OTTHYMO projects only have two pollutants defined: TSS and TP. Therefore, those two pollutants are added in the Pollutant Editor in VOSWMM. In OTTHYM project, the pollutant concentrations are defined based on the type of land use. The pollutant source is defined at hydrograph. Each hydrograph can have its own definition about the percentages of each type of land use. In other words, the pollutant (TSS and TP) concentrations can be different for each hydrograph:
- Hydrograph(j)_avgTSS = sum(LandUse_Percent(i) * avgWQ_TSS(i)) / 100
- Hydrograph(j)_avgTP = sum(LandUse_Percent(i) * avgWQ_TP(i)) / 100
where j is the Hydrograph NHYD, i is the land cover type (i.e. paved surface, roof, etc.), and avgWQ_TSS(i) and avgWQ_TP(i) are the average of water quality used in the batch run.
When importing OTTHYMO project to VOSWMM, the Land Use Editor will add n number of Land Use, where n is the number of hydrographs. The parameters of Land Use in VOSWMM:
- Name = Hydrograph NHYD
- Buildup
- TSS
- Function = None
- TP
- Function = None
- TSS
- Washoff
- TSS
- Function = EMC
- Coefficient = Hydrograph(j)_avgTSS = sum(LU_Perc(i) * avgWQ_TSS(i)), where j is the Hydrograph NHYD and i is the land cover type.
- TP
- Function = EMC
- Coefficient = Hydrograph(j)_avgTP = sum(LU_Perc(i) * avgWQ_TP(i)), where j is the Hydrograph NHYD and i is the land cover type.
- TSS
At the Land Use field of each subcatchment in VOSWMM, the percentage of Land Use Assignment will be:
- Land Use (j) = 100, where j is the hydrograph NHYD (or subcatchment NHYD).
- Land Use (k) = 0, where k is the rest of the rows in the Land Use Assignment table.
In this way, the subcatchment j will only use the concentration from the Land Use j that defines the concentration of TSS and TP of that subcatchment.
