Abstract
Abstract. In this study we propose a multi-source data approach for quantifying long-term flooding and aquifer recharge in ungauged ephemeral rivers. The methodology is applied to the Buffels River, at 9000 km2 the largest ephemeral river in Namaqualand (NW South Africa), a region with scarce stream flow records limiting research investigating hydrological response to global change. Daily discharge and annual flood series (1965–2006) were estimated from a distributed rainfall-runoff hydrological model (TETIS) using rainfall gauge records located within the catchment. The model was calibrated and validated with data collected during a two year monitoring programme (2005–2006) at two stream flow stations, one each in the upper and lower reaches of the catchment. In addition to the modelled flow records, non-systematic flood data were reconstructed using both sedimentary and documentary evidence. The palaeoflood record identified at least 25 large floods during the last 700 yr; with the largest floods reaching a minimum discharge of 255 m3 s−1 (450 yr return period) in the upper basin, and 510 m3 s−1 (100 yr return period) in the lower catchment. Since AD 1925, the flood hydrology of the Buffels River has been characterised by a decrease in the magnitude and frequency of extreme floods, with palaeoflood discharges (period 1500–1921) five times greater than the largest modelled floods during the period 1965–2006. Large floods generated the highest hydrograph volumes, however their contribution to aquifer recharge is limited as this depends on other factors such as flood duration and storage capacity of the unsaturated zone prior to the flood. Floods having average return intervals of 5–10 yr (120–140 m3 s−1) and flowing for 12 days are able to fully saturate the Spektakel aquifer in the lower Buffels River basin. Alluvial aquifer storage capacity limiting potential recharge by the largest floods is a common problem in arid environments, with the largest infiltration volumes favoured by increasing depth to groundwater levels.
Highlights
The methodology is applied to the Buffels River, at 9000 km2 the largest ephemeral river in Namaqualand (NW South Africa), a region with scarce stream flow records limiting research investigating hydrological response to global change
Ephemeral rivers are characterised by an intermittent hydrology, dominated by flood and drought episodes, which has generally meant that water resource management strategies are less well developed than for perennial river basins (e.g. Benito et al, 2009)
As a contribution to improving information on floodrecharge hydrology in ephemeral rivers (e.g. Greenbaum et al, 2002; Morin et al, 2009), we propose a multidisciplinary methodological approach to quantify flood discharge, floodwater volume and aquifer recharge for ungauged ephemeral rivers
Summary
Ephemeral rivers are characterised by an intermittent hydrology, dominated by flood and drought episodes, which has generally meant that water resource management strategies are less well developed than for perennial river basins (e.g. Benito et al, 2009). Ephemeral rivers are characterised by an intermittent hydrology, dominated by flood and drought episodes, which has generally meant that water resource management strategies are less well developed than for perennial river basins G. Benito et al.: Rainfall-runoff modelling and palaeoflood hydrology logistical/monitoring problems that may occur during the occasional large floods that produce flow (Morin et al, 2009). Greenbaum et al, 2002; Morin et al, 2009), we propose a multidisciplinary methodological approach to quantify flood discharge, floodwater volume and aquifer recharge for ungauged ephemeral rivers. The methodology was applied in the Buffels River basin, the largest ephemeral river in Namaqualand (northwest South Africa), an example of a large dryland region 45 000 km2) with virtually no ephemeral river flow monitoring stations The methodology was applied in the Buffels River basin, the largest ephemeral river in Namaqualand (northwest South Africa), an example of a large dryland region (ca. 45 000 km2) with virtually no ephemeral river flow monitoring stations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
