Consequence of El Niño 1997-98 on Manila water resources: new perspectives in water shortage planning and management
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Consequence of El Niño 1997-98 on Manila water resources: new perspectives in water shortage planning and management


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El Niño has become a synonym for the natural weather phenomenon caused by periodic changes in
the Pacific Ocean surface temperature distribution. Its most immediate impact is on the rainfall in
the countries of the Pacific rim, although the effect can be traced to other parts of the world.
In Manila, the capital of the Philippines, the latest El Niño occurrence caused one of the worst
droughts in living memory. The private owned water supply company MWSI was forced to operate
under extremely difficult technical, financial and political conditions. A range of emergency
measures have been taken during the crisis. More importantly, the draught highlighted the need for
long term planning and identification of alternative sources of raw water for the city.
ASTRAN - first Asia-Pacific Technical Seminar on Water and Environment. Hong Kong 12th-13th march 1998.



Publié par
Publié le 09 avril 2013
Nombre de lectures 43
Langue English


Consequence of El Niño 1997-98 on Manila water resources: new perspectives in water shortage planning and management
1and 2 M. DETAY
Lyonnaise des Eaux Philippines – Suite 801–802, 8F, The Taipan Place – Emerald Avenue, Ortigas Center, Pasig city 1605 – Philippines. Maynilad Water Services, Katipunan road, Balara, Quezon city – Philippines.
drought, supply shortage management, El Niño, Manila, Philippines
Abstract El Niño has become a synonym for the natural weather phenomenon caused by periodic changes in the Pacific Ocean surface temperature distribution. Its most immediate impact is on the rainfall in the countries of the Pacific rim, although the effect can be traced to other parts of the world. In Manila, the capital of the Philippines, the latest El Niño occurrence caused one of the worst droughts in living memory. The private owned water supply company MWSI was forced to operate under extremely difficult technical, financial and political conditions. A range of emergency measures have been taken during the crisis. More importantly, the draught highlighted the need for long term planning and identification of alternative sources of raw water for the city.
I – BACKGROUND At 120 years old, the Metropolitan Waterworks and Sewerage System (MWSS) stands as one of the oldest water systems in Asia. Nevertheless, in 1997, only two-thirds of the Metro Manila population was officially receiving potable water, through 815,000 connections. A total of 3,200 million liters per day (Mld) was produced, 97% coming from a unique resource (the Angat 3 Reservoir, with 950 Mm capacity). Supply was intermittent in 50% of the service area and non-revenue water (NRW) was as high as 65%. The water and sewerage services of Manila (12 million inhabitants) have been privatized after an st international bidding. On August 1 , 1997, two new private companies were commissioned to provide water services to Metro Manila. During the first year of operation, Maynilad Water Services Inc (MWSI), the Benpres - Suez Lyonnaise des Eaux consortium, concessionaire of the Western part of Manila (7.2 million inhabitants) had to prove its competency under very difficult conditions: Overcoming low public perception of water quality of services; Addressing the El Niño induced water shortage and related quality problems; Handling the reactions of politicians to the water shortage situation in an election year; Start up a concession contract and deliver better service in a financial crisis (Peso-US$ from 26 to 42). This paper aims to describe the various actions taken by MWSI in order to supply drinking water during the critical El Niño induced drought period of 1997-98.
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II – The El Niño drought management El Niño usually occurs irregularly approximately every two to seven years. To estimate the historical impact of El Niño on the Manila water resources, MWSI conducted an analysis of the relationship between the El Niño Southern Oscillation (ENSO) index and the Angat Reservoir inflow (Figure 1). This relationship, established in early October 1997, enabled the forecast of a very difficult situation during the dry season 10 months in advance. It also served to support the subsequent drastic measures of water allocation reduction.
100 90 80 70 60 50 40 30 20 10 0
Angat Inflow Jan n+1/Aug n+1
ENSO Index Dec.n/Jan n+1 -3
Figure 1 Correlation between ENSO index and Angat inflow
Since Angat Reservoir is a multipurpose facility (providing water for irrigation, power generation and drinking water supply), allocation for irrigation and power generation was initially suppressed in October 1997. As the crisis deepened, drinking water supply allocation was progressively reduced as showed in Figure 2.
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Raw water allocation % of water rights
Figure 2 Restriction in raw water allocation due to El Niño 2/9
2.1 - MWSI Shortage Crisis Management Operations A Crisis Management Committee was created in November 1997 within MWSI to monitor the shortage situation and coordinate the actions of the different operating units [1]. Weekly meetings of the El Niño Joint Committee ensured close coordination with the MWSS. Despite constraints in supply, transport and hydraulics (i.e.,bringing water areas),to elevated the following initiatives have succeeded in bringing potable water to West Zone areas rendered waterless by the El Niño drought. 2.1.1 Water Distribution Strategy Considering that the distribution network is based mainly on a gravity system, optimizing water supply required daily valving operations, which allow areas to be served alternately. A Piccolo hydraulic model was used to define the best operational scheme, taking into consideration restrictions in allocation. Aside from daily valving operations, special valving operations were conducted to provide water through the network at least three (3) times a week in the so-called “no water” areas. 2.1.2 Leak Repairs With 65% of Non Revenue Water (NRW), the starting situation was very critical. This made repairing leaks in a reasonable time frame a priority job. After the takeover in August 1997, the backlog on existing surface leaks was more than 3,000. A crash program of leak repairs involving up to 100 teams per day has reduced this backlog to a manageable number of around 300 leaks, with an average reaction time of 2 to 3 days from detection to repair. More than 55,000 reported leaks were repaired in the first year of the MWSI operations. 2.1.3 Water Tankers In order to provide to the population a minimum amount of potable water, a strategy of water delivery both through mobile and stationary water tanks was implemented. The program comprised the deployment of mobile tankers and the establishment of 40 watering points 3 consisting of stationary tanks of 10 m , installed in the more critical areas. Hospitals and schools were treated as priority delivery points. Memoranda of Agreement (MOA) were entered into with local authorities (i.e.,barangay captains) for the management Theof water delivery. population supplied by tankers on a daily basis amounts to about 8,000 families, or 65,000 inhabitants. 2.1.4 Water Quality: network issues Poor sanitary conditions in a large part of the service area have compounded the water shortage situation and considerably increased public health risks. Incidents of pollution in the network were frequent due to a number of factors. These included physical leaks in the distribution system, extremely low pressure, improper use of booster pumps to withdraw water from the network and proliferation of illegal water connections. The latter (so called “spaghetti” type connections) involved substandard tapping to the mainline, especially in the depressed areas. The following chlorination strategy has been implemented in response to the health issues: increase of the residual chlorine at the outlet of the treatment plants up to 1.5 mg/l; reduction of turbidity of the treated water at less than 1 NTU; increase frequency of monitoring through bacteriological analysis (600 monthly) and residual chlorine measurements (2,400 monthly) ; local additional chlorination of the network trough 10 mobile chlorinators in case of positive bacteriological analysis. 2.1.5 Water quality: raw water issues
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The monitoring of Angat raw water quality was carried out on a monthly basis starting from January 1998. Chemical and physico-chemical parameters were analyzed at 10 meter intervals from the surface to the bottom of the lake. The observed water quality profiles revealed an increasing stratification of the water body, showing a significant eutrophication of the lower part of the lake. During early September 1998, while the water level in the reservoir was at its lowest historical level, the septic water was still confined below the level of the intake, and therefore was not affecting the treatment process. However, in late September a sudden inflow due to a Super-Typhoon brought anoxic water rich in iron and manganese to the surface. Consequences were also felt downstream in the system, with many complaints received for discolored water due to high manganese content in the network (up to 1 mg/l Mn). Within two weeks, an emergency treatment using potassium permanganate was implemented for the whole production (1,300 Mld), solving the problem definitively.
218 213 208 203 198 193 188 183 178 173 168 163 158
Rule Curve No 1
Figure 3 Angat rule curve and water level during El Niño occurences.
2.1.5 Water Supply to Depressed Areas
Before privatization, so-called “squatters” could not connect to the MWSS system legally because of the government requirement for title of property. This caused the proliferation of illegal bypass and outright illegal connections, especially in blighted/depressed areas. Combined with poor sanitary conditions, these illegalities, in turn, increased public health risks causing outbreaks of water-borne or water-related diseases. To address this situation, and as part of its pro-poor public service orientation, MWSI continued the MWSS public faucets program, starting with a MOA with the City of Manila to provide water to depressed areas in the City. The public faucets program was particularly important during the El Niño drought, when cooperation between the Government and the private sector helped ensure equal access of water to all.
2.1.6 Call Center, Public Affairs and Information
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To cope with the increasing number of complaints received due to the El Niño crisis, MWSI established a 24-hour Call Center with a public hotline number served by three 8-hour shifts. An average of 1,000 calls were addressed daily (up to 2,500 per day during the manganese occurrence), of which the bulk were no-water complaints (46%) and reports of pipe leaks (43%). MWSIs Corporate Affairs arm maintained a proactive relationship with media and the public, immediately disseminating scheduled water service interruptions, public health bulletins and, in case of emergency breakages, the status of ongoing repairs. 2.2 – El Niño contingency program In August-September 1998, the Philippines were still under the influence of the strongest El Niño in living memory and the early signs of the coming La Niña were still controversial. It was during this time that MWSS and its concessionaires decided to undertake investigations of water supply emergency projects that could be realized in six (6) months, if handled with urgency and under appropriate emergency conditions. These projects were aimed to guarantee a significant complement of water during the 1999 dry season, in case of poor recovery of the dam storage (Figure 3). The following contingent program was prepared: 2.2.1 New Surface Water Resources Apart from the existing long-term projects (Umiray-Angat Transbasin Project: +800 Mld; Manila III - Laiban Dam: +1,900 Mld; BOT Cavite: +300 Mld); which would require several years for completion, three sources of surface water can be used in case of emergency: the Taal Lake, Laguna de Bay, and the Marikina river. Taal Lake In 1979, Taal Lake was determined to be a potential source of water supply for the MWSS [2]. However, the project was not pursued because of the marginal water quality and the danger of volcanic action. The crisis circumstances dictated reconsideration of this 18-year-old project for the following reasons: 2 Taal Lake occupies the caldera of a large volcanic complex. At 240 km in size and 100 m in average depth, the volume of the reservoir is 25 times that of Angat Dam.The firm yield of the Lake for water supply was estimated at 10 CMS (860 Mld). Water quality is appropriate even without sophisticated treatment in case of emergency situations. The only problem is a relatively high level of salt (chlorides = 0.5 g/l), as confirmed by the analysis conducted by MWSI. concept of works and economic analysis wasA program for development including a proposed for 860 Mld (PhP1.3 billion in 1979). Development of this resource does not require major civil works such as construction of a dam, tunnel, or sophisticated treatment plant. The emergency project consists in building or laying down: an intake – pumping station (for a head of 140 m); 5 km of pressure pipe; head reservoir; 40 km of gravity pipe (pressure of 12 bars, soft pipe). The 1979 study considered a 2.7-m iron pipe as sufficient to carry the projected yield of 860 Mld. In an emergency situation, the use of new technologies (soft pipes) may enable implementation of the project in a short period of time (about 6 months). These “soft pipes” are 1,000 mm in diameter and can convey 120 Mld. They are available in rolls of 600 meters. The emergency project could include 2 to 4 pipelines (i.e.,240 to 480 Mld). The cost of this project was estimated at PhP 2 billion PhP for 2 pipelines. Laguna de Bay Laguna de Bay, a shallow brackish lake with an average depth of about 3 meters, can be considered a potential source of drinking water. Lake water can be treated with an appropriate water treatment plant (WTP). Considering the difficulty of building a treatment plant in six months, the only solution appears to be to convey Laguna de Bay water through “soft pipes” to the nearest existing WTP (e.g. Balara WTP, Quezon City).
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In any case, the treatment process would have to be adapted to the new raw water quality. The pipes can pass through the Marikina River up to a road connecting Marikina River to the WTP. The emergency project consists of building/laying down: floating intake in Laguna de Bay; about 10 km of “soft pipes” (6 bars, on-line booster pumps; rehabilitating/optimizing the WTP to adapt the treatment process to the new raw water quality. A floating pumping station would have to be erected. The first estimate for this emergency project is approximately PhP 1 billion for 2 pipelines (250 Mld). Water from the Marikina river The Marikina River used to be a source of raw water for the Balara WTP. It is possible to rehabilitate the pumping station(s) and to re-use the River as a source of water in an emergency situation. It might be necessary to create a small dam in the Marikina River, especially during the dry season. A technology of rubber dam such as those currently used in California and Florida can be used. The dam can be inflated with air or water and can be deflated very quickly in case of flood (half an hour). Those dams can be as high as 4 meters and 100 meters long and can create a substantial reserve of raw water. 2.2.2 - Groundwater resources The whole Metro Manila aquifer is exploited by more than 3,400 deep wells and 30,000 shallow wells, which presently draw an estimated 1,000 Mld. About 1,200 other deep wells are abandoned for various reasons, most notably coastal saline intrusion [3]. Groundwater is a key 2 element, as the whole Metro Manila aquifer system covers 790 km . The groundwater development plan includes: Inventory and rehabilitation of abandoned wells and the El Niñotemporary utilization during crisis situation. As a first estimate, 50 to 100 Mld should be recovered (100 to 200 wells) for an estimated budget of PhP 200 M. Drilling of new wells. Technically, a deep well can be completed in 10 days with appropriate logistics. As an emergency program, mobilization of 15 drilling rigs would enable production of 150 Mld in 6 months. The emergency program should focus on highly populated and depressed areas, where it is difficult to provide water with the network. It is also possible to drill new wells using Laguna Lake bed infiltration in populated areas along the lakeshore. As a first estimate, the cost of this program is about PhP1 billion for 150 Mld. Lake bed induced infiltration with wells in Laguna Lake. As proposed by B. Z. Haman [4], some 100 wells can be drilled into Laguna Lake for a yield of 520 Mld. As those wells will capture infiltrated water from the Lake, the solution of directly treating the lake water may be more appropriate. Table 2 Cost-benefit analysis of the contingent program.
Contingent program Taal Lake Laguna – Balara WTP Marikina river Rehab. of inactive wells New wells Wells in Laguna Lake
Yield (Mld) 480 250 200 75 150 300
Cost (MPhP) 4,000 1,000 400 200 1,000 5,000
MPhP/100 Mld 833 400 200 260 667 1,667
2.3 – Emergency measures In this section, some palliative measures are described, aimed at addressing extremely critical situations of shortage of water. These are designed to provide minimum amount of required drinking water to the population. 2.3.1Ultrafiltration Units
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MWSI can mobilize very quickly about 10 emergency ultrafiltration units based on the Lyonnaise des Eauxmembrane technology: 3 /h,Sirroco: 5 units of 20 m 3 UF Citep: pilot unit of 10 m /h 3 Aquachoc: 2 units of 5 m /h 3 Ultrasource: 4 units of 10 m /h These units enable production of high standards of potable water regardless of the source of fresh water. They can provide small amounts of water for critical purposes (hospital/school use, etc.). 2.3.2 Sea Transport Water barges can be used in a crisis situation to transport drinking water. A new technology using large water bags floating on the sea could be used in the Philippines. This technology is currently used in the Mediterranean Sea to provide water to Cyprus Island from Turkey. A cluster of 3 10,000 m /unit water barges, floating on the sea, and pulled by tugboat, would shuttle between 3 the filling and delivery sites (Manila harbor). The cost of such service is about US$10 perm . 2.3.3 Rail Transport The railway can be used to convey fresh water to Metro Manila. The water can come from the 3 Calamba-Santa Rosa Groundwater Reservoir (estimated potential recharge of 5.1 m /s [2]) that is crossed by the Philippine National Railways. This water can be delivered to the population along the railway, using stationary tanks or taken directly from the wagon. 2.3.4 Water Bags Distribution of water bags can be undertaken, but only for drinking water purposes. One unit can deliver 3.600x1 liters bagperhour. The production cost of one liter bag is less than PhP1. The purchase cost of one unit is about PhP4.5 M. Water bags can complement water wells or ultrafiltration units. 2.3.5 Water Rationing Beyond classic measures such as prohibition of car washing, watering of streets, gardens and golf course greens which require passage of local ordinances for enforcement  in an emergency situation, the use of water can be restricted to priority usages (drinking water, food industries, hospital, school,etc.). To limit water consumption, a ceiling can be imposed through a prohibitive penalty for high consumption. Industrial water usage can be also regulated and private wells accordingly turned over for drinking water purposes.
III – RESULTS Between the end of September and the beginning of November 1998, three Super Typhoons enabled the full recovery of the Angat reservoir (from 157 to 213 m), confirming the return of the wetter La Niña condition, putting an end to the worst El Niño drought of the Philippines history. An analysis of the crisis management in the aftermath of this difficult period resulted in the following conclusions: have been wellDespite some understandable complaints, the shortage situation seems to accepted by the population of Metro Manila. No major outbreaks of illness occurred. During the election period in May 1997, while the shortage situation was the most severe, the privatization of the water operations never became a political issue. Despite the Asian financial crisis, MWSI and its shareholders met all the necessary expenses to mitigate the effects of El Niño. MWSS, using a special government fund, was also able to finance some of the emergency works.
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Moreover, this experience showed the strength and effectiveness of the relationship between the private company and government agencies (MWSS, Regulatory Office, Department of Health) and their preparedness to face unexpected and difficult situations.
IV – NEW PERSPECTIVES IN WATER RESOURCE MANAGEMENT Water supplies to megacities have to be secured in competition with the demands of agriculture, hydroelectric generation, industry, and wildlife and environmental conservation. Water resources development thus needs to be approached in a comprehensive manner with a view to achieve the best allocation of scarce resources, taking into consideration the economic value of water utilized by the different users [5]. Climate change could have an appreciable effect on water resources available for municipal supply and this should be considered when preparing long-term water resource plans. Technical, management and political assessment will be required to capture lessons learnt, update drought contingency planning, to make immediate improvements and to re-consider long term investments taking into account water demand and price elasticity. Decisions on these matters are likely to be influenced by political factors, in addition to technical, economic, social and financial considerations (Figure 4). Regional climate change studies need to be carried out and the results incorporated in future water resource strategies. The understanding of the El Niño occurrence needs to be developed b y scientists. 1997-1998 El Niño shortage situation, so severe in many countries around the Pacific, challenged successfully MWSI and the MWSS, highlighting the feasibility of a new strategy in water resource / demand management. Some major goals for hydroclimatologic research must include (1) improved understanding of the interaction between the hydrologic cycle and the general circulation of the coupled ocean-atmosphere system, and (2) elucidation of the role of this interaction in maintaining climate and influencing its variabilities.
References 1.J. Abrera, M. Detay, D. Gaujous, L. Veroy  Consequence of El Niño on Manila water resources. First Asia-Pacific Technical Seminar on Water and Environment, Hong Kong, 32-39 (1998). 2.Alternative sources study. Manila Water Supply III Project  Vol. 2A Presidential Inter-Agency Committee for the Re-Study of the Marikina River Project. Electrowatt Engineering Services (1979). 3.Study for Groundwater Development in Metro Manila, JICA, 1992. 4.Manila GroundwaterB. Z. Haman  On the Sustainability of Withdrawal from the Metro System and Availability of Additional Groundwater Resources, in Philwater International 96, 148-190 (1996). 5.M. Detay  Water resources management for megacities in Asia: the Manila worldwide th reference. 16 Technology transfer seminal, Lyonnaise des Eaux, Paris (1998).
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