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How water, as an indispensahk means of subsistence is going to be provided for the future generations. with the ever increasing population, is a
serious matter in question. Water crisis is predicted in not far a future due to
rise in demand for this vilal life suhslame. Thcrcrore it is not only necessary
to have a clear understanding of vater needs m: threct human consumption. agricultural. and industia! projects but to plan ror the most economical and
Jficicnt use of water in these areas. Afor the design of pressurized irrigation systems, data are needed regarding crop water us based upon environment,
soil. water and climatological conditions. In this study water need in a pressurized irrigation system in Guilan area, mainly Rasht cnvirionmental
conditions has been evaluated. In an agicuhural pattern of tea plantation (50%), groves and orchards (16.5%), summer crops (4.5%), forage crops
(4%), and dry farming (25%) in Rasht and Foumnat, water need was determined using Blaney and Criddle method. Maximum monthly water need
was 210, 115.5, 170, 172 mm for tea, groves and orchards, summer crops and forages respectively, using pressurized irrigation system of 95C;'c, efficiency.
Yearly water need is respectively 480, 268, 350 and 430 mm for tea. groves and orchards, summer crops and forages, taking into account the overall
efficiency. Net yearly volume of water needed at the beginning of the irrigation netwok for the said plantation pattern is 4257 3m/ha.