Evapotranspiration capture and stream depletion due to groundwater pumping under variable boreal climate conditions: Sudogda River Basin,Russia

Groundwater pumping and changes in climate-induced recharge lead to lower groundwater levels and significant changes in the water balance of a catchment. Water previously discharged as evapotranspiration can become a source of pumpage. Neglecting this effect leads to overestimated streamflow depletion. A small river basin (Sudogda River Basin, Russia) with a boreal climate and with long-term records of groundwater head and streamflow rate (showing that the measured stream depletion is less than the pumping rate) was investigated. The role of evapotranspiration in the water balance was analyzed by a hydrogeological model using MODFLOW-2005 with the STR package; the annual variation in recharge was obtained with the codes Surfbal and HYDRUS. The Sudogda River Basin was classified according to landscape and unsaturated-zone texture classes, and for each classified zone, the unsaturated-zone flow simulation was used to calculate the annual recharge dynamics for the observation period. Calibration of the regional flow model was conducted using flow and head observations jointly for two steady-state flow conditions—natural (before pumping started) and stressed (pumping). The simulations showed that pumped water originates from three sources: intercepted baseflow (75% of the annual total pumping rate), the capture of groundwater evapotranspiration discharge plus increased groundwater recharge (17%), and induced stream infiltration (8%). Additionally, multi-year precipitation records were analyzed to detect any long-term recharge and pumping water-budget changes. The results showed that increasing groundwater recharge by natural precipitation leads to (1) decreased intercepted baseflow and induced streamflow infiltration and (2) increased intercepted evapotranspiration discharge, thereby reducing stream depletion.     

Mixing in Shallow Waters： Measurements, Processing, and Applications

Microstructure profiling measurements taken on a shallow Black Sea shelf and in Lake Banyoles and Boadella reservoir (Both in Spain) are analyzed to investigate the influence of boundary-layer-induced turbulence of various sources on mixing in the water interior. The state of turbulence in shallow waters is examined and details of microstructure data processing and error analysis are discussed. The dependence between averaged activity parameter AG and buoyancy Reynolds number Reb for the shelf turbulence indicates that for Reb < 1 the state of turbulence can be described by the fossil turbulence model, which postulates AG-Reb1/2. For Reb> 1, however, the influence of Reb on AG is weak, signifying that the buoyancy Reynolds number can no longer serve as the governing parameter for active turbulent mixing. The generation of turbulence by a one-minute long wind bursts (the Boadella reservoir) increases the averaged dissipation rate (e) of the surface mixed layer by more than 5 times (up to 3×10-6 W kg-1). The influence of the wind bursts was also traced below the ther-mocline, where turbulent patches with     

The Ca II triplet lines in Starburst and AGN

In the frame of the Starburst Model for AGN, we show that the evolution of a massive stellar cluster in a high metallicity environment can reproduce the observed equivalent widths of Ca II triplet lines in absorption in Starburst and active galactic nuclei. In the case of Starburst galaxies, this strength, together with the emission-line ratio [O II]/[O III], can be used to determine the age of the cluster. The strength of the Ca II lines is mainly governed by the age of the stellar cluster through the presence of red supergiant stars.     

Multi-proxy climate and environmental records from a Holocene eutrophic mire,southern taiga subzone,West Siberia

Palaeoenvironmental reconstructions from peat are strongly focused on ombrotrophic mires, but this study demonstrates that eutrophic mires can also be used. A multi-proxy approach was applied to a eutrophic mire on a floodplain terrace in the southern taiga of West Siberia. The results of the reconstruction were considered in the wide geographic context of the surrounding regions, including Siberia and Central Asia. Different palaeoecological proxies (analysis of plant macrofossils, testate amoebae, oribatid mites, molluscs, peat humification, ash content and spectral characteristics of humic acids) were used in this study. The results of different proxies showed a high level of consistency among themselves, which allowed for a robust interpretation of Holocene mire development. Throughout the ~7800 years history of the mire, there was a high level of surface wetness. The presence of mineral matter in the peat between 7800 and 5100 cal. a BP indicates regular flooding caused by the intensive fluvial activity, apparently resulting from increased precipitation. This was followed by a trend towards a gradual decrease in surface wetness from conditions of high surface moisture (stagnant water) between 5100 and 3000 cal. a BP to present day conditions of moderate surface moisture with a water table slightly below the mire surface. This pattern is consistent with the well-documented long-term trend from palaeoecological records throughout the taiga and arctic zones in West Siberia and central arid Asia. Our data further support the idea that the westerlies were the dominant driver of climate for the southern taiga of West Siberia during the Middle to Late Holocene.     

Construction and screening of a functional metagenomic library to identify novel enzymes produced by Antarctic bacteria

A metagenomic fosmid library of approximately 52 000 clones was constructed to identify functional genes encoding cold-adapted enzymes. Metagenomic DNA was extracted from a sample of glacial meltwater,...     

Imposex levels and concentrations of organotin compounds (TBT and its metabolites) in Nassarius nitidus from the Lagoon of Venice

Specimens of Nassarius nitidus were collected in seven stations of the Venice Lagoon to assess the levels of tributyltin (TBT) and its metabolites monobutyltin and dibutyltin in the tissues and monitor their effect on organisms, in particular the phenomenon of imposex (superimposition of male sexual characteristics on females). The following values of population indices were found: vas deferens sequence: 1.2+/-0.7-4.0+/-0.5; relative penis length: 6-47%. The least impacted station was situated in the northern part of the Lagoon, where females without imposex were found and Butyltin (BuTs) concentrations in the organisms (average sum of BuTs=43+/-14 ngSng(-1)w.) were significantly lower than in the other stations (range of average sum of BuTs: 101+/-22-217+/-27 ngSng(-1)d.w.). Population indices were found to be related to the TBT content in the tissues. In particular VDSI had a significant logarithmic correlation: r=0.95, n=8, p<0.05.     

Measure of the exponential splitting of the homoclinic tangle in four-dimensional symplectic mappings

Using four-dimensional symplectic maps as a model problem, we numerically compute the unstable manifolds of the hyperbolic manifolds of the phase space related to the single resonances. We measure an exponential dependence of the size of the lobes of these manifolds through many orders of magnitude of the perturbing parameter. This is an indirect numerical verification of the exponential decay of the normal form, as predicted by the Nekhoroshev theorem. The variation of the size of the lobes turns out to be correlated to the diffusion coefficient.