Flow of Water Basic Observations

The direction of flow of water is controlled by two major factors  

Four basic modes of water flow are observable in daily life (Fig. 2.11)  

Free fall, as in water that is released from a tilted bottle or as in rain. All directions are hydraulically free (three-dimensional degrees of hydraulic freedom), and the water is free to flow vertically under the force of gravity (Fig. 2.11a). 

Lateral overflow, as in water reaching a filled tub. The water that fills the tub blocks the downflow direction of the added water (two-dimensional degrees of hydraulic freedom), and the latter overflows, that is, it flows laterally toward the bases of drainage (Fig. 2.11b). The observation that the water flows laterally indicates its surface (water table) is slightly tilted by the critical angle of flow. The latter is defined by the water viscosity. The water present in the deeper part of the tub does not flow—it is stagnant, bounded in a dead volume situated under 

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