January to June is the season of winter because there is little or no water increase meaning there is a lack of moisture. Therefore, there is no vegetation growing in these months and the soil moisture is charged resulting in a surplus.
July to April is the spring as there is a vast amount of water increase due to the snow melting. Again runoff is increasing and the vegetation is beginning to grow.
The summer season is from April to September as the graph displays the water, decreasing due to the growth of vegetation. Therefore, soil moisture