Soil moisture can be a determining factor in hydrological processes. However, the monitoring of soil water content is difficult to perform because of its spatiotemporal variability and because field measurements are expensive and time-consuming. Thus, the use of the Tank Model and also a moisture index derived from this model can be very useful in hydrological studies and in the management of natural disasters. The study area is located in the rural area of Rio Negrinho municipality, north of the state of Santa Catarina. It was divided into square cells, with a resolution of 1 meter, in each of which the Tank Model was applied, where: S is the water height of the model (mm); P is precipitation (mm.d-1); ETR the actual evapotranspiration, in mm.d-1; Qs is the surface runoff in mm.d-1; Qb is the percolation for the lower layers of the soil, in mm.d-1; a1, a2 e b1 are the coefficients of surface flow; And a0 infiltration coefficient. The total flow (Q) is given by the sum of all flows (qs1 to qs3), and the goal is to check the feasibility of the Tank Model.
The present work adopted the method proposed by Tarboton (1997), to determine the direction of the flows in each cell. This method calculates the flow direction (represented by an angle between 0 and 2π), which is determined by the steepest direction of the eight triangular facets formed on a grid of 3×3 pixels centred on the pixel of interest.