Managing the Tigum Aganan Watershed – 2


By: Edgar Mana-ay

AS I HAVE pointed out in Part 1 of my column on the Tigum Aganan Watershed (TAW) a week ago, this watershed is the only source of both surface and underground water for Metro Iloilo. The upland or mountainous portion of the TAW has an area of 332.8 square kilometers (sq. km.) while its plain portion has a 311.8 sq. km. area, for a total of 644.6 sq. km. of land that catches an average rainfall of 5,042 millimeters (mm) per year, then deliver it back to the seas via surface and underground flow all passing Metro Iloilo.

The initials in the world famous H&M wardrobe store are really an initial of the inverted phrase of “Made in Heaven”.  Any hydro-geologist worth his salt, when shown the map of TAW, will always remark: “Pare wala kayo problema sa tubig sa Iloilo City”!

Metro Iloilo is really in a “Made in Heaven” location as it is the drainage outlet of a large watershed that receives tremendous rainfall annually! But why oh why do we suffer this perennial water shortage since we can remember as evidenced by stinking toilets, no water at the second floor, and, lately, a frantic call from the Pavia athletes at the Sta. Barbara District meet for the Pavia Fire Department to bring them water as they cannot cook their food nor take a bath nor flush their stinking toilets!

It is the height of paradox and ambiguity that billeted athletes in a town where the water processing plant of MIWD is located will make a water distress call back home to bring them water! What ails our water system, what boo-boos and blunders have we made and what measures have we ignored in the past that all resulted in the present predicament?

At present, Metro Iloilo water demand is about 140,000 cubic meters per day (cmd), one cubic meter is 1,000 liters, but MIWD can only supply about 62,000 cmd including that of its bulk water supplier. If we consider the non revenue water (the sugar coated term for water loss due to an inefficient system) of about 40%, actual supply would even be less!

But why does Metro Iloilo continues to progress rapidly when the water utility CANNOT supply more than 60% of its water requirement? This is because of the 8,000 to 10,000 “tasok”, shallow and deep wells (400 of these exceed 100 feet in depth), almost all privately owned, plus the water tankers deliveries that covers up for the short fall in supply of MIWD.

Giant establishments like Gaisano, SM City, Plazuela de Iloilo, Megaworld and the like have their own bulk water processing plants drawing water from deep wells. Being near the sea, the water their deep wells supplies are brackish so they have to resort to a Reverse Osmosis (RO) process to convert salty and brackish water into fresh water which is expensive.

Smaller establishments that cannot afford a deep well and an RO plant, which will cost about P30 million for a 2,000-cmd capacity plant, will have to resort to tanker deliveries whose water quality is NOT assured. Hotels and restaurants, which get water from these tankers, will usually admonish their guests not to drink from the faucet, instead they provide bottled purified water.

By the way even technical people wrongly call a bottle of purified water as mineral water! Water with high mineral contents such as calcium, magnesium, sodium, potassium and others is NOT good to drink because it overloads the function of the kidney! The best water to drink is PURIFIED WATER which is free of minerals!

Signs of a sick watershed are: Minimum rain infiltration, hence no water to feed the rivers during summer. Surface waters of Tigum and Aganan rivers at only 3 inches deep during summer. More runoff results in increase frequency and magnitude of flooding, erosions that resulted in a mud laden river water up to 1,500 ntu (nephelometric turbidity unit) turbidity. This mud settles in the MIWD supply pipes from Maasin to its Sta. Barbara Plant reducing capacity to only 30%!

Here are some basic concepts on watershed management if we wish to heal it. The entire upland and plain area including Metro Iloilo is part of the watershed. The rice lands are the best portion of the watershed since the rice paddies holds rainfall allowing maximum time to infiltrate the ground to be part of underground water regime. No more conversion of rice lands into subdivisions! The main objective in the management of watersheds is: MAXIMUM RAIN INFILTRATION AND MINIMUM RUNOFF.

Generally for upland areas we should aim for absence of human activities to maintain rain forest conditions. This requires political will from the concerned mayors to implement total ban on kaingin, rearing of animals, and living in the mountains.

For the plain and urban areas including Metro Iloilo, it should adopt a LOW IMPACT DEVELOPMENT (LID) program wherein the HYDROLOGIC CONDITIONS ARE MAINTAINED BEFORE AND AFTER DEVELOPMENT. Some examples: the new parking lot at SM City is made of concrete hollow blocks to allow rain to infiltrate, series of interconnected retention ponds and less impervious surfaces in subdivisions.

So many bright boys and girls in the past 40 years have managed the TAW but no improvement was made. Hopefully the present Technical Working Group under the leadership of Pavia Municipal Mayor Michael Gorriceta can make a difference.  For according to Bradshaw (1983): “The acid test of our understanding is not whether we can take ecosystem to bits and pieces on paper, no matter how scientific, but whether we can put them together into practice and make them work”.

Note: The author is the Hydro-geology Consultant of the Municipality of Pavia and a Professional Member of the National Ground Water Association of the U.S. (NGWA).

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