Little is known about the particular climate in Lam Pa Chi Basin (Manton et al., 2001) which due to its Southwestern mountain range is supposed to differ from the typical either Pacific or Himalayan influenced Southeast Asian climate. It is influenced by the southwest monsoon during the period from May to October and also the tropical cyclonic storms from the South China Sea at the end of the rainy season from September to October (Biltonen et al., 2003). According to the Köppen classification, the LPCRB belongs to the Aw group, with hot tropical climate (with average temperatures of all months above 18°C) including wet summers and relatively dry winters. 

Temperatures in the hottest month, April, reach an average temperature of 32°C while December is  the coldest with an average of 25°C.


According to the precipitation data available (3 stations) the annual precipitation ranges from 990 to 1180 mm. Almost 85% of the total precipitation falls during the wet season from May until November. During the rainy season heavy rain events occur causing one of the main environmental problems in the region: soil erosion. Figure 6 shows the inter-annual variation of monthly precipitation and discharge for the period 1967-2013 at the three stations. For instance at the station 47161 located in the center of the basin at 110 m.a.s.l., it can be seen that May, September and October are the months with the highest precipitation with average values of 160, 203 and 261 mm, respectively, while December until February are the driest months with average values under 15 mm.


For comparison, the average values for precipitation and discharge for Thailand are shown in the following figure:

This shows that the Lam Pa Chi river basin is exposed to a particular climate compared to the Thai mean, with two monsoon peaks, one in May and one in October. Mean rainfall is higher for entire Thailand during the whole year compared to Lam Pa Chi, only in October the rainy season by far exceeds the Thai mean. Consequently, discharge also differs with two peak flow seasons in May and October.


References and further reading:

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LDD (2000) Soil Erosion in Thailand. Land Development Department, Ministry of Agriculture and cooperatives.

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