بررسي ويژگي هاي هيدروليكي روش آبياري نشتي- زيرسطحي و توسعه روابط حاكم بر جريان

Investigation of hydraulic characteristics and developed equations for subsurface leaky irrigation system

آﺑﯿﺎري ﻧﺸﺘﯽ-زﯾﺮﺳﻄﺤﯽ ﯾﮑﯽ از روش ﻫﺎي ﻧﻮﯾﻦ آﺑﯿﺎري اﺳﺖ ﮐﻪ ﺑﻪ دﻟﯿﻞ ﻗﺮارﮔﯿﺮي ﻟﻮﻟﻪ ﻫﺎ در زﯾﺮ ﺳﻄﺢ ﺧﺎك و ﺗﻮزﯾﻊ آب در ﻣﻨﻄﻘﻪ ﺗﻮﺳﻌﻪ رﯾﺸﻪ ﺑﺎ ﻓﺸﺎر ﮐﻤﺘﺮ از ﯾﮏ ﻣﺘﺮ ﺳﺘﻮن آب ﻣﯽ ﺗﻮاﻧﺪ ﮐﺎرﺑﺮد زﯾﺎدي در ﺑﺎﻏﺎت ﮐﻮﭼﮏ ﺑﺎ ﻣﺤﺪودﯾﺖ ﮐﻤﯽ و ﮐﯿﻔﯽ آب داﺷﺘﻪ ﺑﺎﺷﺪ. ﻃﺮاﺣﯽ ﺑﻬﯿﻨﻪ اﯾﻦ روش ﻫـﺎ ﻧﯿﺎزﻣﻨـﺪ ﺷﻨﺎﺧﺖ ﺗﺄﺛﯿﺮ ﭘﺎراﻣﺘﺮﻫﺎي ﻣﺨﺘﻠﻒ ﺑﺮ ﺳﺮﻋﺖ ﻧﻔﻮذ آب ﺑﻪ داﺧﻞ ﺧﺎك و ﺷﮑﻞ ﭘﯿﺎز رﻃﻮﺑﺘﯽ اﺳﺖ. ﺑﻪ ﻫﻤﯿﻦ دﻟﯿﻞ در اﯾﻦ ﺗﺤﻘﯿﻖ ﺳﺮﻋﺖ ﻧﻔـﻮذ آب ﺑـﻪ داﺧـ ﻞ ﺧﺎك در ﻣﺮاﺣﻞ ﻣﺨﺘﻠﻒ آﺑﯿﺎري ﺑﺮاي دﺑﯽ ﻫﺎي 0/2 ،0/1 و 0/35 ﻟﯿﺘﺮ ﺑﺮ ﺛﺎﻧﯿﻪ و ﺣﺠﻢ آب ﮐﺎرﺑﺮدي 60 ،30 و 90 ﻟﯿﺘﺮ ﻣﻮردﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓـﺖ. ﻫﻤﭽﻨـﯿﻦ ﭘﺮوﻓﯿﻞ ﻋﻤﻘﯽ رﻃﻮﺑﺘﯽ ﺧﺎك ﻧﯿﺰ در اﻧﺘﻬﺎي ﻫﺮ آزﻣﺎﯾﺶ ﺑﺎ ﺣﻔﺮ ﮔﻮداﻟﯽ در ﻧﺰدﯾﮑﯽ ﻣﻨﺒﻊ ﻧﺸﺖ آب اﻧﺪازه ﮔﯿﺮي ﺷﺪ. ﻧﺘـﺎﯾﺞ ﻧﺸـﺎن دﻫﻨـﺪه ﺗـﺄﺛﯿﺮ ﺑﯿﺸـﺘﺮ دﺑـﯽ ورودي آب ﺑﻪ داﺧﻞ ﺳﯿﺴﺘﻢ ﺑﺮ ﺳﺮﻋﺖ ﻧﻔﻮذ آب داﺧﻞ ﺧﺎك در ﻣﺮﺣﻠﻪ ﺗﻐﺬﯾﻪ ﺑﻮد. در ﻣﺮﺣﻠﻪ ﺗﺨﻠﯿﻪ ﻧﯿﺰ ﺳﺮﻋﺖ ﻧﻔﻮذ آب ﺑﻪ داﺧﻞ ﺧﺎك ﺑﯿﺸـﺘﺮ ﺗﺤـﺖ ﺗـﺄﺛﯿﺮ ﺣﺠﻢ آب ورودي ﻗﺮار داﺷﺖ. ﺑﺮرﺳﯽ ﭘﯿﺎز رﻃﻮﺑﺘﯽ در اﻧﺘﻬﺎي آزﻣﺎﯾﺶ ﻧﯿﺰ ﻧﺸﺎن داد ﻧﻔﻮذ ﻋﻤﻘﯽ آب ﺑـﺎ اﻓـﺰاﯾﺶ دﺑـﯽ ورودي ﺣـﺪود 17% اﻓـﺰاﯾﺶ ﯾﺎﻓـﺖ. ﻣﺪل ﻫﺎي ﺗﻮﺳﻌﻪ داده ﺷﺪه در ﻓﺎز ﺗﻐﺬﯾﻪ و ﻣﺮاﺣﻞ ﺗﺨﻠﯿﻪ و ﺗﻐﺬﯾﻪ در ﺣﺎﻟﺖ ﻏﯿﺮآزاد داراي ﺿﺮاﯾﺐ ﺗﺒﯿﯿﻦ 0/77 ،0/66 و 0/69 ﺑﻮده ﮐﻪ ﻧﺸﺎن دﻫﻨﺪه دﻗﺖ ﺑﺎﻻﺗﺮ آن ﻫﺎ ﻧﺴﺒﺖ ﺑﻪ ﺳﺎﯾﺮ ﻓﺎزﻫﺎي آزﻣﺎﯾﺶ اﺳﺖ.

Subsurface leaky irrigation systems are one of the novel irrigation systems developed in recent years. In this system, the pipes are located below the soil surface and water is distributed in root zone with a very low pressure of less than one meter water column. This system can be widely used in small gardens with quantitative and qualitative water restrictions. Optimal design of these systems depends on the effect of different parameters on water infiltraion and wetting pattern. For this reason, the volume of water infiltration is investigated at different Subsurface leaky irrigation strategies. The inlet discharge and volume of applied water at each strategy differs from 0.1, 0.2 and 0.35 liters per second and 30, 60 and 90 liters, respectively. The humidity of the soil is also measured in wetting area at the end of each experiment. The results show that inlet discharge in feeding stage has dramatic effect on water infiltration, while the volume of applied water has more effects in discharg stage. Measurements of wetting pattern at the end of experiments also showed that water infiltration increased by 17% with increasing the inlet discharge into the system. The developed models in feeding phase and discharge and feeding phase in non-free surface flow had correlation coefficients of 0.69, 0.77 and 0.66, respectively, which show their higher accuracy in comparison with other phases.