The current drought in California, which started three years ago, is believed to be the driest period in the state's history.

Drought is not something new for the most populous state in the United States. It even had droughts that lasted for a decade or two and "megadroughts" that lasted for more than a decade.

One of the "megadroughts" began in 850 and lasted for 240 years and another one took place sometime in 1140s and lasted for approximately 180 years.

However, based on the study of tree rings, sediments and other natural evidences, Lynn Ingram, a paleoclimatologist at UC Berkeley said that the current drought is the driest one in over four decades. In addition to her study, California has received the lowest level of rainfall in more than six decades last year.

Scientists worry that typical "megadroughts" in California will recur. If such happens now, it would definitely cause tragic effects, especially on farmers.

Everyone will surely be affected but farmers will certainly suffer the most.

"Cities would be inconvenienced greatly and suffer some. Smaller cities would get it worse, but farmers would take the biggest hit. Cities can always afford to spend a lot of money to buy what water is left," said Department of Water Resources' chief hydrologist Maurice Roos to San Jose Mercury News.

According to the Calif. Department of Water Resources, farmers utilize 80 percent of the 43 million acre-feet of water diverted from lakes, rivers, and groundwater. If this drought persists, there would be much less water. Large water dams and reservoirs can even go dry.

Scott Stine, a professor of geography and environmental studies at Cal State East Bay told San Jose Mercury News, "We continue to run California as if the longest drought we are ever going to encounter is about seven years."

"We are living in a dream world," he added. His message implied that they can't tell how long this current drought will last.