Baseflow separation and temporal changes in the Juma River, China

Digital filtering method with improved regression constant, the Chapman-Maxwell method, was used to separate baseflow from daily runoff in Zijinguan hydrological station in Juma River, China, with temporal trends of baseflow investigated. Modified receding water constant (α = 0.993) calculated from Chapman-Maxwell method were found suitable to separate baseflow compared with experienced receding water constant (α = 0.925). Annual runoff and baseflow presented decreasing trends with abrupt changes around 1967. Abrupt changes for annual baseflow were found to be earlier than for annual runoff. Changes in baseflow were found to make up to 35.8%, 42.51%, and 52.20% of changes in runoff in flood, normal, and drought years. It is concluded that baseflow presents steady characteristics than changes in runoff, this plays a vital role in maintaining integrity of river ecosystem.