Continuous daily hydrograph simulation using duration curves of a precipitation index

Abstract

The paper describes a parsimonious approach for generating continuous daily stream-¯ow time-series from observed daily rainfall data in a catchment. The key characteristic in the method is a duration curve. It is used to convert the daily rainfall information from source rain gauges into a continuous daily hydrograph at the destination river site. For each source rain gauge a time-series of rainfall related`current precipitation index' is generated and its duration curve is established. The current precipitation index re¯ects the current catchment wetness and is de®ned as a continuous function of precipitation, which accumulates on rainy days and exponentially decays during the periods of no rainfall. The process of rainfall-to-runo conversion is based on the assumption that daily current precipitation index values at rainfall site(s) in a catchment and the destination site's daily¯ows correspond to similar probabilities on their respective duration curves. The method is tested in several small catchments in South Africa. The method is designed primarily for application at ungauged sites in data-poor regions where the use of more complex and information consuming techniques of data generation may not be justi®ed.

Importance of maximum snow accumulation for summer low flows in humid catchments

“…The influence of snow conditions on summer low flow will likely decrease due to predicted air temperature increase during winter and thus the decrease of S/P ratio and SWE at middle elevations. The snow fraction has an important effect on not only annual discharge (Berghuijs et al, 2014;Speich et al, 2015;Zhang et al, 2015) but also on summer low flows as documented by Godsey et al (2014) in the western United States and Laghari et al (2012) Switzerland, and based on these studies, we may conclude that summer low flows are significantly sensitive to any SWE changes. Although our study did not focus on existing trends in data, we expect a reducing effect of snow on late summer low flows in the highest-elevation catchments.…”

Standardized precipitation index‐based approach to predict environmental flow condition

“…Many hydrological methods are available for estimation of EF, but Tennant method is quite popular worldwide. Smakhtin and Masse (2000) proposed a method for the generation of time series of daily flow data using the observed daily precipitation in a catchment. The application of the approach suggested was demonstrated on the various catchments located in South Africa and is very useful for the ungauged or poorly gauged sites.…”

Estimating daily inflows of large lakes using a water‐balance‐based runoff coefficient scaling approach

“…This method can be easily operated, but it cannot account for the spatial and temporal rainfall differences between the ungauged catchments and the reference catchment. The flow duration curve (FDC)-based nonlinear spatial interpolation methods are another commonly used tool to estimate daily flow at ungauged catchments (e.g., Atieh et al, 2017;Smakhtin & Masse, 2000;Zhang, 2017). For this method, a daily FDC is first estimated for the ungauged catchment.…”