Completed: September 2010
Prepared by: Dr. Emelina G. Regis
Funded by: University Research Council, ADNU
A dam is a structure constructed across a stream to capture water in order to obtain various benefits. These are for irrigation of arid land, control of flooding in lowland areas, generation of hydroelectric power, water supply for towns and cities as well as for recreation. The impounding area for water is called a reservoir and dams above 15 meters high are considered large dams (Miller 2000). With this additional structure, the river is considered regulated (Smith & Smith 1998). Some regulated rivers however can result to negative impacts. A dam for instance can reduced downstream flow of water causing several ecological effects. These are 1) accumulation of silt behind the dam eventually filling up the reservoir; 2) nutrients from silt then become unavailable to plants along the riparian zone downstream making farmers dependent on commercial fertilizer; 3) accumulated salts (International River Network, 2001) resulting from the silt could not be flushed downstream, salinization then follows with consequent disappearance of wildlife, thereby reducing biodiversity in the water and riparian zones in both the reservoir and backwater as well as downstream portion of the dam (Smith & Smith 1998, Miller 2000).
The most devastating impact of dam construction is flooding of areas at the backwater of the dam. These areas may be forest, agricultural land or worst, human habitation. It is in this context that the study of the Libmanan-Cabusao Dam Project (LCDP) of the National Irrigation Administration (NIA), Region V was done. LCDP was approved by the national government with the following objectives: “1) to optimize the use of water and land resources by replacing the pump used to irrigate the present system with a concrete diversion dam [in general], and 2) [specifically] to cut down the cost of operation and increase farm income in aid of farmer beneficiaries.”
What is disturbing about this dam is that, it is not being constructed in the Municipalities of Libmanan and Municipality of Cabusao which are lowland areas and have ample supply of water within their jurisdictions. Rather, it is being constructed upstream in Sipocot River with backwater intended to inundate the town proper of Lupi and some agricultural areas along the Lupi and Sipocot Rivers. It was also difficult to understand that while, Sipocot River is connected downstream to Libmanan and Cabusao and this segment is known as Libmanan River which is already being used for irrigation purposes, the proponent opted to create a dam where its reservoir will convey water through a canal that will still connect to a pumping station downstream. This was the reason for the fear of concerned citizens of Lupi who requested for assistance from INECAR, Ateneo de Naga University and Bishop Jose Rojas, Jr. of the Diocese of Libmanan which includes the Municipality of Lupi. INECAR’s initial investigation in October 2009 concluded that the dam is not needed to provide irrigation water for Libmanan and Cabusao since these municipalities have rivers and creeks within their land territories. It is also unjust to sacrifice the people of Lupi and Sipocot and their ecosystems just to provide this need. There are also other alternatives to obtain water for irrigation that are less costly with less impact to the environment and to the human communities.
Objective of the study
This study intends to strengthen the initial investigation conducted by the INECAR in October 2009 by determining the specific and extent of the areas that will be impacted upon completion of the dam. These are: a) areas to be inundated by water, b) agricultural areas, c) fishery resources in the rivers/creeks, and d) wildlife resources.
Scope and delimitation
The research covered only certain concerns that will be directly impacted by the dam, thus the parameters are only limited to the physico-chemical attributes of sediments and rocks and areas of inundation. Only the agricultural crops of farms along Lupi (Sulong) River and Sipocot (Sipocot-Polantuna) River were included in the assessment. For wildlife resources, fish and bird species were observed and photographed and/or documented whenever possible but species identification was not done; instead, the local names based on usage by local communities were obtained from the respondents. Additional information such as a mammal and a unique aquatic plant which may be important, were also photodocumented.