变化环境下北江下游年径流量的加权马尔可夫链预测

Forecast of yearly river runoff in lower reaches of Beijiang River by Weighted Markov-Chain Method in changing environments

在气候变化和人类活动的影响下,西北江的水文环境发生了重大变化,导致北江下游的来水条件发生变化。采用斯波曼检验(Spearman’s rho test)和Mann-kendall法系统地分析了北江下游的年径流量的变化趋势和变异情况,在此基础上建立了北江下游变化环境下年径流量的加权马尔可夫链预测模型。结果表明:西北江近50年来的大规模联围筑闸、大规模无序采掘河床泥沙等剧烈的人类活动,导致北江下游三水水文站年径流量在1990年左右发生了变异;所建立的加权马尔可夫链预测结果表明,从变异后的序列中统计出来的状态"转移概率"矩阵,能准确地反映出环境变化后年径流量之间的关系,所建立的加权马尔可夫链法预测变化环境下的年径流量是可行的,预测效果也比较好;按文章确定的分级标准,依现有的资料信息推断,环境发生变化后,在未来长期过程中,北江下游出现平水年的机会最大,但年际间的丰枯波动概率也不小。这一结果值得水资源管理部门注意。

Hydrological conditions of Xijiang and Beijiang River（two tributaries of the Pearl River in south China,intersecting at Sixianjiao） have changed greatly due to climate changes and human activities,resulting in the change of flow in lower reaches of Beijiang River.Spearman＇s rho test and Mann-kendall method were used to analyze the trend change of yearly discharge and associated causes in lower reaches of Beijiang River,and a Weighted Markov-Chain model was thus proposed to forecast the yearly flow series.Land reclamation,dam construction and channel dredging of sand in the last 50 years were found to be the main reasons for the abrupt trend change at Sanshui Station in 1990;state transfer probability matrix of Markov derived from the flow series after 1990 reflected well the flow pattern under new conditions,and were applied in the river flow forecasting,yielding a reasonable result.According to the classification of three categories of normal,dry and wet year,the flow in lower reaches of Beijiang River was calculated with the highest probability to be normal year under changing environment,while the probability of shift to either wet or dry year is also high,which needs to be considered in water resource management or risk prevention.