"The fuel shortage and power cuts have undermined an already precarious infrastructure, severely disrupting the provision of basic services, including health, water and sanitation," he said in a statement. "The onset of winter is certain to make things even worse."
Falk said the only power plant in Gaza Strip closed down three weeks ago because of a fuel shortage. Most Gazans have power for about six hours per day.
This lack of electricity has crippled much of the region's infrastructure. Falk said about 3,000 residents of the Gazan neighborhood of Az Zeitoun have been wading through raw sewage because a treatment plant there overflowed as a result of a power failure.
Falk warned that other water treatment facilities may soon run out of petrol to feed their generators. He said he's worried about the situation may expose Gazans to the risk of serious disease.
"The situation in Gaza is at a point of near catastrophe," he said in a statement.