Sequential Characterization of Contaminant Plumes Using Feedback Information

In many practical field problems, it may not be possible to identify the actual characteristics (location, magnitude and duration of contamination) of the groundwater contaminant sources in a contaminated aquifer. Also, most of the time, very sparse information regarding spatiotemporal contaminant concentration is available initially, which is inadequate for reliable identification and simulation of the contaminant plume. Simulation of the contaminant plume movement is necessary to predict the future distribution of the contaminant in the groundwater aquifer. Reliable simulation and prediction are also essential for developing an efficient contamination monitoring strategy. To address this practical problem of data inadequacy, an interactive methodology is proposed, incorporating the sequential design of optimal monitoring networks. These sequentially developed and implemented monitoring networks provide feedback information on measured concentrations. This measurement information helps in progressively improving the prediction of the contaminant plume, starting with very sparse initial information about the contaminant sources and spatial distribution of concentration. The proposed methodology is based on an optimization model that utilizes feedback information obtained from sequentially designed contaminant monitoring sites to sequentially characterize the contaminant plume when adequate initial concentration measurements are not available, and the contaminant sources are unknown

Climate change impacts on groundwater recharge- uncertainty, shortcomings, and the way forward?

An integrated approach to assessing the regional impacts of climate and socio- economic change on groundwater recharge is described from East Anglia, UK. Many factors affect future groundwater recharge including changed precipitation and temperature regimes, coastal flooding, urbanization, woodland establishment, and changes in cropping and rotations. Important sources of uncertainty and shortcomings in recharge estimation are discussed in the light of the results. The uncertainty in, and importance of, socio-economic scenarios in exploring the consequences of unknown future changes are highlighted. Changes to soil properties are occurring over a range of time scales, such that the soils of the future may not have the same infiltration properties as existing soils. The potential implications involved in assuming unchanging soil properties are described. To focus on the direct impacts of climate change is to neglect the potentially important role of policy, societal values and economic processes in shaping the landscape above aquifers. If the likely consequences of future changes of groundwater recharge, resulting from both climate and socio-economic change, are to be assessed, hydrogeologists must increasingly work with researchers from other disciplines, such as socio-economists, agricultural modellers and soil scientists