Korama nau'in ruwa ne tare da saman ruwa yana gudana a cikin gado da bankunan tashar . Ana gudanar da kwararar rafi ta hanyar bayanai guda uku - ruwan saman, ruwan karkashin kasa da kuma ruwan ƙasa. Ruwa da ruwa na ƙarƙashin ƙasa suna canzawa sosai tsakanin lokutan ruwan sama. Ruwa na ƙasa, a gefe guda, yana da shigarwar da ba ta da yawa kuma ana sarrafa ta sosai ta tsarin ruwan sama na dogon lokaci. Ruwa ya ƙunshi saman ƙasa, ƙarƙashin ƙasa da ruwa mai gudana wanda ke amsa yanayin ƙasa, geomorphological, hydrological da biotic controls. Dangane da inda suke ko wasu halaye, ana iya ambaton rafi da sunaye iri -iri na yanki ko na yanki. Dogayen manyan rafuffuka galibi ana kiran su da koguna . Kõramu suna da muhimmanci kamar yadda conduits a cikin ruwa sake zagayowar, kida a ruwan karkashin kasa recharge, kuma farfajiyoyi ga kifi da kuma namun dajin hijirarsa. Mazaunin halittu da ke kusa da rafi ana kiranta yankin rafi. Ganin matsayi na gudana Holocene nau'i nau'i, kõguna taka muhimmiyar corridor rawa a haɗa da fragmented habitats kuma haka a kare rabe-raben halittu .