Incorporation of the Effects of Volcanic Eruptions in Stochastic Precipitation Model in Watershed. Tungurahua Volcano Case in the River Watershed Ambato

Studies have shown that the variability of precipitation depends primarily of climatic factors, wind, temperature, and atmospheric pressure, however in the past twenty years the continuous eruptive process of volcano Tungurahua has been a natural factor that contributed to the variability of precipitations in short term and to the extension of the watershed of Ambato River. To incorporate the effects of the eruptive process of a volcano over precipitations, initially the study zone was selected, the weather stations located within a 100 km radius from the volcano’s location, and the sub periods for the study. An ARIMAX model is build, which consists of two components: the first one is a deterministic exogenous component; to estimate this component, it is necessary to determine the concentration of SO2 in air produced by the eruptive events over the watershed and its conintegration with the precipitation series is established.