Thongjaorok River & its Present State

The Thongjaorok River a key rain-fed waterway in Manipur, originates in the Laimaton hills, flows through Bishnupur, and empties into Loktak Lake, playing a significant role in the region’s ecology and hydrology. Historically, it maintained a balanced, rocky ecosystem, but in recent years, it has become a major source of siltation, bringing sediments into the Loktak lake. It rises about 2 km west of Laimaton village in the Laimaton range (1664m above sea level). It traverses rugged hills for about 5 km and approximately 7 km through the plains, passing through Bishnupur and Khoijuman before entering Loktak Lake near Tekra Pat. Thermoluminescence dating of the river’s terrace sediments indicates an age of roughly 14,800 years.
The river flows through an asymmetrical basin consisting of rocks from the Disang and Barail groups. In the past, the river was characterized by an abundance of boulders, rocks, and sand, which helped regulate its current and maintain soil moisture in surrounding areas. Thongjaorok river was considered a source of life that brought prosperity to the surrounding Khoijuman village, with tales of overflowing, nutrient-rich soil in the past. The basin covers about 28.55 sq. km, characterized by an asymmetrical shape with tributaries on the western side of the hills.Traditionally a source of water for agriculture and a source of gravel/boulders for construction.It acts as a crucial water source, though it faces severe degradation due to unregulated sand and stones quarrying, causing it to dry up and impacting local livelihoods.
The myth of the Thongjaorok River in Manipur canters on a belief that its waters and fish were completely independent of the adjacent Loktak Lake, with legends claiming no sand from the river entered the lake and no fish migrated between them. This, along with the belief in the Thongjaorok Lairembi (a guardian goddess), highlights the river’s deep cultural, spiritual, and ecological significance in the Moirang region. The core belief held that despite their proximity, the Thongjaorok River and Loktak Lake operated in isolation, with no exchange of silt or aquatic life. In Meitei mythology, the river is presided over by the deity Thongjaorok Lairembi, one of the river goddesses revered in the Sanamahism tradition. The river is often associated with the folklore of the Moirang region, which is famous for the epic love story of Henjunaha and Lairoulembi.
This long-believed myth has been proven false by environmental studies. The Thongjaorok is now known to be a major contributor of silt, sand, and pollution, accelerating the degradation of Loktak Lake. Due to deforestation and climate change, the formerly perennial river has largely become a seasonal stream, contrary to its mythical, ever-flowing reputation. Traditionally, there was a belief that no sand from the Thongjaorok River flowed into Loktak Lake and no fish from the lake migrated into the river. Environmental studies, now show that deforestation and environmental changes have turned the river into a primary cause of siltation in Loktak Lake. It now carries substantial amounts of clay, pebbles, and plastic waste into the lake.
The river is prone to breaching its banks, resulting in flooding of agricultural fields, such as in the Kwashiphai and Khoijuman area. Concerns over its degradation have led to local efforts, such as tree plantation drives along the riverbank, as reported by E-Pao. The river remains vital for the irrigation of paddy fields in the Bishnupur district specially for Toubul, Khoijuman and Kwashiphai but faces significant challenges from rapid environmental degradation. Traditionally a source of water for agriculture and a source of gravel/boulders for construction. Uncontrolled excavation has led to the depletion of mineral resources and caused the river to dry, resulting in a loss of soil moisture and fertility in surrounding areas.
Out of the total catchment’s area about 15.75 sq. km lies in the hilly terrain and remaining 12.8 sq.km in the plain. Total length of the river from its source to the confluence with the Loktak Lake at Tekra Pat is about 15.5 km, out of which about 8.5 km is spread in the hilly and remaining 7 km is in the valley portion. Though it is a very small, but one of the most active rivers of the Loktak catchment which contributes maximum amount of debris to the lake.
Geologically, the study area forms a part of Indo-Myanmar Ranges. The geological formations occurring in the basin belong to the Disang, the Barail groups of rocks and recent alluvium. At most of the places in the area, the Disang-Barail contact is of gradational nature but in the Thongjaorok basin it forms a structural contact due to a reverse fault. The Disang Group of rocks in the study area is observed near Chinil Ingkhol as small outcrop. It is characterized by dark grey colour, thinly-laminated, highly splintery shales. The overlying Barail Group of rocks occupies the rest of the catchment’s area. The Barail Group of rocks is characterized by the rhythmic intercalations of shales and fine-grained sandstones, which gradually grade into coarse-grained, thickly bedded sandstones. Sedimentary structures, like ripple-mark, cross-beddings and trace fossils are very common, which indicate shallowing of the depositional basin.
In order to minimize the erosion in the catchments area and siltation of the Loktak Lake, it is necessary to check the jhum cultivation and the local inhabitants should be made aware and be encouraged for practicing terrace cultivation on moderate to gentle hill slopes. The high hill slopes should be reserved for forests. Low-lying water logged areas near the Loktak Lake can be best utilized for the aquaculture. The Bishnupur district administration has issued bans on quarrying and excavation to protect the river. Weirs and mini-barrages  are being constructed for irrigation and water management.
Writer can be reached at:sjugeshwor7@gmail.com