Groundwater Recharge

[hbeaugrand]

Hi there,

I am trying to calculate groundwater recharge with outputs from the UBC Watershed Model, emulated in RAVEN. I understand that within the 'WatershedStorage' output the 'Soil Water[2]' and the 'Soil Water[3]' columns are representative of the upper groundwater storage and lower groundwater storage, respectively. Is this column representative of recharge or total storage? And if total storage, can we calculate groundwater recharge by examining the differences in the daily reported storage? Thanks for your guidance on this.

Best,

HBeaugrand

[jrcraig]

Hi HBeaugrand,

The watershed storage file contains the watershed average storage in groundwater - SOIL[2] is the shallow groundwater and SOIL[3] is the deep groundwater - if you want watershed-averaged recharge estimates, then you can go about getting them in the way you indicated. The best way to get fine resolution recharge distributions is to use the custom output option. For example, to get monthly average recharge in each HRU, you can use the following command in the .rvi file:

:CustomOutput MONTHLY AVERAGE SOIL[2] BY_HRU
:CustomOutput MONTHLY AVERAGE SOIL[3] BY_HRU

And use the same differencing to estimate recharge rates.

That being said, be wary of relying on the UBCWM water exchange with groundwater as a proxy for actual system recharge - UBCWM is designed to accurately characterize stream discharges, but without additional data, recharge estimates could be inappropriately low or high to accommodate, e.g., inaccurate estimates of AET. If you are only judging the quality of your model and calibration with stream discharge observations only, you should take recharge estimates with a grain of salt.

[Michaelorack]

Hi everyone,

I use MIKESHE for simulation of water table rise in shallow water tables. after analysis of mass balance in a one cell case, I saw rechage to groundwater was greater than infiltration rate Is it possible?


Thanks

[rchlumsk]

Hi Michaelorack

You would have to review the mass balance on the groundwater cells to see if there are any other sources or processes providing water; it may be possible there is another process moving water into cells other than infiltration. It may also be possible that the cell already had excess water storage such that a greater water flux was provided to groundwater than was provided from infiltration. However, it does seem peculiar and is likely worth looking into.

I cannot comment too much further as I am not as familiar with MIKESHE, but there are a couple ideas for you to check.

Cheers,
Rob