THE IMPACT OF AGRICULTURAL DEVELOPMENT ON KARSTIC GROUNDWATER OF THE SAÏDA MOUNTAINS, ALGERIA

Kvaliteta vode od velike je važnosti za javno zdravstvo te ovaj rad prikazuje praćenje kvalitete podzemnih voda u odabranome području u Alžiru. Dobro upravljanje vodnim resursima ovisi o nizu kvalitativnih mjera te određivanju uzroka zagađenja (poljoprivreda), mjerenju kvalitete i predviđanju ponašanja vodonosnika tijekom dužega razdoblja. U radu se utvrđuju kemijski facijesi, podrijetlo i kvaliteta vode u krškim vodonosnicima planina Saïda u Alžiru. Te planine sastoje se od karbonatnih masiva (vapnenačko-dolomitne stijene) ranoga i srednjega jurskog doba. Vodonosnik planina Saïda napaja se oborinama i relativno gustim privremenim hidrografskim sustavom. Planine su važan vodonosnik sjeverozapadnoga Alžira. Antropogeni utjecaji neprestano mijenjaju fizičko-kemijska svojstva vode u njemu. Koncentracije antropogenih parametara [NO3- (62 mg/l), SO42- (173 mg/l), Cl- (123 mg/l)] u mjernim točkama dostižu kritične vrijednosti rizične za stanovništvo. Interpretacija grafikona antropogenih parametara vode pokazuje kako je primarni izvor onečišćenja poljoprivredna djelatnost, koja se znatno povećala na istraživanome području. Međutim, naša istraživanja i razgovori s voditeljima vodnih resursa pokazuju da i dalje postoje velike poteškoće u provedbi preporučenih zaštitnih mjera.Water quality is a public health issue and this article includes related causes, issues and descriptions for the monitoring of groundwater quality in Algeria. Good water management depends on many qualitative issues, their origin (agriculture), the monitoring of quality and prediction of those parameters during a longer period. The establishment of this work aims at identifying the chemical facies, the origins and the drinking of karstic groundwater of the Saïda Mountains. These mountains are composed of carbonate massifs (limestone-dolomite rocks) of Lower to Middle Jurassic age. They are fed by precipitation and by a relatively dense temporary hydrographic system. The mountains represent an important water reservoir for northwestern Algeria. Anthropogenic impacts have continuously modified the physico-chemical characteristics of the water in this aquifer [NO3- (62 mg/l), SO42- (173 mg /l), Cl- (123 mg/l)]. This represents critical values that pose risks to the population. An interpretation of graphs of anthropogenic water parameters shows that the primary source of pollution is agricultural activity, which has increased significantly in the study area. However, our investigations and interviews with water resource managers showed that great difficulties persist in the implementation of recommended protective actions

A study of karst hydrosystem recharge at the parcel scale, using modeling and correlation analysis - Low noise underground laboratory of Rustrel site

La caractérisation des flux d’eaux qui rechargent réellement les hydrosystèmes souterrains reste un frein à la compréhension du fonctionnement hydrogéologique des milieux souterrains. Lors d’événements pluvieux, quelle part de l’eau est évapo-transpirée ? Quelle part est temporairement stockée dans le sol ? Ces incertitudes sont particulièrement fortes dans le cas de la recharge des milieux hétérogènes tel que le karst. En général, les calculs de recharge des hydrosystèmes karstiques se basent sur une représentation simplifiée de l’évapotranspiration qui considère seulement le climat et pas le fonctionnement de la végétation. Dans cette étude, un modèle de végétation permettant de simuler les transferts d’eaux entre le sol et l’atmosphère en contexte forestier (le modèle CASTANEA), a été appliqué à une parcelle de Chêne vert. L’infiltration efficace (un indicateur de la recharge) estimé avec CASTANEA a été comparée à celle estimée par des approches classiques ainsi qu’à des séries long terme de flux d’eaux souterraines (9 années). Les résultats de cette analyse révèlent que l’infiltration efficace modélisée à partir d’un modèle de végétation comme CASTANEA est plus satisfaisante que les approches classiques ne tenant pas compte du fonctionnement de la végétation. Ce travail ouvre des perspectives intéressantes pour mieux tenir compte du fonctionnement de la végétation et de l’usage du sol sur la recharge des hydrosystèmes karstiques.Assessing the recharge of underground hydrosystems remains an obstacle to understand their hydrologeological functioning. During a rain event, which part of the rain is evapotranspired ? And how much is temporarily stored within the soil ? These questions are particularly relevant in heterogeneous media such as karst hydrosystems. Currently, the models used to compute recharge of karst hydrosystems, rely on simplistic formulations of evapotranspiration that do not account for vegetation functioning. In this study, we used the vegetation process based model CASTANEA, which is designed to compute water transfer between soil, plant and atmosphere. We computed effective infiltration (an index of recharge) with CASTANEA and with other classical approach (based on precipitation minus ETP), and for a welldocumented holm oak site in Provence. Our results provide evidences that effective infiltration computed with CASTANEA yield more satisfactory correlation with measured outflow than simulations based on the classical approach. Our results provide a promising way to improve the simulation of karst hydrosystem recharge

Coupling hydrogeological and speleological data : interest of the approach through a comparison between the studies in LSBB and statements made in the sinkhole of Autrans

International audienc

L’eau

L’eau. On croit connaître son importance. Mais sait-on que le stock d’eau disponible sur terre ne varie pas ? Connaît-on les différentes qualités de l’eau ? Comprenons-nous ce que signifie l’empreinte de l’eau ? En une centaine de pages, avec de nombreux graphiques et un lexique, les auteurs proposent une large synthèse des connaissances concernant cette ressource précieuse et, paradoxalement, rare

Carbone organique total (COT) et magnésium (Mg2+) : deux traceurs complémentaires du temps de séjour dans l'aquifère karstique

International audienc

Characterization of flows in the vadose zone by direct measurements in karst aquifer

International audienc

Hydrogeophysical study of karst unsaturated zone structure and functionning

International audienc

Use of Total Organic Carbon (toc) as Tracer of Diffuse Infiltration in a Dolomitic Karstic System: the Nerja Cave (andalusia, Southern Spain)

[1] Recent studies in several karstic systems in France have highlighted that Total Organic Carbon (TOC) was a relevant parameter in order to characterise the behaviour of aquifers, to differentiate the water types that participate in karstic flow (fast infiltration, unsaturated zone, saturated zone) and to evaluate their vulnerability. This study on TOC dynamics at the experimental site of the Nerja Cave has been performed to test the potential of this tracer in a particular climatic (Mediterranean climate), lithologic (dolomitic marbles) and hydrodynamic (diffuse flow behaviour) context. TOC evolution, compared to those of classical tracers used in hydrogeology, permits the understanding of the hydrodynamical behaviour of the unsaturated zone of this dolomitic aquifer, whose response to precipitation is slower than that commonly obtained in karstic aquifers of calcareous nature

Historical monthly rainfall-runoff database on Fontaine de Vaucluse karst system: review and lessons,

International audienceMany studies have been carried on the Fontaine de Vaucluse karst system (south-east of France) and have proved the complexity of the hydrodynamic behaviour of this system. The question of water storage and water movement in this karst system must still be considered. This spring, famous for its considerable mean flow rate of around 20 m3/s, with maximum flow rate of 100 m3/s, has been time object of curiosity for a long, and, since 1877, the runoff of the spring has been regularly noted. Thus, at present, a 127 years long database of runoff measurement is available. After a review of the old data (1877-1965), the bias induced by the displacement of the gauging station in 1965 has been quantified. We then built a complete and homogeneous monthly runoff database. The analyse and the comparison of monthly runoff and rainfall databases confirms a rapid time response of the system, compared to the large surface of the recharge area. But this analyse has also pointed out unusual high runoff during dry periods occurring after long humid periods (several decades). Whereas an expected deficit is observed on runoff if the dry period occurred after a period characterised by mean amount of precipitation. This seems to confirm the existence of a routing zone of great capacity, characterised by slow water transfer. Thus, it is of great importance to take correctly into account the role of this zone in the response of the system to precipitation, especially to improve the rainfall-runoff simulation