The effect of streamflow, ambient groundwater, and sediment anisotropy on hyporheic zone characteristics in alternate bars

The hyporheic exchange is the main driver for the biogeochemical transformations of nutrients within a river bed. The current study addresses the variations in hyporheic zone (HZ) characteristics in alternate bars due to different streamflow, ambient groundwater, and sediment anisotropy. Several simulations, using a sequentially coupled surface water‐groundwater model of a synthetic reach with fully developed alternate bars morphology, were performed. Two HZs exist within the streambed; a shallow zone that is more linked to surface water, and a deep one that is more influenced by the groundwater variations. Increasing streamflow, and therefore bar submergence, decreases the hyporheic flow. The residence times distribution is bimodal, which implies the existence of two HZs . This bimodality is enhanced by anisotropic sediment conditions, while it is much milder in isotropic ones. The shallow zone residence times increase when streamflow value rises, while the residence times in the deep HZ are less affected. The mean and median residence times decrease by increasing streamflow in partially submerged case, and they are larger in fully submerged case. The hyporheic flow, area, residence times, and extent decrease by increasing groundwater fluxes. The deep zone is the most affected by the groundwater fluxes. Hyporheic flow and extent values are significantly larger in isotropic conditions than in anisotropic ones. The change in residence times values is different between the deep and shallow zones. A predictive model is driven to predict the hyporheic flux, residence times, and hyporheic depths dependence on bar submergence, ambient groundwater, and sediment anisotropy

Half-happy architecture

A reflection around Aravena's Prizker Price and the upcoming 2016 Venice Biennale

Bajo escasez. ¿Media casa basta? Reflexiones sobre el Pritzker de Alejandro Aravena

RESUMEN: El artículo construye una agenda política de transgresión disciplinar contra el capitalismo a partir de las razones que valieron para Alejandro Aravena un Premio Pritzker y la curatoría de la Bienal de Venecia 2016. En ambos casos, las instituciones patrocinantes han informado que se reconoce el rol de Aravena como arquitecto social con una agenda orientada a ayudar a las personas de escasos recursos. A lo largo del artículo se expone la naturaleza ideológica de estas nominaciones y se expone la necesidad de emancipar la arquitectura de la subyugación a los objetivos de la rentabilidad, acumulación de capital y reproducción de ciclos de poder. Se argumenta que este sometimiento al capital ha destruido la naturaleza creativa de la disciplina generando una crisis cuya salida puede darse con más teorización, organización colectiva y explorando nuevos modos de producción. Se convoca a salir de la zona de confort y abrazar la crítica como un camino posible hacia la liberación disciplinar. ABSTRACT: This article proposes a political agenda for a disciplinary transgression against capitalism based upon the reasons that amounted to Alejandro Aravena a Pritzker award and his curatorial job in Venice Biennale 2016. In both cases, the sponsoring institutions argued that Aravena embodies a social architect with an agenda oriented to aiding people living on scant resources. Throughout the article the ideological nature of these nominations are revealed, and the need to emancipate architecture from the subjugation to profitability, capital accumulation and the reproduction of the cycles of power is exposed. It is argued that the subjugation to capital has destroyed the creative nature of the discipline, triggering a crisis whose release may be tackled through more theory, collective organization, and exploring new modes of production. The article promotes leaving the comfort zone in order to embrace critique as a possible path toward disciplinary liberation

Self-consistent coupling between driven electron tunneling and electromagnetic propagation at terahertz frequencies

An accurate procedure for coupling (time-dependent) driven electron tunneling and electromagnetic propagation at terahertz frequencies cannot be developed neither with equivalent electric-circuit approximations nor using standard electromagnetic solvers. Alternatively, in this work, a full-physical time-dependent self-consistent algorithm for such coupling is presented. In order to demonstrate the numerical viability of the algorithm and to show the great interest of driven electron tunneling devices for terahertz applications, a transistorlike tunneling device (coupled to lossy transmission lines) is designed for developing a rectifier, a harmonic generator, and an amplitude modulator at terahertz frequencies

An innovative framework for real-time monitoring of pollutant point sources in river networks

Simultaneous identification of the location and release history of pollutant sources in river networks is an ill-posed and complicated problem, particularly in the case of multiple sources with time-varying release patterns. This study presents an innovative method for solving this problem using minimum observational data. To do so, a procedure is proposed in which, the number and the suspected reaches to the existence of pollutant sources are determined. This is done by defining two different types of monitoring stations with an adaptive arrangement in addition to real-time data collection and reliable flow and transport mathematical models. In the next step, the sources’ location and their release history are identified by solving the inverse source problem employing a geostatistical approach. Different scenarios are discussed for different conditions of number, release history and location of pollutant sources in the river network. Results indicated the capability of the proposed method in identifying the characteristics of the sources in complicated cases. Hence, it can be effectively used for the comprehensive monitoring of river networks for different purposes

Economic analysis of flood risk applied to the rehabilitation of drainage networks

Over time, cities have grown, developing various activities and accumulating important economic assets. Floods are a problem that worry city administrators who seek to make cities more resilient and safer. This increase in flood events is due to different causes: poor planning, population increase, aging of networks, etc. However, the two main causes for the increase in urban flooding are the increment in frequency of extreme rainfall, generated mainly by climate change, and the increase in urbanized areas in cities, which reduce green areas, decreasing the percentage of water that seeps naturally into the soil. As a contribution to solve these problems, the work presented shows a method to rehabilitate drainage networks that contemplates implementing different actions in the network: renovation of pipes, construction of storm tanks and installation of hydraulic controls. This work focuses on evaluating the flood risk in economic terms. To achieve this, the expected annual damage from floods and the annual investments in infrastructure to control floods are estimated. These two terms are used to form an objective function to be minimized. To evaluate this objective function, an optimization model is presented that incorporates a genetic algorithm to find the best solutions to the problem; the hydraulic analysis of the network is performed with the SWMM model. This work also presents a strategy to reduce computation times by reducing the search space focused mainly on large networks. This is intended to show a complete and robust methodology that can be used by managers and administrators of drainage networks in cities

Role of the hyporheic zone in increasing the resilience of mountain streams facing intermittency

5openInternationalItalian coauthor/editorWe investigated the impact of intermittence in previously-perennial Alpine stream reaches, targeting the role of the hyporheic zone in increasing the resilience of these aquatic systems. We selected a perennial and an intermittent site in a reach of the Po River (North-Western Italy). We installed piezometers reaching −1 m (permanent and intermittent site), and −3 m (intermittent site) and monitored three supraseasonal droughts over a period of three years. We classified the hyporheic fauna into three categories of increasing affinity to life in the hyporheic (stygoxene, stygophile, stygobite), and used communities composition, abundance, beta-diversity and functional groups: (1) to compare assemblages at the same depth but with different hydrological characteristics, as well as assemblages from two depths at the intermittent site, and (2) to assess how the connection with surface water and the direction of the vertical aquifer flow determined the faunistic assemblages. Different taxonomic groups responded differently to intermittence, the hyporheic zone acted as a refuge increasing the resilience of the system, but resilience decreased with increasing degree of affinity to hyporheic life. Disentangling the effects of intermittence on the different faunistic component in the hyporheic zone can help guiding effective protection and restoration measures of river systems with temporary reaches.openBruno, M.C.; Doretto, A.; Boano, F.; Ridolfi, L.; Fenoglio, S.Bruno, M.C.; Doretto, A.; Boano, F.; Ridolfi, L.; Fenoglio, S

Role of the hyporheic zone in increasing the resilience of mountain streams facing intermittency

We investigated the impact of intermittence in previously-perennial Alpine stream reaches, targeting the role of the hyporheic zone in increasing the resilience of these aquatic systems. We selected a perennial and an intermittent site in a reach of the Po River (North-Western Italy). We installed piezometers reaching -1 m (permanent and intermittent site), and -3 m (intermittent site) and monitored three supraseasonal droughts over a period of three years. We classified the hyporheic fauna into three categories of increasing affinity to life in the hyporheic (stygoxene, stygophile, stygobite), and used communities composition, abundance, beta-diversity and functional groups: (1) to compare assemblages at the same depth but with different hydrological characteristics, as well as assemblages from two depths at the intermittent site, and (2) to assess how the connection with surface water and the direction of the vertical aquifer flow determined the faunistic assemblages. Different taxonomic groups responded differently to intermittence, the hyporheic zone acted as a refuge increasing the resilience of the system, but resilience decreased with increasing degree of affinity to hyporheic life. Disentangling the effects of intermittence on the different faunistic component in the hyporheic zone can help guiding effective protection and restoration measures of river systems with temporary reaches

Role of the hyporheic zone in increasing the resilience of mountain streams facing intermittency

We investigated the impact of intermittence in previously-perennial Alpine stream reaches, targeting the role of the hyporheic zone in increasing the resilience of these aquatic systems. We selected a perennial and an intermittent site in a reach of the Po River (North-Western Italy). We installed piezometers reaching ??1 m (permanent and intermittent site), and ??3 m (intermittent site) and monitored three supraseasonal droughts over a period of three years. We classified the hyporheic fauna into three categories of increasing affinity to life in the hyporheic (stygoxene, stygophile, stygobite), and used communities composition, abundance, beta-diversity and functional groups: (1) to compare assemblages at the same depth but with different hydrological characteristics, as well as assemblages from two depths at the intermittent site, and (2) to assess how the connection with surface water and the direction of the vertical aquifer flow determined the faunistic assemblages. Different taxonomic groups responded differently to intermittence, the hyporheic zone acted as a refuge increasing the resilience of the system, but resilience decreased with increasing degree of affinity to hyporheic life. Disentangling the effects of intermittence on the different faunistic component in the hyporheic zone can help guiding effective protection and restoration measures of river systems with temporary reaches