camiloramirezgo
commented
3 years ago Remake the calculations for groundwater stress. The Groundwater footprint needs to be properly calculated (as of the nature paper) and the right aerial extent for each cluster needs to be accounted. Then, this can be related to the water stress index. However, for what I am seeing the water stress index will yield much higher values than the water stress indicator.
Given the focus of the paper is a specific aquifer, I understand the authors’ choice of a groundwater stress indicator. However, they do not provide a clear definition (formula) of their measure of groundwater stress, aside from providing a citation (Section 2.2, p. 7).
Specifically, what is groundwater footprint and how is it measured? Is the groundwater stress typically an indicator for the entire aquifer, or could it vary within the aquifer? (For example, see your ref # 45, Fig. 2 for spatially varying groundwater groundwater stress calculated for U.S. aquifers). Do you have any evidence that indicates certain parts of the NWSAS are more stressed than others? If so, how would these relate to your GIS-based clusters?
What is the basis for the scale of groundwater stress measurements used in Fig 5, where <1 is low and >20 is extremely high?
Moreover, given the SDG theme in the paper, have the authors considered using SDG 6.4.2 Water Stress Indicator (%)? This is:
*Water Stress (%) = 100TotalFreshwater Withdrawal / (TotalRenewableWaterResources-Environmental FlowRequirements)**
Source: www.fao.org/nr/water/aquastat/data/popups/itemDefn.html?id=4550
Can you relate SDG 6.4.2 water stress indicator to your groundwater stress indicator? According to the FAO, the three countries situated over (and relying on) the NWSAS--Libya, Tunisia and Algeria—are all “critical” in terms of water stress (see here). Yet, the baseline groundwater stress indicator used in this paper suggests the stress level is “medium to high”, which is two levels below extremely high (and does not sound particularly bad). If total freshwater withdrawals in these three countries are dominated by groundwater withdrawals, then wouldn’t one expect the two metrics to be broadly consistent?