Aquatic animals, such as freshwater turtles, are much dependent on the water bodies where they live. Here we describe the size distribution of a population of Phrynopsgeoffroanus complex that died after the total drought of the artificial water reservoir where it lived in Caatinga. Amongst the 438 animals we found dead in the Cedro water reservoir, we measured the maximum carapace length of 72 individuals. The population was mainly composed of adult individuals and dead turtles measured in areas that kept water for longer were larger than animals from areas that dried up early.