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A study was carried out in Kashan to make optimum usage of water resources in arid zones so that
green areas could be fully established and develop. Determination of crop water requirement is essential in irrigation scheduling and optimum usage of water resources. In this research, long-term climatological data (27 years), Penman- Monteith formula and plant characteristics were used to determine water requirement for six kinds of plant cover during irrigation season with 10 day irrigation intervals.
The six kinds of plant cover were:
I) Intensive arboriculture with rather drought tolerant trees (i.e. Ash, Elm from deciduous trees
and Shiraz cypress from evergreen trees)
II) Like the first kind, but with low-density plantation
III) Intensive arboriculture with highly drought tolerant trees (i.e. Varnish tree, Pistachio-tree from
deciduous trees, and Arizona cypress, Arbor vitae from evergreen trees)
IV) Like the third group but with low-density plantation
V) Single arboriculture (one or two row arboriculture in streets)
VI) Green grass spaces
After determination of the effective rainfall, the net water requirement of different kinds of plants
has been estimated for ten day periods. This method seems reliable for use in other similar regions.