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AWL coastal water transport
AWT replenishment ship

Even where rainfall is abundant, access to clean water may be restricted by the contamination of water resources, the lack of adequate storage facilities, and the absence of effective delivery systems. Small island may face severe constraints in terms of both the quantity and the quality of freshwater due to their particular geographical, geological, topographic, and climatic conditions.

Beautiful Xisha Islands are lacking in freshwater, so a "rainwater squad", the only unit of the troops that is in the military formation, was created to be specifically responsible for collecting and purifying rainwater and transporting fresh water. Fresh water is scarce on the island, so the runway and tarmac of the airport on the Yongxing island is designed with a 5 decline in order to collect rainwater, which is then treated professionally by the naval troops. The treated rainwater reaches national standard for drinking water without adding any medicine and is used by island residents. A rainwater collection and purification plant was completed in the Xisha Islands in 1999. In the past decade or so, sailors in the rainwater squad has collected and purified more than 1.2 million ton rainwater, which is equivalent to 66.67 million barrels of 18L that's commonly seen in the market. If this amount of water is transported by "Qiongsha-3" liner with the load capacity of 750 tons from Hainan, the liner has to sail back and forth for 1,600 times.

In cases where water is completely lacking or inadequate, and no other conventional supplies are available, it may be necessary to transport water by tanker from another source far removed from the point of use. When such water transfers require shipment across the sea, motorized water tanker vessels are commonly used. Islands which suffer regular droughts may consider providing permanent off-loading facilities, including storage, as a component of their water distribution systems.

Barging of water involves the physical transportation of water from one location to another by sea, using a barge or similar tank vessel. Barges should contain storage tanks of adequate size to maximize the value of the volume of water transported relative to the cost of transportation. The storage tanks must be suitably constructed and cleaned to prevent contamination of the water; generally, they should be single-purpose vessels and not used for the transportation of other liquids. Barges may be self-propelled, but are generally towed by another vessel such as a tugboat. Once the barge arrives at a suitable port, it is secured and the water transferred by pumps to storage tanks or vehicles on land. The water is then either pumped directly into the water distribution system from the storage tanks, or distributed to consumers using tanker trucks. Protecting the purity of transported drinking water is essential, and the quality of the water should be monitored.

Water boats and barges are ships especially constructed and equipped to receive and provide water for both potable and non-potable water systems on board ships when direct shore delivery is not practicable. These boats have water tanks, water hoses and fittings, pumps and independent pipe systems to provide potable water to onboard systems. Hoses used exclusively for the delivery of potable water should be kept on each ship. The ends should be capped when not in use. Keeper chains will prevent misplacement of caps. The hose needs to be handled to prevent contamination by dragging ends on the ground, pier or deck surfaces or by dropping into the harbor water. Reception, handling, storage and delivery to ship water systems need to be carried out under controlled, sanitary conditions. All hoses, fittings and tools need to be stored in designated lockers that are closed and clean. Operators need to possess knowledge of water hygiene and good sanitary practice. Facilities for disinfection, when and where necessary on board, need to be available. Regular cleaning and disinfection of hoses and fittings should be performed. Plans for construction of ships must show filling lines, storage tanks, pumping equipment and protective measures for approval by the port health authority or other designated authority. The main operational problem experienced in the use of marine vessels is weather delays. Based on the experience in the Bahamas, barges are unable to operate on an average of approximately 25 days per year. The second most frequent problem experienced is mechanical breakdown of the vessels, which can halt water transportation for a period of 1 to 7 days per incident. Approximately 15 days per year are lost due to mechanical problems.

The level of government participation in the conveyance of water using marine vessels is usually very high. The scale of this type of operation is so large that only organizations involved in public water supply or large resort operators could consider it as an option. Transporting water by marine vessels is generally more costly than other alternatives. However, this form of waterborne transport does have merit during emergencies.

The key to low-cost water transportation by barge or tanker is transporting large quantities using large tankers continously over the long term. Economies of scale significantly reduce the unit cost of water transported in this manner. However, for this type of transportation to be effective, there must be very efficient loading and unloading facilities. If these do not already exist, they can be very expensive to construct.

This method of transporting water is suitable for most coastal areas where there are suitable berthing facilities for barges and the infrastructure is in place to store or distribute the water after it is unloaded. The technology does not require highly skilled personnel to operate it. It may be cost-effective, depending on the costs of the available alternatives. But there is a lag period before the technology can be implemented; start-up times to charter a ship are generally about 3 to 6 months. Operations are affected by the weather; shipping may be halted when winds are greater than 27 knots and the seas higher than 11 ft. The cost of transportation is high and in some cases may be prohibitive. Transportation times are relatively slow. The quality of the water at the point of use may be difficult to assure, owing to possible contamination by seawater and/or other contaminants during transportation.

Water is delivered to ships by hoses on the dockside or transferred to the ship by water boats or barges. Designated filling hoses must be provided at each pier or wharf for the use of ships not equipped with them. Facilities for the direct delivery of water from shore sources to the filling line for the ship's potable water system include piping, hydrants, hoses and any other necessary equipment.

In order to make water conveyance by marine vessels more efficient, infrastructure must be put in place to allow for the immediate distribution of barged water to consumers once the barge arrives in a port. This requires that pumps, treatment or disinfection facilities, and transmission lines be in place at the port. Considering that in many cases this infrastructure might only be used every 5 to 7 years, during drought periods, it becomes difficult to justify such an investment. Thus, inexpensive portable off-loading facilities that can be used in times of emergency would be a desirable future development.

The Greek Island Hydra was named for its water. Historically, circa 300 years ago and more, Hydra had a number of freshwater springs to supply residents with their drinking water. By the mid 20th Century, the demand for good drinking water couldn't be met by the island's resources and the Greek Orthodox Church helped to implement a water boat to deliver spring water from the mainland to Hydra on a daily basis. Originally this service worked very efficiently, provided good water that was drinkable and was a low cost solution to Hydra's water problems. Water would arrive daily with the water boat mooring at the end of the jetty (opposite the Historical Archives Museum of Hydra), connected to the pipes and then water would be pumped to the various holding tanks higher up. Then as households needed it, the water would come down into the town mainly with gravity to supply homes. This method of providing water to Hydra worked well until the beginning of the 21st Century when demand, brought about because of modern living and tourism out-paced supply. In addition to not being able to cope with demand, the quality of the water decreased and the its cost along with spiralling transport costs meant that an alternative solution was required. In early 2014 the water boat was finally decommissioned when the state of the art desalination plant went on line in Mandraki.

The use of this technology is well accepted in the Caribbean islands where the water bome transportation of water is feasible. Marine vessels were used in Antigua during the drought of 1982-1983. More than 20 million gallons of water were barged during that emergency. Currently the Morton Salt Company in Inagua, Bahamas, and the Bahamas Water and Sewerage Corporation in New Providence use vessels to transport water. The Water and Sewerage Corporation has chartered a 5 000 deadweight ton (dwt) water tanker and a 14 000 dwt motorized barge/water tanker on time charter, to operate continuously between Andros and New Providence. In New Providence, 54% of all water consumed comes from the island of Andros.

The Water and Sewerage Corporation on Andros employed one person, periodically assisted by a second, to manage the charter operation. The need of the Corporation for spare parts is minimal (repairs are undertaken by the charter operator) and the skill level required to fill and empty the barge is very basic. Of greatest concern to the Corporation is assuring the purity of the transported water. The Corporation maintains its own laboratory to test the water, and treatment facilities are available to provide any necessary treatment before the water is introduced into the supply system.

The cost of barging water from the island of Dominica to the island of Antigua was $20/1000 gal landed in Antigua; to transport the 1000 gal by truck from the port of St. John costs between $25 and $50. The shipment cost of water transported in the Bahamas between Andros Island and New Providence is about $3.41/1000 gal, including fuel costs. Factoring in the cost of the shore facilities (the Water and Sewerage Corporation owns both the production facility on Andros and the receiving facility in New Providence), the total cost of the water is approximately $5.84/1 000 gallons shipped.

The transport of water from Andros to New Providence started in 1976 after the failure of the reverse osmosis and distillation plants on New Providence, which had produced up to 2 mgd each. The production and cargo landing sites and vessels (tugs and barges) were placed in operation within a year, and began transporting 1.8 mgd. This was planned as a temporary solution to the problem, but since it remains the least costly option for providing New Providence with good quality water, the practice continues. Andros now produces 5 mgd of freshwater for New Providence. (While groundwater extraction on New Providence has a lower unit cost than water shipped from Andros, the volume of groundwater available has remained constant for the past 20 years mainly because additional land for well-field expansion cannot be acquired; thus, increased water demands in the future will have to continue to be met by the shipment of water from external sources.)

This technology also was effective in augmenting the water supply in Antigua during the severe drought of 1982-83. However, it was determined that it could not supply the needs of the island on a continuing basis because of the prohibitive transportation costs. For this reason, a desalination plant was constructed in 1987 to provide an assured water supply.

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Page last modified: 25-12-2019 18:42:41 ZULU