By: Dr. Ali G. Macawaris & Prof. Medior P. Mamoko
Paper presented to the Seminar on “Man and Environment: The Case of Lake Lanao,” August 16,1991, Mindanao State University, Marawi City, hosted by the Department of Sociology and/the Office of the Vice Chancellor for Research and Extension. Dr. Ali G. Macawaris was a Professor of the College of Engineering, Mindanao State University Marawi City and served as the Chancellor of MSU Naawan before his demise. Prof. Medior Mamoko is also an Associate Professor at the same college before retiring.
Note: Figures for this article will follow.
I. INTRODUCTION
The raging controversy on the consequences of the operation of AGUS 1 hydroelectric Power Plant (AGUS 1) has been discussed on numerous occasions by interested parties. Dr. Datumanong Sarangani, Chancellor of MSU-Marawi, upon the recommendation of Dr. Cosain Derico, Vice Chancellor for Research and Extension, created on February 16, 1991 the MSU Special Task Force on Lake Lanao. The purpose of the Task Force is to study the effects of the operation of Agus 1 on the Maranaos residing around Lake Lanao and the ecology of the lake.
The twelve-member Task Force consisted of 11 faculty members and one administrative staff of the College of Engineering of which Dr. Ali G. Macawaris and Prof. Medior P. Mamoko are the, Chairman and Vice-Chairman, respectively.
Dr. Macawaris and Prof. Mamoko presented the findings of the MSU Special Task Force on Lake Lanao before the Senate Task Force on AGUS 1 Lake Lanao of the Senate Committee on Mindanao Affairs on May 21,1991 at the Philippine Senate, Manila. This article is a summary of their testimony. It dwells mostly on the technical consequences of operating Agus 1 on Lake Lanao and the recommendations to alleviate their adverse effects.
II LAKE LANAO WATERSHED AND AGUS POWER PLANTS
The Lake Lanao watershed includes Lake Lanao, about thirty rivers feeding water into the lake and the Agus River which is the only outlet of the lake. The four biggest rivers are Ramain, Taraka, Gata, and Masiu Rivers. It is shown in Fig. 1.
Lake Lanao has a surface area of 356.6 square kilometers. It is shallowest in the northern portion and becomes progressively deeper towards the south. An extensive area with depth greater than 110 meters is located at Balut Maito and Masla Islands. Its maximum depth is about 112 meters. Its volume is about 21.5 cubic kilometers and the records of maximum and minimum surface elevation are 702.92 and 698.59 meters, respectively.
The National Power Corporation (NAPOCOR) regulation dam started controlling the outflows of the lake to the Agus River in Marawi City in 1978. It consists of a 24-meter wide dam made of removable concrete blocks. During its construction about 70,000 cubic meters of river bed materials were dredged from the lake fronting the dam and the intake of Agus 1. The depth of dredged materials varies from three to five meters. The elevation of the base of the dam is about 695 meters.
The NAPOCOR plans to construct seven hydroelectric power plants along the Agus River. They are Agus I, Agus II, and Agus III, Agus IV, and Agus V, Agus VI, and Agus VII. Agus I is located near the mouth of the Agus River while Agus VII is near the terminus of the river at Iligan Bay. Agus 1 was scheduled to operate in October 1990 yet but was delayed because of the opposition of Save Lake Lanao Movement (SALLAM) against its operation. Agus III is still in the pre-construction stage. The existing power plants with their capacities are shown in Fig. 1.
Agus I Hydroelectric Power Plant is located in Amai-Pakpak, Marawi City. Its construction cost is P2, 441.7 million consisting of U.S. $30.53 million or P854.14 million from foreign sources and P 1,586.86 million from local sources.
It has two turbines of 40 MW capacity each or a total of 80 MW. Its powerhouse and turbines are located at about 97 meters below the ground level. These are constructed inside the twin pits which are open at the top. Their sides are protected by cylindrical walls made of heavily reinforced concrete. Its underground tunnels are located about 100 meters below the ground level and each is about 1.3 kilometers long. Its surge tanks were also constructed underground.
III ANALYSIS OF HISTORICAL DATA
The historical data were gathered from the National Power Corporation. The analysis of the historical data shows the following:
1. The pattern of variation of monthly inflows and outflows of water from the lake is similar as shown in Fig. 2 and Fig. 3.
2. By superimposing these two figures as shown in Fig. 4, it could be easily noted that starting the year 1977 the average monthly outflows of water of Lake Lanao have always been greater than the average monthly inflows of water to the Lake. This explains why the water surface elevation has continuously decreased up to the present.
3. As shown in Fig. 5, which depicts the variation of the average monthly inflow from 1948 to 1990, there is little inflow of water to the lake during the months of January, February, March, and April. This is so because these months correspond to the dry season all over the country.
4. A graph of the average monthly elevation of Lake Lanao from 1948 to 1988 is shown in Fig. 6. The maximum and minimum elevations occurred in 1956 and 1985, respectively.
IV LAKE LANAO SURFACE ELEVATION STUDIES
The MSU Task Force used as inputs the studies on Lake Lanao by Dr. David Frey and Harza, (a foreign consulting firm), data from the National Power Corporation (NAPOCOR) and the NAPOCOR lake operation rules when Agus I is in operation. It predicted the future inflows to the lake from 1991 to 2005 which is shown in Fig. 7. Finally, computer simulation studies were conducted on the lake elevation for several scenarios of power generation of Agus I. It started first with 40 MW up to 80 MW of power generation.
The lake inflow forecast was done by means of the following steps:
a. A mass-curve analysis was used to test the consistency of the inflow records from 1978 to 1990 with respect to records from 1948 to 1977. NAPOCOR started operating the regulation dam in 1978 to 1990 records were found to be inconsistent with the earlier records.
b. The records from 1978 to 1990 were homogenized with the records from 1948 to 1977.
c. Finally, the Thomas-Fiering Stochastic Model was used to predict the inflows to the lake from 1991 to 2005.
The predicted inflows to the lake and the NAPOCOR lake operation rule when Agus I is in operation were used in the lake water surface elevation studies. The operation rules are as follows:
1. Agus I water requirement to generate one MW is 1.983 cmc.
2. The maximum allowable level of the lake is at elevation 702 m. The maximum operating level is at 701.65 m. The difference of 0.35m is allowance for wave actions, and anticipate, mitigate, and control flooding of lake.
3. The minimum operating level of the lake is at elevation 699.15 m or a maximum drawdown of 2.5 m.
4. The rate of drawdown of the water in the lake shall not be more than 1.5 meters per year.
Computer simulation studies were conducted for several power generated by Agus I ranging from 40 MW to 80 MW. Only two of them are presented here, namely:
a. To initially generate 80 MW. This means that 80 MW will be generated initially and continue to do so only when the incoming water to the lake is equal or greater that what is needed to generate 80 MW when within the range of operating level; and
b. To initially generate 40 MW. This means that 40 MW is generated initially and continue to do so when the incoming water to the lake is equal or greater than what is needed to generate 40 MW when within the range of operating levels.
Fig. 8 shows an average monthly elevation of Lake Lanao from 1992 to 2001 when Agus I initially generate 80 MW. Starting at elevation 700.95 m, the average elevation at the start of a year from 1978 to 1989. It will be determined that for the first three months of operating Agus I the elevation of the lake will abruptly decrease from 700.95 m to 699.45 m reaching the maximum allowable drawdown of 1.5 meters per year set by NAPOCOR lake operation rules. For the next nine months, the elevation will be maintained at 699.45 m. During the second year of operation, the elevation will decrease to 699.15 m in the first month reaching the minimum allowable elevation of the lake and will be maintained for the remaining eleven months and eight years. The elevation will be in its minimum allowable value of 699.15 m most of the time or 81.67% of the ten year period.
Fig. 9 shows an average monthly elevation of the lake from 1992 to year 2001 when a 40 MW power is initially generated. Starting at elevation of 700.95 m, the elevation will increase to its maximum allowable value after six months of operation. The elevation will be at its maximum value for the next six months and also during the second year of operation. After two years of operation, the elevation will vary and in 1998, there will be an abrupt decrease of elevation from 701.48 m to 699.98 m reaching an allowable drawdown of 1.5 m per year. The elevation will be near to its allowable minimum value for the last four years and it will be 699.15 m for the last four months of the year 2000 and for the first four months of the year 2001 which is the minimum allowable elevation. The elevation will be minimum for only eight months or 6.7% of the period of ten years.
V ADVERSE EFFECTS OF THE FLUCTUATION OF LAKE WATER SURFACE
The water surface fluctuation of Lake Lanao has adverse effects on the following areas;
1. Fisheries
Lowering the water level will expose the littoral zone to direct sunlight. The littoral zone is a very shallow vegetal portion of the lake. It serves as a feeding, spawning, and nursery ground for practically all the fish species of the lake. The exposure of the littoral zone to direct sunlight will result in the destruction of the eggs of fish deposited on the various kinds of vegetation found in this zone. Also, consequently the small fries will be deprived of the place where they can seek refuge against predators.
2. Agriculture
The lowering of the water level of Lake Lanao has affected badly the lowland rice fields in the surrounding areas. Firstly, the rain-fed areas are no longer producing two cropping per year. During the months of January to May, the areas are no longer suited to rice farming. This also changes the rice-farming pattern in the area. Instead of planting two rice cropping per year, the rice farmers are shifting to corn in the months of January to May, while rice is only planted during the months of June to November. This means that only one rice cropping is now done in the surrounding areas in Lake Lanao.
As a result of this, Lanao del Sur has to increase its corn production but decrease its rice production. The resulting economic gross loss by substituting rice with corn in one cropping could be computed to be P157.5 million per year.
3. Transportation System of the Lake
As a result of drawdown of the water surface of the lake, practically all the existing piers of mosques are now very far away from the shores. Also several big boulders near the shoreline become exposed. This fact compounds the difficulty of the boats in approaching the shore for the discharge of passengers and cargoes and consequently increase the labor cost for cargoes and fares of the passengers.
The four major rivers which feed water to the lake may no longer be effective as means of transportation since they are now very shallow when the water elevation is at 699.15 m. In fact, with this minimum water surface elevation, people could just wade across some of the rivers.
4. Religious Practices of Maranaos
As a result of the recession of water far away from the piers, the Muslims are inconvenienced in performing their religious obligations because they have to walk a certain distance, at many points up to 200 meters, between the lake water and the mosques to perform their ablution.
5. Domestic Water Needs
The Maranaos around the lake are using the lake water as drinking water to satisfy their health and hygiene needs. The lowering of the water level is causing them inconvenience because they have to walk a certain distance, in some cases 200 m, bathing and washing purposes.
VI. RECOMMENDATIONS
The following are the recommendations on the conditions to which Agus I may be allowed to operate and the measures intended to alleviate the conditions of people adversely affected by its operation.
1. The Creation of the Lake Lanao Development Authority is highly recommended. Its main functions are developing, conserving, preserving and monitoring the use of the lake resources. It could be coordination with the NAPOCOR establish fixed meters for the purpose of allowable minimum water surface elevation of the lake and monitoring the water surface elevation.
2. The National Power Corporation should comply with the requirements of PD 1586 otherwise known as Environmental Impact Assessment Law. The environmental impact studies shall focus on the effects of the operation of AGUS I in the lake resources and the Maranao residing around the lake.
3. The National Power Corporation may be allowed to operate Agus I provided it will initially generate 40MW of power and will generate power beyond 40 MW only when the incoming water to the lake is equal or greater to the water needed to generate 40 MW. In so doing, the present experience on power shortage because of low inflows could be experienced only for eight months in a period of ten years.
4. There should be a total logging ban in the Lake Lanao watershed. Excessive logging may accelerate the “demise” of the lake or shorten its usefulness.
5. Some Recommended Alleviation Measures. As a result of the inevitable drawdown of the water surface or recession of water from the shore the following alleviation measures are hereby recommended.
a. The operation of Agus I should not be such that it will cause abrupt lowering of the water surface. Sudden drawdown in the water surface would abruptly destroy the littoral zone, which is the feeding, spawning, and nursery ground for practically all fish species in the lake.
b. To help farmers who greatly affected by the water surface drawdown of the lake, irrigation water should be provided to their communities through the help of the National Irrigation Administration (NIA) and a portion of the cost of electricity shall be borne by NAPOCOR.
c. To help mitigate the resulting transportation problem, it is recommended that either the existing piers be condemned and new ones constructed or an extension of the new piers be made and, also to dredge the rivers at their entrance to allow the boat to move freely through the river. This may be done by the Department of Public Works and Highway (DPWH).
d. The local Utilities and Waterworks Administration should help the affected Maranao residents around the lake by providing their communities with water supply system. This is done in cooperation with the NAPOCOR.
VII. CONCLUDING REMARK
It is our fervent hope that the facts that were unearthed in the course of this Policy Study will be found informative and could contribute even in a small way towards the resolution of the on-going Lake Lanao issue.
{ 7 comments }
hello! I am a student researching on Lake Lanao. Thank you very much for sharing this information. Where can I find the images found on this particular report by Dr. Macawaris and Prof. Mamoko? It would really help if you could give me the site where this was taken from. Thank you very much! God bless!
Hello! I just sent you the figures you needed. I will upload the figures when I have stable internet connection. I hope it helps you.
Assalamu ‘alikom. I am an OFW in Jeddah, Saudi Arabia.
Alhamdolillah, your very informative post give me a very clear pictures of what happened to the movements called SALAM and thier so called officers and leaders. They became in-active in pursuing the right of their people after getting what they want “Power and Wealth” from NPC and the National Government. I hope we deprived Maranaos) will get our constitutional rights in fair distribution from the so called great development of Lake Lanao and the Agus River.
Thank you for making this piece of information available online..I’m doing a water quality assessment on the Agus river and this info have been very helpful..thanks much ^_^
Hello!can you please send me the figure for the variation of monthly inflow and outflow in the lake..?please..thanks soo much
Salam! Eid Mubarak. I still could not upload some of the figures for this article. I hope I will be able to do so one of these days. Anyway, for those who requested for the figures, I already sent them to your email. Just kindly leave a message if you also need to have a copy.
Eid Mubarak wa Kollo Aamon wa Antom Bikhair,
It amazed me after learning that the total power output coming from the Agus River Hydro projects (I – II – IV – V – VI – VII) was 527.1 MW. If the income of these power output distributed properly, I and our fellow Bangsamoro OFW working abroad may not be in different parts of the globe struggling for jobs. We will be more develop and financially stable than our neighbors. Or better than the oil producing countries.
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