Impact of Climate Change on Flow Regime in Himalayan Basins, Nepal
Date
2014
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Faculty of Hydrology and Meteorology
Abstract
This research studied the hydrological regime of three glacierized river basins in
Khumbu, Langtang and Annapurna regions of Nepal using the Hydraologiska Byrans
Vattenbalansavde (HBV), HVB-light 3.0 model. Future scenario of discharge is also
studied using downscaled climate data derived from statistical downscaling method.
General Circulation Models (GCMs) successfully simulate future climate variability
and climate change on a global scale; however, poor spatial resolution constrains their
application for impact studies at a regional or a local level. The dynamically
downscaled precipitation and temperature data from Coupled Global Circulation
Model 3 (CGCM3) was used for the climate projection, under A2 and A1B SRES
scenarios. In addition, the observed historical temperature, precipitation and discharge
data were collected from 14
different hydro-metrological locations for the
implementation of this studies, which include watershed and hydro-meteorological
characteristics, trends analysis and water balance computation. The simulated
precipitation and temperature were corrected for bias before implementing in the
HVB-light 3.0 conceptual rainfall-runoff model to predict the flow regime, in which
Groups Algorithms Programming (GAP) optimization approach and then calibration
were used to obtain several parameter sets which were finally reproduced as observed
stream flow. Except in summer, the analysis showed that the increasing trends in
annual as well as seasonal precipitations during the period 2001 - 2060 for both A2
and A1B scenarios over three basins under investigation. In these river basins, the
model projected warmer days in every seasons of entire period from 2001 to 2060 for
both A1B and A2 scenarios. These warming trends are higher in maximum than in
minimum temperatures throughout the year, indicating increasing trend of daily
temperature range due to recent global warming phenomenon. Furthermore, there are
decreasing trends in summer discharge in Langtang Khola (Langtang region) which is
increasing in Modi Khola (Annapurna region) as well as Dudh Koshi (Khumbu
region) river basin. The flow regime is more pronounced during later parts of the
future decades than during earlier parts in all basins. The annual water surplus of 1419
mm, 177 mm and 49 mm are observed in Annapurna, Langtang and Khumbu region,
respectively.
Description
Keywords
Climate change, Water discharge, Water balance, Global warming