Huay Ma Nai catchment

Huay Ma Nai is located in Northern Thailand, Phrae Province, and is divided into 2 nested sub-catchments (total 93 ha), on siltstone and sandstone soils. Slope gradient is 12-50%, and rainfall is about 1100 mm per year.

Land use change: switch from cassava + maize + fallow + orchards to maize mono-crop.

Hydro-meteorological and soil losses surveys

Sediment sampler at Huai Ma Nai catchment (photo: J.-L. Janeau)

Water level and sediment monitoring at weir 1 in Huay Ma Nai catchment (photo: J.-L. Janeau)

Soil erosion measurements with 1 m² plots in Huay Ma Nai catchment (photo: J.-L. Janeau)

Rainfall simulation experiment in Huay Ma Nai catchment (photo: J.-L. Janeau)

Off-site effects measurements of Maethang reservoir

The Maethang reservoir is located at the outlets of several catchments of the Maeyom watershed, including the Huay Ma Nai catchment. Upstream soil erosion generated by surface runoff may alter the quality of reservoir water, generating “off-site” effects: increased sedimentation, excess nutrients and suspended sediment inputs that may induce important environmental changes to the water column with respect to biological communities, and dissolved oxygen and trace element concentrations that may potentially be toxic. The Maethang reservoir is monitored since 2002.

Spillway of Maethang reservoir (photo: J.-L. Janeau)

Reservoir Area = 220 ha

Irrigated Area = 3520 ha

Maximum Depth = 43 m

Storage Volume = 31 million m³