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Wednesday, June 14, 2006
Osmeña: Cebu’s water resources
By Antonio V. Osmeña
Estatements
Mayor Tom Osmeña is correct when he said that certain non-government organizations have exaggerated Cebu’s future water problem.
The water we use comes from two sources—surface and groundwater. Surface water flows in streams and rivers and is stored in natural lakes, wetlands and in reservoirs constructed by humans. Surface water flowing from rivers and streams to the sea is called runoff. This source is renewed fairly rapidly, from 12 to 20 days, in areas with average volume of precipitation.
Water that seeps into the ground, where it may be stored for long periods, is slow moving and renews underground reservoirs or groundwater.
At present, Cebu’s main source of water comes from groundwater reservoirs.
Most of the supply of freshwater worldwide comes from groundwater, which is 3,000 times more than the total volume of all the world’s rivers at any given time and 33 times that which is found in lakes.
The island of Cebu is indeed lucky since its climate patterns, porous limestone base and soil type allow most of the rainwater falling on land to slowly percolate through the soil until it reaches a layer or stratum of rock.
Water builds up in the overlying sand and rocks above the impervious rock layer and fills all the openings and cracks. The soil and rock become saturated up to a certain level, which is called the water table. Above the water table, the soil is relatively dry.
Some experts believe that while 75 percent of Cebu’s land area is mountainous, abundant wild shrubs on mountains catch rainwater and help replenish the aquifer (groundwater reservoir).
The rate of flow toward the oceans is determined by the difference in the elevation of the aquifer and sea level, and by the permeability of the intervening sediment or rock.
The difference in elevation between one place and another in an aquifer cause hydraulic pressure at the lower point. If a well taps a confined aquifer, the hydraulic pressure may be so great that the water will flow freely out of the well without the use of pumps, such as what occurred in Talisay City sometime in the early 1950s.
What people should be concerned with is, that because aquifers are found deep underground, it is difficult—if not impossible—to clean it up once it has been polluted.
Mining spoils and garbage in landfills or dumpsites are merely among the types of wastes that cause underground water pollution.
Although we can’t increase Cebu’s supply of water, we can effectively manage what we have.
Some water resource experts favor a “hard path,” trying to increase water supply in an area by building large-scale dams, reservoirs and canals to transfer the resource.
Others favor a “soft path,” emphasizing voluntary and compulsory water conservation programs coupled with price increases to reflect the true cost of using water for agriculture, industrial, commercial, and domestic purposes.
The technological breakthrough of removing dissolved salts from seawater, or desalination through reverse osmosis process, can be used to increase Cebu’s supply. Cebu, after all, is surrounded by sea.
Increasing the supply of water for an area is important. But many water experts argue that water conservation is a quicker and cheaper way to provide much of the additional water needed. They point out that many people waste water.
Concerned non-government organizations should recommend a water conservation system in Cebu similar to Israel where the volume of wasted water is decreased by a combination of reduced evaporation, trickle irrigation and extensive water conservation.
For Bisaya stories from Cebu. Click here. (June 14, 2006 issue)
Write letter to the editor.Click here.
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