Data were processed by the Statgraphics Plus 5 program in order to obtain the average values, standard deviations and confidence limits. The Statgraphics software allowed investigation of the existence of a normal distribution for the data values. The analysis of variance (ANOVA) was applied to data values when normal distribution was observed, and the Kruskal-Wallis test was used when no normal distribution law was observed, in order
to deduce spatial distributions for heavy metals in the Tepuxtepec Dam. The statistical methods were performed
with a 95% confidence interval (CI; α = 0.05).