برآورد ضرايب نفوذ و ضريب زبري مانينگ در دو رژيم جريان پيوسته و كاهشي

Estimation of infiltaration parameters and Manning roughness coefficient under two continuous and cutback flows regims

ﺗﻮﺟﻪ ﺑﻪ اﯾﻨﮑﻪ ﻫﻨﻮز درﺻﺪ ﺑﺎﻻﯾﯽ از اراﺿﯽ ﮐﺸﺎورزي ﺑﻪ ﺻﻮرت ﺳﻄﺤﯽ آﺑﯿﺎري ﻣﯽﺷﻮد ﯾﺎﻓﺘﻦ راهﺣﻠﯽ ﺑﻪ ﻣﻨﻈﻮر اﺻﻼح روشﻫﺎي ﻣﺬﮐﻮر ﺑﺎ ﻫﺰﯾﻨﻪﻫﺎﯾﯽ ﺑﻪ ﻣﺮاﺗﺐ ﮐﻢ ﺗﺮ از آﺑﯿﺎري ﺗﺤﺖ ﻓﺸﺎر ﺿﺮوري ﺑﻪ ﻧﻈﺮ ﻣﯽرﺳﺪ. ﺿﺮﯾﺐ زﺑﺮي ﻣﺎﻧﯿﻨﮓ و ﻣﻌﺎدﻟﻪ ﻧﻔﻮذ از ﻣﻬﻢ ﺗﺮﯾﻦ ﭘﺎراﻣﺘﺮﻫﺎي ارزﯾﺎﺑﯽ ﺳﺎﻣﺎﻧﻪ آﺑﯿﺎري ﺳﻄﺤﯽ اﺳﺖ. ﺿﺮاﯾﺐ ﻣﻌﺎدﻻت ﻧﻔﻮذ ﻧﻘﺶ اﺳﺎﺳﯽ در ارزﯾﺎﺑﯽ و ﻃﺮاﺣﯽ ﺳﺎﻣﺎﻧﻪﻫﺎي آﺑﯿﺎري دارﻧﺪ؛ ﺑﻪ ﻫﻤﯿﻦ دﻟﯿﻞ ﺑﺮاي اﻓﺰاﯾﺶ ﺑﺎزده آﺑﯿﺎري ﺿﺮوري اﺳﺖ ﮐﻪ اﯾﻦ ﺿﺮاﯾﺐ ﺑﺎ دﻗﺖ ﺑﺎﻻ ﺗﺨﻤﯿﻦ زده ﺷﻮﻧﺪ. ﻫﺪف از اﯾﻦ ﺗﺤﻘﯿﻖ ﺑﺮآورد ﺿﺮاﯾﺐ ﻧﻔﻮذ و ﺿﺮﯾﺐ زﺑﺮي ﻣﺎﻧﯿﻨﮓ در دو رژﯾﻢ ﺟﺮﯾﺎن ﭘﯿﻮﺳﺘﻪ و ﮐﺎﻫﺶ ﺟﺮﯾﺎن ﻃﯽ ﺳﻪ رﺧﺪاد اول آﺑﯿﺎري ﺑﺎ اﺳﺘﻔﺎده از ﻣﺪلﻫﺎي SIPAR_ID ،INFILT و EVALUE اﺳﺖ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﻣﯿﺎﻧﮕﯿﻦ درﺻﺪ ﺧﻄﺎي ﻧﺴﺒﯽ در ﻣﺪلﻫﺎي SIPAR_ID ،INFILT و EVALUE ﺑﻪ ﺗﺮﺗﯿﺐ 5/2 ،16/6 و 11/2 و ﺣﺪاﮐﺜﺮ ﺧﻄﺎ ﺑﻪ ﺗﺮﺗﯿﺐ 0/7 ،1/6 و 1/1 ﻣﺘﺮﻣﮑﻌﺐ اﺳﺖ ﮐﻪ ﻣﯽﺗﻮان ﻧﺘﯿﺠﻪ ﮔﺮﻓﺖ ﻣﺪل SIPAR_IDﺧﻄﺎي ﮐﻢ ﺗﺮي ﻧﺴﺒﺖ ﺑﻪ دو ﻣﺪل دﯾﮕﺮ دارد. ﻫﻤﭽﻨﯿﻦ اﯾﻦ ﻣﺪلﻫﺎ در ﺑﺮآورد ﻧﻔﻮذ در آﺑﯿﺎري ﻧﻮاري دﻗﺖ ﺑﺎﻻﺗﺮي ﻧﺴﺒﺖ ﺑﻪ آﺑﯿﺎري ﺟﻮﯾﭽﻪاي داﺷﺘﻪاﻧﺪ. ﻫﻤﭽﻨﯿﻦ ﺳﺎزﻣﺎن ﺣﻔﺎﻇﺖ ﺧﺎك آﻣﺮﯾﮑﺎ )(SCS ﻣﻘﺪار ﺿﺮﯾﺐ زﺑﺮي ﻣﺎﻧﯿﻨﮓ را ﺑﺮاي ﺟﻮﯾﭽﻪﻫﺎي آﯾﺶ در آﺑﯿﺎري اول 0/04 ﭘﯿﺸﻨﻬﺎد ﮐﺮده اﺳﺖ ﮐﻪ ﺑﺎ ﻣﻘﺎدﯾﺮ ﺗﺨﻤﯿﻨﯽ ﻣﺪل SIPAR_ID ﮐﻪ از ﻣﻘﺪار 0/038 ﺗﺎ 0/089 ﺗﻔﺎوت زﯾﺎدي دارد.

Surface irrigation is still main irrigation system in agricultural land, so it is necessary to finding a solution for improving these systems. Manning roughness coefficient and infiltration parameters are the most important parameters in evaluation of surface irrigation systems. Infiltration parameters play an essential role in the evaluation and design of irrigation systems; therefore, it is necessary to estimate these coefficients, accurately The purpose of this study was to estimate infiltration parameters and manning roughness coefficient in continuous and cutback flows during the first three irrigation events using INFILT, SIPAR_ID and EVALUE models. The results showed that the average relative error percentage in the INFILT, SIPAR_ID and EVALUE models were 16.6, 5.2 and 11.2, respectively, and the maximum errors were 1.6, 0.7, and 1.1 m3, respectively. The SIPAR_ID model has less error than the other two models. These models also had higher accuracy in estimating infiltration in the border irrigation than furrow irrigation. The US Soil Conservation Service (SCS) also proposed a Manning roughness coefficient for fallow furrows in the first irrigation 0.04, which is very different from the estimated values of the SIPAR_ID model from 0.038 to 0.09.