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This paper presents and discusses the water and gas geochemistry of a large number of thermal springs occurring along the N-S trending Strymon Valley, from its source, near Sofia (Bulgaria), to the Aegean Sea (Greece). In Bulgaria springs have markedly alkaline p H, relatively low Total Dissolved Solids and prevalent Na-HCO 3 to Na-Cl(SO 4) in composition while the associated gas phase is mostly N 2 -dominated. When moving to the Greek sector, the thermal springs, Ca(Mg)-HCO 3 to Na-HCO 3 , become less alkaline and more saline whereas the associated gas phase is CO 2 -dominated. The abrupt geochemical change in the Greek sector is caused by a variation in the thickness and nature of the sediments filling the Strymon Valley, the latter being characterized by a relevant amount of Neogene marine material. Such changes occur south of an important E -W lineament named Middle Mesta, south of which marble formations extensively crop out and are likely occurring below the sedimentary succession. The presence of these carbonate sequences embedded in the Neogene sediments is explaining the CO 2 -rich gases associated to the Greek springs. Water isotopes indicate a meteoric origin for the studied waters. From a geothermometric point of view, solute (previous studies) and gas (this work) geothermometers suggest that no high enthalpy systems occur in the Bulgaria and northern sector of Greece with estimated temperatures <120 °C. Consequently, these thermal springs can be regarded as tectonically-derived along the many fault systems that border the Strymon Valley. The convective circuits are thus originated from rainfall in the crystalline massifs that border the valley, i.e. the Serbo-Macedonian to the west and the Rhodope to the east. • Water and gas discharges from the Strymon Valley (Bulgaria-Greece) were investigated. • Chemical and isotopic differences between the Bulgarian and Greek samples occur. • No high-enthalpy systems were recognized. • Fluid discharges are mostly driven by tectonic lineaments. • A conceptual model of fluid circulation is proposed. [ABSTRACT FROM AUTHOR]

Abstract: Three R.E.MO.S. (Remote Environmental MOnitoring System) telemetric networks have been installed in the catchment area of River Nestos, by research team PERSEAS. The first network has been installed in Nestos Delta. This network consists of two Remote Stations (R.S.): [•] The first one is called R.S. “Nestos” and is settled in Nestos Delta in Chrysoupoli and [•] the second one is called R.S “Agiasma” and is settled in the homonymous Lagoon. This paper deals with R.S. “Agiasma”, which operates in Agiasma Lagoon, an area of great environmental importance in the west part of River Nestos Delta. The gradients of the water quality and quantity monitored parameters are very important for the ecological preservation of the lagoon. Moreover, this case can be an excellent example of how the real-time monitoring data can work as an alarm system to prevent environmental hazards. The scientific issues this paper is focused on are: [1.] The three years systematic daily electronic monitoring data (1/1/2000–31/12/2002). The monitored parameters are Water level—H (cm), Salinity—Sal (‰), Redox Potential—RP (mV), Dissolved Oxygen—DO (mg/l), Water Temperature—T w (oC) and Air Temperature—T a (oC). [2.] The assessment of water quality and quantity parameters and the aquatic environment of Agiasma lagoon. [3.] The detection of trends, using the non-parametric Spearman''s criterion. This trend analysis proved the existence of trends for the parameters H, Sal and RP. [4.] The necessity of real-time monitoring, which can prevent and confront possible natural hazards and disasters and work as an alarm system for the local authorities. [Copyright &y& Elsevier]

Abstract: The dynamics of the dissolved oxygen in water bodies is the result of complex interactions involving physical and biological processes. Understanding how the balance of these influences determines the amount of oxygen available for living organisms is a key factor to interpret the water body conditions, and eventually to use dissolved oxygen as an indicator of the water quality. In this paper we present a Qualitative Reasoning model developed to improve understanding of changes in the amount of dissolved oxygen in different segments of the river Mesta in Bulgaria. Effects on dissolved oxygen result from changes in physical, chemical and biological processes induced both by natural and anthropogenic activities within the watershed. To explore the possibility of establishing a landmark value that may change according to specific conditions, we developed the concept of flexible value mapping, which dynamically captures changes in the dependencies between the landmark value and the values of other quantities as the conditions of the system change during the simulations. The paper also discusses the concept of dominance of a specific process over other competing processes affecting a quantity. With the model described here, we aim to discuss possible solutions to interesting modelling problems and to provide the community of ecological modellers support for educational activities and water resources management. [Copyright &y& Elsevier]

Abstract: Using satellite data for flood forecasting in catchments located in mid-latitudes is challenging to engineers and model developers, in no small part due to the plethora of data sets that need to be retrieved, combined, calibrated and used for simulation in real time. The differences between the various satellite rainfall data products and the continuous improvement in their quantity and quality render the development of a single software tool, able to read and process all the different data sets, particularly difficult. Even if such an endeavour was undertaken, the degree of flexibility and extensibility that such a tool would require to accommodate future versions of data sets, available in different file formats as well as different temporal and spatial resolution should not be underestimated. This paper describes the development of a flood forecasting system that addresses this issue through a modular architecture based on the use of the Open Modeling Interface (OpenMI) standard, which facilitates the interaction between a number of separate software components. It is suggested that this approach greatly simplifies programming and debugging and eliminates the need to create spatial and temporal transformation functions without significantly compromising the overall execution speed. The approach and system were tested for forecasting flood events within a particularly challenging transboundary catchment, the Evros catchment, extending between Greece, Bulgaria and Turkey. The system uses two sets of data sources, as an example (NASA’s TRMM 3B42 and 3B42RT satellite data sets) to forecast flooding in the Evros catchment. Results indicate that OpenMI greatly facilitates the complex interaction of various software components and considerably increases the flexibility and extensibility of the overall system and hence its operational value and sustainability. [Copyright &y& Elsevier]

Abstract: In this paper, the question of freshwater induced stratification at the mouth of two dam-controlled Greek rivers is addressed. Results from a monitoring program are presented along Strymon River estuary and Nestos River coastal zone, two of the most important freshwater suppliers in the North Aegean Sea. Strymon River flow is man-controlled through Kerkini Dam, while Nestos River discharge patterns depict significant alterations, due to the operation of two hydropower dams. Moreover, a stratification–mixing model was developed based on the water column potential energy ϕ TOTAL, which accounted separately for the local contributions to stratification (solar heating and freshwater buoyancy) and mixing (wind and bottom shear stresses). The model was run under two different scenarios: a) the influence and the absence of Kerkini Dam for the case of Strymon River, and b) the presence and absence of the hydropower dams for the case of Nestos River. Results show that Kerkini Dam affects the stratification conditions in Strymon River mouth during spring and early summer (April to June), by reducing ϕ TOTAL by approximately 13%. In Nestos River mouth, the water column dynamics are highly affected by river damming, as ϕ TOTAL appeared reduced during November to July, by approximately 50.2%. [Copyright &y& Elsevier]

Summary: River flow forecasting consists one of the most important applications in modern hydrology, especially for the effective hydropower reservoir management. In this paper, an innovative non-linear time-series fitting and forecasting model is proposed, consisting of the following sub-modules: (a) the division of the time-series into generations, by identifying the structural change points, (b) the generation decomposition into linear trend, harmonic component and autoregressive component, consisting of several gene ARMA models, (c) the use of fuzzy methods to determine the relative weight of each gene model, and (d) the time-series expansion for the optimal forecasting. The method was applied to the mean monthly Nestos River discharge data for the 1966–2006 period, recorded at the Greek–Bulgarian border, serving as inflow to the Thissavros Hydropower Reservoir. The selected series was divided into five distinctive generations representing periods of gradual surface runoff reduction. It occurred that mean monthly discharge during the fifth generation was almost halved, compared to the corresponding value of the first generation. Harmonic decomposition produced periods in agreement with the large-scale atmospheric fluctuations, while ARIMA modeling performed on the residuals from a pre-defined gene model-base, produced satisfactory fitting to the measured flow series. Model expansion for the last 2 years (2005–2006) of the time-series illustrated reasonable good approximations. Model forecasts during 2005 followed closely the recorded variability, with MAPE and RMSE statistics indicating increased model accuracy. Overall, it is evident that the model slightly underpredicts Nestos River discharge, while slight overestimation occurs under high river flow conditions (winter 2006). Although current research proved model’s distinct capability and advantages in river flow fitting and medium-scale forecast, future improvement could facilitate the use of more elaborative models (ARCH, fuzzy, ANN), in the developed gene model-base. [Copyright &y& Elsevier]