Notes

As farms and cities grew, people turned first to the water that was close at hand. This meant using surface water.

In the Central Valley, farmers relied on the San Joaquin and Sacramento rivers. These rivers bring water down from the mountains that surround the valley. Farmers used this river water to irrigate their lands because rainfall alone was not enough for many crops. The valley soon bloomed with crops of all kinds.

These big rivers could be unpredictable, though. In dry years, they would run low on water. In very wet years, they would flood. Farmers needed a reliable supply of water.

Some farmers used new machines that could pump groundwater to the surface. Cities also began pumping water from wells. This supply of water was reliable and seemingly endless.

Groundwater has limits, however. If pumping is heavy, rains cannot refill underground wells, causing groundwater levels to drop. In 1906, parts of San Diego County faced this problem. Wells there had pumped out too much groundwater. As a result, seawater from the nearby ocean seeped into wells. Salty water began flowing from taps. Saltwater is not good for drinking or farming.

Marshy delta land is too wet to grow crops unless farmers drain the water off. For farmers, having too much water can be just as bad as having too little.
Usually, farmers had too little water, but sometimes they had too much. This was the problem in the delta where the San Joaquin and Sacramento rivers meet. A delta is an area near a river's mouth where the water fans out across the land and deposits silt, like fine sand or clay.

Although the soil in the delta is excellent, it was marshy and wet in the 1800s. Before people could use the land, they had to drain off the water. To do this, they dug ditches across the marshland so that the water could seep into the low ditches. Then the marshes dried out, allowing the farmers to plant crops.

Flooding was also a problem in the delta. To prevent floods, people built levees along the riverbanks. Levees are raised walls of earth that help keep a river from overflowing its banks.

A different kind of flood occurred near the Imperial Valley, a desert area in the southeastern corner of the state. In the early 1900s, farmers began irrigating the land there. They used water that was diverted from the Colorado River, which turned the dry desert into a rich garden.

Then the Colorado flooded. Raging waters widened a break in the riverbank. The flood washed out the irrigation canal, and many gallons of water spilled into the desert. The water collected at a low spot, forming a new lake. This lake, called the Salton Sea, is still there today.