These figures suggest the RWCF ammonia load plays a major role in the ammonia concentration in the channel. This is important because ammonia concentration accounted for 60% of the variability in a stepwise regression model describing total BOD in the DWSC. The regression model contained both ammonia concentration and carbonaceous BOD and accounted for 91% of the total BOD variance in 2001 (n=103). Substituting total pigment for the carbonaceous BOD only decreased the total variance explained by the model to 86%. The results were similar for 2000. This graph further suggests that although the ammonia from the RWCF is relatively small compared to the potential ammonia available from the breakdown of the upstream TON, ammonia from the TON isn't sufficiently large (or breakdown fast enough) to mask the impact of the RWCF ammonia on the DWSC. This finding also supports the use of BOD data and not oxygen demand from TON-N to assess the contribution of upstream load to oxygen demand in the DWSC.