Coastal reservoir

Aerial view of Plover Cove coastal reservoir.

Coastal reservoir is a type of reservoir to store fresh water on sea coast area near a river delta. Saemanguem in South Korea, Marina Barrage in Singapore, Qingcaosha in China and Plover Cove in Hongkong, Delta Works in Netherlands, Thanneermukkom Bund in India etc are few existing coastal reservoirs.

Advantages

Unlike land based water reservoirs there is no land submergence in case of coastal reservoirs. They store water without disturbing people and natural habitat by replacing standing salt water on the sea area by river flood water. The coastal reservoir area is separated from the sea by building earth dike by dredging. Water is pumped from these reservoirs for municipal and industrial purposes. Some times used for flood control and land reclamation from the sea. The social and environmental impacts of coastal reservoirs are negligible compared to land based water reservoirs. The construction cost is few times less than the cost of land based reservoirs since there is no expenditure for acquiring the vast land area, the submerged immovable properties and the rehabilitation of displaced people. The sea side of the coastal reservoir can also be used for locating deep sea harbor.

Future projects

There are vast deserts in all continents (western part of South America, Northern and south western Africa, Middle East in Asia, South eastern part of USA, Australia, etc.) and also water surplus regions nearer to these deserts. It is technically and economically feasible to construct man made fresh water coastal reservoirs / lagoons on the continental shelf of the sea up to 20 meters depth from the coast line to supply fresh water to desert areas from nearby water surplus/high rainfall areas. Excess water from the high rainfall regions will be collected in the coastal reservoirs at sea level and this fresh water is pumped to irrigate desert lands from the other end of the lengthy coastal reservoirs. In other words, the proposal is interconnecting rivers with a sea level / sub sea level contour canal (at least five km wide) to facilitate water transfer.

The coastal reservoirs earth dikes extending up to 8 m msl high, is in the form of two parallel dikes separated by 1000 meters gap. The main purpose of the twin dikes is to prevent any sea water seepage into coastal reservoir as its water level is below the sea water level. The water level between the dikes is always maintained up to 1 m above the sea level by pumping fresh water from the coastal reservoir to the 1000 m gap between the dikes. The higher level water barrier between the two dikes fully eliminate any sea water seepage in to the coastal reservoir by establishing fresh water seepage to the sea. The rain water falling on the coastal reservoir area and run off water from its catchment area is adequate to cater the seepage and evaporation losses from the coastal reservoir. The 70 km long, 1000 m gap between the two dikes is also used as deep water mega harbor for shipping, ship breaking, ship building, etc. For shipping purpose, the breakwater outer dike facing the sea is envisaged with few locks fitted with twin gates for access to the open sea. The top surface of inner dike would serve as access to the main land from the mega harbor with rail and road links. The coastal reservoir whose full reservoir water level (FRL) is at 0.0 m msl, would also reduce drastically the cyclone damage and flooding in coastal areas. It would also greatly improve the irrigated coastal lands drainage. The coastal reservoir area can also be used for locating floating solar power plants to generate the needed water pumping power. The dikes are built by dredging sand and clay from the nearby shallow sea bed to reduce the construction cost. Also top surface of the inner dike of the coastal reservoirs can also be used as coastal road & rail rout.

Wherever existing ports/waterways and famous beach resorts are to be preserved, the long coastal reservoir is broken in to parts and interconnected by sub sea ducts/pipes of suitable length. However the negative aspects of these man made lagoons are to be evaluated in detail and proper remedial steps shall be incorporated to minimize the damage to coastal ecosystem by the presence of fresh water lagoon as barrier to the sea.

The following are the feasible projects in each continent:

• Hangzhou Bay area in south eastern China can be used for coastal reservoir to supply fresh water available from Yangtze estuary for the needs of agriculture, city water supply, etc in entire China.
• Water transfer from the west central Africa (Congo River basin, etc) to Northern Africa (Sahara desert) and South West Africa (Namibia and South Africa deserts)
• Water transfer from the south east Africa (Zambezi River basin, etc) to North east Africa (Somalia, Ethiopia. Sudan, Egypt, etc).
• Water transfer from the north western part of South America continent (south of Panama Canal) to desert lands of Chile and Peru.
• Water transfer from the Papua New Guinea island (South east Asia) to Northern Australia.
• Water transfer from the north and south coastal areas of western 'North America continent' to south western region of USA and central parts of Mexico.
• Water transfer from India and Bangladesh to water deficit parts of India from Ganga and Bramhaputra flood waters with a coastal reservoir on Bay of Bengal sea.
• Water transfer from Andhra Pradesh state in India from Krishna and Godavari rivers flood water to Tamil Nadu state in India with a coastal reservoir on Bay of Bengal sea.
• Water transfer from India and Sri Lanka to Pakistan and Iran with lengthy coastal reservoir on Arabian sea along the west coast of India from Rameshwaram to Strait of Hormuz.

The above gigantic coastal reservoir projects would cover most of the desert areas of the world except the high lands of central Asian deserts. Water needs of these areas can be fully met by diverting water of Siberian rivers. Thus most of the lands which are not available for cultivation and forestry can be turned in to habitat to copious greenery which would help to mitigate the global warming process.

See also

• Polavaram Project
• Kalpasar Project
• Pollution of the Ganges
• Water export