ﺑﺮرﺳ ﯽ آزﻣﺎﯾﺸﮕﺎﻫﯽ ﺗﻮزﯾﻊ رﻃﻮﺑﺖ در ﺳﯿﺴﺘﻢﻫﺎي آﺑﯿﺎري ﻗﻄﺮهاي ﺳﻄﺤﯽ و زﯾﺮﺳﻄﺤﯽ

Laboratory Study of Moisture Distribution in Surface and Subsurface Drip Irrigation Systems

ﺗﻮزﯾﻊ رﻃﻮﺑﺖ در ﺧﺎك ﺗﺤﺖ ﺗﺄﺛﯿﺮ ﻋﻮاﻣﻞ ﻣﺨﺘﻠﻔﯽ از ﺟﻤﻠﻪ دﺑﯽ و ﻧﻮع ﺳﯿﺴﺘﻢ ﻫﺎي آﺑﯿﺎري ﻣ ﯽﺑﺎﺷﺪ. در اﯾﻦ ﭘﮋوﻫﺶ ﺳﻌﯽ ﺑﺮاﯾﻦ اﺳﺖ ﮐﻪ ﺗﻮزﯾﻊ اﻓﻘﯽ و ﻋﻤﻮدي رﻃﻮﺑﺖ، ﺗﻮزﯾﻊ ﻣﺠﺪد رﻃﻮﺑﺖ در ﺧﺎك و ﻣﺴﺎﺣﺖ ﺧﯿﺲ ﺷﺪه در ﭘﺎﯾﺎن آﺑﯿﺎري در دو ﺳﯿ ﺴﺘﻢ آﺑﯿﺎري ﻗﻄﺮهاي ﺳﻄﺤﯽ و زﯾﺮﺳﻄﺤ ﯽ ﻣﻘﺎﯾﺴﻪ ﮔﺮدد. ﺑﺪﯾﻦ ﻣﻨﻈﻮر آزﻣﺎﯾﺸﯽ در ﻗﺎﻟﺐ ﯾﮏ ﻣﺪل ﻓﯿﺰﯾﮑﯽ ﺷﯿ ﺸﻪ ﺑﺎ اﺑﻌﺎد1 ×1/20×0/5 ﻣﺘﺮ، دو ﻋﻤﻖ ﻧﺼﺐ ) 0و 30 ﺳﺎﻧﺘ ﯽﻣﺘﺮي( و ﺳﻪ دﺑ ﯽ)Q2=4 ،Q1=2 و Q3 =8 ﻟﯿﺘﺮ ﺑﺮ ﺳﺎﻋﺖ( ﺑﻪﺻﻮرت ﻓﺎﮐﺘﻮرﯾﻞ و در ﻗﺎﻟﺐ ﻃﺮح ﭘﺎﯾﻪ ﮐﺎﻣﻼ ﺗﺼﺎدﻓﯽ در ﻃﯽ ﺷﺶ ﺳﺎﻋﺖ آﺑﯿﺎري ﺑﺮاي ﺑﺎﻓﺖ ﺧﺎك ﺷﻨﯽ اﻧﺠﺎم ﮔﺮدﯾﺪ. ﺗﻮزﯾﻊ ﻣﺠﺪد رﻃﻮﺑﺖ آﺑﯿﺎري ﭘﺲ از 68 ﺳﺎﻋﺖ، ﺑﺮرﺳﯽ ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد در ﺳﯿﺴﺘﻢ ﻗﻄﺮه اي زﯾﺮﺳﻄﺤﯽ ﺑﺎ دو ﺑﺮاﺑﺮ و ﭼﻬﺎر ﺑﺮاﺑﺮ ﺷﺪن دﺑﯽ، ﻣﺴﺎﺣﺖ ﺧﯿﺲﺷﺪه ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﻪ ﺳﻪ و ﭘﻨﺞ ﺑﺮاﺑﺮ اﻓﺰاﯾﺶ ﯾﺎﻓﺘﻪ وﻟﯽ درﺳﯿﺴﺘﻢ ﺳﻄﺤﯽ ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﻪ دو و ﭼﻬﺎر ﺑﺮاﺑﺮ ﺗﻐﯿﯿﺮ ﯾ ﺎﻓﺘﻪ اﺳﺖ. ﻫﻤﭽﻨﯿﻦ ﺗﻐﯿﯿﺮات ﺗﻮزﯾﻊ ﻣﺠﺪد رﻃﻮﺑﺖ در ﺳﯿﺴﺘﻢ ﻗﻄﺮهاي زﯾﺮﺳﻄﺤﯽ ﺑﯿﺸﺘﺮ از ﺳﻄﺤ ﯽ ﺑﻮده اﺳﺖ، زﯾﺮا در ﺳﯿﺴﺘﻢ ﻗﻄﺮهاي ﺳﻄﺤﯽ آب ﺑﻪ ﺻﻮرت آزاداﻧﻪ ﺗﺮي در ﺧﺎك ﺣﺮﮐﺖ ﻣ ﯽﮐﻨﺪ و ﺑﯿﺸﺘﺮﯾﻦ ﺗﻐﯿﯿﺮات در ﺟﺒﻬﻪ رﻃﻮﺑﺘﯽ در آن، ﭘﯿﺶ از ﺗﻮزﯾﻊ ﻣﺠﺪد اﻧﺠﺎم ﺷﺪه اﺳﺖ. در ﻧﻈﺮﮔﯿﺮي ﺗﻐﯿﯿﺮات ﻣﺠﺪد اﻟﮕﻮي رﻃﻮﺑﺘﯽ ﺑﺮاي ﻃﺮاﺣﯽ ﺳﯿﺴﺘﻢ ﻫﺎي آﺑﯿﺎري ﺑﺴﯿﺎر ﺣﺎﺋﺰ اﻫﻤﯿﺖ اﺳﺖ ﭼﺮاﮐﻪ ﺑﺎﻋﺚ ﻣﺪﯾﺮﯾﺖ ﺑﻬﺘﺮ ﺗﻮزﯾﻊ رﻃﻮﺑﺖ و ﺟﻠﻮﮔﯿﺮي از ﺗﻠﻔﺎت ﻋﻤﻘﯽ ﻧﺎﺷﯽ از آن ﻣﯽﮔﺮدد.

Soil moisture distribution is affected by various factors such as discharge and the type of irrigation systems. In this study, it is tried to compare the horizontal and vertical distribution of moisture, redistribution of moisture in the soil and the wetting area at the end of irrigation in two surface and subsurface drip irrigation systems. For this purpose, an experiment in the form of a glass physical model with dimensions of 1 × 0.5×1.20 m, two installation depths (0 and 30 cm) and three discharges (Q1=2, Q2=4 and Q3=8 liters/hour) for sandy soil texture was performed during six hours of irrigation as factorial and in a completely randomized design. Irrigation moisture redistribution was investigated after 68 hr. The results showed that in the subsurface drip system with doubling and quadrupling the discharge, the wetting area increased to three and five times, but in the surface system it changed to two and four times, respectively. Also, changes in moisture redistribution in the subsurface drip system have been more than the surface drip system, because in the surface drip system, water moves more freely in the soil and most changes in the moisture front were made before redistribution. Considering the moisture redistribution is very important for the design of irrigation systems because it leads to better management of moisture distribution and prevention of deep losses.