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This study aimed to detect trends in the long-term hydro-climatic series using non-parametric methods. The annual and seasonal linear trends of rainfall, temperature, runoff, water level and evaporation were analysed for stations in downstream Kaduna River Basin during 1975-2014. The non-parametric Mann-Kendall and Sen's estimator of slope procedures were adopted to identify if there exists an increasing or decreasing trend with their statistical significance at 95% level of confidence. The datasets were checked to account for auto-correlation prior to determining trends using Mann-Kendall test. The existence of abrupt changes was detected by means of Cumulative Sum Charts and Bootstrapping analysis. The results of study indicated increasing trends for seasonal and annual temperature and runoff series. Water level and evaporation revealed statistically decreasing trends both on annual and seasonal periods. However, for the period 1975 to 2014 no significant distinctive trend was observed for rainfall at the investigated stations. Change-points in time series were identified in all the investigated hydro-climatic records for the sub-basin. Generally, the detection of the trend for hydro-climatic variables by Mann-Kendall test conforms to Sen's test results. It is concluded that the basin is sensitive to climate variability and water stress impacts which will affect food security. So, it would be necessary to make adjustments in the adaptive water-use strategies being adopted at present in the catchment.

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The Tunga-Kawo Dam has a reservoir capacity of 22 Mm 3 , and was designed to irrigate 900 ha of land in the Midland region of Nigeria. This paper examines the quality of surface water and groundwater within the scheme. In particular, the seasonal variation of the concentrations of nitrate, phosphate, dissolved oxygen and hydrazine during the year 2000 is discussed. Three sample points: SF1, SF2 and SF3, were selected for monitoring the surface water quality at the upstream, impounded water and downstream sections, respectively. The quality of groundwater was monitored using samples from a well near the dam (GW2) and the downstream section (GW3). Water samples were taken on a weekly basis from the sample points during the year 2000. It was found that the concentrations in the surface water were higher than the WHO standards for drinking water. For example, the nitrate level in SF3 increased from 0.0 mg l -1 before application of fertilizer to 74.1 mg l -1 after fertilizer was applied, while the phosphate level rose from 1.2 mg l -1 to 19.2 mg l -1 during the same period. Similarly, the level of hydrazine increased from 62 µg l -1 to 102 µg l -1 . In particular, the concentrations of the determinants in the samples from the downstream section exceeded those in the impounded water and water from the upstream section. In addition, the level of DO at the downstream section SF3 was lower than that of the upstream section. The level was lower than the minimum level required to support a balanced population of desirable flora and fauna. This difference was attributed to the agrochemicals used by the farmers. Although the quantity of fertilizer applied by the farmers is below the quantity required for optimum yields, the excess chemicals in surface and groundwater could be attributed to the techniques and timing of application. The magnitude of these impacts can be reduced by efficient methods of source control of the pollutants.