Tue | Apr 23, 2019

Desilting Dam is not the answer

Published:Thursday | July 2, 2015 | 12:00 AMEdmond Campbell

HEAD OF the Water Resources Authority (WRA) Basil Fernandez has argued that doubling the size of the Mona Reservoir or desilting the Hermitage Dam to increase storage capacity, without a sustainable inflow of water, is not the answer to improving output to communities, hit hard by the perennial drought problems affecting large sections of the country.

Fernandez, who is the managing director of the WRA told journalists yesterday that an analysis done at the Mona Reservoir has indicated that unless there is a constant inflow of water, the existing rainfall and run-off are not going to fill an expanded reservoir.

"We have done the analysis on doubling the size of Mona, and we have found that all that would happen is that you would get one million gallons of water more per day. If you started out with a very full reservoir, you would not significantly increase the output and the cost benefit analysis does not make sense," he contended.

Fernandez explained that when the reservoir is expanded, a wider surface area would be created, which "means that there will be higher evaporation rates and losses. Building dams is not an answer to improving output."

artificial recharge

The veteran public servant with some 40 years in the water resources sector, said the Government should go the route of "artificial recharge, where the rainfall is collected and stored underground. (This) makes a lot more sense because you already have existing wells".

A United Nations Environment Programme newsletter describes artificial recharge as "a planned, human activity of augmenting the amount of groundwater available, through works designed to increase the natural replenishment or percolation of surface waters into the groundwater aquifers, resulting in a corresponding increase in the amount of groundwater available for abstraction."

Acting president of the National Water Commission (NWC) Mark Barnett, agreed, in part, with Hernandez, noting that while there were benefits to be gained from desilting the dam, "it's not going to provide us with an extended supply of water as we believe."

He said the NWC has received grant funding from the Caribbean Development Bank (CDB) to carry out preparatory work before the Hermitage Dam is desilted.

"We are now in the process of inviting proposals from qualified persons, not only within Jamaica but right across CDB contributing countries. The procurement process has started," Barnett said.

He said before the removal of the silt, an environmental impact study would have to be done first, to determine how the silted material is treated and disposed of and the social implications for the communities that are located along the route to the dam.

Minister of Water, Land, Environment and Climate Change Robert Pickersgill said the storage levels at the Mona Reservoir as at June 29 were 32.8 per cent or 264.8 million gallons, out of a capacity of 808.5 million gallons. Inflows from the Yallahs River have moved from 17 million gallons per day to five million gallons per day, while the Hope River is moving from an inflow of 15 million gallons per day to almost nothing.

At the same time, the storage levels at the Hermitage Dam as at June 29 were 173.8 million gallons or 44.2 per cent out of a capacity of 393.5 million gallons.

At the Hope Treatment Plant, production has dipped from 3.7 million gallons per day to six million gallons per day. Production levels are also significantly reduced at the Mona and Constant Spring treatment plants owing to the severe drought conditions impacting the country.