Analysis of stochastic characteristics of the Benue River flow process

Stochastic characteristics of the Benue River streamflow process are examined under conditions of data austerity. The streamflow process is investigated for trend, non-stationarity and seasonality for a time period of 26 years. Results of trend analyses with Mann-Kendall test show that there is no trend in the annual mean discharges. Monthly flow series examined with seasonal Kendall test indicate the presence of positive change in the trend for some months, especially the months of August, January, and February. For the stationarity test, daily and monthly flow series appear to be stationary whereas at 1%, 5%, and 10% significant levels, the stationarity alternative hypothesis is rejected for the annual flow series. Though monthly flow appears to be stationary going by this test, because of high seasonality, it could be said to exhibit periodic stationarity based on the seasonality analysis. The following conclusions are drawn： （1） There is seasonality in both the mean and variance with unimodal distribution. （2） Days with high mean also have high variance. （3） Skewness coefficients for the months within the dry season period are greater than those of the wet season period, and seasonal autocorrelations for streamflow during dry season are generally larger than those of the wet season. Precisely, they are significantly different for most of the months. （4） The autocorrelation functions estimated ＂over time＂ are greater in the absolute value for data that have not been deseasonalised but were initially normalised by logarithmic transformation only, while autocorrelation functions for i = 1, 2 365 estimated ＂over realisations＂ have their coefficients significantly different from other coefficients.

Benue 河流速及流水量过程的随机的特征在数据严峻的条件下面被检验。流速及流水量过程为 26 年的一个时间时期为趋势， non-stationarity 和 seasonality 被调查。有 Mann-Kendall 的趋势分析的结果测试在年平均分泌物没有趋势的表演。与季节的 Kendall 测试检验的每月的流动系列在趋势显示积极变化的存在一些月，特别 the months of 8 月， 1 月，和 2 月。为 stationarity 测试，而，日报和每月的流动系列看起来静止在 1% ， 5% ，和 10% 重要层次， stationarity 选择假设为年径流系列被拒绝。尽管每月的流动看起来静止经过这测试，因为高 seasonality，基于 seasonality 分析展出周期的 stationarity 能被说。下列结论被得出：(1 ) 与单峰的分发在平均数和变化有 seasonality。(2 ) 有高平均数的天也有高变化。(3 ) 为在旱季时期以内的月的偏斜度系数比湿季节时期的那些大，并且为流速及流水量的季节的自相关通常在旱季期间比湿季节的那些大。精确，他们是显著地不同的大多数这些月。( 4 )“随着时间的过去”估计的自相关函数在为一直不是 deseasonalised ，但是当自相关为 i =工作时，被对数的转变开始仅仅使正常化的数据的绝对值是更大的 1 ， 2 ，...， 365 “在认识上”估计了有他们与另外的系数显著地不同的系数。