Use of the continuous slope-area method to estimate runoff in a network of ephemeral channels, southeast Arizona, USA

SummaryThe continuous slope-area (CSA) method is an innovative gaging method for indirect computation of complete-event discharge hydrographs that can be applied when direct measurement methods are unsafe, impractical, or impossible to apply. This paper reports on use of the method to produce event-specific discharge hydrographs in a network of sand-bedded ephemeral stream channels in southeast Arizona, USA, for water year 2008. The method provided satisfactory discharge estimates for flows that span channel banks, and for moderate to large flows, with about 10–16% uncertainty, respectively for total flow volume and peak flow, as compared to results obtained with an alternate method. Our results also suggest that the CSA method may be useful for estimating runoff of small flows, and during recessions, but with increased uncertainty.

► The CSA runoff-estimation method was tested in sand-bedded ephemeral stream channels.
► The method provided an efficient way to quantify duration and volume of runoff.
► Results displayed between 10% to 16% uncertainty.
► As implemented, the method provided direct estimates of transmission losses.
► The method is satisfactory for moderate to large flows, less so for small flows.