Magudanan ruwa

"Definition of "Perennial Stream"". Office of Surface Mining - US Department of the Interior. Archived from the original on October 7, 2006. Retrieved March 28, 2007.Rafi ko kogin da ba ya dawwama shine rafi ko kogi (tashar) wanda ko da yaushe yana gudana a wasu sassa duk shekara a cikin shekarun da aka saba da shi.Water Supply Paper 494. Rafukan rafukan da ba su da yawa sun bambanta da rafuffuka masu tsaka-tsaki; wanda yawanci yakan daina kwarara na tsawon makonni ko watanni a kowace shekara. Hakanan sun bambanta da rafukan da ke gudana na tsawon sa'o'i ko kwanaki bayan ruwan sama. A cikin shekarun bushewa da ba a saba gani ba, rafi na iya daina gudana. A cikin fari, ƙila ba za su gudana ba har tsawon watanni. Bambance-bambancen da ke tsakanin rafukan shekara-shekara, tsaka-tsaki, da ƙoramar ephemeral ba daidai ba ne kuma suna iya canzawa idan ƙungiyoyi daban-daban suna amfani da matakan daban-daban.

A cikin bushewar yanayi mai yiwuwa ba za a iya ganin ruwan yana gudana ba, ko ganin wani ruwa kwata-kwata. A cikin rafukan da ke da tsakuwa, yashi ko dutsen ƙasa, ruwan na iya gudana ƙarƙashin ƙasa ko tsakanin duwatsu. A cikin ilmin halitta, rafi yana gudana idan akwai isasshen ruwa don tallafawa rayuwar ruwa, ciki har da kifaye da amphibians masu numfashi, kwari na benthic, crustaceans, da mollusks. Waɗannan suna iya rayuwa a cikin ƙaƙƙarfan ruwa mai zurfi a ƙarƙashin duwatsu ko katako. Magudanar na iya zama ƙanƙanta ta yadda ba za a iya auna shi ta hanyar kayan auna magudanar ruwa[2].

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