf’s average salinity. On a local scale, both desalination and climate change cause salinity increases bigger than 1 PSU. The areas prone to extreme salinity increase are typically shallow and sheltered. The simulated salinities at these locations are extreme in the reference case too. Seasonal salinity extremes typically increase with double the year averaged salinity increase. Weekly variation only increases slightly in specific cases. In general, the simulations indicate that extreme salinities tend to become more extreme due to desalination capacity increase and climate change. In the centre and north of the Gulf, increased desalination capacity and climate change barely affect the salinities, except for sheltered locations. The Bay of Iran is prone to salinity accumulation as a result of climate change driven increase in evaporation. In Kuwait Bay, salt accumulation is driven by climate change and increased desalination capacity, of which the latter dominates. Extreme increase of desalination (reference capacity times 10) in Kuwait Bay expands the spatial range of salinity increase to the shallow area in front of Kuwait Bay, towards and around Failaka island. The extreme salinities in the Gulf of Salwah that occur in the summer are simulated to increase significantly. In the southeast of the Arabian Gulf a clear distinction can be made between the shallow sheltered Central United Arabian Emirates (UAE) coast and the relatively open east coast of Qatar and eastern coast of the UAE. The central UAE coastal zone is simulated to be imposed by salinity rise due to both climate change and desalination capacity increase. The more open east coast of Qatar and eastern UAE coast are more strongly affected by increase in gross oceanic inflow. Simulations show that increasing effects on salinity by increasing rates of evaporation and desalination are compensated by decreasing effects on salinity due increasing flushing rates. Future extreme scenarios show drops in salinity at locations along these open coastlines, that are remote from desalination plants. It was found that wind fluctuations, average wind velocity and wind direction dominate evaporation and internal transport patterns in the Arabian Gulf and strongly affect the salinity distribution. Wind velocity increased by 50% provides for an increase of evaporation of the same order evaporation rate increase induced by air temperature rise of 4.5 oC. The uncertain development of the future wind climate introduces uncertainties in the simulations of future salinity distribution.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
Link to this item:http://purl.utwente.nl/essays/79579
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