Effects of the sediment load of a tropical North-Australian river on water column characteristics in the receiving impoundment
Griffiths, D. J.; Faithful, J. W.
The Burdekin River drains a catchment of ca. 130,000 km² in north-eastern Australia and supplies water to Lake Dalrymple (20°36'S, 147°11'E) the principal watersupply for the Burdekin Irrigation Area. The catchment is characterized by long dry periods interspersed by intense wet season rainfall events. River flow generated by these events invariably has a high concentration of suspended silt and clay derived from natural weathering and soil erosion. The sediment load of the two main inflowing arms of the river affects density gradients within the impoundment and the distribution of the sediment load in the water column is, in turn, affected by temperature gradients. The high turbidity of surface water strongly attenuates the downward flux of photosynthetically active radiation but causes considerable backscatter. Phytoplankton biomass in the lake is limited by light availability and makes a significant contribution to light attenuation only after a long period of no river flow (i.e. low turbidity).