Climatic Variability and Estimation of Supplementary Irrigation Water Needs of Selected Food Crops in the Sokoto-Rima River Basin, Nigeria

Abstract

The study investigated the effects of rainfall and temperature variability on crop water requirements of selected food crops in the Sokoto-Rima River Basin, Northwest of Nigeria. Rainfall and temperature datasets were obtained from the Climatic Research Unit (CRU) TS 3.21 of the University of East Anglia, Norwich, for a period of 70 years (1943-2012). The suitability of CRU datasets were verified by correlating the datasets with measured rainfall data of Yelwa synoptic station, from the Nigerian Meteorological Agency. Selected food crops were used for estimating supplementary irrigation water needs in the River basin. Results of Mann-Kendal, Spearman’s Rho and linear regression tests showed strong evidence of increasing annual temperature and potential evapotranspiration with corresponding decrease in rainfall amounts, especially in the northern parts of the basin which houses big irrigation projects and dams such as the Goronyo Irrigation and the Bakolori Dam and Bakolori Irrigation Project. This will impact on the water availability within the basin, through reduction in surface and ground water supply for ongoing irrigation and other water resources projects. Water requirements for selected crops were modeled to ascertain crop sensitivity to climatic variability which will aid in the design of supplementary irrigation water needs models. Results showed that even in the rainfall months, supplementary irrigation of varying quantity is required to complement rainfall, most especially, in the northeast of the basin. Surprisingly, the month of May which marks commencement of rainfall, recorded the highest water need and this has implication for agriculture yields in the region.