The Water Yield Pattern for Annual and Monthly Scales Through a Unifying Catchment Water Balance Model

Abstract

Long-term scheduling and short-term decision-making for water resources management often require understanding the relationship of water yield pattern between the annual and monthly scales. As the water yield pattern mainly depends on land cover/use and climate, a unifying catchment water balance model with factors has been adopted to derive a theoretical water yield pattern with annual and monthly scales. Two critical values at the parameters ε=1-√2/2 and ϕ=1.0 are identified. The parameter ε referring to the water storage (land use/cover) and evaporation (climate) changes can make more contribution than ϕ for water yield when ϕ>1.0, especially with ε<1-√2/2. But there is less contribution made by ε when ϕ<1.0. The derived theoretical water yield patterns have also been validated by the observed data or the simulated data through the hydrological model. Due to the bias of the soil moisture data, a lot of the estimated parameter ε values are over its theoretical range, especially for the monthly scale in humid basins. The performance of the derived theoretical water yield pattern at annual scale is much better than that at monthly scale while there are only a few data sets from the arid basin at every months fall within their theoretical ranges. Even the relative contributions of ε is found to be bigger than those of ϕ due to ε<1-√2/2 and ϕ>1.0, there are no significant linear relationships between annual and monthly parameters ε and ϕ. Our results not only validate the derived theoretical water yield pattern with the estimated parameter directly by the observed or simulated data rather than the calibrated parameter, but also can guide for further understanding physical of water balance to conversion time scales for the combing long-term and short-term water resources management.