The research is aimed to study influence of rainfall distortion on hydrograph lag time in three
periods of normal climate (1966-1987), transition (1988-2008) and climate change (2009-2015)
over the first-order stream watershed covering natural hill-evergreen forest in mountainous land.
The results found the total average annual rainfall 2,046.5 mm from the periods of 2,084.1 mm
(plus another fog drift 2.3% of annual rainfall) for 1966-1987, 2,021.8 mm for 1988-2008 and
1,993.3 mm for 2009-2,015; falling 155 rainy days; humidity ranging 58.5-89.7%, pan evaporation
3.1 mm/day; average temperature 16.7-23.3 oC with extreme maximum 35 oC and minimum
4.5 oC, and wind speed 5.4-22.6 km/hr. Measuring streamflow was approximately 1,2233 MCM/
km2 which divided to wet flow 57% and dry flow 43%. Accordance with 3-period rainfall of
normal climate (1966-1987), transition (1988-2008), and climate change (2009-2015) played
vital role in decreasing lag time 18, 13, and 9 hours due to the distortion of rainfall quantity
but the first-order stream watershed covering with dense-nature hill-evergreen forest was still
functioned on its flow regime without interruption. The abundances of organic matter, clay
minerals, high soil porosity, deep soil profile and plant cover over 80% are regulated to rainwater
absorption for continuously feeding streamflow all the year, even the driest and wettest years.
Keywords
Watershed hydrology; First-order stream watershed; Hydrograph lag time; Soil water
ENIVRONMENT ASIA
Published by : Thai Society of Higher Education Institutes on Environment Contributions welcome at : http://www.tshe.org/en/
By using our website, you acknowledge that you have read and understand our Cookie Policy and Privacy Policy.