With about 38 million residents, California is the most populous state in the country. A moderate climate, abundant scenic beauty and lots of economic opportunity have driven Americans to relocate to the Golden State.

This has put an extraordinary strain on California’s water supplies. One measure: the watershed of the Sacramento-San Joaquin Delta, which collects runoff from the state’s two largest rivers and supplies about 50 percent of all the state’s freshwater. It has been estimated that the State Water Resources Control Board, which controls water rights, has allocated about five times more water in the Delta watershed than it produces in an average year. This is a direct result of a growing state’s need for more water.

This demand has made shortages harder to manage, because more people are clamoring for roughly the same amount of freshwater. In the drought of 1976-77, long considered the worst in state history, California had about 23 million residents. Now it has 15 million more, an increase of about 65 percent. And there’s no sign the growth is stopping: The state Department of Finance estimates that by 2050, California will add another 10 million people.

Aggravating the problem is the fact that the fastest growth is occurring in California’s interior counties, where real estate is cheaper. But these counties – within the Central Valley and the Inland Empire of Southern California – have hotter, drier weather that boosts water demand. A new residential lawn in Fresno County, for instance, requires much more water to keep green than a new lawn in Monterey, even though both cities have roughly the same climate.

The state’s agricultural industry has also undergone major shifts in how it consumes water. Throughout the Central Valley, the heart of the state’s agricultural community, many farmers have shifted from growing annual crops like lettuce, peppers and tomatoes to permanent crops such as wine grapes, almonds, pistachios, mandarin oranges and pomegranates, largely because they are more lucrative.

Retaining lots of farmland in annual crops is important to help the state survive droughts. If a farmer doesn’t have water to grow tomatoes, he doesn’t plant a crop that year, the field sits dormant, and the water he would have used is available for someone else. But if he was growing almonds trees instead, which take four years to mature and produce nuts for decades, the field can’t go without water or the trees will die. Because almonds are more valuable, many farmers can afford to purchase the water they need even when there’s less to go around. As a result, water demand remains the same, despite the drought.

Almonds are just one telling example. Global demand for almonds has soared, and California has become the world’s leading producer. In the 20 years ending in 2013, California farms more than doubled their almond acreage, to about 840,000 acres. Because the crop is so valuable, farmers have continued to plant more of the crop despite the drought: The U.S. Department of Agriculture estimates that an additional 48,000 acres of new almond orchards were planted in 2014.

In addition, more than 40 percent of California farm acreage is still watered by some form of flood irrigation, an ancient method of irrigating crops in which water is delivered to the field by ditch, pipe, or or some other means and simply flows over the ground through the crop. However, this is wasteful compared to newer methods like drip irrigation or microsprinklers, in part because of evaporation losses.

Agriculture uses about 80 percent of the “developed” water in California, meaning water that is conveyed by pipeline. The remaining 20 percent goes to urban areas. So changes in water use by agriculture can have large ripple effects on the state.