Pressure and flow are two different things while many people find it apparently difficult to distinguish between the two things. Pressure and flow are both related to the passage of water from a place and can be distinguished from each other in a strictly scientific manner. These days, the demand of water has certainly risen due to the increase in the amount of water being used by the common public for the general use in the day. The water for this use needs to be generated in many water bodies and hence only because of this the daily demands of the water of the public are met. Dams and barrages are both created to cater for the local water demand of the public and are hence transported to the water stations so that the public can gain access to this water for house hold purposes. However, dams and barrages cannot be created very simply and a wide criteria and a set of things needs to be looked after while creating these water giving facilities. The place of the dams has got to be selected with great care and after a lot of surveys and researches. This is particularly important because in this the pressure and the flow of the water comes in to action and they have to be considered and catered for in many ways so that the specifications of the dam and the barrage are met. Pressure can be defined as the pressure of water or the potential energy that the water contains at a specific height. In general scientific terms, it is also described as head and can be called as this as well. The pressure of water is subjected to changes with the change in height as the head drops and rises as the height of the place drops and increases respectively. This makes pressure altitude based and flow is not as in the case of pressure. Flow can be described as the total volume of the water that is passing a place in a specific time period.