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Aquifer analysis: Methods used by The Desert Sun

September 8th, 2013 | by Ian James | Comments

The Desert Sun, in an effort to analyze the state of the Coachella Valley’s aquifer, obtained records of water levels in all 346 wells for which the valley’s largest water agencies have measurements. The Coachella Valley Water District provided records for 307 wells, and the Desert Water Agency provided records for 39. Some records go back as early as 1926, while many wells have been drilled in recent decades.

READ THE SPECIAL REPORT: Coachella Valley aquifer at risk

CVWD and DWA together serve about 75 percent of the Coachella Valley’s water customers, and the wells they measure span the entire valley. The Desert Sun chose to focus on the extensive records provided by these two agencies, and did not analyze the records of three smaller water agencies that cover fewer wells and have records that don’t go back as far.

During a three-month review of the data, the water level measurements were transferred to spreadsheets and analyzed in multiple ways. For years in which multiple measurements of water levels were taken for a single well, an annual average was calculated for the well. A rate of change in feet per year was then calculated for each well and for each year. If a well was missing data from the previous year, no rate of change was entered for that year. Annual average rates of change were then calculated for all wells, revealing trends by year and by decade.

Sixty-three of the oldest wells — with records that start in the 1960s or earlier — were analyzed separately in order to assess long-term trends.

The approximate locations of all 346 wells were plotted on a map to help identify trends. Check the map to see wells in your neighborhood and changes in water levels over time.

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