age of vegetation in clalculations

Adrienn, The calculation of irrigation water required in WEc1 does not accommodate the age of the vegetation. This calculation is very rough; the factors - evapotranspiration rate in July, vegetation species, density, and microclimate factors, and water delivery system and controller efficiencies - entail so much variability that another variable based on vegetation age would not add to our certainty that we are successfully predicting irrigation requirements.

Adrienn, if I'm understanding your question correctly, you could effectively achieve this by separating the vegetation by age, and assign a different ks, kd and kmc. For example, let's say that for variety, you choose to plant 10,000sf of saplings of vegetation type x, and 15,000sf of mature 5-10 year old vegetation type x. If the saplings require more irrigation, you could use the average value for ks, kd and kmc respectively. For the more mature vegetation, you could assign a low ks,kd and kmc. If, however, the vegetation when established is expected to require little to no irrigation, then I would just use the low values for all and not make the distinction. I hope that helps, and that I interpreted your question correctly.

William, you make an interesting point, which I had not considered. But the project team might want to anticipate the review team asking for some sort of technical back up if assumptions of ks and kd differ from reference guide values. Changes in kmc are interesting to think about (thick vegetation creating a more water-efficient micro-climate) but would probably be very hard to document. As interesting as the idea is, the project team might want to be satisfied that they have the 50% reduction by means that are likely to be more familiar to the review team.

I was thinking more simplistic than that. On your table in the template, you can input two separate line items for the vegetation type. Let's say it's a tree, just as an example. In line item 1, for the tree saplings, you can label it tree, and use the tree average values from the chart in the reference guide: .5, 1 and 1. In line item 2, for the 5-10 year trees, again label it tree and use the low values from the chart: .2, .5 and .5. Personally, I think it would be better/easier to just use the low values for all if they are anticipated to need little water once established. But, I don't see any reason why this approach wouldn't work. The values would be completely justifiable from the table in the reference manual.