![]() Une méthode est proposée, qui combine les procédures existantes de modélisation probabiliste inverse des eaux souterraines et une méthode nouvelle pour l’EDAI. L’hétérogénéité du sous-sol nécessite une évaluation du compromis entre les avantages d’une information supplémentaire destinée à réduire le risque lié à des décisions erronées et le coût de la collecte de cette information. Dans le cas d’une planification de l’exploitation et de l’abaissement des eaux souterraines dans les zones où des risques-comme l’affaissement du sol, l’assèchement des puits, le drainage des cours d’eau et des zones humides-sont présents, le besoin de mesures de sécurité réduisant le risque doit être soigneusement évalué et géré. Une procédure est présentée qui vise l’évaluation de l’analyse des informations (EDAI) dans le but de déterminer le besoin en connaissances supplémentaires quand on estime l’effet de plusieurs alternatives de conception pour gérer les perturbations futures au sein des systèmes hydrogéologiques. The method is demonstrated for a case study of a planned tunnel in Stockholm, Sweden, where additional investigations produce a low number of benefits as a result of low failure rates for the studied alternatives and a cause-effect chain where the resulting failure probability is more dependent on interactions within the whole system rather than on specific features. In comparison with existing approaches for VOIA, the method can assess multiple design alternatives, use hydrogeological parameters as proxies for failure, and produce spatially distributed VOIA maps. The method results in (1) a prior analysis where uncertainties regarding the efficiency of safety measures are estimated, and (2) a pre-posterior analysis, where the benefits of expected uncertainty reduction deriving from additional information are compared with the costs for obtaining this information. A method is suggested that combines existing procedures for inverse probabilistic groundwater modelling with a novel method for VOIA. The heterogeneity of the subsurface calls for an assessment of trade-offs between the benefits of additional information to reduce the risk of erroneous decisions and the cost of collecting this information. When planning for groundwater extraction and drawdown in areas where risks-such as land subsidence, wells running dry and drainage of streams and wetlands-are present, the need for risk-reducing safety measures must be carefully evaluated and managed. Studio Express Groundwater calculates retention pond recovery times in aquifers like this.A procedure is presented for valuation of information analysis (VOIA) to determine the need for additional information when assessing the effect of several design alternatives to manage future disturbances in hydrogeological systems. Looking to calculate the recovery times or mounding analysis (unsaturated and saturated) for retention ponds in shallow sandy aquifers? Check out Studio Express Groundwater feature. Retention Pond Recovery in Shallow Aquifers In the example below, it shows that the WQv fills the pond up to elevation 102.5 and it takes around 15.4 hours to completely drain. Drain Time plot will reveal the elevation in the pond that represents that volume as well as its time to drain. Just make adjustments to your outlet devices until the desired drain time is achieved.įor example, if you have chosen to include a water Quality Volume (WQv) in Step 1, the Stage vs. This chart provides an excellent visual guide as shown below. Drain Time plot is available at Step 3 – Add Outlets in the Pond Designer. Once the outflow in the pond gets below 0.01 cfs, the drain time calculations stop and it is assumed the pond is, for all practical purposes, empty. Hydrology Studio computes time to empty until the flow, Qave, reaches 0.01 cfs. Qave = average outflow from Stage n to Stage n-1Īs shown in the table below, it would take 3.49 hours for this particular pond to drawdown from Stage 0.35 feet. Time = incremental drawdown time from Stage n to Stage n-1ĭStor = change in storage from Stage n to Stage n-1 Drawdown times are computed at each Stage shown on the Output Table where you enter your outlet devices. Hydrology Studio uses the “average head/average discharge” method to compute drawdown time. ![]()
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