Abstract
In this paper a new approach to gas leakage detection in high pressure natural gas transportation networks is proposed. The pipeline is modelled as a Linear Parameter Varying (LPV) System driven by the source node massflow with the gas inventory variation in the pipe (linepack variation, proportional to the pressure variation) as the scheduling parameter. The massflow at the offtake node is taken as the system output. The system is identified by the Successive Approximations LPV System Subspace Identification Algorithm which is also described in this paper. The leakage is detected using a Kalman filter where the fault is treated as an augmented state. Given that the gas linepack can be estimated from the massflow balance equation, a differential method is proposed to improve the leakage detector effectiveness. A small section of a gas pipeline crossing Portugal in the direction South to North is used as a case study. LPV models are identified from normal operational data and their accuracy is analyzed. The proposed LPV Kalman filter based methods are compared with a standard mass balance method in a simulated 10% leakage detection scenario. The Differential Kalman Filter method proved to be highly efficient.

Abstract
A new approach to gas leakage detection in high pressure distribution networks is proposed, where two leakage detectors are modelled as a linear parameter varying (LPV) system whose scheduling signals are, respectively, intake and offtake pressures. Running the two detectors simultaneously allows for leakage location. First, the pipeline is identified from operational data, supplied by REN-Gasodutos and using an LPV systems identification algorithm proposed in [1]. Each leakage detector uses two Kalman filters where the fault is viewed as an augmented state. The first filter estimates the flow using a calculated scheduling signal, assuming that there is no leakage. Therefore it works as a reference. The second one uses a measured scheduling signal and the augmented state is compared with the reference value. Whenever there is a significant difference, a leakage is detected. The effectiveness of this method is illustrated with an example where a mixture of real and simulated data is used.

Abstract
The assessment of contaminants dispersion in Controlled Dumps (CD) of Municipal Solid Waste (MSW) is possible through the combination of geophysical, geochemical and geostatistical methods as described in this paper. The methodology applied in this study will contribute to evaluate the environmental consequences of the Matosinhos CD (N Portugal), which is set in a granitic crystalline geological context with a permeability controlled by differential weathering associated with fracturing. The statistical methods here described (Lepeltier, 1969; Matschullat et al. 2000) are adapted to use in geophysical data obtained from the resistivity profiles performed in the CD surroundings by the electrical resistivity method. Groundwater samples were collected in piezometers; upstream and downstream of the CD, with the aim of directly confirming the presence of contaminants indirectly detected by the geophysical and geostatistical methods. The combination of these different approaches allows an approach to the detection and delineation of contaminant plumes from these deposits.

Abstract
In a multidisciplinary approach, geological, geomorphologic, structural, hydrogeochemical and isotopic surveys were conducted on the Serra da Estrela groundwater system (central Portugal) in order to establish/develop a conceptual circulation model of the Caldas de Manteigas thermomineral system. A detailed study of the isotopic and geochemical composition of surface waters (e.g. Zzere River), shallow groundwaters (cold dilute springs), and thermomineral waters was carried out to characterize the distribution of isotopes in waters of this mountainous region, and to determine the origin and possible recharge locations of the thermomineral system. Special attention was dedicated to isotopic tracers and their role in the definition of the thermomineral waters' conceptual model, considering: (1) the delta(18)O fractionation gradient; (2) the mean isotopic composition of the thermomineral waters in the region; and (3) the estimation of snowmelt contribution as a source of groundwater recharge at Serra da Estrela. The recharge of the thermomineral aquifer takes place on the more permeable zones of the granitic massif, associated with the main tectonic structures, whereas the recharge of the shallow aquifers seems to take place mostly in the plateaus, although another part of the recharge may occur in the slopes of the Zzere River valley.

Abstract
The main goal of this study is to assess the current environmental state of the Matosinhos Controlled Dump (CD) and its surroundings. Until the end of last century the Matosinhos CD was an open area where all the wastes produced in Matosinhos were deposited. The CD lies in a granitic crystalline geological context with fissure controlled type permeability, which is not common (Mota et al., 2004) in the Portuguese context. With our set of 2D resistivity profiles was possible to detect the presence of two resistivity anomalies indicative of contamination in the Matosinhos CD surrounding, with particular emphasis in the downstream area (unsealed part). The upstream anomaly, with resistivity values lower than 30 O.m, is vertically limited by a more resistive material, a few meters from the northern boundary of the CD. The other one, more extensive, is located in the southern part of the CD, with resistivity values lower than 7 O.m. It was possible to detect that both contamination anomalies were decreasing with the increasing distance of the CD. Comparing the conductivity measurements in water samples collected from upstream piezometers with the values of downstream piezometer the presence of a strong influence of contamination downstream of the CD was found and thus confirmed and correlated with the electrical resistivity data. © 2011 LNEG - Laboratório Nacional de Geologia e Energia, IP.

Abstract
Mountain areas are the source of high quality and socioeconomic relevance water resources. The sustainable management of such regions is fundamental to maintain the water supply to populations in wide areas all over the planet. Serra da Estrela is the origin of water resources of strategic importance to Portugal. In the highest part of the mountain, especially above 1400 m a.s.l., the use of road de-icing chemicals (NaCl and, accessorily, CaCl) may affect both groundwater and surface water as well as soils and therefore is a major environmental concern that should be investigated. This article presents a multidisciplinary methodology meant to support the study of water pollution as a result of the use of road de-icing salts in a mountain environment. This methodology encompasses contributions from Hydrogeology, Hydrogeochemistry, Isotope Geochemistry, Hydrogeophysics, GIS supported geological mapping and mathematical modelling. The main purpose of the application of this methodology in Serra da Estrela is to prepare a hydrogeological conceptual model focused in the processes related to groundwater pollution by NaCl from road de-icing. Another objective is to improve the sustainability of water resources and to provide new guidelines for water exploration and exploitation in the region.