2024-03-29T10:24:47Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/179352022-05-24T09:25:04Zcom_10261_50com_10261_8col_10261_303
2009-10-22T11:44:32Z
urn:hdl:10261/17935
Flood routing and alluvial aquifer recharge along the ephemeral arid Kuiseb River, Namibia
Morin, Efrat
Grodek, T.
Dahan, Ofer
Benito, Gerardo
Kulls, C.
Jacoby, Y.
Langenhove, G. Van
Seely, M.
Enzel, Yehouda
Alluvial shallow aquifer
Aquifer recharge
Arid zones
Flash flood infiltration
Transmission loss
Africa
14 pages, 14 figures, 4 tables
Flood water infiltrates ephemeral channels, recharging local and regional aquifers, and it is the main
water source in hyperarid regions. Quantitative estimations of these resources are limited by the scarcity
of data from such regions. The floods of the Kuiseb River in the Namib Desert have been monitored for 46
years, providing a unique data set of flow hydrographs from one of the world’s hyperarid regions. The
study objectives were to: (1) subject the records to quality control; (2) model flood routing and transmission
losses; and (3) study the relationships between flood characteristics, river characteristics and
recharge into the aquifers. After rigorous quality-testing of the original gauge-station data, a flood-routing
model based on kinematic flow with components accounting for channel-bed infiltration was constructed
and applied to the data. A simplified module added to this routing model estimates aquifer
recharge from the infiltrating flood water. Most of the model parameters were obtained from field surveys
and GIS analyses. Two of the model parameters—Manning’s roughness coefficient and the constant
infiltration rate—were calibrated based on the high-quality measured flow data set, providing values of
0.025 and 8.5 mm/h, respectively. This infiltration rate is in agreement with that estimated from extensive
direct TDR-based moisture measurements in the vadose zone under the Kuiseb River channel, and is
low relative to those reported for other sites. The model was later verified with additional flood data and
observed groundwater levels in boreholes. Sensitivity analysis showed the important role of large and
medium floods in aquifer recharge. To generalize from the studied river to other streams with diverse
conditions, we demonstrate that with increasing in infiltration rate, channel length or active channel
width, the relative contribution of high-magnitude floods to recharge also increases, whereas medium
and small floods contribute less, often not reaching the downstream parts of the arid ephemeral river
at all. For example, more than three-quarters of the floods reaching the downstream Kuiseb River (with
an infiltration rate of 8.5 mm/h) would not have reached similar distances in rivers with all other properties
similar but with infiltration rates of 50 mm/h. The recharge volume in the downstream segment in
the case of higher infiltration is mainly contributed by floods with magnitude P93rd percentile, compared
to floods in the 63rd percentile at an infiltration rate of 8.5 mm/h.
2009-10-22T11:44:32Z
2009-10-22T11:44:32Z
2009
artículo
Journal of Hydrology 368: 262–275 (2009)
0022-1694/
http://hdl.handle.net/10261/17935
:10.1016/j.jhydrol.2009.02.015
eng
http://dx.doi.org/10.1016/j.jhydrol.2009.02.015
closedAccess
Elsevier