Catchment hydrological progress has been greatly influenced under the background of intensive variability in precipitation, temperature, and land cover/land use due to climate changes and human activities. It is desired to explore the causes of hydrological changes in the basin to achieve sustainable management of water and soil resources. This paper employed Mann-Kendall trend test and Mann-Kendall abrupt point test to analyze the temporal variation of runoff in the Tao River and the Daxia River. Results showed that annual runoff had a significant decreasing trend with a rate of -1.85 mm/a in Tao River and -1.36 mm/a in Daxia River during the past 57 years (1961-2017). We analyzed the breakpoint of the annual runoff of the two rivers and split the whole period into two sub-periods at the breakpoint (period 1:before the breakpoint; period 2:after the breakpoint). The annual runoff in the Tao River can be divided into the base period from 1961 to 1987 and the human activity affected period from 1988 to 2017, whereas the base period is 1961-1985 and the human activity influenced period is 1986-2017 in the Daxia River. In order to detect the major cause for the runoff decline, the elasticity of runoff from the Choudhury-Yang equation that is a water-energy balance equation based on Budyko hypothesis was applied. The change of annual runoff from period-1 to period-2 was the catchment hydrological response of the change to the precipitation, potential evaporation and land use/cover (represented by ΔP, ΔET₀, Δω), and we calculated the runoff change based on the elasticity of runoff. Elasticities of runoff were calculated in the two rivers based on their climate condition (represented by the aridity index, ET₀/P) and landscape condition (represented by the parameter, ω). The results indicated that land use/cover was the dominant factor accounting for more than 60% of runoff variation in the Tao and Daxia catchments, followed by precipitation, and the weakest was potential evapotranspiration, accounting for approximately 10%. The impact of land use/cover change mainly came from vegetation increase due to reforestation during soil and water conservation practices in the past 30 years and also partially due to climate variability especially temperature increase. In a word, the underlying surface changes are the main factors causing the change of runoff in the study area. It can be predicted the runoff change in the two catchments under the future climate scenario without direct human impact based on elasticity of runoff from historical hydroclimatic data.