Calculating change in storage in Hydrus 2D

[annorris]

Hello,

I am trying to calculate the change in storage on a daily time step in HYDRUS 2D in order to calculate total storage on a daily time step because my modeled time is longer (113 years total) than the allowable 10,000 print times in the Balance.out file.

I have tried to generate a water balance using the outputs in the CumQ.out file on a daily time step and use these to calculate storage but the resulting daily storage volume is not equal to the Volume estimated in the balance.out file for the 10,000 print times. The error between the two is increasingly greater over the modeled period of record. To Calculate the change in storage, I have tried cInfiltr-CEvapor-CumQr-CumQ6 on a daily time step which in my model should equate to Actual Precipitation-Actual Evaporation-Actual Transpiration-NetInfiltration. Initially, the difference between the total storage volume I calculate could be attributed to the impact of reported digits of the values in the output files and is less than the estimated WatBalT[V], but after about 5000 days, the difference between my calculated total storage and the HYDRUS total storage is larger than the estimated WatBalT[V] for that time step and increases over the modeled time. I am uncertain why this is occurring. I also tried CumQA + CumQr + CumQ6 to calculate the daily change in storage, although that still didn't work, and then I tried to run the same calculations on the modeled time steps and then us those values to calculate the daily change in storage but the error was still occurring, regardless of the time step I used to calculate the change in storage.

Could you please provide some guidance on how to calculate change in storage on a daily time step in Hydrus 2d? And could you provide any insight into the potential reason for the error in my calculations of change in in storage?

Thank you!

[Jirka]

HYDRUS calculates at each time step the actual and relative mass balance errors, reported in Balance.out, from boundary fluxes reported in CumQ.out and water and solute volumes (storage) reported in Balance.out. How these errors are calculated is described in the Technical manuals. If you add the correct values, you must get exactly the same results. J.