Infiltration and Artificial Recharge at the Al-Alb Dam, Riyadh

Fritz Kalwa1, Sebastian Bauer1, Randolf Rausch2
1 Institut für Geowissenschaften - CAU Kiel
2 GIZ International Services, Riyadh, Saudi Arabia

P 10.5 in Hydrogeology of arid zones

The more than 250 dams in Saudi-Arabia are filled up by flash floods regularly. Due to the huge amounts of sediments which are carried into the barrier lakes by flash floods, the lake beds consist of fine-grained, low-permeable sediment, resulting in very slow infiltration and a long superficial sojourn time with high evaporation losses.
The study is set up to evaluate two different techniques for improving the infiltration/evaporation ratio - via slug wells or via percolation through the higher permeable downstream sediments - using the example of the Al-Alb Dam near Riyadh. To compare the effect of slug wells, downstream percolation and pure lake bed infiltration, three different scenarios were set up for the discharge after a rainfall event.
To estimate the effect of slug wells, the barrier lake, wherein slug wells had been installed several years ago, was observed over a long time after a rainfall event. For an estimation of infiltration via the sediments inside the lake and downstream of the dam, double-ring infiltrometer tests (DRIT) and a laboratory permeameter after Hartge (1966) were executed. Both methods showed comparable results, but also revealed problems for some soil types. Lateral leakage via mud cracks in the very fine-grained lake-bed sediment during execution of DRIT caused problems, as well as problematic conditions for sample-taking for the permeameter - especially from very coarse-grained soils.
Both the flooding of the downstream sediments as well as the installation of slug wells increases the infiltration/evaporation ratio significantly. Since results for both techniques range in a similar magnitude, neither of the two shows a clear advantage compared to the other one.

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last modified 2013-11-04