3-D Transient Hydraulic Tomography in Unconfined Aquifers with Fast Drainage Response

We investigate, through numerical experiments, the viability of three-dimensional transient hydraulic tomography (3DTHT) for identifying the spatial distribution of groundwater flow parameters (primarily, hydraulic conductivity K) in permeable, unconfined aquifers. To invert the large amount of transient data collected from 3DTHT surveys, we utilize an iterative geostatistical inversion strategy in which outer iterations progressively increase the number of data points fitted and inner iterations solve the quasi-linear geostatistical formulas of Kitanidis. In order to base our numerical experiments around realistic scenarios, we utilize pumping rates, geometries, and test lengths similar to those attainable during 3DTHT field campaigns performed at the Boise Hydrogeophysical Research Site (BHRS). We also utilize hydrologic parameters that are similar to those observed at the BHRS and in other unconsolidated, unconfined fluvial aquifers. In addition to estimating K, we test the ability of 3DTHT to estimate both average storage values (specific storage Ss and specific yield Sy) as well as spatial variability in storage coefficients. The effects of model conceptualization errors during unconfined 3DTHT are investigated including: (1) assuming constant storage coefficients during inversion and (2) assuming stationary geostatistical parameter variability. Overall, our findings indicate that estimation of K is slightly degraded if storage parameters must be jointly estimated, but that this effect is quite small compared with the degradation of estimates due to violation of “structural” geostatistical assumptions. Practically, we find for our scenarios that assuming constant storage values during inversion does not appear to have a significant effect on K estimates or uncertainty bounds

Monetary policy before and after the euro: evidence from Greece

We model Greek monetary policy in the 1990s and use our findings to address two interrelated questions. First, how was monetary policy conducted in the 1990s so that the hitherto highest-inflation EU country managed to join the euro by 2001? Second, how compatible is the current ECB monetary policy with Greek economic conditions? We find that Greek monetary policy in the 1990s was: (i) primarily determined by foreign (German/ECB) interest rates though still influenced, to some degree, by domestic fundamentals; (ii) involving non- linear output gap effects; (iii) subject to a deficit of credibility culminating in the 1998 devaluation. On the question of compatibility our findings depend on the value assumed for the equilibrium post-euro real interest rate and overall indicate both a reductio n in the pre-euro risk premium and some degree of monetary policy incompatibility. Our analysis has policy implications for the new EU members and motivates further research on fast-growing EMU economies

Current account imbalances and real exchange rates in the Euro area

Global current account imbalances have been one of the focal points of interest for policymakers during the last few years. Less attention has been paid, however, to the diverging current account balances of the individual euro area countries. In this paper we consider the dynamics of current account adjustment and the role of real exchange rates in current account determination in the EMU. After controlling for the effects of income growth, we find the relationship between real exchange rates and the current account to be substantial in size and subject to non- linear effects. Overall, we argue that real exchange rates can offer further insights, beyond the effects of the income catch-up process, relevant to current account determination in the EMU

The Greek debt crisis: likely causes, mechanics and outcomes

We use insights from the literature on currency crises to offer an analytical treatment of the crisis in the market for Greek government bonds. We argue that the crisis itself and its escalating nature are very likely to be the result of: (a) steady deterioration of Greek macroeconomic fundamentals over 2001-2009 to levels inconsistent with longterm EMU participation; and (b) a double shift in markets’ expectations, from a regime of credible commitment to future EMU participation under an implicit EMU/German guarantee of Greek fiscal liabilities, to a regime of non-credible EMU commitment without fiscal guarantees, respectively occurring in November 2009 and February/March 2010. We argue that the risk of contagion to other periphery EMU countries is significant; and that without extensive structural reforms the sustainability of the EMU is in question

Corruption as a form of extreme individualism: an economic explanation based on geography and climate conditions

We present a simple model explaining corruption on geography and climate conditions. We test the model’s validity in a cross-section of 115 countries. Controlling for all other corruption’s determinants we find evidence supporting the model’s predictions. Corruption increases with temperature and declines with precipitation and non-cultivatable land. Corruption also declines with per capita GDP, democracy, median age and British colonial heritage; and increases with natural resources, bureaucracy and communist past. Finally, corruption declines with the ratio of internet users to total population. This new finding is interpreted as capturing the beneficial interaction of economic development, human capital/education and independent news

A Field Proof-of-Concept of Aquifer Imaging Using 3-D Transient Hydraulic Tomography with Modular, Temporarily-Emplaced Equipment

Hydraulic tomography is a field scale aquifer characterization method capable of estimating 3-D heterogeneous parameter distributions, and is directly sensitive to hydraulic conductivity (K), thus providing a useful data source for improving flow and transport models. We present results from a proof-of-concept field and modeling study in which we apply 3-D transient hydraulic tomography (3DTHT) to the relatively high-K and moderately heterogeneous unconfined aquifer at the Boise Hydrogeophysical Research Site. Short-duration (20 min) partially penetrating pumping tests, for which observed responses do not reach steady state, are used as the aquifer stimulation. To collect field data, we utilize a system of temporarily emplaced packer equipment to isolate multiple discrete intervals in boreholes. To analyze the data, we utilize MODFLOW combined with geostatistical inversion code based on the quasilinear approach of Kitanidis (1995). This combination of practical software allows inversion of large datasets (\u3e250 drawdown curves, and almost 1000 individual data points) and estimation of K at \u3e100,000 locations; reasonable runtimes are obtained using a single multicore computer with 12 GB of RAM. The K heterogeneity results from 3DTHT are cross-validated against K characterization from a large set of partially penetrating slug tests, and found to be quite consistent. The use of portable, modular equipment for field implementation means that 3DTHT data collection can be performed (including mobilization/demobilization) within a matter of days. Likewise, use of a practical, efficient and scalable numerical modeling and inversion strategy means that computational effort is drastically reduced, such that 3-D aquifer property distributions can be estimated quickly

The EMU sovereign-debt crisis: fundamentals, expectations and contagion

We offer a detailed empirical investigation of the European sovereign debt crisis based on the theoretical model by Arghyrou and Tsoukalas (2010). We find evidence of a marked shift in market pricing behaviour from a ‘convergence-trade’ model before August 2007 to one driven by macro-fundamentals and international risk thereafter. The majority of EMU countries have experienced contagion from Greece. There is no evidence of significant speculation effects originating from CDS markets. Finally, the escalation of the Greek debt crisis since November 2009 is confirmed as the result of an unfavourable shift in country specific market expectations. Our findings highlight the necessity of structural, competitiveness-inducing reforms in periphery EMU countries and institutional reforms at the EMU level enhancing intra-EMU economic monitoring and policy co-ordination

A new solution to the purchasing power parity puzzles? Riskaversion, exchange rate uncertainty and the law of one price: insights from the market of online air-travel tickets

We argue that even in perfectly frictionless markets risk aversion driven by exchange rate uncertainty may cause a wedge between the domestic and foreign price of a totally homogeneous good. We test our hypothesis using a natural experiment based on a unique micro-data set from a market with minimum imperfections. The empirical findings validate our hypothesis, as accounting for exchange rate uncertainty we are able to explain a substantial proportion of deviations from the law of one price. Overall, our analysis suggests the possibility of a new solution to the purchasing power parity puzzles

Hydrological Parameter Estimations from a Conservative Tracer Test with Variable-Density Effects at the Boise Hydrogeophysical Research Site

Reliable predictions of groundwater flow and solute transport require an estimation of the detailed distribution of the parameters (e.g., hydraulic conductivity, effective porosity) controlling these processes. However, such parameters are difficult to estimate because of the inaccessibility and complexity of the subsurface. In this regard, developments in parameter estimation techniques and investigations of field experiments are still challenging and necessary to improve our understanding and the prediction of hydrological processes. Here we analyze a conservative tracer test conducted at the Boise Hydrogeophysical Research Site in 2001 in a heterogeneous unconfined fluvial aquifer. Some relevant characteristics of this test include: variable-density (sinking) effects because of the injection concentration of the bromide tracer, the relatively small size of the experiment, and the availability of various sources of geophysical and hydrological information. The information contained in this experiment is evaluated through several parameter estimation approaches, including a grid-search-based strategy, stochastic simulation of hydrological property distributions, and deterministic inversion using regularization and pilot-point techniques. Doing this allows us to investigate hydraulic conductivity and effective porosity distributions and to compare the effects of assumptions from several methods and parameterizations. Our results provide new insights into the understanding of variable-density transport processes and the hydrological relevance of incorporating various sources of information in parameter estimation approaches. Among others, the variable-density effect and the effective porosity distribution, as well as their coupling with the hydraulic conductivity structure, are seen to be significant in the transport process. The results also show that assumed prior information can strongly influence the estimated distributions of hydrological properties