Texas oil magnate T. Boone Pickens, an advocate for U.S. energy independence and a proponent of natural gas as an alternative source for energy, is being hit hard by the downturn in energy prices that he's profited from before.

It's already left one of his hedge funds that focuses on energy stocks down almost 30 percent through August.

According to The Wall Street Journal, Pickens' hedge funds have lost around $1 billion so far this year. That includes $270 million of personal losses.

In addition, a small commodity-focused fund is down 84 percent.

"It's my toughest run in 10 years," Pickens told the Journal.

Pickens' energy-stock fund started the year at $2 billion. It's returned a compounded annual return of 27 percent over seven years, one investor told the Journal.

The commodity fund, which started the year at about $600 million, has had similar strong performance.

According to Reuters, hedge funds have fallen 3.49 percent so far this month. The year-to-date loss is 8.37 percent, according to Hedge Fund Research's HFRX Global Hedge Fund Index.

Hedge funds could have an unprecedented level of cash pulled out by investors this quarter in reaction to SEC's temporary ban on short-selling which it announced last week, according to The Independent.

Economist Nouriel Roubini says worse is to come. He believes there will be an increase in client withdrawals and a shake-up of how funds are regulated.