Thanks for your comments!
I also dunno why the right side is darker.
Anyway, I was there with my gf along the causeway of the reservoir relaxing, enjoying the breeze. As we were going back, at the end of the causeway where we U-turn the car, we noticed that the sun was setting. So I quickly parked the car, got out and snapped this pic. No tripod and had to hurry as the sun was setting rather quickly.
I also particularly liked the top part, the clouds and the skies looked nice.