Clarification on Water Quality Variable Mapping and Units for SWAT+ Calibration

[Tulsi Ram Pokhrel]

Hi Celray,
Greetings!

Thank you so much for your continued support throughout this process.

I have a question regarding the preparation of monthly in-situ water quality data for calibration in SWAT+ toolbox. My dataset includes the following parameters collected from river water at the watershed outlet:

• Nitrogen as (NO₃ + NO₂), mg/L
• Total N (Ammonia as NH₃), mg/L
• Total N (Ammonia as N), mg/L
• Dissolved Phosphorus, mg/L
• Total Phosphorus, mg/L
• Total Dissolved Solids (TDS), mg/L
• Total Solids (TS), mg/L
• Total Suspended Solids (TSS), mg/L

I would greatly appreciate your guidance on the following:

1. Could you please help me map each of the above variables to their corresponding SWAT+ Toolbox output variables (e.g., River Nitrate (NO₃), River Nitrite (NO₂), River Ammonia (NH₄), River Total Nitrogen, River Total Phosphorus, River Sediment, River Soluble Phosphorus, River Sediment Phosphorus)?
2. Additionally, I would like to confirm the required units for these variables in SWAT+. For example, should the observed values be converted from mg/L to kg/day or kg/month as per the Toolbox documentation before calibration?

Thank you again for your time and support.

Best regards,
Tulsi
Research Scholar