Answer:
During a drought, there is less water available for the plants. There is less runoff and less infiltration. During a drought, less water is returned to the atmosphere by the plants through transpiration, and there is a decrease in the plants' rate of photosynthesis.
CO2 + H2O = O2 m + C6H12O6 photosynthesis
C6H12Og + O2 = CO2 + H2O + ATP respiration