Desert in Disguise
These maps, published in the November 1993 edition of the National Geographic Magazine, shows the water supply, delivery, and use patterns in the state of California.
Maps by the National Geographic Cartographic Division
Idea for Use in the Classroom
Explore California’s watershed by first analyzing precipitation patterns using the Supply map. Have students use the map key to identify geographical areas with the highest and lowest mean annual precipitation. Students can use this desert encyclopedic entry to estimate how much of California classifies as a desert. Focus on specific areas by using the map and chart to compare average and monthly precipitation levels between Palm Springs and Eureka. Direct students to the Delivery map and review how to read a topographical map. Students can identify trends between both maps and then use their observations to propose reasons for similarities and differences in precipitation between locations. Have students use the Delivery map to describe how drier areas, like Palm Springs, receive non-precipitation water supplies.
Next, read through the Supply, Delivery, and Use sections. Identify the units used to measure water as acre-feet and explain that one million acre-feet of water is enough to cover a football field-sized area under one foot of water. Students can reference the Use map to identify which area uses the most total water. Then have students compare water usage (agricultural vs. urban) for different areas to highlight how much water is used for agriculture. Based on their analysis, have students discuss why California is sometimes referred to as a desert in disguise. Encourage students to cite evidence from the maps to support their claims.
Finally, challenge students to propose a fourth map visualizing some aspect of California’s watershed. Proposals should include how data would be visualized and why this information might be useful.
unit of measure equal to .4 hectares.
having to do with farmers, farming, or their way of life.
area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.
mathematical value between the two extremes of a set of numbers. Also called the average.
all forms in which water falls to Earth from the atmosphere.
having to do with city life.
entire river system or an area drained by a river and its tributaries.