Oxygen can be consumed by organisms in the sediment. This process is referred to as sediment oxygen demand (SOD). Measurement of SOD can be undertaken by measuring the change of oxygen in a box on the sediment (benthic respirometer).
The change in oxygen deficit due to consumption by sediment is described as
where 
*  is the depth of the river [m]
*  is the SOD 
* D is the saturation deficit .
* is the reaeration rate [].
The range of the SOD is typically in the range of 0.1 – 1  for a natural river with low pollution and 5 – 10  for a river with moderate to heavy pollution.