Author(s): Romeji Ngangbam; Yadav Mukesh Kumar; Keisam Gunadas; Ng Jayalaxmi; Kh Sushilchandra

Linked Author(s): Ngangbam Romeji Singh

Keywords: Biodiversity; SWAT; TOPMODEL; Sub–tropical; Physio–ecological; Environmental

Abstract: The eastern montane region of Manipur, India, which shares a long stretch of boundary with Myanmar, is abundant in biodiversity and an unperturbed hydrological regime. Maklang–Tuyungbi–Taret lok river system encompassing a catchment area of nearly 2278.8 sq km in a sub-tropical climatic region, can be ascribed as a hydrologically and climatologically undiscovered river system in Manipur Indian Himalayan Region (IHR) mainly due to its remote location, demography and outflow to the Chindwin river in Myanmar. The catchment comes under the Shokvao–Mapithel–Kasom hill ranges in Ukhrul and Kamjong districts of Manipur state, India. The region is rippled with mid-range hills (913 m to 3114 m in elevation) and striped by an array of rivers. The catchment is characterized by a diversified sub-tropical monsoon type of climate with an annual average rainfall of 1,763.7 mm. The Taret lok (literally meaning Seven rivers) and Tuyungbi rivers (located at 24°39ʹ37″ N nd 94°26ʹ34″ E, comprises a multi-component river catchment system. Tuyungbi River originates from Shanshak, Shokvao, Ramva and Leishi situated on the southern part of Ukhrul District, Manipur IHR. Tuyungbi River is located at latitude of 24°39’37’’N and longitude of 94°26’34’’E. Maklang river, originating from Shirui hill ranges in Ukhrul district of Manipur, is one of the major rivers in the system. Adaptive hydrological model analysis in SWAT and TOPMODEL platforms using rainfall and weather data of the most proximate stations i.e. Ukhrul and Tegnoupal (2012 to 2020), were recursively performed to initially estimate the hydrological variables of this ungauged river system. The objective of the study is to correlate the hydrological attributes to the climate dynamics that has altered the river eco-hydrologic system, and find rational solutions for its resilience to climatic and anthropogenic factors. Field hydrographic observations were carried out in selected reaches of the Maklang–Tuyungbi–Taret lok river system, wherein flow discharge were found to range widely from 6.56 to 28.18 m³/s, with a mean sediment discharge of 12.71 kg/day. On the other hand, the spatially distributed hydrological models: SWAT yielded an annual average runoff of 56.4 mm while TOPMODEL estimated an annual runoff of 64.8 mm for the simulation period 2012 to 2020 daily scale. Both the models however gave almost parallel maximum runoff prevailing in the month of October, to an average high of about 147.6 mm. Sensitivity analysis in adaptation of the parameters were conducted to derive a range of environmental flows in the range of 12.6 to 18.8 m³/s incorporating the physio–ecological characteristics of the river system. Viable stream restoration measures to sustain the minimum environmental flows, such as rock chutes, block ramps, etc at selected reaches were suggested as an outcome of the study.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022960

Year: 2022