INTRODUCTION 
A dam is an impervious barrier production at some point of a river to keep water. The difficulty on which water receives gathered is referred to as the upstream difficulty, and the alternative difficulty of the barrier is referred to as the downstream difficulty. The lake of water that`s gathered withinside the upstream difficulty is referred to as as reservoir. This water is then completed as and whilst it's miles needed. 
PURPOSE OF A DAM 
1.  manage the water for irrigation 
2. divert the water for home makes use of 
3. deliver water for Industrial makes use of 
4. broaden hydroelectric power plant to provide power 
5. boom water depths for navigation 
6.  create garage location for flood manage 
7. domesticate the beneficial aquatic lifestyles 
8. For leisure abilities. 
Multipurpose Reservoirs 
A reservoir deliberate and built to serve now not most effective one purpose however numerous abilities collectively is referred to as a multipurpose reservoir. 
Reservoir, designed for one purpose, through manner of way of the way serving one in all a type abilities, shall now not be referred to as a multipurpose reservoir. 
Hence a reservoir designed to defend the down glide regions from floods and furthermore to keep water for water deliver, irrigation, business needs, hydroelectric abilities etc. is probably referred to as as MULTIPURPOSE RESERVOIR. 
FACTORS GOVERNING SELECTION OF SITE FOR DAM 
1. 
Suitable foundations need to be to be had on the net net webweb page on line decided on for a selected kind a dam. For gravity dams, sound rock is essential. For earth dams, any sort of foundations is appropriate with right treatment. 
2. 
The river cross-phase on the dam net net webweb page on line need to ideally have a slim gorge to lessen the length of the dam. However, the gorge need to open out u/s to offer huge basin for a reservoir. 
 CLASSIFICATION OF DAMS 
Dams may be categorized into specific categories, depending upon the concept of the classification. 
i. Storage Dam : 

Storage dam is constructed to keep water to its upstream detail withinside the path of the durations of more supply withinside the river (i.e. withinside the path of moist season) and is used withinside the path of periods of horrible supply. 
ii. Diversion Dam : Diversion dam supply will increase the water diploma slightly withinside the river and consequently offers head for wearing or diverting water into ditches, canals or specific conveyance systems to the place of use. 
iii. Detension Dam : A detention dam is constructed to keep water withinside the path of floods and release it frequently at a everyday fee at the same time due to the fact the flood reduces.