Structures for Display!!!

Napindan Hydraulic Control Structures is one of the projects by the Philippine Government worth visiting as far as its function is concern. It was completed in 1983 under ADB funds designed by Japanese Consultant for the purpose of salinity control of Laguna Lake. It has four flood gates and navigatonal lock to regulate the flow of salt water from Pasig-Marikina River to Laguna Lake via Napindan Channel and to allow small boats and barges to enter in and out Laguna Lake, respectively. Secondly, the Napindan Channel drains  flood waters from Laguna Lake resulting from discharges diverted from Marikina River through Mangahan Floodway and inflows from twenty one tributaries around the lake.

In 2002, through the wish of then MMDA Chariman Bayani Fernando, it was transferred from DPWH to MMDA. From 2002 to 2011, it was poorly  maintained because the funds were not included in the package.  Since then, the floodgates and the navigational lock were always open through out the years as the gates corroded for lack of maintenance and lubricants.

So what happens now to regulating  salt water intrusion to Laguna lake.  Logically, free flow from Pasig-Marikina River to Laguna Lake and vice versa due to diurnal tide fluctuations and seasonal highs and lows of lake level proved  the structures to be futile. With and without the structures,  polluted salt water from Manila Bay comes in and out the lake. Environmentalists  suggest to close the gate whenever the water level of Pasig-Marikina River is higher than the lake stage or during  high tide to prevent pollution to enter the lake. However, it is contended  by  fishefolks because they claim that they need salt water to  propagate their fingerlings during dry season in the lake.

Normal rule is that the floodgates are opened during flood times whenever high discharges  from Marikina River occur to allow inflow to Laguna Lake to prevent downstream overflow, that is Manila area. During high lake stage when most of the coastal towns are flooded, the  gates must remain open to drain the high lake stage. On occasions that the lake stage is higher than the Pasig River, the floodgates must be closed, which seldom occur.  At the moment  there is lack of river stage data in relation to lake stage to established its relationship..

The main purpose of the Napindan Hydraulic Control Structures is for salinity control and secondarily for flood control. With the floodgates open most of the time, ostensibly the project is functionally worthless.