ISIMIP3a+b: H08 withdraws all groundwstor files #75

The H08 model development team, found the following errors in their submitted files. We
apologize for any inconvenience that may have been caused. The correct files will be uploaded
shortly.

Issue:
The file includes the sum of Terrestrial Water Storage (TWS) and groundwater depletion.
Correction:
To make groundwstor consistent with TWS, the file will be replaced with the renewable groundwater storage (see Hanasaki et al. 2018).

Detailed explanation:

H08 Water balance components:
The H08 global hydrological model comprises five water storage components: soil moisture (SM), renewable groundwater storage (RGW), snow water equivalent (SWE), river water storage (RIV), and reservoir water storage (RES). In groundwater abstraction, H08 first takes water from RGW. When it is depleted, H08 is permitted to continue abstracting groundwater from non-renewable groundwater storage (NGW). Note that NGW neither receives recharge nor produces baseflow, while water is assumed to be available in unlimited quantities. Consequently, NGW takes zero or negative values. The amount of water taken from NGW is recorded, and by modifying the dimensions, the flux [kg/s] can be converted into the storage term [kg/m2]. We refer to this as groundwater depletion (GWD), which can be taken as the sixth component of water storage. RGW corresponds to the groundwater storage output variable in the ISIMIP3 protocol, while there are no output variables corresponding to GWD.

TWS:
The TWS includes RGW while excludes GWD. Because all the terms are compatible with the ISIMIP3 protocol, we adopt TWS and submit the results. Although there seems no corresponding output variable in the ISIMIP protocol, TWSG is useful in analyzing the long-term effect of groundwater overuse. We provide TWSG upon request.

The error:
Recently, it was found out that, by mistake, TWSG was reported as groundwater storage (groundwstor). Figure 1 shows the original submissions, including errors. Because the data includes all the storage components, the seasonal amplitude is substantial. They also exhibit a significant decreasing trend due to the constant and continuous groundwater depletion (GWD). Figure 2 shows the resubmissions. The corrected groundwater storage (RGW) shows a regular seasonal cycle with little trend. For reference, all five storage components and TWS are plotted as well.

Acknowledgement
We thank Amar Deep Tiwari and Franklin Robertson for bringing this issue to our attention.

It has been overlooked that groundwater storage (groundwstor) data in ISIMIP3a is affected by the issue as well.