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In order to evaluate how current speed, salinity and water temperature stratification
behaves under the influence of a freshwater source in a tidal domain, a 25 hour survey
campaign was performed in the upper sector of the Vouga River estuary, the major
source of freshwater of Ria de Aveiro, a coastal lagoon located in the Northwest of the
Iberian Peninsula.
The sampling campaign started at 10:30 AM of January 15th 2004 and ended next day,
covering two tidal cycles, during neap tide condition (tidal range of about 1.7 m) and low
river runoff (58 m3 s-1). Observations of the thermohaline properties and currents were
undertaken at an anchor station located about 9 km upstream of the mouth of the lagoon.
Local meteorological variables were also measured.
Vertically lunar hourly profiles of salinity, water temperature and current speed were
obtained and the results indicate that the estuary is forced by semi-diurnal tides. The
profiles of current intensity indicated an asymmetry between flood (v>0) and ebb (v<0)
being the ebb currents higher than the flood ones, with maximum values of about -1.1
and 0.7 m s-1, respectively. The major ebbing velocity was enhanced by the freshwater
runoff. The lunar hourly variations of salinity and water temperature reveal that during the
ebb, the vertical stratification decreases, increasing during the flood period. The salinity
ranges between 0 and 32 psu and the water temperature between 10.9 and 13.7 ºC.
Near the surface, the water temperature is influenced by the air temperature, decreasing
along the day. At mid-water and near the bed the salinity and water temperature
increases during the flood periods, decreasing during the ebb. From the time mean
salinity and current profiles for the 25 hours period were obtained the stratification and
circulation parameters of the classical Stratification-Circulation Diagram (Hansen and
Rattray, 1966), revealing that the estuary can be considered partially mixed-highly
stratified.

The subject of this article is the estimation of quantitative (hydrological) and qualitative
parameters in the catchment of Ronnea (1800 Km2, located in south western Sweden)
through the application of the Soil and Water Assessment Tool (SWAT). SWAT is a river
basin model that was developed for the U.S.D.A. Agricultural Research Service, by the
Blackland Research Center in Texas. The SWAT model is a widely known tool that has
been used in several cases world-wide. It has the ability to predict the impact of land
management practices on water, sediment and agricultural chemical yield in large
complex watersheds. The present work investigates certain capabilities of the SWAT
model which have not identified up to now. More in specific, the main targets of the work
carried out are the following:
• Identification of the existing hydrological and qualitative conditions
• Preparation - Processing of data required to be used as input data of the model
• Hydrological calibration - validation of the model, in 7 subbasins of the Catchment
of Ronnea
• Estimation and evaluation of the simulated qualitative parameters of the model
All available data were offered by the relevant Institutes of Sweden, in the framework of
the European program EUROHARP. The existing conditions in the catchment of Ronnea,
are described in detail including topography, land uses, soil types, pollution sources,
agricultural management practices, precipitation, temperature, wind speed, humidity,
solar radiation as well as observed discharges and Nitrogen and Phosphorus substances
concentrations. Most of the above data were used as input data for the application of
SWAT model. Adequate methods were also used to complete missing values in time
series and estimate additional parameters (such as soil parameters) required by the
model.
Hydrological calibration and validation took place for each outlet of the 7 subbasins of
Ronnea catchment in an annual, monthly and daily step. The calibration was achieved by
estimating parameters related to ground water movement and evaluating convergence
between simulated and observed discharges by using mainly the Nash & Sutcliffe
coefficient (NTD). Through the sensitivity analysis, main parameters of the hydrological
simulation, were detected. According to the outputs of the SWAT model, the water
balance of Ronnea catchment was also estimated.
Hydrological calibration and validation is generally considered sufficient in an annual and
monthly step. Hydrological calibration – validation in daily step, generally does not lead to
high values of the NTD indicator. However, when compared to results obtained by the
use of SWAT in Greece, a relatively high value of NTD is achieved in one subbasin.
Finally, a comparison between the simulated and observed concentrations of total
Phosphorus and Nitrogen was carried out.

Agriculture is an economic activity that contributes significantly to the gross national
product of a country, securing at the same time the viability of the rural sector and the
social coherence. On the other hand, it can generate an environmental externality,
especially concerning water resources that, in the name of higher crop productivity, are
often overexploited or polluted. Most agricultural decision analysis studies are primarily
focusing on farmers’ welfare optimization. Therefore, this externality is only examined as
a negative environmental effect of different farming and agricultural policy scenarios.
However, a proper decision analysis in the field of agricultural policy should be guided by
the goal of finding a unique “optimal” solution out of a great number of possible
alternatives that arise from a complex integrated socio-economic and environmental
system, which incorporates significant conflicted interests.
The main objective of this paper is to create, apply and evaluate a model that aims at the
simultaneous maximization of farmer’s welfare and the minimization of the consequent
environmental burden. More specifically, weighted and lexicographic goal programming
techniques are employed. These techniques are implemented on a representative area in
the Loudias River Basin in Greece to seek for a compromising solution - in terms of area
and water allocation (under different crops) - resulting in figures that will come as close as
possible to the decision maker’s economic, social and environmental goals.
The information that is incorporated into the selected goals includes farmers’ welfare,
characterized by securing income and employment levels, as well as environmental
benefits, such as water resources protection from excessive application of fertilizers and
from unsustainable use of irrigation water. Several weights or priority levels can be
assigned on these goals, according to the intentions of the decision maker, that are likely
to differentiate the final allocation of resources. Hence, the analysis is undertaken under
different policy scenarios (e.g. environmental friendly, farmers’ friendly and compromising
scenarios) and the results are well elucidated. In addition, it is further examined the
different final outcome that may arise when the targets of the various economic and
environmental goals are relaxed in order to reduce the information bias from the decision
maker as well as to better perceive the indirect relationship between some competitive goals.

Two Integrated Surface water - Groundwater flow Models (ISGMs) have been developed
at the National Technical University of Athens (NTUA), Greece and Cardiff University
(CU), UK to investigate surface water-groundwater interactions. The models are based on
physical processes and are capable of describing more accurately the recharge and
discharge flow paths between surface and ground waters.
The NTUA ISGM consists of a 3-D surface water flow sub-model (FLOW-3DL) and a 3-D
saturated groundwater flow sub-model. The CU ISGM is based on the 2-D surface water
model DIVAST, which has been extended to include 2-D saturated groundwater flow.
Both models use the finite difference method and orthogonal grids. The momentum and
mass conservation equations are the governing equations for both surface and
groundwater flows.
The ISGMs have been applied to two simple cases and their results have been compared
to computations using only surface water models (FLOW-3DL and DIVAST) to
demonstrate the need to use ISGMs for accurate and satisfactory calculations.
Furthermore, the results of the two ISGMs are compared for a channel, which fully
penetrates an aquifer. The two ISGMs show a similar behaviour; the NTUA ISGM exhibits
a slightly slower response of the aquifer water levels to the water level changes in the
channel than the CU ISGM.