Volume 14 - 2012

Systematic measurements of sediment transport rates and water discharge were conducted in the
Nestos River (Greece), at a place located between the outlet of Nestos River basin and the river
delta. This basin area is about 838 km2 and lies downstream of the Platanovrysi Dam. Separate
measurements of bed load transport and suspended load transport were performed at certain cross
sections of the Nestos River.
In this study, relationships between sediment transport rates and stream discharge for the Nestos
River are presented. A nonlinear regression curve (4th degree polynomial curve; r2 equals 0.62)
between bed load transport rates and stream discharge, on the basis of 63 measurements, was
developed. In addition, a nonlinear regression curve (5th degree polynomial curve; r2 equals 0.95)
between suspended load transport rates and stream discharge, on the basis of 65 measurements,
was developed.
The relatively high r2 values indicate that both bed load transport rates and, especially, suspended
load transport rates can be predicted as a function of the stream discharge in the Nestos River.
However, the reliability of the regression equations would have been higher if more measured data
were available.

The main objective of this study was to characterize the organic matter present in raw water and
along the treatment process, as well as its seasonal variation. A natural organic matter fractionation
approach has been applied to Lever water treatment plant located in Douro River, in Oporto
(Portugal).
The process used was based on the sorption of dissolved organic matter in different types of ion
exchange resins, DAX-8, DAX-4 and IRA-958, allowing its separation into four fractions: very
hydrophobic acids (VHA), slightly hydrophobic acids (SHA), charged hydrophilic (CHA) and
hydrophilic neutral (NEU). The dissolved organic carbon (DOC) determination was used to quantify
dissolved organic matter. Samples were collected monthly, during approximately one year, from raw
water captured at the surface and under the bed of the river, and after each step of the treatment:
pre-filtration in sand/anthracite filters, ozonation, coagulation/flocculation, counter current dissolved
air flotation and filtration (CoCoDAFF) and chlorination.
The NEU fraction showed a seasonal variation, with maximum values in autumn for the sampling
points corresponding to raw water captured at the surface and under the bed of the river. It was
usually the predominating fraction and did not show a significant decrease throughout the treatment.
Nevertheless their low concentration, the same occurred for the CHA and VHA fractions. There was
an overall decrease in the SHA fraction throughout the water treatment (especially after CoCoDAFF
and ozonation) as well as in the DOC.
The TSUVA254 values obtained for raw water generally varied between 2.0 and 4.0 L mgC-1 m-1 and
between 0.75 and 1.78 L mgC-1 m-1 for treated water. It was observed a decrease of TSUVA values
along the treatment, especially after ozonation.
These results may contribute to a further optimization in the process of treating water for human
consumption.

The hydrochemical characteristics of groundwater in the island of Lesvos, Greece, were studied
based on chemical analyses of groundwater samples collected from 30 locations covering all the
island’s major aquifers hosted in different lithological formations. The Plagioclase dissolution was
found to be responsible for the observed high concentrations of Na and Ca in the majority of volcanic
aquifers. Ultrabasic rocks enrich groundwater with magnesium while intense hydrothermal activity
and extensive alteration zones, which exist locally as a result of a recent volcanic activity, are
associated with the existence of sulphate type groundwater and acidic pH in some areas. Seawater
intrusion was found to be associated with high Cl- concentrations in three sampling locations. Based
on sodium adsorption ratio, percent sodium, and the US salinity diagrams, the vast majority of
groundwater samples were evaluated as suitable for irrigation purposes.

A regional model was developed in the present study for the determination of the flow duration curve
at ungaged catchments, in western and northwestern Greece, which is a hydrologically homogenous
region. A flow duration curve indicates the water availability at a site and is important for the
estimation of the hydropower potential. A flow duration curve was generated for each of seven
available stations at different rivers and then the parameters of the flow duration curves were
correlated with geomorphological and climatic characteristics of the drainage basins for the
derivation of the equations of the regional model. The model was verified using three hold out
stations, in which the error ranged from 0.3 to 1.1%.