Geography of Purnia

Purnia located close the international borders with Nepal is spread over an aarea of 3,229 km² and is divided into 4 sub-divisions and 14 blocks. Because of the pleasant weather which persists round the year, the city is also known as “Poor man’s Darjeeling”. Purnia coordinates at 25.78°N and 87.47°E and enjoys moderate climate. A historical city today it has grown into a town which has both economic and strategic importance.

Geology of Purnia

Purnia lies in the fertile terai zone of the Gangetic Plains. The Ganges which originates from the Himalayan region, flows down and traverses through Purnia before eventually draining into the Bay of Bengal. The district lies in the extremely fertile alluvial zone of the river inundated with the fertile alluvium deposits. To the north of the city can be found the Kankar zone which is mainly composed of the big boulders from the Himalayas which are deposited here. To the south of Purnia lies the Bhangar zone of extremely fertile alluvium deposits consisting of fine silt and sand. Since the district is a part of the Gangetic plains the soil is of sub-montane alluvial type. There is a calcerous belt which lies to the north which called Chotapahar located near Manihari.

Rivers in Purnia

There are four important rivers which traverse the city and also divide the district into four distinct zones. The rivers which traverse the city are Kosi in the west, Panar in the northeast, Mahananda in the east and Ganga in the south. Kosi is the most important rivers in Purnia and is often known as the sorrow of Bihar. This is because the river has a tendency to frequently shift its trajectory thereby leaving behind a trail of destruction every monsoon. It is because of this that a barrage was built over the river called the Bhimnagar Barrage which is an irrigation control, hydropower project.


It also helps to maintain the peak flow to prevent flooding during the monsoon season. Apart from this, the river also brings heavy boulders from the hilly terrain where it originates and deposists it on either side of its border making the region extremely infertile and not fit for crop cultivation. The main tributary of Kosi is the Saura river and joins Kosi near Mirganj. The river flows thrugh the eastern side of the town and divided the old and the new townships of Purnia.

Climate in Purnia

Purnia enjoys a very pleasant weather all through the year earning the city the nickname of “Poor man’s Darjeeling”. The weather is humid temperate type with an average of 28C. The city with moderate climate has temperature ranging from 5°C in the winters to 30°C in summers. Purnia reports the largest amount of rainfall in the state ans the bulk of the rainfall is during June to September months. Since the city lies in close proximity to the Bay of Bengal, many of the tropical cyclones which originate in this part of the ocean also cause heavy rainfall and flooding in the district.

Forests in Purnia

Purnia is covered with forests mainly of monsoon type which is typical of the region. The main trees of the regions are Sal, Sakhua, Teak, Semal, Peepal etc. Most of the forests have been cleared to give way to infrastructure and commercial farming. The district is one of the fastest growing districts in the state and this can be seen in the increasing infrastructural facilities in the city.

Minerals in Purnia

Though agriculture is the principal occupation with almost 80% of the population involved in agriculture, mining is also gaining importance in the district. There is availability of limestone in the calcerous node in Chotapahar near Manihari. Due to the frequent changes in the course of river Kosi, there is heavy deposits of Kankar which is making the region unsuitable for cultivation. But the rich sand deposits are being mined these days and there is a growing industry thriving around the activity. There is also some attempt at oil extraction in Araria by ONGC which is an ongoing project.

Agricultural Lands in Purnia

Purnia is well endowed with perennial rivers which traverse the region. It is one of the districts which is well watered and also receives adequate amount of rainfall during the monsoon season. The area which is located around the Kosi river shows sandy deposits while the area around Mahananda shows Loamy deposits. Since there is frequent flooding of the banks of the river, the region is well suited for Jute and Paddy cultivation. The other important crops grown in the region are wheat, potato, maize, tobacco, masoor, barley, sugarcane, chillies etc. Rice is the major crop. The region is also known for makhana cultivation which is gaining prominence in recent times.

Geographical Details of Purnia

State: Bihar
Altitude: 171.2 Feet
Latitude: 25°-13'-80" ~ 27°-07'-59" N
Longitude: 86°-59'-06" ~ 87°-52'-35" E
Winter temperature: 5°C
Summer temperature: 35°C
Average Rainfall: 1,470.4 mm
Major Rivers and Lakes : Kosi, Mahananda, Ganges, Gandak etc.