Carberry says Hope Canal an unnecessary excursion

Feb 20, 2010 News

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…Persaud says works will commence in six weeks

The construction of the Hope/Dochfour Canal that the government proposes to build to help drain water from the East Demerara Water Conservancy (EDWC) is an unnecessary excursion, Opposition Parliamentarian Lance Carberry argued yesterday.
But the government insists that the project is technically sound and is necessary to avoid flooding communities in the Mahaica Creek.
Minister of Agriculture, Robert Persaud, told the National Assembly during the 2010 Budget Debate that works on the canal will start within six weeks.
He said that the Canal would be built about three meters above the ground level of the area and would require a bridge across the East Coast Demerara highway.
In any case, he said that the present configuration of the canal will not do the job.
The design for the Canal has been finalised and the tender process for its construction is expected to start in the latter part of this month.
The draft design, which was completed last December, proposed two options. The first is for a shallow outfall channel with a high crested weir (fall), and is preferred by engineers. This design boasts a one-kilometer long outfall to the Atlantic Ocean with a discharge capacity of 62.1 cubic metres per second. The cost for the construction of that design is $3.6B.
The second option comprises a deep outfall channel with a low invert sluice and among its features is a low level reinforced concrete outfall sluice with a discharge capacity of 66 cubic metres per second. This design costs $3.2B.
However, the engineering team is not inclined to go with the latter design since periodic dredging of the channel will be needed, thereby incurring additional cost.
Carberry argued that construction of the canal is unnecessary since desilting the Mahaica Creek and the four discharge sluices currently used could do the job at times when the EDWC is at a dangerously high level and discharge is necessary.
Furthermore, given the risk building the dam poses to surrounding communities in the event it collapses, he said that a better option, as suggested by the consultants, is a canal between Mahaica and Flagstaff.
However, Persaud accused Carberry of misrepresenting the technical work that has been done. He said that before a decision was taken to proceed the government procured the services of an international consultancy, which after six months of work, suggested that the utilisation of Hope/Dochfour was the most technically viable option.
The Conservancy has been a source of grave concern recently, given usual periods of heavy rainfall. When the conservancy, which holds water to irrigate farmlands during the dry season, is overwhelmed, it threatens the integrity of the dam, which, if compromised could cause widespread flooding on the heavily populated East Coast Demerara.
In recent years, during the rainy season when the water builds up in the Conservancy, the government has had cause to ease the water into the Mahaica and Mahaicony Rivers, flooding out the farming communities along the rivers.
Some residents have had to abandon their homes and farmlands and have taken up housing offered by Food for the Poor.
The World Bank in 2007 approved what it called The Conservancy Adaptation Project, which cost overall, US$3.8 million.
The project aims at strengthening the government’s and donor understanding of the EDWC system and coastal drainage patterns through the integration of advanced mapping and engineering analysis.
The project also aims at implementing infrastructure investments to improve drainage performance, to strengthen the institutional capacity for managing water and floodwater levels, and to guide interventions to reduce Guyana’s vulnerability to floods.
The Conservancy system includes a reservoir, fronted by an earthen dam; drainage channels, used to release excess water from the reservoir during the rainy season; and a network of canals, used to provide drinking water and irrigation during the dry seasons. Because of this system, farmers are able to realise two harvests of sugar cane and rice annually.
The drainage relief structures were created to protect the EDWC dam from overtopping and collapsing during rainy seasons.
As the sea levels rise, the hydraulic head between the EDWC water control structures and sea outlets is significantly reduced.  The smaller head reduces both the flow rate and discharge window available to discharge excess water from the system.
In addition, sea level rise has shortened the discharge window for the coastal plain.  At present, flood control is managed on an emergency basis and control efforts focused on responding to immediate needs rather than the development of long-term control strategies.
This ad-hoc system of flood control is no longer effective and there are limitations on the ability to manage water levels in the coastal plain and prevent flooding and hence the need to better manage the Conservancy.

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