A dam is basically an artificial wall built across a river, and water is allowed to collect behind this wall in a reservoir.
A system of artificial canals channelizes water from the reservoir to the region downstream for irrigation.
Dam
The Bhakra Dam, the first project to be taken up after India's independence, is built across the Sutlej (alternatively spelled as Satluj) river, near the border of Punjab and Himachal Pradesh.
The dam is part of the larger Bhakra Nangal project that aims at preventing floods in Sutlej-Beas river valley, to provide irrigation to adjoining states, and to provide hydro-electricity.
The mountainous and hilly regions of north and west on the other hand do not allow adequate seepage.
So, groundwater is mostly limited to lower lying areas such as valleys.
The peninsular areas of our country also do not allow proper absorption of water, and therefore do not have large continuous aquifers.
Though the coastal plains are a rich source of groundwater, they can be contaminated by salt water inflow caused by over-pumping of groundwater.
The Gangetic plains are, however, rich in groundwater since the aquifers keep getting recharged and restored.
