Abstract:

Miyun reservoir is the only source of surface water for the life water supply in the city of Beijing, and Chaobaihe basin is the district of runoff formation for the reservoir. The change in the annual runoff in Chaobaihe river basin influences directly the water resource security in Beijing. According to the theory of decomposing and synthesis in the analysis of time series, the determinant and stochastic components of annual runoff series in the resource region of Chaobaihe river were decomposed, and the fit calculation of determinant components and the frequency calculation of stochastic components were conducted separately. The determinant forecasting value and stochastic design value were synthesized, and the past and present as well as future frequency distributions were obtained for the resource region of Chaobaihe river. The security problems for water resources in Beijing were analyzed from the change of annual runoff frequency distribution in the river. The overall trend in the change of the annual runoff decreases year by year, and Miyun reservoir inflow also reduces in normal and dry years; therefore, Miyun reservoir may not be able to ensure the water resources for the sustainable development in Beijing in the 21 century.

Key words: annual runoff, frequency distribution, water resources security, time series