US$20M sought from World Bank for flood control
December 5, 2006
An aerial view of the Flagstaff end of the East Demerara Water Conservancy. (Stabroek News file photo)
In the aftermath of two years of disastrous flooding, the government is seeking a US$20M loan from the World Bank to design a Master Plan and fund changes to the problematic East Demerara conservancy so that it can drain 35% more efficiently.
The project document released by the bank yesterday said that considering the accumulated and expected impact of the sea level rise, the current ad-hoc approach to flood control is no longer viable and it is critical that government and the donor community start a comprehensive programme to strengthen the system.
The Project Information Document (PID) prepared on November 20, is set for appraisal on December 19 with an estimated date for board approval next February. The project is a drainage and irrigation one but focuses extensively on the East Demerara Water Conservancy (EDWC). In the last two years the condition of the EDWC has been seen as a key contributing factor to various types of flooding.
Flooding that has occurred in Guyana recently demonstrated the increased vulnerability of the existing drainage system and shortcomings in the current infrastructure, the bank document noted. The project was therefore designed with the objective of guiding a comprehensive upgrading programme of the EDWC aimed at increasing discharge capacity and improving water level management. It would provide a framework for future donor intervention in addition to developing the technical baseline for adaptation measures. The project will also include pilot infrastructure improvements to help cope with the immediate threats to the system.
Recently the Minister of Agriculture Robert Persaud in an interview told Stabroek News that as a result of the 2005 and 06 floods a number of commitments were given. One of these was to create additional outlets from the conservancy in a westerly direction, should there be a sudden rise in the EDWC level, to the Kofi outlet and "we have made moves to strengthen it." In 2005 and 2006 the level of the EDWC rose very quickly and could not be reduced quickly enough to avoid overtopping and emergency releases into the Mahaica River.
During the interview the Minister also revealed that personnel at the conservancy were draining the EDWC to such an extent in preparation for the rainy season that it was almost dry. The five-door sluice at Land of Canaan which drains the EDWC into the Demerara River, he pointed out, was working in addition to "maintenance work we've been doing." He added "what we have been doing is having a very controlled release through the Maduni sluice" into the Mahaica River.
Two Dutch engineers Nisa Nurmohamed and Olaf van Duin, who were in Guyana to review local drainage and irrigation structures in the midst of the 2005 Great Flood noted that the EDWC dam is a fragile construction. About 30% of the eastern section of the northern dam is in critical condition and about 10% of the rest of the northern and the western dam is in a poor state.
The engineers recommended substantially upgrading the emergency works on strengthening the dam, using contractors with floating equipment.
Among their recommendations was the inspection of dysfunctional outlets and identification of customised solutions for each structure in order to facilitate discharge, while maintaining the ability for closure during high tide. Additionally there should be improvement in the drainage functions of the outlet structures at the conservancy dam and the seawall. It was suggested that in the medium to long term, rehabilitation works be prioritised (outlets, culverts, drains and the EDWC dam), in order to achieve - despite budget limitations - the best preparation for future flood threats.
The PID said that any programme to strengthen and upgrade the system would have to take into account the impact of climate change. This is so, according to the document, because given the forecasted impact of sea level rise the risk of future flooding even during normal weather events is increasing year after year. The project document is the first step in the critical works to be executed by the government and the donor community to strengthen the current system.
According to the project document, an analysis of tide gauge records from 1951 to 1979 shows the trend in sea level rise for Guyana to be in excess of 10 mm/year, which implies a net change in sea level of 0.9 ft for the 28-year period examined. Assuming that the rate found remains constant then the net change in the sea level from 1951 - 2005 is some 1.8 feet. According to the studies quoted in the PID, sea level rise in the region of Guyana is 2 to 5 times faster than the global estimate.
Evidence was also found through the Initial National Communications and Nation-al Vulnerability Assessment, 2002 that since 1960 the trend has been toward below average rainfall and increased intensity of rainfall events.
Climate model estimates developed by the United Kingdom Meteorological Office's Hadley Centre also support the prediction that Guyana would experience a general drying trend. The models in fact predict Guyana would be among the most affected countries in the world, with average precipitation decreasing by roughly 1 mm/day by 2050.
Such a drying trend would lead to increased intensity of rainfall and a greater reliance on the EDWC water storage system during the dry seasons. To meet this need storage water would have to be kept at high levels to support agricultural and urban centres on the coastal plain, highlighting the need for effective capacity to manage water levels in the EDWC system.
Focusing on coastal drainage and the flood control system the document said drainage during rainfall events has been managed through the use of gravity based systems augmented with pumps. This system is under increased stress and is suffering from the impacts of sea level rise because an adequate discharge window is no longer guaranteed. The maximum safe operating level of the EDWC was about five feet above the peak 1951 sea level, which leaves a narrow opening window for emergency discharges during times of heavy rain. As sea levels continue to rise, the maximum safe level has closed to three feet and as the discharge window shrinks, the ability to manage water levels is being compromised.
It was contended in the document that the problems associated with flooding and the EDWC stem from the fact that the coastal drainage and irrigation system in Guyana was constructed some 150 years ago. The sea level rise since then is estimated at 1 metre drawn from studies that suggest a 1 mm per year rise of sea level every year for the last 150.
This raises concerns relating to the additional stress on the system with regard to the possible collapse of the EDWC. If the discharge flow is not increased or amplified, and the system continues to be managed without regard to climate change-related rises in sea level, rainfall collection in the system will outpace the ability to release excess water (because the period available to discharge continues to shrink), causing the EDWC to overtop and levees to breach, the document cautioned.
The project is designed to finance the development of a master plan for future interventions within the EDWC and lowland drainage systems, as well as specific upgrading works and operational improvements aimed at enhancing the flood control capacity of the EDWC. Further, the tools developed under the analytical component of the project would be used by the government and donor agencies to guide future investments.
Components of the project include pre-investment studies for engineering design of works at a cost of US$2.45M. This first component would provide the hydrologic baseline necessary for considering interventions aimed at increasing the current discharge capacity of the flood control system. The objective would be achieved through detailed topographic and land use mapping, hydrologic modelling of coastal lowlands, assessment of the EDWC system integrity, EDWC hydraulic modelling, pre-feasibility studies for coastal lowland interventions and operational capacity building.
The second component is investment in specific adaptation measures at US$17.2M, and the objective is to counteract the effects of sea level rise, which has diminished the government's ability to manage water levels of the EDWC dam during heavy rains by improving internal water flows in the EDWC and increasing EDWC drainage relief capacity to the Deme-rara River and eventually the Atlantic Ocean. This would seem to suggest that there are no plans to open northern outlets from the EDWC directly to the Atlantic.
It is envisaged that widening of key drainage relief canals, improvement of the water flow system within the EDWC, upgrading of water control structures, selected equipment purchase and installation and major infrastructure civil works and operational improvements would lead to the achievement of the specific adaptation measures.
By the end of this project the capacity of the EDWC to drain to the Demerara River should be increased by roughly 35%.
The third component involves institutional strengthening and project management at the cost of US$0.35M. It involves putting together a contingency plan for flood events, institutional analysis of the drainage sector, monitoring and evaluation of project progress and project management.
Limited improvements of drainage would be made to water control systems under this project, which are of an urgent nature and required to add a safety relief capacity to the EDWC system. This additional capacity is to allow EDWC operators the ability to reduce water levels behind the dam in a more timely fashion considering the current fragile condition of the structure and limitations in present relief capacity. Specifically, two control structures the Maduni and the Lama sluices are presently used as options of last resort to reduce water levels below critical elevations. When theses gates are used inhabited areas like Mahaica and Mahaicony downstream of the structures are flooded therefore future drainage improvements are designed to limit the need for using the Maduni and Lama sluices. (Christopher Yaw)