Spatial And Temporal Distribution Of Rainfall And Hydrological Responses In Poyanghu Watershed

Precipitation usually varies greatly in space and time in the hilly region which results in watershed runoff generation. Investigation of precipitation variations is thus very important for modeling of soil moisture contents, groundwater recharge and streamflow, and is also useful for water resources planning and management.This study is firstly focused on investigation of spatial and temporal variations of rainfall. The time series analysis was used to analyze the main periods and trend of precipitation series. Also, Fourier transformation and wavelet analysis were used to extract the main periods of precipitation series; least square method, wavelet analysis method and Mann-kendall method were adopted to analyze the precipitation trend. The spatial variation analysis is based on the spatial interpolation. For analyzing the influence of the rainfall station density on spatial interpolation precision, we partitioned the precipitation stations into several grid sizes. The stations were then reduced in different proportions. The Kriging method and inverse distance weighting method were used to interpolate precipitation. Mean relative error, covariance, deterministic coefficient were calculated to evaluate the interpolation precision.Hydrological response to temporal and spatial variations of rainfall was further investigated by using a monthly hydrological model that integrating topography and precipitation variations. The observation data of rainfall, evapotranspiration and streamflow from 1979 to 1984 and 1985 to 1987 were used to calibrate and validate the modal, respectively. In order to analyze the hydrological response on rainfall variations, spatial variations of soil moisture content and runoff related to rainfall were described in detail.The study results showed that precipitation series present four inapparant main periods, i.e. 3, 4, 7 and 11 years. Since 90th last centure, precipitation series has presented a significant increase trend. Spatial variations of rainfall interpolated by the Kriging method and IDW method are almost similar. Study results also demonstrated that the monthly hydrological model is reliable in rainfall and runoff simulation. Rainfall variations take a significant influence on soil moisture content, but are less sensitive on runoff.