Unit hydrographs for estimating surface runoff and refining the water budget model of a mountain wetland

The level of ecological awareness with respect to living organisms and their habitats in mountain wetlands has risen in recent years. Understanding hydrological conditions and habitat characteristics are essential for wetland conservation and restoration. Surface runoff is one of the significant water gains in mountain wetlands but is challenging to measure in situ and might influence water budget estimations. This study conducts hydrological investigations to establish a synthetic unit hydrograph (SUH) to estimate the surface runoff levels and improve the water budget model (WBM) of the Menghuan wetland, which is the only natural habitat of Isoetes taiwanensis. The findings show that maintaining a water depth ranging from 26 to 57 cm might help I. taiwanensis to compete with other aquatic plants in the dry season. The inlet surface runoff results that were calculated by the SUH were approximately twice those of gully runoff. After using the SUH calculation results, the residual WBM decreased significantly. The results reveal an advantageous opportunity to replace traditional surface runoff surveys in mountain wetlands. The water budget model modified herein is a valuable tool for estimating water requirements in a small-basin mountain wetland. •A synthetic unit hydrograph was developed to determine the surface flow of a mountain wetland.•The residuals of the water budget model (WBM) decrease significantly after incorporating the synthetic unit hydrograph.•The modified WBM helps to manage the water conservation of the endemic aquatic fern species Isoetes taiwanensis.