Huay Ma Nai catchment
The 93.2 ha Huay Ma Nai catchment is located in northern Thailand, in the Phrae Province. Elevation ranges from 380 to 490 m above sea level and slopes range from 15 to 65%. Huay Ma Nai catchment is included in the Maethang watershed (121 km²).
The coordinates of the Huay Ma Nai catchment are 100°23’40’’E, 18°13’20’’N.
The climate is tropical sub-humid. It usually can be divided into 3 seasons: a dry and fresh season lasting from October to February, a dry and hot season lasting from March to April and a wet and hot season from April to October. The annual rainfall measured in the catchment over the past 15 years varies from 1028 to 1493 mm. In average, about 90% of rainfall occurs between May and October. At Phrae Airport the maximum annual rainfall recorded over the past 50 years is 1461 mm.
The stream flow is intermittent. Currently, 2 sub-catchments are monitored (Huay Ma Nai and Weir 1).
The most common rock types are siltstone and sandstone.
The most common soils are Inceptisol (20%) and Alfisol (80%).
Vegetation and land use
Since 1999, soybean and fruit trees cultivation has been replaced by intensive corn. Corn is now grown as a single crop within the catchment since 2004.