Bihar is a vast stretch of fertile plain. It is drained by the Ganges River, including its northern tributaries Gandak and Koshi, originating in the Nepal Himalayas and the Bagmati originating in the Kathmandu Valley that regularly flood parts of the Bihar plains. The total area covered by the state of Bihar is 94,163 kmÂ². the state is located between 21Â°-58′-10″ N ~ 27Â°-31′-15″ N latitude and between 83Â°-19′-50″ E ~ 88Â°-17′-40″ E longitude. Its average elevation above sea level is 173 feet (53 m).The Ganges divides Bihar into two unequal halves and flows through the middle from west to east. Other Ganges tributaries are the Son River, Budhi Gandak, Chandan, Orhani and Falgu. Though the Himalayas begin at the foothills, a short distance inside Nepal and to the north of Bihar, the mountains influence Bihar’s landforms, climate, hydrology and culture. Central parts of Bihar have some small hills, for example the Rajgir hills. To the south is the Chota Nagpur plateau, which was part of Bihar until 2000 but now is part of a separate state called Jharkhand.