Jornal de Geologia e Geofísica
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Study on Climate Change Induced Precipitation Variability and Its Impact on High Mountains of Nepal (A Case Study of - Kaligandaki River Basin, North of Nepal)

Lekha N. Bagale

The goal of this study is to develop different scenarios of water resource availability in near upstream of Kaligandaki River basin, under climate change-induced parameters such as precipitation and temperatures variability, considering a potential doubling of the atmospheric CO2 concentration in the next 100 years. Climate models suggest that global warming could bring warmer, drier conditions to Nepalese high Mountains due to the large topographical differences of the climate parameters. Although precipitation increases are projected by some models, on the glaciers of the Nepalese high Mountains, a detailed knowledge of mass-balance observation and discharge measurement are considered and the combination of both will be analyzed by means of either Water Balance Model (WatBal) or General Climate Model (GCM) with multi criteria model performance evaluation. To obtain reasonable and ensemble result, the discharge measurements should be taken during the melting season which demonstrates that timing of runoff. In most cases, the Water Balance Model CLIRUN3 was combined with 20 years of basic climate information records (precipitation, potential evapotranspiration and water flow) to simulate monthly river runoff in the river basin. Ultimately the flow of river is part of the watershed while the others belong to forest lands. The model will be calibrated and run for both watersheds under scenarios with temperature increments of +1 and +2°C, while the precipitation changes considered were ±15% for the locality and ±20% for the overall river basin. It was observed that the monthly runoff tends to considerable decrease of the mean value in the watersheds when temperature increases and precipitation decreases. If both temperature and precipitation increase, the mean runoff value in the region will be reduced by considerable amount as 5 to 35% from monsoon to non-monsoon season. In the basin of the locality, this will also cause to potential evaporation. Thus, soil moisture and water availability may decrease over much of Kaligandaki river basin with serious consequences for rained and irrigated agriculture, urban and water supplies, hydropower and ecosystems. However, the assessment of global warming impacts on locality is an uncertain task because the projections of different models vary widely, particularly for precipitation, and because it performs poorly in reproducing the observed climate condition of Kaliganadaki. At the end, this will help to formulate numerical flow line glacier model on high Mountains of Nepal at upstream of Kaligandaki river, also this paper concludes with a brief discussion of some other areas of uncertainty in the hydrological modeling of Kaligandaki River flows and possible alternative, external forcing mechanisms for flows in the next few decades.