Grandpa Ruben answered that "there are both natural and artificial causes for this, Gabriellita. A lack of precipitation is one cause. You know what precipitation is, Juanito?" Yes Grandpa, Juan replied. "It is rain, hail, or even snow when the clouds in the sky open up, Grandpa." Beaming proudly, Grandpa Ruben said: "You are both caring children and I am so proud of you both, mi Juanito y mi Gabriellita."
Gabriella was still curious. "Is that the only reason, Grandpa?" "Low ground water reserves is a second major natural cause, mija" Grandpa Ruben answered. "In our lovely city, San Antonio, Edwards Aquifer is our groundwater source. Unfortunately, ground water pollution and wrong uses of land are man-made causes.", Grandpa Ruben mused, "al fin."