In calendar year 2020, total water consumption increased by approximately 6% to 98,279 acre-feet compared to calendar year 2019. This was the highest total annual demand. highest in Tucson Water since the early 1990s.
Water consumption per person also increased in 2020, by 6 gallons, to 82 gallons per person, from 76 in 2019.
But the 2019 total water use of 91,920 acre-feet was the utility’s lowest annual water use since the 1980s, said Candice Rupprecht, Tucson Water’s water conservation programs manager. One acre-foot will cover a football field about 1 foot deep with water.
The utility doesn’t yet have a total water use figure for 2021, but “we know it’s been down from 2020,” Rupprecht said.
In a hot, dry year, there is less precipitation to feed the plants, which requires more water from garden hoses.
But, less obviously, plants also need more water because they and the surrounding soil release more moisture into the air through evapotranspiration. It causes the soil to evaporate and the plants to release water into the atmosphere as vapor via stomata – tiny pore-like structures on the leaf surface.
Lack of soil moisture during prolonged hot and dry periods is also a significant factor that increases water consumption, Rupprecht said. Drier soils require more saturation before plants can absorb water from them, she said.