Abstract
Continuous runoff needs to be estimated in ungauged catchments to interpret hydrological phenomena and manage water resources. Researchers have used various methods to estimate runoff in ungauged catchments, but few combined different methods to improve the estimation. A model parameter-based method named the parameter transfer (PT) method and a flow-based method of area ratio (AR) were combined and tested in eight catchments in a lake basin. The performance of the PT method depended on the model simulation and donors, which were related to physical and climate characteristics of the catchments. Two AR methods were compared and the results showed that the standard AR method was suitable in this study area with the area ratio between donor and target ranging from 0.46 to 1.41. ENS and R2 values suggested that the PT method used in this study showed a better result than the AR method in 75% of the considered sites, but the total runoff deviation was lower for the standard AR method than that for the PT method. We used the standard AR method weighted by the PT method, and compared three versions weighted with daily, monthly, and average ENS values of the PT and AR methods and one unweighted version. The results of the combined methods were promising. The version weighted with daily ENS performed best and gave improved R2 and daily ENS values for 75% of the receivers. The unweighted combined method performed stable in all sites. The combined method gave better simulation of daily and monthly continuous runoff in ungauged catchments than each individual method.
Highlights
Continuous runoff data is prerequisite for hydrological forecasting and water resource management.The reliability of hydrological decision-making increases as the accuracy of the runoff time series increases
We explored a combined transfer method which could be used to estimate continuous runoff in ungauged catchments
Seven parameters were estimated during the manual calibration, including the lower zone nominal storage, LZSN; the index to infiltration capacity, INFILT; the groundwater recession parameter, AGWRC; the fraction of groundwater inflow that goes to inactive groundwater, DEEPER; the upper zone nominal storage, UZSN; the interflow inflow parameter, INTFW; and the interflow recession parameter, IRC
Summary
Continuous runoff data is prerequisite for hydrological forecasting and water resource management. The reliability of hydrological decision-making increases as the accuracy of the runoff time series increases. Because of the limitations of monitoring technology and the cost of monitoring, continuous runoff data is not always available, and frequently there are inadequate or no measurements for river basins [1]. In China, a single hydrological station may control an area of more than 3000 km , so there are monitoring stations on most large rivers, the number of stations is small relative to the size of the watershed. Monitoring stations are generally unevenly distributed, and many small catchments remain ungauged. The estimation of continuous runoff is important
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