Spatial patterns of climatic variability and water budget over Sudan Savannah Region of Nigeria

The study examined the effect of climatic variability on climatic water balance over Sudan Savannah, Nigeria. Temperature and Rainfall data were collected for the period 1943-2012 from the Nigerian Meteorological Agency. The data were divided into two climatic years 1943-1977 and 1978-2012. On the whole, rainfall amount decreased from a very high mean value of 981.5 mm in Yelwa (Lat. 10.88 N; Long. 4.75 E) to a very low value of 656.1mm in Katsina (Lat. 13.02 N; Long.7.68 E). This pattern reveals gradual/potential extension of dryness from the Lake Chad area in Nigeria in northeast, towards the Sudan savannah, northwest of Nigeria. Annual temperature, PET, moisture deficit distributions revealed very strong evidence of upward trend at α<0.01 with corresponding decrease in rainfall in the second climatic period, an indication of changing climate. However, in Yelwa, Sokoto and Gusau, there was little evidences of significant downward trend in annual rainfall distribution at α =0.10, but rather a quasi–periodic pattern, even though there were signs of statistical rise in temperature. The general pattern of deviation in PET from the first climate period were 1.4, 3.7, 2.7, 1.9% for Yelwa, Sokoto, Gusau and Katsina respectively, while moisture deficits were 5.0, 4.2, 4.0 and 7.9% for Yelwa, Sokoto, Gusau and Katsina respectively. This general observation may suggest that water balance parameters during the second climatic period deviated from patterns Observed in the first climatic period (1943-1977). Repetition of drought within the present climate regime could be expected and should be planned for. For temperature, there is strong evidence of increasing trends for all the stations in the region which agrees with global trend. This has implications for socio-economic development of the study area especially coupled with the attendant consequences of increasing population and economic activities in the region. There is thus need to plan for and design sustainable water resources management techniques in different sectors-agriculture, irrigation and dams, water supply to adapt to the quasi-periodic patterns of rainfall fluctuation.   Key words: Thornthwaite, Sudan Savannah, water balance, climate change, rainfall and temperature.