The research was carried out in the Nanay River Basin, Maynas, Loreto, to determine the concentration levels of Cadmium (Cd) and its relationship with toxicity in the cocoa crop. It is a quantitative, descriptive, analytical, horizontal and predictive research. The secondary information used from the environmental monitoring of the water was carried out by the National Water Authority (ANA) in the years 2012 - 2021. The study analyzes information from 22 sampling points in different locations for monitoring the parameters of surface water and the variations in the cadmium concentration. A database of time series of cadmium concentrations, their computer processing, analysis, modeling and prediction was built using the Holt-Winters mathematical model. The levels of cadmium concentration in the lakes of the lower and middle basin of the Nanay river: Llanchama, Moronacocha, Rumo cocha and Z...