Osimiri Ikpoba

Osimiri Ikpoba bụ ụzọ mmiri dị na ndịda Nigeria, na-agafe Steeti Edo ma na-enye ihe ndị bi na Benin City na mpaghara ndị gbara ya gburugburu ji eme ihe. Ọ na-amalite site na Ikpo ugwu Ishan Plateau, na-asọba site na Benin City ma na-asọpụta n’ime mpaghara mmiri (basin) ruru ihe dị ka 922 km² (356 sq mi).

Ọ na-enye mmiri dị ọhụrụ (freshwater), na-emepụta ike eletrik site na mmiri (hydroelectric power) ma na-akwado ịmị mkpụrụ ugbo site n’irrigation. Ụdị mmegharị mmiri ya (hydrology) na-adabere na mgbanwe nke mmiri ozuzo oge dị iche iche.

Baseflow na-etinye ihe dị ka 56% nke ngụkọta mmiri ọ na-ebupụ (discharge), ebe 44% fọdụrụ si na mmiri na-asọba n’elu ala (overland flow). N’akụkụ elu osimiri ahụ, ọ na-egosi usoro mgbasa mmiri dendritic (dendritic drainage pattern) ma na-enweta nkwado site na mmiri n’okpuru ala (groundwater) si na Benin Formation, nke na-eme ka mmiri ya na-asọkarị n’ụzọ kwụsie ike n’afọ niile.

Nnyocha achọpụtala ọla arọ (heavy metals) dịka cadmium, lead, na mercury, nke na-ebute nchekasị gbasara nsị sitere n’ihere ọrụ ụlọ ọrụ na nsị ụlọ obibi (industrial na domestic waste pollution).

Nsogbu gburugburu ebe obibi na-emetụta Osimiri Ikpoba gụnyere mgbukpọ ọhịa n'akụkụ osimiri ya, nke mgbasawanye ọrụ ugbo na mmepe obodo ukwu na-akpali. Ọnụnọ nke mmetọ sitere na ụlọ mmanya, ebe a na-egbu anụ, na ebe a na'ịgbapụta nsị emetụtala gburugburu ebe obibi nke osimiri ahụ. Iji belata mmetụta ndị a, Gọọmentị Steeti Edo amalitela mgbalị iji kpochapụ ma kpochapụ osimiri ahụ, na-ezube ibelata idei mmiri na mpaghara ndị dị ala nke Benin City. N'agbanyeghị ihe ịma aka ndị a na gburugburu ebe obibi, Osimiri Ikpoba ka bụ ihe enyemaka maka ịkụ azụ, njem, na obere mmepụta ọkụ eletrik mmiri. Atụmatụ iji ike mmiri ya eme ihe enweela ọganihu, na nyocha nke ime ihe na njikọ aka na United Nations Industrial Development Organization (UNIDO) iji mepụta ike na-agbanwe agbanwe site na mmiri ahụ. Osimiri ahụ na-arụ ọrụ na mmepe mpaghara na usoro ihu igwe.

 Ụzọ na mmiri 
The Ikpoba River, a sixth-order river flowing through Benin City in Edo State, Nigeria, originates from the Ishan Plateau and spans a catchment area of approximately 922 km2 (356 sq mi).[2] It follows a southward course, beginning in highland regions and meandering through both urban and rural landscapes before joining a larger drainage system. The river's coordinates range from 6°19′12″N, 5°24′0″E to 6°22′48″N, 5°51′7.2″E, indicating its reach across multiple ecological zones.[2] Hydrological studies suggest that, despite minor seasonal variations, the river maintains relatively stable water levels year-round due to a combination of groundwater inflows and surface runoff.[3] In studied sections, the river's width ranges between 10 and 12 meters, with depth fluctuations influenced by precipitation levels and local topography.[2]

Isi mmalite mmiri nke Osimiri Ikpoba gụnyere mmiri ozuzo na-adaba ozugbo, mmiri n’okpuru ala (groundwater) na-apụta site na Benin Formation, yana mmịnye mmiri sitere n’aka ọtụtụ obere osimiri na-asọba n’ime ya (tributaries).[1] Nnyocha hydrograph na-ekpughe na ndagwurugwu na-eme ihe dị ka 56% nke ngụkọta ya, na-eme ka ọrụ mmiri na-abanye n'okpuru ala na-eme n'ịkwado oke osimiri ahụ.[1] 44% fọdụrụnụ na-abịa site na mmiri na-asọ asọ n'ihi ihe omume mmiri ozuzo na mmiri na mmiri na ya, na-enye aka na mgbanwe nke oge mmiri.[1] N’oge mmiri ozuzo (na-adịkarị site n’ọnwa Eprel ruo Ọktoba), mmiri ozuzo siri ike na-eme ka ọsọ na ọnụọgụ mmiri na-asọba bawanye, ebe n’oge oge akọrọ, ogo mmiri na-ebelata, mgbe ụfọdụ na-eme ka akụkụ osimiri (riverbanks) na ntinye sedimenti (sediment deposits) pụta ìhè..[4]

Ka osimiri ahụ na-agafe Benin City, ihe dị iche iche na-emetụta ya, gụnyere mmiri ozuzo, nsị ụlọ ọrụ, na mmiri nsị ụlọ.[4] Ihe omume ndị dị ka ịsa ụgbọala, ịsa ahụ, na igbu azụ - ọkachasị n'okpuru mmiri nke Ikpoba Bridge - agbanweela mmiri ya, na-ewebata mmetọ ndị na-emetụta ogo mmiri.[5] Mmekọrịta ya na gburugburu obodo emeela ka mgbanwe dị na njirimara mmiri, gụnyere mbuze na mkpokọta ala.[5] Nkọwa hydrodynamic na-egosi na mpaghara ndị nwere ọkwa dị elu nke ime obodo na-egosipụta ọnụego dị ala nke ịbanye, na-eduga n'ịbawanye mmiri na ihe ize ndụ dị elu nke idei mmiri n'oge nnukwu mmiri ozuzo. [6]

Otu akụkụ hydrology dị mkpa nke Osimiri Ikpoba bụ Ikpoba Reservoir, nke e kere site na Ikpoba Dam, nke e mechiri mmiri ya nke mbụ n’afọ 1975 ma na-eje ozi dịka isi iyi mmalite mmiri a na-eji enye Benin City..[3] Dam ahụ na-enyere aka ịchịkwa mmiri na-aga, na-ebelata mgbanwe nke oge mgbe ọ na-enye mmiri maka iji ụlọ na ụlọ ọrụ.[3] Otú ọ dị, sedimentation aghọwo nchegbu, na nyocha na-eme atụmatụ na 23.16% nke ikike nchekwa nke ọdọ mmiri ahụ efunahụla n'ihi mkpokọta ala.[7] Nke a emeela ka ọ dị mkpa ka a na-egwu mmiri oge na mgbalị ndị a na-eme iji mee ka mmiri ahụ na-arụ ọrụ ma hụ na mmiri na-aga n'ihu.[6]

Mgbanwe ihu igwe na mgbanwe nke iji ala eme ihe n'ime mmiri ya na-emetụta mgbanwe mmiri nke osimiri ahụ.[2] Mgbukpọsị oké ọhịa n'ebe ndị dị n'elu mmiri emeela ka mmiri na-asọbawanye, belata ọnụ ọgụgụ na-abanye n'ime mmiri, na mmebi nke mmiri na-eme ka mmiri na osimiri ka njọ.[2] Tụkwasị na nke a, mmepe obodo nke Benin City agbanweela usoro mmiri nke osimiri ahụ, yana ebe ndị ọzọ a na-eme ka mmiri dị n'okpuru ala belata.[4] Nnyocha atụwo aro usoro nchịkwa mmiri na-adịgide adịgide iji dozie nsogbu ndị a ma kwado ọrụ gburugburu ebe obibi na akụ na ụba nke osimiri ahụ.[8]

 Geology na geomorphology 
Osimiri Ikpoba na-agafe Benin Formation, otu nhazi ala (geological unit) nke mejupụtara nke ukwuu site na aja (sand) na-adịghị akpọkọtara, nkume nta (gravel) na ájà dị nro (clay), nke malitere n’oge Late Tertiary.

Nhazi ala a bụ akụkụ nke Niger Delta Basin ma mara ya maka nnukwu porosity na permeability, nke na-eme ka mmiri n’okpuru ala (groundwater) na-abanye ma na-akwado osimiri. Mmekọrịta dị n’etiti osimiri na sedimenti ndị dị n’okpuru ya na-emetụta ijide mmiri (water retention), mbufe sedimenti (sediment transport), na ịdịkwasi ike nke ala osimiri (stability of the riverbed).

Ọdịdị sedimenti ndị a nwere nkume buru ibu (coarse-grained sediments) na-akwado baseflow kwụsie ike, na-eme ka osimiri nwee ike ịga n’ihu na-asọ mmiri ọbụna n’oge oge akọrọ, mgbe mmiri na-asọba n’elu ala (surface runoff) na-ebelata.[[1]]

Omume mmadụ dịka ichapụ aja (sand mining) na igbutu ọhịa (deforestation) agbanweela nkesa sedimenti, nke kpatara mbibi ala n’ógbè ụfọdụ (localised erosion) na mgbanwe ọsọ mgbasa mmiri (variations in flow velocity). .[4]

Ọdịdị ala nke osimiri ahụ na-emetụta usoro mmiri na ntinye aka mmadụ. N'elu ya, osimiri ahụ na-agafe n'ebe ndị dị n'oké ọhịa ebe ahịhịa na-eme ka osimiri kwụsie ike ma belata mbuze. Ka ọ na-agafe mpaghara ndị mepere emepe nke Benin City, ọwa ahụ na-agbanwewanye n'ihi owuwu mmiri na mgbakwunye aka. Ntọala nke ihe mgbochi ndị a emebiwo njem nke ihe okike, na-akpata nkwụsị n'ebe ụfọdụ ka ọ na-eme ka erosion dị ngwa na ndị ọzọ.[4] Ihe owuwu nke Ikpoba Dam emetụtala ọdịdị ala nke osimiri ahụ site na ijide ihe ndị dị n'elu mmiri ma gbanwee usoro mmiri na-agbadata. Dam ahụ emeela ka mkpokọta nke ezigbo ihe dị n'ime ọdọ mmiri ahụ, na-ebelata ikike nchekwa ya ka oge na-aga. Nnyocha na-egosi na 23.16% nke ngụkọta nke ọdọ mmiri ahụ efunahụla n'ihi siltation, na-achọ ka a na-agbanye mmiri oge.[7]

Ụzọ mbuze na-agbanwe n'akụkụ osimiri ahụ dabere na ojiji ala na ọnọdụ mmiri. A hụla ọnụ ọgụgụ dị elu nke erosion n'akụkụ Ikpoba Bridge, ebe ọrụ ụmụ mmadụ dị ka ịsa ụgbọala, ịta ehi, na ịdọrọ ájá emeela ka osimiri ghara ịdị mma. Omume ndị a na-eme ka ibu nke ala dịkwuo elu ma na-eduga n'ịkụcha ala. N'ụzọ dị iche, ebe ndị dị n'okpuru mmiri na-enwe nnukwu nkwụsị nke sediment, karịsịa n'ihi mbelata ọsọ mmiri na mbata nke nsị ụlọ ọrụ. Ụlọ ọrụ na-emepụta mmanya n'ógbè a na-ewepụ mmiri na-adịghị mma n'ime osimiri ahụ, na-eduga na mmekọrịta kemịkal nke na-eme ka mkpụmkpụ nke ala dịkwuo elu. Nke a emeela ka e nwee ebe a na-etinye ihe n'ime ala ebe a na'ime ala na-agbakọta, na-emepụta apịtị ma na-agbanwe ụzọ osimiri ahụ.[5]

Mpaghara dị n’akụkụ osimiri (riparian zone), nke a na-ekpuchi mbụ site na achara achara mba ala (native bamboo – Bambusa vulgaris), emerụla emebi n’ihi igbutu ọhịa maka ọrụ ugbo na mmepe obodo. Ịla n’iyi ahịhịa na osisi emeela ka mmiri na-asọba n’elu ala (runoff) bawanye, belata nbanye mmiri n’ime ala (groundwater infiltration) ma mee ka mbibi ala (erosion) sie ike.

N’ebe ụfọdụ, e ji akụkụ konkiri (concrete embankments) kwado akụkụ osimiri (riverbanks) iji gbochie ịla n’iyi ala ọzọ. Ọ bụ ezie na owuwu ndị a na-enye nkwụsi ike nwa oge, ha agbanweela ụzọ mgbasa mmiri osimiri (hydrodynamics), mee ka ọsọ osimiri bawanye ma tinye aka n’ịba ụba mbibi ala n’ebe dị n’ala osimiri (downstream erosion).

Na mgbakwunye, iwepu ahịhịa na osisi dị n’akụkụ osimiri (riparian vegetation) emetụtala ebe obibi anụmanụ bi n’ime mmiri na ndị na-ebi n’akụkụ mmiri (aquatic na semi-aquatic species), na-emetụta ịdị iche iche nke ndụ (biodiversity).[2]

Sedimentation within the reservoir remains a concern. The total volume of silt in the reservoir is estimated at 347,378.41 m3 (12,267,553 cu ft), reducing its capacity to store water for hydroelectric power generation and urban supply. If unchecked, sediment accumulation could lead to increased overflow risks and reduced efficiency of the dam's operations.[3] The Edo State Government has recognised this challenge and directed dredging of the Ikpoba River to restore its capacity and mitigate flooding risks. The Benin City Rainstorm Master Plan is being updated to integrate erosion control measures specific to the Ikpoba watershed. These efforts aim to balance development needs with ecological sustainability.[6]

 Ụdị dị iche iche na gburugburu ebe obibi 
Osimiri Ikpoba na-akwado usoro gburugburu ebe obibi nke gụnyere ihe dị iche iche dị n'ime mmiri na nke ala. Osimiri ahụ na-enye ebe obibi maka ụdị azụ, anụmanụ ndị dị n'ime ala, nnụnụ ndị dị n"osimiri, na ahịhịa mmiri. Otú ọ dị, mmetọ ígwè dị arọ, mgbasawanye obodo, na mgbukpọ ọhịa emetụtala ụdị dị iche iche nke Osimiri Ikpoba, na-eduga na mgbanwe na ụdị na ọnụ ọgụgụ mmadụ. Nnyocha achọpụtala na nsị ụlọ ọrụ mmepụta ihe na nsị ọrụ ugbo na-ewebata mmetọ dịka cadmium (Cd), ntutu (Pb), na mercury (Hg) n'ime osimiri, na-akpata mkpokọta nke ihe ndị a na ihe ndị dị n'ime mmiri. E jikọtara ọnụnọ nke mmetọ ndị a na mgbanwe na anụ ahụ azụ, gụnyere mmetụta na gills, imeju, na ọrụ akụrụ.[9]

Obodo azụ dị na Osimiri Ikpoba gụnyere Tilapia zillii, Clarias gariepinus, Clarias anguillaris, na Oreochromis niloticus - ụdị ndị ọkụ azụ obodo ahụ nwetara. Ndị bi na Tilapia egosila ihe ịrịba ama nke mkpokọta ígwè dị arọ, na oke nke okpu na cadmium achọpụtala na anụ ahụ ha, ọkachasị na ụdị ndị anakọtara site na ngalaba ndị dị n'okpuru mmiri dị nso na ebe mmepụta ihe. Azụ n'ógbè ndị a na-egosipụtakwa ọdịdị ọdịdị na mbelata ihe ịga nke ọma ọmụmụ, na-eme ka ihe ize ndụ gburugburu ebe obibi metụtara mmetọ pụta ìhè.[9] Obodo invertebrate nke dị n'okpuru ala, na-eje ozi dị ka ihe na-egosi ịdị mma mmiri, emetụtawokwa ya. Nnyocha achọpụtala mbelata nke ụdị ọgaranya n'akụkụ nke osimiri ahụ na-ahụ maka nsị ụlọ ọrụ, na ụdị na-anabata mmetọ na-aghọwanye ihe kachasị. N'ụzọ dị iche, ebe ndị dị n'elu mmiri nwere obere mmetọ na-aga n'ihu na-akwado ọnụ ọgụgụ dị iche iche nke macroinvertebrate, gụnyere ụdị dị nro nke chọrọ ọkwa oxygen dị elu.[4]

Mmebi ebe obibi na mmetọ emetụtawokwa ọnụ ọgụgụ nnụnụ ndị dị n'akụkụ Osimiri Ikpoba. Ụdị nnụnụ dị ka Pied Kingfisher (Ceryle rudis), Little Egret (Egretta garzetta), na African Fish Eagle (Haliaeetus vocifer) na-adabere n'osimiri maka nri, akwụ́, na ọmụmụ. Mfu nke ahịhịa ndị dị n'akụkụ osimiri na mmụba nke nsogbu mmadụ belatara ebe obibi dịnụ, na-eduga na mbelata nke ọnụ ọgụgụ nnụnụ ụfọdụ. Nnyocha achọpụtala na nnụnụ dị iche iche kachasị elu na mpaghara osimiri nwere ahịhịa na-enweghị nsogbu, ebe ebe ebe ndị na-enwe mgbukpọ ọhịa na mmeri n'obodo ukwu na-egosi mbelata nke ụdị nnụnụ.[5] Iwepụ osisi achara n'akụkụ osimiri - nke nyere ebe obibi maka nnụnụ na anụ ọhịa ndị ọzọ - emeela ka ọnụ ọgụgụ nnụnụ belata.[2] Tụkwasị na nke a, mmetọ ụlọ ọrụ mmepụta ihe emetụtala nnụnụ na-eri azụ, na-eduga na mbelata ihe ịga nke ọma n'etiti ụdị dị ka kingfishers na egrets.[5]

Ahịhịa na osisi bi n’ime Osimiri Ikpoba agbanwewokwa n’ihi itinye nri kemịkal (nutrient loading) sitere na mmiri na-asọba site n’ubi ugbo (agricultural runoff) na mmepụta nsị ụlọ ọrụ mmepụta ihe (industrial discharges). Ntinye nri ndị a karịrị akarị emeela ka algae na osisi mmiri ndị na-abụghị nke ala (invasive aquatic plants) too ngwa ngwa, ụfọdụ n’ime ha na-emebi usoro mgbasa mmiri nke osimiri ma belata ogo oxygen dị n’ime mmiri.

Mgbasa nke osisi ndị na-abụghị nke ala, dịka water hyacinth (Eichhornia crassipes), emewo ka nsogbu pụta n’ihi igbochi ụzọ mmiri na igbanwe ebe obibi anụmanụ mmiri. Ọnụnọ algal blooms nke bawanyere emeela ka mbelata oxygen n’ógbè ụfọdụ (localised oxygen depletion) pụta, ihe a na-akpọ hypoxia, nke nwere ike ibute ọnwụ azụ (fish kills) na mbelata ịdị iche iche nke ndụ (biodiversity)..[2]

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