Search

This article deals with stakeholders' interactions and institutional capacity influencing water resource management where competitive demands co-exist. For the case study area of Axios Delta, Northern Greece, a water deficit in the agricultural sector, an unmet environmental flow and a reduced capacity for urban supply during drought conditions are observed. An egocentric network analysis based on desk-study and a series of semi-structured stakeholder interviews reveals how weak stakeholder ties lead to ineffective multilevel governance and, as a result, low water efficiency practices. There is a lack of understanding of other users' priorities as well as of the risks related to climate change and/or seasonal variability. This is reflected in the flat rate abstraction licence for agricultural purposes which reduces environmental flow to below acceptable standards. There is no transboundary cooperation between Greece and the Republic of North Macedonia which hinders an integrated management approach. A limited exchange of information to support an evidence-based allocation plan is observed. Suitable interventions identified through a DPSIR approach are evaluated in a multi-criteria analysis considering cost effectiveness, delivered benefits as well as ease of implementation. Suitable technical practices include the development of a local and catchment-scale monitoring network for surface water and groundwater, climate-adaptive agriculture and treated-water reclamation. Updated management policies involve the institutional prioritisation of environmental flow through an adaptive allocation plan as well as the strengthening of transboundary cooperation. This research shows how the coordination of aggregated diverging interests in multilevel multi-stakeholder environments appears to be key in supporting positive water budgets in an uncertain climate future., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A mechanistic understanding of processes controlling the transport and viability of bacteria in porous media is critical for designing in situ bioremediation and microbiological water decontamination programs. We investigated the combined influence of coating sand with iron oxide and silver nanoparticles on the transport and viability of Escherichia coli cells under saturated conditions. Results showed that iron oxide coatings increase cell deposition which was generally reversed by silver nanoparticle coatings in the early stages of injection. These observations are consistent with short-term, particle surface charge controls on bacteria transport, where a negatively charged surface induced by silver nanoparticles reverses the positive charge due to iron oxide coatings, but columns eventually recovered irreversible cell deposition. Silver nanoparticle coatings significantly increased cell inactivation during transit through the columns. However, when viability data is normalised to volume throughput, only a small improvement in cell inactivation is observed for silver nanoparticle coated sands relative to iron oxide coating alone. This counterintuitive result underscores the importance of net surface charge in controlling cell transport and inactivation and implies that the extra cost for implementing silver nanoparticle coatings on porous beds coated with iron oxides may not be justified in designing point of use water filters in low income countries., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The formation of preferential flow paths in the partially saturated zone, and in naturally structured media, is well known. This study examines non-uniform flow in uniform sand columns under different pressure and infiltration/drainage conditions. Experiments were carried out in a vacuum box, with applied suction set to three different heads, and with infiltration fixed at two different flow rates. Tailing observed in some conservative tracer breakthrough curves suggests the formation of immobile resident water pockets which slowly exchange mass with the flowing water fraction. The applied suction controlled the degree of water immobilization whereas flow rate had minimal effect on the dynamic behavior. Trapping and exchange of water occurred repeatedly during successive infiltration and drainage cycles, implying a (hysteretic) memory effect of the previously formed preferential flow paths. Flow and solute transport modeling suggests that these dynamics can be described by a mobile-immobile model that corroborates measurements suggesting preferential flow path formation. These findings have implications for the natural attenuation of contaminants in the partially saturated zone, but also for the persistence of a contamination source exposed to repeated conditions of infiltration and drainage., (Copyright © 2014 Elsevier B.V. All rights reserved.)