Shouldn't sustainable water management include charging the water users for exactly the water they consume, i.e., evapotranspirate?I replied with
We can find this with remote sensing/satellite imagery now.
It is impossible to know exactely what every user extracts from aquifers, it is also impossible to know well how much water the irrigator really uses as with the older techniques a lot of water comes available for downstream users and is not lost...
So maybe we should charge users only for what they consume (evapotranspirate)?
That's what they do now [in some places], charge for "consumptive use" -- net water loss.To which JH replied:
OTOH, EV water is less than that, since some "consumption" goes to g/w (the environment, other users)...
Although it may make sense to charge for EV only (measurement issues aside), it may encourage people to use wasteful irrigation methods, methods that may NOT allow non-EV "waste" to be used elsewhere...
They use some average relation EV / returnflow but of course this depends on soil moisture, season, crop, etc., so actually (remotely) measuring it would be better I think.*Indeed. So what do you guys think?
Percolation to g/w could be pumped up by water users downstream which would be charged as well exactely for their consumption = EV. Natural areas (environment) could also consume from this aquifer, depending on catchment characteristics. Question of good water accounting, isn't it?
Anyway, maybe we'll better continue disccusing in the comment section of the post on this issue?
Should irrigators be charged for ET, as the BEST method? Please tell us the costs and benefits.
* JH continues: As far as I know, the only place where these things are pilotted so far is in the Hai Basin in China [pdf]. Evapotranspiration quotas, monitored by remote sensing. That's an interesting future. Of course you can think on pricing and trading schemes behind this, but the main problem in agricultural water management is right now that no proper monitoring of water consumption can be done by administration or private owner, it's too easy to cover up groundwater abstractions, no way to control that. If monitoring is ok, quotas can be traded without any problem and a healthy 'water economy' might be viable.