PHYSICAL SETTING

Posted by on 1/30/2003 12:42:59 PM
Post Comment PHYSICAL SETTING Nigeria

Geology and Soils: The northwest and south ern parts of the state are underlain by granites, schists and gneisses of the basement complex. The ancient PreCambrian rocks of the basement com plex are separated from the younger sediment of the Chad Formation by a hydrological divide, which runs through Kiyawa, Dutse and Yankwashi.

The Emir's Palace, Hadejia
The Emir's Palace, Hadejia

The Chad formation occupies the northeastern parts of the state. However, the basement complex rocks have undergone weathering to give rise to fairly deep soils which are often covered by a sheet of lat erite which has been exposed by denudation in some places.

The Chad sediments are concealed by sand dunes with no surface outcrops. The sandy beds formed over the impervious clays of the Chad Formation form the main source of water supply in the dry season. The soils are generally sandy at the top and compact at depth with often hard pans.

Aeolian deposits from the Sahara Desert form substantial part of soils in the state especially towards the northern parts. The mixing of the subsoil in these deposits has given rise to clayey subsoil, which dominates the northern parts of the state.

Relief and Drainage: The relief is generally undulating, but rock outcrops are common in areas of Basement complex rocks. In the southern part of the state, the relief is about 500-600 metres above sea level.

Some of the hill formations in the areas underlain by these old hard rocks consist of lateritic capped erosional survivals on deeply weathered soils. Surface outcrops are absent in the areas cov ered by sedimentary rocks of the Chad Formation and the relief is usually below 400 metres above sea level.

Any undulations in the relief of such areas consist of fossils, dunes and dune ridges separated by depressions which contain water during the rainy season. Broad shallow valleys are characteristic of the crystalline rock areas, where the river beds are usu ge rocks, the valley formation hardly exists.

Durbar, Dutse
Durbar, Dutse

Rather, the waters of the Hadejia meander through numerous channels that constitute part of the Hadejia Nguru ial wetlands. Many of the water channels dry up during the dry season, when water for domestic use is obtained by digging holes in the sandfilled river ito beds.

Climate: The climate of Jigawa state is semi arid, characterised by a long dry season and a short ird wet season. The climatic variables vary consider ier ably over the year and are erratic. The temperature out regime is warm to hot. The mean annual tempera he ture is about 25C but the mean monthly values its range between 21 C in the coolest month and 31 C ni in the hottest month.

However, the mean daily tem perature could be as low as 20C during the months of December and January when the cold dry har mattan wind blows from the Sahara Desert. Evapo transpiration is very high and relative humidity is th highest in August (up to 80 per cent) and low in January through March (twentythree to thirty per he cent) when it is moderated by the harmattan. The year is characterised by wellmarked dry and wet of seasons.

Wet season is roughly four months (June to September) and dry season is seven to eight he months (October to May). The rainy season may of start in May but early rains in April are not unusual. The bulk of the rainfall comes in June through September. Violent dust storms, followed by tornado and lightening, usually herald the onset of the in rains in May/June and their retreat in September or ed early October.

The total annual rainfall ranges from dy 600mm in the north to 1000mm in the southern ad parts of the state. Great variations occur in the in annual total rainfall and may result in severe and he prolonged droughts, which cause crop failures, is. death of livestock and overall human sorrow.

Vegetation: Most of the state falls within the in Sudan Savannah vegetation belt, but traces of l, Guinea savannah vegetation are found in parts of the southern districts. Extensive open grasslands, with few scattered stunted trees, are characteristics of the vegetation.

Animal-Drawn Carte for Goods Transportation, Duste
Animal-Drawn Carte for Goods Transportation, Duste

The original vegetation has long as since been removed, giving rise to farm parkland of vegetation. Due to annual cultural land clearing, almost all the original tree species were removed as for most parts of the state; only few trees mostly of tic the Mimoceae and Ceselpinaceae families existed .

The Neem tree, a native of India and Burma, has naturalised in the state, to the extent of replacing on the original native trees, especially in towns and villages. Despite deforestation, there still exist remnants of former climatic climax vegetation in some ed sparsely settled districts, especially near water many courses; Acacia species tend to be plentiful in such areas.

Ecological Problems: The major ecological problems in Jigawa state are drought, desertification and the menace of soil and wind erosion. As the state is located in a relatively dry part of the country, the sparse vegetation renders the bare surface deposits very susceptible to erosion.

Gullies are rampant, resulting in soil removal from farm lands and the collapse of roads, bridges and other structures. Gullying is particularly a problem in Dutse LGA, where more than sixteen gully sites have been identified. These include villages like Zai, Limawa, Butela, Katangare, Galamawa, lyaka, etc.

The other ecological hazard, desertification, is more pronounced in the northern fringes of the state. Most of the dunes have however been stabilised and the state government has been embark ing on a comprehensive programme to tackle the problems posed by gully erosion and desertification. Such programmes include massive afforestation, channelisation and wellplanned land use schemes.




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