conservation.
Methods
We conducted field surveys in 10 tributaries of the River Nam Ou, Phongsali Province, Northern Laos, in 2012 (Fig. 1).
Annual mean temperature in Phongsali is 19.8 ºС and annual rainfall is 1,511 mm [23]. Due to monsoonal atmospheric circulation patterns, the Nam Ou Basin is characterized by alternating rainy and dry seasons. Precipitation during summer monsoons results in widespread flooding, and during dry seasons stream discharges are much lower [23]. Approximately 80% of annual runoff occurs during the summer monsoon (June-October). Many Northern Laos summer river levels exceed winter base-flow levels by 1.5–2.0 m, and discharge during wet seasons may increase 5–6x [23].