HISTORICAL HYDROLOGICAL DATA GENERATION FOR UNGAUGED WATERSHED BY WATER BALANCE TOOL

Abstract

: Effective water resources planning and management need accurate historical hydrological data
for simulation and prediction. Many watersheds in Thailand are ungauged and many have unreliable or
incomplete data. This study focuses on using available meteorological data to generate accurate monthly
hydrological data, including direct runoff, evapotranspiration, and groundwater recharge for Lam Takhong
watershed in Buriram Province, Thailand, as a case study. The Lam Takhong River is a tributary of the Mun
River in northeastern Thailand covers an area of 1,560 square kilometers. This study examined nine years of
daily meteorological data, including rainfall, temperature, relative humidity, and solar radiation obtained from
a meteorological station, Buriram 436401, Royal Meteorological Department, from January 1, 2006 to
December 31, 2014. Direct runoff values were evaluated from rainfall data using SCS-CN method. The CN
and λ parameters were evaluated from accurate GIS maps of soil and land-use. Evapotranspiration values were
determined from recorded climatic data using Morton's CRAE method. Results from the study period indicated
that the wettest and driest years were 2008 and 2007, respectively. Groundwater recharge occurred every year
except in 2007 with the greatest recharge occurring in 2011. Water balance was demonstrated to be a valuable
tool for generating accurate historical hydrological data.