Simulation de la recharge artificielle de nappe en oued par un modèle à réservoirs

Dans la zone semi-aride de Tunisie centrale, un grand barrage a été construit en 1982 sur l'oued Zeroud, dont l'infiltration des crues naturelles constituait jadis la principale source d'alimentation des nappes de la plaine de Kairouan. Ce barrage est destiné à l'écrêtement des crues, l'irrigation et à la recharge des nappes à l'aval de la retenue.Entre 1988 et 1996, plus de 70 millions de m3 d'eau ont été mobilisés sous forme d'ondes de lâchers à partir du barrage pour la recharge artificielle par infiltration dans le lit de l'oued. Le suivi des ondes de lâchers est effectué sur 3 stations de contrôle disposées sur une distance de 40 km le long du lit. L'analyse de l'évolution des débits a révélé que la capacité d'infiltration du lit augmente progressivement avant de se stabiliser, mettant en évidence l'effet de l'air sur le processus de recharge.Un modèle conceptuel à réservoirs conjuguant fonctions de production et de transfert avec discrétisation spatiale a permis de modéliser la propagation et l'infiltration des ondes de lâchers le long de l'oued. Son ajustement sur un échantillon de six événements de lâchers a fourni des résultats satisfaisants. Même si la validation reste insuffisante en raison de la rareté des données, ce modèle peut constituer un premier outil d'évaluation de l'efficacité de la recharge et de prédiction de son impact sur la nappe souterraine de la plaine de Kairouan.In semi-arid central Tunisia, flood infiltration through the streambed of the ephemeral Zeroud Wadi has long been the principal mechanism of recharging aquifers beneath the plains of the city of Kairouan. In addition to controlling infiltration, a dam built on the Zeroud in 1982 to supply water to Kairouan also protects the city from floods.From 1988 to 1996 over 70 million cubic meters of dam-held water were mobilized in the form of flood waves over the stream channel to recharge the Kairouan aquifers. Analysis of flow discharges measured at three control stations spanning 40 km of the stream reveals that infiltration is reduced during initial flood-wave spreading and increases gradually before stabilizing. The differential rate of infiltration is thought to be caused by interstitial air initially present.A conceptual reservoir model based on production and transfer functions with spatial discretization was used to simulate flood-wave propagation and infiltration along the Zeroud. After calibration with six flood events the model produced satisfactory results. Though current data scarcity prevents its validation, the model constitutes a prototype for the evaluation of recharge efficiency and for the prediction of recharge impact on Kairouan aquifers

Hydrologic Evaluation of Gemini Photographs of Fringes of the Sahara, Africa

Hydrologic evaluation of Gemini photographs of fringes of Sahara, Afric

Behavior canola (<i>Brassica Napus</i>) following a sewage sludge treatment

International audienceIn this study, two types of sludge were being used, while the first was with urban dominance, the second was with industrial dominance. The effects of sewage sludge had been studied in a Brassica Napus field. The mineralogical, chemical and microscopic study of the sludge showed that industrial sludge had very high levels of Cr, Pb and Cd. These metals existed mainly under the form of daubreelita Cr2FeS4, brezininaite Cr3S4, wattersite Hg5CrO6, crocoite PbC2O4, pheonicochroite Pb2O(CrO4) and Pb-oxalate PbC2O4. The results showed that sludge significantly improves the growth of the underground part of the plant (root) and the upper part (stem, leaves etc...). This improvement is more important for urban sludge. However, this beneficial effect was accompanied by a change in the composition of the plant some trace element metals. An abnormal accumulation of Cr was found in the roots, stem, leaves, and siliques when the industrial sludge was brought which reflected the richness of the latest. The dose-effect sewage sludge was very clear at the levels of Pb in the roots especially for industrial sludge which exceeded the threshold values of toxicity starting from the dose of 25t/ha of industrial sludge. Cd levels only increased with the addition of 100t/ha of industrial sludge. For Ni, Cu, Co and Zn, especially at roots level, the increase depends on mud's dose and especially on its type. On the contrary, levels of iron, and to a less extent manganese levels, had been reduced due to sludge despite their richness with these elements. That was probably due to antagonism with one or more particular elements especially Zn

Les monts d'Ougarta d'après SPOT 1

D'après une image SPOT, un exemple de cartographie géomorphologique en zone aride (Sahara algérien)

Impact of heavy metals in sewage sludge on soil and plants (colza and wheat)

National audienceWe are testing the impact of heavy metals in sludge from urban and industrial wastewater treatment plants. We try to understand their influence on plant growth and their bioaccumulation. We chose two plants: the wheat and rapeseed to their specific characteristics; wheat is a herbaceous low accumulator of heavy metals, however rape (colza) is a plant of the family Brassica napus, is an excellent bio-accumulator of heavy metals. The mean levels found in the soil are organized in the following order: Fe >> Mn> Zn> Pb> Cu> Ni> Co> Cd. The contents of heavy metals in the sludge is made very high and exceed European values allowed for that type of use but remain in the standard NT106 Tunisia. The effects of the contribution of sludge are manifested by a significant increase in the weight gains of the whole plant, these results in a variation of the ratio between the aerial part and roots of the plant; this ratio tends to increase with dose of mud brought in soil increase. The roots of both plants show high levels of Zn even on the ground untreated control. The contents of Ni, Pb and Zn compared to Cu and Co are higher in the roots of rape than wheat

Transfer heavy metal from soil treated to colza

International audienceThe impact of heavy metals were tested in sludge from urban and industrial wastewater treatment plants, trying to understand their influence on colza growth and their bioaccumulation. We chose the colza to their specific characteristics. The colza is a plant of the family Brassica Napus, is an excellent bio-accumulator of heavy metals. The mean levels found in the soil are organized in the following order: Fe >> Mn> Zn> Pb> Cu> Ni> Co> Cd. The contents of heavy metals in the sludge are very high and exceed European values allowed for that type of use. The effects of the contribution of sludge are manifested by a significant increase in the heavy metals of the colza, these results in a variation of the ratio between the aerial part and roots of the plant; this ratio tends to increase with the dose of mud brought in soil. The roots of plants show high levels of Zn even on the ground of untreated soil. The contents of Ni, Pb and Zn, compared to Cu and Co, are higher in the roots of colza

Reversible 6-Squares

A reversible word square is one in which every row can be read backwards, and every column upwards. Every word must be either a reversible word such as LANRET (TERNAL in reverse) or a palindrome, which is a special kind of reversible word. In this article, the term reversible word does not include palindromes. In general, counts include valid rotations and reflections

Twin Places and Other Top Anagrams

The trigger for this article was finding a twin for a town mentioned by Darryl Francis (in the sense that one, El Canbaro, was a permutation of the letters of the other, Barcelona, W03-277). I thought it might be amusing to see how many twin places existed, as it seemed to be as good as basis for town twinning as the reasons often given for these excuses for mayoral junketing. I was overwhelmed: more than one third (about three-quarters of a million) of all places participate in twins, but also nearly a quarter of a million exist in triplets, and so on