I’ve already featured Pangasinan’s San Roque Dam back in 2006 and there I showed a side-by-side satellite imagery of the area before the dam was completed and after the dam was completed and the reservoir was filled up.
Well, I recently saw that Google added some high-resolution satellite imagery in Pangasinan dated last April 3, 2010 and it dramatically showed the effect of the El Niño phenomenon on the water level of the reservoir. Quite visible in the satellite imagery is the light fringe surrounding the reservoir which depicts how much lower the water level is at the dam. Below is a side-by-side illustration of the water level at the dam at its peak level (imagery taken on November 25, 2006) and the April 3 imagery. You can see both images for yourself on Google Earth using the historical imagery feature. Notice that in the 2006 imagery, the water level has reached the spillway to the left of the dam while in the 2010 imagery, the water level is far from it.
Using Google Earth, I estimated the water level in the 2006 image to be around 280 meters above sea level while the 2010 water level is around 240 meters. That’s a difference of about 40 meters! I don’t know how much that translates into cubic meters of water. (Note: these water levels are just estimates since Google’s terrain data, which is based on SRTM, is not high-resolution.)