PHYSICAL SETTING

Posted by on 1/30/2003 12:45:40 PM
Post Comment PHYSICAL SETTING Nigeria

Geology: Geologically, more than fourfifth of Kano is underlain by quartzite, undifferentiated metasediments and basement complex rocks of the preCambrian upper cambrian origin. Prolonged weathering of the rocks produced deep clayrich regoliths, which have been subjected to laterization.

A Traditional Procession on horse back during "Hawan Daushe"
A Traditional Procession on horse back during "Hawan Daushe"

The lateritic outcrops dot the interfluve areas of the upland plain serving as caps for regolith hills e.g. Gwauron Dutse and Dala hills. Welljointed younger granites of Jurassic origin occur in ring complexes in the extreme south. A narrow strip of the Chad Formation occurs to the east (Olofin 1981). In height, the relief ranges from lower plains ( 500 m) to highlands of more than 1,000m above sea level. The landforms include: the Rishi hills: plains with grouped hills: sandy plains; and alluvial channel complexes.

Soils: In their natural state, the soils divide into four main groups. The ferruginous tropical soils formed on crystalline acid rocks occupy about two fifth of the State to the south, southwest and south east; the brown and reddish brown soils and latosols occur in the northern half; the brown and reddish soils are in the northeastern corner; and the juvenile and hydromorphic soils occur along the alluvial channel complexes.

The soils largely reflect the influence of parent materials. Intensive use of the soils and addition of manure and chemi cal fertilisers have altered their character, profile, texture, structure and chemical characteristics.

Climate: Mean annual rainfall ranges from over 1,000mm in the extreme south to a little less than 800mm in the extreme north. The rains last for three to five months. Mean temperature ranges from 26C 33C.

There are four seasons: a dry and cool season, Kaka, (midNovember to February), marked by cool and dry weather plus occasional dusty haze: the dry and hot season, bazara (MarchmidMay) when temperatures climb up to 40C and which is a transition period between the harmattan and the wet season; the wet and warm season, damina (midMay to September), is the proper wet season when the lowest diumal temperature is recorded; and a dry warm season, rani (October to midNovember) marked by high humidity and high temperature next to bazara in hotness.

Tiga Lake

Vegetation: The natural vegetation consists of the sudan and the guinea savannah both having been replaced by secondary] vegetation. Fourfifth of the state is now composed of farmed parkland, dotted with patches of shrub savannah. The savan nah woodland, which is the second largest zone, is typified by the Falgore Game Reserve. There are few forest plantations of exotic trees.

Drainage: Rivers Kano, Challawa, Watari, Jatau and Dudurun Gaya join the Hadejia, which empties into the Lake Chad while Gari, Tomas and Jakara disappear into the sands of the Chad Formation further east. Several manmade lakes such as Tiga, Challawa Gorge, Gari, Jakara, Watari, Guzuguzu, Kafin Chiri, Dudurun Gaya, Bagauda have been constructed to improve portable water supply to towns and villages and to provide water for irrigation (Appendix 1).

Ecological Problems: Kano experiences great temporal variation in rainfall amount and dura tion. During the 197073 drought, Kano recorded only forty eight per cent of the annual mean. This phenomenon and occasional pest infestation pose major dangers to crop and animal lives and, conse quently, human lives.

Hydroagriculture has led to the erosion of top soil, resulting in considerable loss of the fine soil particles which contribute to the high sediment yield of the main rivers. High sediment yield, especially from areas with basement complex rocks, has led to rapid reservoir siltation, thereby reducing the life span of most of the reservoirs (Oloyin, 1991).

Dam construction has resulted in the drying out of downstream fadama lands. Overgrazing of fadamas "results in soil compaction and reduces vegetation cover, both of which lead to increased surface runoff in the wet season and reduced water holding capacity of the soils." Wind erosion of surface soil is common.




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