After the simulation runs, the Water Balance window becomes available for subcatchments, Addhyds, and LIDs.
Start by selecting one of the subcatchments, such as NHYD 1. In the Simulation Table, click on the Water Balance icon to open the corresponding results.
Year Tab
The Water Balance window includes tabs for Year, Month, and Season. This explanation focuses on the Year tab, but the interpretation applies similarly to the other tabs.
All values are displayed in cubic meters.
- Precipitation is the total input volume. Since no temperature data was assigned, the model considers all precipitation as rain—no snow or snowmelt is calculated.
- ET (Evapotranspiration) and GWI (Groundwater Infiltration) are outputs that leave the system.
- INFIL is infiltration within the subcatchment and is treated as an internal process, not an output.
- Runoff represents the surface flow leaving the subcatchment.
- ΔStorage is the change in stored water within the system.
In this example, for NHYD 1:
ΔStorage = Precipitation – ET – GWI – Runoff = 4390 – 372.783 – 4 – 2151.585 = 1861.63 m³
Addhyd 4 Interpretation
Now, select Addhyd 4 in the Water Balance window.
This addhyd aggregates the values from subcatchments NHYD 1 and NHYD 2. Since no LID exists upstream of Addhyd 4, the presented values are just the summation of the Addhyd’s upstream.
LID Example – Soakaway Pit
Next, select the Soakaway Pit (NHYD 5).
In the LID system, the only input is inflow from upstream, while the outputs are:
- LID GWI
- LID ET
- Outflow
- Overflow
- Underdrainflow
So, the ΔStorage is calculated as:
ΔStorage = Inflow – LID GWI – LID ET – Outflow – Overflow – Underdrainflow
= 4303.166 – 20.93 – 0 – 1207.458 – 3061.99
= 12.93 m³
Important Note 1:
LID GWI should always be less than or equal to LID Infiltration. If it is not, it likely indicates incorrect properties for the native soil, which should be revised.
Addhyd 8 – With LID Upstream
Finally, select Addhyd 8, which has an LID (the soakaway pit) upstream.
- Precipitation, ET, GWI, Runoff, and ΔStorage here are the totals from all upstream subcatchments (NHYD 1, 2, and 3) and LIDs.
- INFIL includes both the subcatchments’ infiltration and the LID infiltration.
Important Note 2:
The Runoff shown in Addhyd 8 represents the total runoff the addhyd’s upstream.
