The dependence of stream depletion by seasonal pumping on various hydraulic characteristics and engineering factors

Compensation pumping is used to alleviate deficiencies in streamflow discharge during dry seasons. Short-term groundwater pumping can use aquifer storage instead of catchment-zone water until the drawdown reaches the edge of the stream. The capacitance is a complex, dimensionless parameter of an aquifer system that defines the delayed effect on streamflow when there is groundwater pumping. This parameter is a function of aquifer hydraulic characteristics, pumping time, and distance between the well and stream edge; the latter can involve stream leakance and vertical leakance of an associated aquitard. Three typical hydraulic cases of combined water systems (major catchment-zone wells close to the stream and compensation pumping wells) were classified depending on their capacitance structure (i.e. the relationship between surface water and groundwater): (1) perfect hydraulic connection between the stream and aquifer; (2) imperfect hydraulic connection between the stream and aquifer; and (3) essentially imperfect hydraulic connection between the stream and the underlying confined aquifer. The impact of various hydraulic characteristics and engineering factors on stream depletion was examined by conceptual and numerical modeling. To predict the suitability and efficiency of a combined water system application, regression tests were undertaken on unit stream depletion and capacitance, and power dependencies were defined.     

A numerical study of the stabilization effect of steepness

We present the results of numerical experiments about the influence of steepness on the resonant structure, stability and diffusion in a 4-dimensional symplectic map. The map is designed so that by changing a parameter, we smoothly switch steepness on and off by the change of the so called steepness coefficients. In both cases we measure the diffusion coefficients of the actions within a resonance. According to Nekhoroshev theorem we find that, in the steep case, the diffusion coefficients are definitely smaller than in the non steep one, thus confirming the threshold effect of the steepness coefficients which comes from the proof of Nekhoroshev theorem.     

Some results on the global dynamics of the regularized restricted three-body problem with dissipation

We perform an analysis of the dynamics of the circular, restricted, planar three-body problem under the effect of different kinds of dissipation (linear, Stokes and Poynting–Robertson drags). Since the problem is singular, we implement a regularization technique in the style of Levi–Civita. The effect of the dissipation is often to decrease the semi-major axis; as a consequence the minor body collides with one of the primaries. In general, it is quite difficult to find non-collision orbits using random initial conditions. However, by means of the computation of the Fast Lyapunov Indicators (FLI), we obtain a global view of the dynamics. Precisely, we detect the regions of the phase space potentially belonging to basins of attraction. This investigation provides information on the different regions of the phase space, showing both collision and non-collision trajectories. Moreover, we find periodic orbit attractors for the case of linear and Stokes drags, while in the case of the Poynting–Robertson effect no other attractors are found beside the primaries, unless a fourth body is added to counterbalance the dissipative effect.     

From picket fences to iron gates: suburbanization and gated communities in Phoenix,Las Vegas and Seattle

Suburbanization has been a prominent urban process in the United States since the World War II. It has transformed American cities in profound ways in every single aspect of urban development; from population and wealth distributions, through political organization and affiliations, to the built environment. This paper investigates the link between gated communities and the process of suburbanization in the context of socio-economic inequality. It has been shown time and again in the scholarly literature on suburbanization, that suburban neighborhoods in American cities have been traditionally more affluent and less diverse than central cities. The research on gated communities in the US also shows that they are, on average, more affluent compared to other communities in terms of family income and housing values. Are gated communities then simply a new form of suburban communities? Is the gated community in fact a suburban community with the added element of security features? The paper investigates these questions based on segregation and spatial analyses. The research contributes to the long line of studies on suburbanization, gating and the larger issues of urban inequality.     

Integrating statistical information concerning historical floods: ranking and interval return period estimation

The importance of the historical information in flood analysis has previously been underlined. In this context, we present an integral methodology aimed at the establishment of return periods of different flood units on the unique basis of historical data. Specifically, the reconstruction of the flood chronology extended back to 1900, complemented with a new (historical data-based) event intensity index, and the return period estimation will be addressed. Since some of the historical data are collected from interviews and other sources with different degrees of precision and reliability, two kinds of uncertainty will be considered; namely the statistical variability and the imprecision. We propose an innovative methodology involving intervals (ranges), fuzzy sets, and weights to formalize and average the criteria that determine the importance of the different events. On the other hand, to take into account the statistical variability, we propose to estimate the return period in a flexible and efficient way by considering bootstrap confidence intervals. The methodology is particularly useful at ungauged, or partially gauged, flood inundation areas, where the existing flow gauge stations do not give the flood series at the point of interest. A case study developed in Spain is discussed. The results are supported by two recent events, which have been mapped at 1:5000 scale.     

Antecedent controls on the spatial organization of yardangs on the Puna Plateau,north-western Argentina

Yardangs are streamlined ridges that form in arid environments on Earth and Mars through wind-driven abrasion of consolidated substrates. Currently, there is limited consensus on the mechanisms that initiate and establish patterns of yardangs on the landscape. In this work, we examine the spatial organization of yardangs in the Campo de Piedra Pómez ignimbrite deposit of north-western Argentina and identify evidence of antecedent controls on yardang patterns and formation. We mapped 14,826 yardangs in the region using a high-resolution digital elevation model (DEM) and satellite imagery. We classified yardangs as points using a two-stage decision rule based on morphology and spectral characteristics. Point pattern analysis shows that yardangs in the study area are not randomly distributed and commonly exhibit directional anisotropy in point pattern. The anisotropic pattern manifests as bands of closely-spaced yardangs oriented transverse to the dominant northwesterly wind direction. We hypothesize that banding is controlled by pre-existing antecedent topography in the bedrock, such as fumaroles or ridges associated with pyroclastic flow deposits. We present evidence from other locations on Earth and Mars to illustrate that the transverse banding is a common pattern in yardang landscapes.     

Extensive hydrated silica materials in western Hellas Basin,Mars

Near-infrared spectral data indicate the presence of hydrated, poorly crystalline silica where high bulk silica contents have been previously identified in Hellas Basin. No other aqueous phases are identified in these regions and the deposits may be nearly pure. The silica-bearing surfaces are sporadically exposed along a 650 km stretch of the western basin rim within a limited elevation range and display a variety of surface textures suggesting that the materials have been reworked, but not transported large distances. The high abundances and lack of associated aqueous phases indicate that high water to rock ratios were present in the region during the Noachian period but without elevated temperatures or for durations necessary for quartz diagenesis. The silica-bearing materials may have formed via direct precipitation from silica saturated groundwater sources, although other formation mechanisms are also plausible.     

Two-dimensional Non-linear Alfvén Wings Generated by the Electrodynamic Interaction between Callisto and the Jovian Magnetosphere

When a highly conducting magnetized plasma passes an object with lower conductivity, or a body with inhomogeneous conductivity, 2-D structures are formed, the so-called `Alfvén wings'. These structures may arise, for example, at a Jovian moon without an intrinsic magnetic field (Callisto). In this case, Alfvén wings could be generated in the magnetized Jovian magnetospheric plasma flow owing to the in homogeneity of the moon's ionosphere/atmosphere conductivity. Such Alfvén wings may be considered as a satellite magnetosphere; the satellite magnetospheric magnetic field is a disturbed field of the Jovian magnetospheric plasma flow. An analytical solution is obtained in a simple proposed model. This revised version was published online in July 2006 with corrections to the Cover Date.