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Web-based tool development to suppor t decision making in aquaculture management in Vietnam

Tim Palmans, Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussel Arnaud De Groof, Spacebel Frederick Lupo, Spacebel

Phan Thi Ngoc Diep, Vietnam Institute of Fisheries Economics and Planning Bruno Samain, Laboratory of Hydrology and Water Management, Ghent University

Valentijn R.N. Pauwels, Laboratory of Hydrology and Water Management, Ghent University Okke Batelaan, Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussel

BIOGRAPHY Tim Palmans, Tim Palmans, Phd-student at the University of Brussels, graduated as a Bio-engineer from the Catholic University of Leuven (2006) and post-graduated in Water resource engineering at the University of Brussels (2007). He is currently involved in research about measuring the water quality of surface waters with remote sensing techniques. Arnaud De Groof, Technical Engineer for Space Applications, graduated as Agricultural engineer from Gembloux Agricultural University in Belgium (2001) and post-graduated in Oceanology from the University of Liège in Belgium (2003). He has seven years of experience in risk management. He joined Spacebel in 2007 as GIS & Remote Sensing Engineer. Frederick Lupo, Frederick LUPO, Technical Manager for Space Applications, graduated as Master in Geo-Sciences. He has ten years of experience with Remote Sensing Applications in various domains (Ocean, Agriculture, etc). He joint SPB in 2004 as a project manager for Remote Sensing projects (Flood risks in Mekong Delta-Vietnam, Landslide in Italy, Mining monitoring in Chile, etc). INTRODUCTION Vietnam is a country with a rich culture and history. The population counts almost 87 million and has a growth rate of 0.977% (July 2009 est., CIA world factbook) and is mainly concentrated in the important deltas of the Red River in the north and the Mekong River in the south. The largest ethnic Vietnamese group (Viet) represents more then 86% of the population. Next to this there are significant ethnic Cambodian (1.4%) and Chinese (1.1%) minorities and the highlands are populated with about 50 minority groups. The number of inhabitants has been rising rapidly in the last decades, as is demonstrated in figure 1.

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Figure 1 - Rise in population in Vietnam from 1961 to 2008. (CIA world factbook & Vietnam General statistic office, 2009). Because of long-lasting war, the loss of some financial support and the rigidities of a centrally-planned economy, the industrial development of Vietnam has stagnated from 1945 through 1980, but in the framework of new economical developments the country is experiencing significant progress in industrial branches like agricultural machinery, car industry, chemical fertilizers, and textile industry, but also tourism is becoming a more and more important source of income for the country (Jansens-Verbeke & Go, 1995). The projects and funding to achieve this progress are the result of cooperation between local and foreign governments, being a good example of the surplus value that can be reached with cooperation among different nations. Although development is going relatively fast in Vietnam nowadays, agriculture is still the primary occupation among the population (CIA world factbook, 2009). The cultivation of rice in the Mekong and Red River deltas is one of the most important rice productions in the world (Ti et al. 2003). The abundant rainfall and the rich alluvial soils in these regions are very well suited for growing this crop (Ninh Nguyen et al., 2007). Fisheries and the increasing importance of aquacultures are also important sources of income in Vietnam, of which shrimp farming is one of the most important examples (Le Cao, 2007). Being an important source of

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proteins and given the fact that the production from wild fisheries has been stagnant over the last decade, the growth rate of aquacultures worldwide has known a strong growth, on average about 8 percent per year over the last thirty years. In 2004, Vietnam was already the third in rank for fish production by aquacultures, producing about 1.2 million tones of fish that year (FAO Fisheries and Aquaculture Department, 2007). The most recent values (see figure 2) show that the output from aquacultures (expressed in tones of fish) has more then doubled in a period of only 4 years.

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Figure 2 - Evolution of total aquaculture production of Vietnam in tones of fish (Vietnam General statistic office, 2009). These facts show that the general development of Vietnam is going very well. However, the rising population and industrialization of the country is also putting more pressure on the natural resources and the environment of the country. One example of this is the rising detrimental effect of deforestation in the highlands as a consequence of new settlements, creating new farm grounds and commercial forestry (De Koninck, 1999). Another example of the rising pressure on the environment is the growing presence of aquacultures along the banks of the above mentioned deltas. Although aquacultures are regarded as a promising and sustainable solution for the future, there are also some concerns because aquacultures can be more environmentally damaging than wild fisheries. These concerns include waste handling, competition between farmed and wild varieties, side-effects of the use of antibiotics and the tendency to produce consumer-desired carnivorous fish, which are much less sustainable then their herbivorous counterparts (Rice, 2008). Because of the growing importance of aquacultures and the concern for the environment, it is important that current practices are monitored so that their sustainability can be evaluated, and improvements for the future can be made efficiently. One of the important inputs needed for this is sharing of the know-how from the industrialized countries, since they have already accumulated knowledge about sustainable practices. It is important, however, to notice that this communication should be organized in two directions. Methods developed in Western countries are not always adjusted to the habits and needs of other regions or cultures, and might thus need revising and adjustments. This form of cooperation

can only be achieved by true sharing of knowledge; expertise and methodology from one side, experience and knowledge on the current state from the other side (Melkote and Steeves, 2001). Another important problem to be tackled in this kind of development work is the fact that consciousness about the environment in developing countries needs to be improved. While it is well known that the interest in environmental problems of developing countries increases as the living standards improve, one cannot disregard the importance of a timely education of the population at large about these issues. This increases the chance that the development can be achieved in a more sustainable way. If the local personnel involved in the projects are conscious about the environment, it can be expected that policy makers take the environment into account as well, so all parties involved will strive for the same goals: economic development in a sustainable way (Melkote and Steeves, 2001). This paper presents the results and the lessons learnt from a cooperative project between Vietnam and Belgium, with as objective to create a tool to evaluate the sustainability of aquacultures along the Mekong Delta riverbanks. Connected to the issues above, a more specific problem encountered in this project is the limited availability of in-situ observed data. This is the result of the limited local know-how and consciousness, and also of limited financial resources. The purpose of this research was to develop a user-friendly web-based tool to offer support for the evaluation of development and sustainability of aquacultures, taking into account the local culture, financial resources, and expertise. These issues are known to often form a bottleneck in development projects. Evaluation of development consists of both environmental as well as socio-economical issues. In this study we focus on the environmental aspects of aquaculture development. To achieve this objective, locally available data sets were used to construct a water quality model of the study area. This local information was provided by local governmental agencies. A training program was organized, in order to allow local civil servants and students to acquire experience in environmental modeling, web applications, remote sensing, and related environmental concepts. An important issue in this program was optimizing the use of existing local development programs and the collaboration among the different interest groups involved. Therefore, it was decided to work towards a result that can be implemented within the locally available system for evaluating agricultural areas. This specific type of evaluation system makes use of an index which is calculated by combining evaluation results about the environment but also about socio-economic aspects. The results of the decision support tool about the sustainability of aquacultures can be used as the environmental input information- to be used in the calculation of a locally developed general evaluation index.

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METHODOLOGY 1. Site description The area of interest (see figure 3) is the Cho Lach district, located in the Ben Tre province, which is one of the 13 provinces of the Mekong delta. Ben Tre is located near the mouth of the Mekong River and is surrounded by the four main rivers; Tien Giang, Ba Lai, Ham Luong, and Co Chien. The main ethnic group populating this area is the Kinh (Sawadee, 2009). The tropical climate of Ben Tre is influenced by monsoons; the rainy season lasts from May to October, during which there are torrential rains and strong wind between September and October. The average annual temperature is 26°C, and the humidity is high due to the monsoon and the presence of many rivers. During the wet season, the average rainfall ranges as high as 1,250 to 1,500 mm, while the precipitation during the dry season amounts to only 2 to 6% of the annual volume (Mercury, 2006). The total area of the Cho Lach district is 189 km² of which 250ha along the banks of the Mekong-river is being used for aquacultures. In 2003 the district had a population of 134,584 inhabitants (Law, 2009). This study site was identified by the Vietnamese partners as highly representative for the entire Mekong delta area (Lupo, 2007).

Figure 3 - Location of the study area 2. Participatory approach From the onset of the project, a strong emphasis was put on the involvement of all stakeholders in the development of the decision support tool. For this reason, training sessions were organized in Belgium and Vietnam, as well as a number of workshops, in order to tune the software with local expertise and requirements. As a first step, a training session was organized by the Belgian project partners and attended by representatives from the Vietnamese Institute of Fisheries Economics and

Planning (VIFEP) and the Vietnamese Association of Seafood Exporters and Producers (VASEP). This training session included web mapping and GIS applications, water quality modeling, remote sensing applications and hydrologic model development. This allowed the partners from both sides to familiarize themselves with the experience of all the project partners. Further, this way the Vietnamese project partners could form an overview of the technical and scientific requirements of the local personnel to efficiently operate the tools developed during the course of the project. A second step focused on the organization of end-users and local farmers. For this purpose, a field visit was performed during which contacts with local farmers were made. This allowed making an inventory of relevant local practices, which was of great help for the model development and application later in the project. A third step involved the organization of a stakeholder workshop in Hanoi, Vietnam. Besides the project partners, representatives of several stakeholders and other institutions attended the workshop [Ministry of Science and Technology (MOST), Ministry of Agriculture and Rural Development (MARD), Ben Tre Department of Agriculture and Rural Development (DARD), The National Directorate of Aquatic Resources Exploitation and Protection (NADAREP)]. First, the Belgian project partners were given the opportunity to present their expertise to all the stakeholders. Then, the modeling tool that was going to be developed was explained in detail, and the requirements with respect to data were listed. During this phase it became apparent that methodologies requiring minimal amounts of in-situ data would have to be applied, due to the limited amount of available datasets. Stakeholders were given the chance to express their concerns regarding user-friendliness and computational complexity of the software. An agreement regarding the collection and transfer of in-situ data was made. During the model development phase, which took place in Belgium, a second training session for Vietnamese partners was held. Training focused on applications of remote sensing. During this week, a meeting was also organized among all project partners, in order to streamline the model development with local needs, and to optimize the use of the available data sets. Finally, after the model development and testing was finished, a final user workshop was organized in Vietnam. The project coordinator, the research teams involved in the model development, and several local organizations and agencies attended this workshop. It consisted of a 4-day training period during which all the steps made in the project, from software installation and data collection to hydraulic/water quality modeling and web mapping applications, were explained to local experts from VIFEP and VASEP. The last day of the workshop was reserved for presenting the results of the project to the officials of VIFEP/VASEP and the officials of the Ben Tre Department of Agriculture and Rural Development (DARD).

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3. Data description In collaboration with the local authorities, a data base for the model development and application could be constructed. The data sets can be classified into a number of categories. A first type of data consists of topographic data. These are of high interest for the hydraulic model development, since terrain slopes are a very important parameter in the determination of stream velocities and consequently river discharges. 76 cross-sections of the Mekong River, plus digitized maps of the locations of these cross-sections were made available. The cross-sections that were used in the hydraulic model are shown in figure 4. Further, digitized locations of streamlines, river banks, mid-river levees, and aquaculture ponds were generated during the course of the project.

Figure 4 - Locations of the measuring stations and the cross-sections Second, river water quantity data were made available. These consisted of daily minimum and maximum water levels for the Cho Lach station for the entire year of 2007, hourly discharge data for the My Thuan station from 2002 through 2007, tidal data for the offshore station of Vung Tau from April through December 2007. Further, daily downstream water level data for Ham Luong and the Tien Giang reaches were available over a 1 year period. With regard to water quality, BOD, H2S, PO4, NO2, NH3, and NO3 measurements were available for 48 ponds during 2008. One measurement of the concentration of the pollutants in the discharge water was available for each pond. Based on these limited data, a water quality model for the region had to be constructed. Two important points thus had to be taken into account. First, the model had to make optimal use of the data sets that were available. Second, the model had to be constructed in such a manner that policy makers can quickly apply the software for scenario analyses. In other words, it should be applicable for a wide range of pollutants, require minimal user input, and be as user-friendly as possible. The approach used in the project to meet these requirements is described in the next section.

4. Development of the model In any modeling study, it should always be kept in mind that a model is always a simplification of reality. Therefore, assumptions always have to be made when developing a model. In this way, reality is discretized into a grouping of variables and parameters that can be calculated, studied and simulated using the available computational facilities. A very important consideration one always has to make in operational model development is the fact that the final objective of the project needs to be kept in mind all the time. On the one hand, a model should of course be based on sound theories and data, and the model should be an approximation of reality. On the other hand, a model which is too complex, even if it can simulate reality almost exactly, is never usable in practice because it is computationally too demanding, and/or because data with sufficient detail are simply not available. In other words, operational modeling activities have to make a trade-off between the complexity and practical applicability of the model. For this reason, a step-by-step modeling strategy was applied in this study. On the one hand, we could not disregard the fact that an adequate modeling of the water quality cannot be achieved without a good modeling of the water quantity. On the other hand, a modeling tool had to be developed, that could be used by policy makers, and that should require minimal computational demands. In this context, it should be noted that the modeling of the water quantity consisted of the application of a hydraulic model on the entire study area. This way, the measurements of water levels and discharge at the inflow and outflow points of the river system could be interpolated to the locations for which model results were desired. Application of a hydraulic model for the study area was computationally rather intensive and requires intensive user involvement. For this reason, it was decided to separately model the water quantity and quality of the study area. This way, the internal discharges and water levels in the study area had to be calculated only once, after which these data could be used in the water quality model (which is computationally much less demanding) for scenario analyses for any number of pollutants. This way, the scenario analyses could be performed without having to re-apply the hydraulic model every time. A further justification of this approach is the fact that hydraulic processes are independent of the water quality values. 4.1 Remote sensing Remote sensing offers the means to circumvent the issue of limited data availability at least partially. On a regional scale, remote sensing can be used for monitoring purposes and as a reference for defining modeling parameters like surface area’s and boundary conditions like the water level. In this context, the use of high resolution optical satellite imagery represents an important opportunity to retrieve very accurate up–to-date geographical data at an affordable cost in time and budget. A particular focus on

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the hydrological network was done to provide hydrological experts with up-to-date information to feed the model. Actually one requirement (among many others) was to have accurate river length and width in order to draw river sections along the branch flowing down and surrounding the Area of interest (the Tien Giang River and the Huam Luong River - Cho lach District). In order to determine these values and to update the existing land use/cover map and the hydrographic network of Cho Lach region, four new satellite images retrieved by the very-high-resolution satellite belonging to the Korean Aerospace Research Institute, KOMPSAT, were acquired (see Table 1). Table 1- Satellite imagery

The use of satellite imagery asks multiple treatments. The Figure 5 summarizes the main steps of the image processing chain from the “ raw” data to the thematic outputs useful for Hydraulic modeling.

Figure 5 - Remote sensing process The first step allowed to compare the data of the vietnamse partners to the satellite data. This analysis was relevant as shown in the results section.

4.2 Hydraulic model 4.2.1 Model selection Several hydraulic models were considered before selecting the one to be implemented in the AQUASID-project. The HEC-RAS program was selected for the following reasons. One of the main reasons is the fact that the program was designed to handle hydraulic problems dealing with great variations in the river system. The reason why this was important for the selection of the model is the fact that the main differences in flow are caused by tidal influence from the ocean, which requires an unsteady flow model. Next to this technical selection criteria, several practical considerations were also made for the selection of the model. The HEC-RAS is freeware, which means it can simply be downloaded from the internet for free from the following link (http://www.hec.usace.army.mil/software/hec-ras/hecras-download.html). This point is important since the project has a limited budget and since the resulting applications coming from the project will mainly be implemented in area’s that do not have a lot of financial capabilities. Another practical consideration for the selection of the HEC-RAS software is the fact that it is quite flexible concerning required data. Data availability has proven to be a big problem in the project, therefore a model was selected that can also run on a limited set of input data. 4.2.2 Application of HEC-RAS in the AQUASID-project The first step in creating the hydraulic model for this project is preparing the geometric data needed to simulate unsteady flow with the HEC-RAS model. To do so, the data set is prepared in Arc-View GIS using the 3D Analyst and Spatial Analyst extensions. The data set contains the river system schematic, cross-section data and the hydraulic structure of the channel. The geometric data set is then converted to a GIS import file using the HEC-GeoRas extension designed to enter and edit geospatial data and then use them to run in Hec-RAS. For practical reasons only two main river branches were modelled. The upper branch of the model is the Tien Giang reach, the lower branch is the Ham Luong reach (see figure 4). The cross section data for both reaches were edited in Hec-Ras. There are two main inputs needed in Hec-Ras for the boundary conditions: upstream and downstream flow or stage hydrograph and initial condition. The upstream flow hydrographs are deducted from the discharge data given for My Thuan station, shown on the map in figure 4. Total discharge in the model is assumed to be 2/3 of the discharge at My Thuan station of which half is assumed to flow through Tien Giang branch, and the other half through Ham Luong branch. Stage hydrograph of the downstream boundary condition is imported from the tidal water level of the Cua Tieu seaport for the Tien Giang reach and of the Cua Ham Luong seaport for the Ham Luong reach. The initial (upstream) condition assumed for each river reach is: Ham Luong: 2000 m3/s, Tien Giang: 1800 m3/s, Tien Giang 1: 1000 m3/s, Tien Giang 2: 1300 m3/s.

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4.3 WQ model 4.3.1 Model selection The governing equation of the water quality model is:

t is the time (s), and x the spatial coordinate (m). c is the concentration (gm−3), V the water velocity (ms−1), D the diffusion coefficient (m2s−1), K the reaction rate (s−1), and S the source-sink term (gm−3s−1). The equation is solved using a Galerkin finite element discretization for the spatial derivatives, and a Crank-Nicholson finite difference discretization for the temporal derivatives. The diffusion coefficient is a pollutant-dependent parameter. For BOD, it is calculated as (Jolankai & Biro, 2000):

Q is the discharge in the channel (m3s-1),

� the slope of

the water line (-), and B the width of the river (m). The reaction rate K is also a pollutant-dependent parameter. For BOD, the value for K can be assumed to be equal 2.66×10-6 s-1 (De Smedt, 1989). The water velocity and the discharge are obtained from the hydraulic model outputs. 4.3.2 Scenario Analysis For the realization of the water quality model in this project, first the assumption was made that the release from groups of ponds in the proximity of a specific cross sections can be treated as a point sources. The hydraulic data for these cross sections that were calculated in the hydraulic model and exported to use as input in the water quality model are the stream velocities, discharges, stream widths and water line slopes. The results were taken for the month April because this is the period with the lowest flows in the river and thus is the most critical period for water quality. Information on the ponds was collected and averaged to attain a representative pollution concentration from the assumed point sources. The location of the separate ponds and the cross sections to which they were assigned are depicted in figure 6.

Figure 6 - Locations of the ponds and the assumed point sources in the WQ model The values used for the source-sink term S were equal to 5, 10, 18, 25, 50, 75, and 100 gm−3s−1. The value of 18 gm−3s−1 was based on in-situ observations, while the other values were used to assess the impact of increased and decreased fish pond pollution. Model simulations were performed for the Tien Giang and the Ham Luong reaches. The ponds were assumed to release the polluted water simultaneously during the four hours with the lowest water level in the reaches. The model was applied using the monthly averaged diurnal cycle of the discharge Q, water velocity V, water line slope

�, and river width B from the hydraulic model.

The model has been applied with a spatial resolution of 100 m, and a temporal resolution of 1 h. 4.4 Web based integration Since several years, the web mapping applications are becoming increasingly popular. Indeed, these applications allow to publish maps and data on the Web and updating information and customizing it for particular needs. Moreover, the power of digital mapping is evident in opposite of the conventional mapping. Thanks to the Internet and the accompanying tools, creating and publishing online maps has become easier and rich with options (Mitchell, 2005). The applications expose select GIS functionality, in an easy-to-use, browser-based map and a wide range of purpose and functionalities (comparison, interrogation,…) are provided with the web application. Relevant for the community, the web mapping can play an important role in the decision system (Juba & al., 2007). Therefore, in the context of the AQUASID project, the web mapping application represents an essential tool:

� to integrate environmental information (and others….) in a unique web service,

� to help in the sustainability development of the aquaculture in Cho Lach district.

From proprietary to open-source softwares, the proposal of web mapping solutions is getting bigger and more and more efficient in terms of geographical use & capabilities. Aiming to development a web mapping application for this project, the selection of a tool represents a critical step. The selection has been undertaken according to a list of criteria: open source,

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ease of deployment, ease to use, ease to update, rapid application development (the scripts are not mandatory), large panel of data connectivity, performance, reactive community of users and possibility to development specific applications. Following these criteria, the MapGuide Open Source software was selected. Note that others tools show good quality but the selected tool represent the best compromise according all the criteria. RESULTS 1. Remote sensing The geographical area studied was covered by four Kompsat-2 scenes (see Table 1). An assemblage of these four overlapping images to create a continuous representation was carried aiming to extract the more relevant data for the hydraulic model. Moreover, the satellite images were compared to the geographical information provided by the Vietnamese partners. The result - after geographical correction according to the satellite imagery - of this analysis showed that:

� The geographical position is not correct in regard of the satellite imagery (see Figure 7a)

� The information is not updated (see Figure 7b) � There is a lack of precision in different area of

the map (see Figure 7c) � The Cho Lach district represents only a small

area of the global case study (see Figure 7d)

Figure 7 - Comparison between information from Vietnamese people and satellite imagery (a: Difference in geo-reference between GIS data and remote sensing data; b: Not updated GIS information when comparing to satellite images; c: Missing information in the GIS data; d: The extent of both the GIS and remote sensing information) This operation allowed to update the data of the Vietnamese partner and showed the added value of the use of satellite imagery. For the extracting the hydrological network of the Mekong River and to digitalize the fish farm ponds, the use of color composite images was applied. This operation allows visualizing spectral information that is not viewed naturally by the eyes, like the infrared band. A specific false color infrared composite was used. This technique associates the sensor’ s near-infrared, red, and green bands with the colors red, green, and blue on the

screen. Many schemes of composite images are possible. This type of composition is specifically use to detect vegetation (appears in bright red); but it is also very efficient also to identify water present a very low reflection (water absorbs practically all wavelengths).

� The extraction of the farm fish ponds The Figure 8 presents the result of the digitalization of the fish farm ponds. The window “Magnification” included in the figure allows zooming to a group of ponds. Although, it was possible to extract information on the farm using an unsupervised or supervised classification, the digitalization of the aquaculture ponds was performed manually in regards of the heterogeneity in the spectral properties and the limited number of fish farms. Following these observations, the digitalization was the best solution.

Figure 8 - Extraction of the fish farm ponds along the Mekong delta in the Cho Lach Region

� The extraction of the hydrographic network of the Mekong river

The Figure 9 presents the hydrological network of the Mekong River in the Cho Lach region. As the hydraulic model doesn’ t ask an important quality in the scale of the network, only the main canals have been extracted.

Figure 9 - Extraction of the hydrographic network of the Mekong river in the Cho Lach Region

� Combination of the two products The Figure 10 presents the combination of the two outputs in a same map.

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Figure 10 - The Mekong river network and the fish farm ponds in the Cho Lach Region In addition to their use for the hydraulic model, these data have been integrated in the web mapping application. 2. Hydraulic model To display some results of the model, the hydrographs for four cross sections are shown in figures 11 through 14. The results calculated with the Hec-Ras model for a one year period show the stage and flow hydrographs for the Ham Luong station upstream (figure 11), for the Tien Giang station upstream (figure 12) and for the first and the second Tien Giang stations downstream (figure 13 and 14 respectively). All results show a typical monthly variation in the flow and stage, more specifically there is a recurring cycle of two high and two low water stages. This can be explained by the tidal influence from the sea on the river, which tends to reach a maximum (and a minimum) twice a month due to the alignment of the sun and the moon, amplifying their gravitational influence. Also the fact that negative flow values are recorded clearly shows that there is an important inflow from the sea into the river. The upstream stations show a more regular variation then the downstream stations, which is probably due to the fact that the water stage and flow is more susceptible to short term variations of the sea level. Also, the stage and flow tend to follow each other very well for the upstream stations, whereas for the downstream stations the stage and flow vary more independently from each other. In both upstream stations there is clear difference between the first and the second part of the year. Vietnam has a single rainy season during the south monsoon (May-September) and during the remainder of the year rain is infrequent and of low intensity. Figures 11 and 12 clearly show an increase in stage and flow starting from the end of May, which obviously can be explained by the start of the rainy season. It can also be seen in the results for the upstream stations that the influence from the sea becomes less pronounced during the rainy season. This can be explained by the fact that the monthly variations mentioned earlier become much less extreme, the fact that there are almost no negative flows recorded in this period and the fact that the discharge is the highest during this period.

The results for the downstream stations show a much lower influence from the rainy season. For the Tien Giang 2 downstream station the variation of the stage is still clearly under the influence of higher river outflows due to the rainy season. The stage recorded in the Tien Giang 2 downstream station, however, shows almost no difference between the dry and rainy season, which means that this reach of the river is much less influenced from river outflow compared to the first Tien Giang reach. Whereas the stage differs significantly for both downstream stations, the flow seems to be relatively similar in both reaches, though the absolute values are larger for the first reach. Both flows show a sudden rise at the start of October and become the lowest around the beginning of the rainy season. It should also be mentioned that for the first reach almost no negative flows are recorded, but that the second reach has mainly negative flow values from April to September. The most extreme variations of flow and stage over the entire year are recorded for the Ham Luong station upstream, with a maximum annual variation of 2.5 meters for the stage and a flow going from -5000 m³s-1 minimum to 15000 m³s-1 maximum. The occurrence of the extremes in this reach is not surprising since the Ham Luong reach is shorter and straighter.

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Tien Giang 1; 28517 m from sea

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Figure 14 - Tien Giang 2 downstream stage and flow. 3. WQ model Figure 15 shows the results of the model application for the Tien Gang River Reach for April, under the scenario with the highest value of 100 gm−3s−1 for the source-sink term S. Similar results were obtained for the Ham Luong River Reach. It can be seen that, even under this high input of BOD, relatively low concentrations (<6.5mg/l) are obtained in the river. This means a maximum rise in BOD concentration of less than 2.5mg/l. Furthermore the results show that 8 hours after the releasing period, the maximum added BOD concentration in the river is less than 1mg/l. This can be explained by the large width of the river, resulting in a large amount of mixing, and the fact that the density of the aquacultures along this part of the river is relatively low. The cumulative effect of multiple release points is also visible in figure 15 as the concentration peaks around the release points become more pronounced over the 4 hour release period (12PM-15PM). After the release period the longitudinal curve spreads out over the length of the river, thus lowering the maximum concentration due to wastewater release from aquacultures. The fact that the peak concentration of these curves first flows a bit upstream (see curve 18PM) can be explained by the tidal flows in the river.

Figure 15 - Progression over time of the BOD-concentration in the Tien Gang River reach for April, using a value of 100 gm−3s−1 for S. Each curve represents the longitudinal concentration in the river for 1 time step. It is clearly visible that the concentration rises during the time of wastewater release (12PM -15PM) and that after this the pollution plume is gradually spread out over the length of the river. 4. Web based integration In order to display the results on the web-based application, the model output files (txt format) were converted into Arc-GIS format and integrated into the web mapping application like many other data such as the aquaculture development plan of the Ben Tre province, hydraulic data and meteorological data. All data can then be displayed using a web-browser. Figure 16 shows an example of such a scenario output for the water quality.

Figure 16 - Concentration as displayed by the web application. In addition to the data integration, the tools available into the application have been configured according the aims of the project and located in the different menus (toolbar, context menu and task frame menu). Moreover, as MapGuide have the possibility to create or adapt tools; four specific functions were developed or configured aiming to display specific result. Description of the specific tools:

� Find “ fish farm ponds”: this function has been customized in order to find the ponds according to the area.

� Export to Google Earth: this function allows to export the different layers of the map in Google Earth.

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� Theme for the water quality: this function allows to change the color of a layer according to the value of its attributes.

� Query: thanks to this function, the end-user have the possibility to request all the layers and all the attribute of them.

DISCUSSION AND CONCLUSION This project must be considered as a first draft of a future global web-based spatial decision support system based on scientifically justified models. It presents the power of a web-mapping application and the potential improvement for the environmental index through remote sensing and water quality modeling. Remote sensing was known in Vietnam, but the use of it for local management as well as higher level authorities is yet to be implemented. The results from the image interpreting and comparison with the maps from previous studies were surprising for the decision makers in Vietnam (VIFEP) because their base maps were not correctly updated. By using the RS technology, the available maps were corrected according to recent information. In this way the usefulness of RS was demonstrated and a first attempt was undertaken to educate local experts through the workshops that were organized. The use of hydraulic and water-quality models for the management of water resources for aquaculture activities and planning was also new for the Vietnamese partners. Especially the idea of seeing the river as a criterion for sustainability seemed to be different from the local evaluation system. River modeling was however indispensable because of the very dynamic environment and it opened the eyes of local experts for other possibilities such as flood predictions and general management of a tide-influenced river-system. Water Quality modeling was able to provide information on the effects of pollutants coming from the aquacultures on the scale of the river, giving local decision makers important information for evaluation and future planning purposes. Further on the results from the water quality modeling showed that in this specific case, even under high pollution input, relatively low concentrations are obtained in the river. However, one has to keep in mind that only effects from aquacultures are being studied here and that in reality the effects of other water uses are contributing to the pollution of the river as well. Finally, the Mapguide application provided in the project proved to be a good tool for combining all the gathered results and information into an easily accessible database. However, the Aquasid web mapping application must still evolve. According to the results and recommendations gathered in this project, it is now essential to keep up the effort aiming to evaluate and improve the data acquisition and the web-based decision support tool. For this, interactions between the different partners are very important and specific requirements must be edited according to the aims of the different

stakeholders and the different constraints highlighted by this project. Next to the technical and scientific value of this project, the participatory approach is also an important aspect from which a lot was learned. In general, as with all cooperative projects, the importance of good communication concerning possibilities, requirements and expectations between the different partners is indispensible. More specifically, limited knowledge and data availability is an important drawback to take into account. Educating (e.g. in the form of workshops) local experts and decision makers will not only broaden their insight in the issue but also make them more aware of how the knowledge and techniques were originally acquired so that not a “quick-fix” solution is expected but the gradual development of a (locally applicable) integrated monitoring and evaluation system is made feasible. REFERENCES CIA world factbook on Vietnam [online]. Available at https://www.cia.gov/library/publications/the-world-factbook/geos/vm.html De Koninck R.(1999). Deforestation in Vietnam [online]. Available at http://www.idrc.ca/en/ev-9318-201-1-DO_TOPIC.html De Smedt F. (1989). Introduction to river water quality modelling. Hydrologie-VUB Nr. 16 FAO Fisheries and Aquaculture Department, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, ROME, 2007. The State of world fisheries and aquaculture 2006 [online]. Available at http://www.fao.org/docrep/009/A0699e/A0699E00.HTM Jansens-Verbeke M., Go F. (1995). Tourism development in Vietnam. Tourism Management, Volume 16, Issue 4: 315-321 Jolankai G. & Biro I. (2000). Water Quality Modelling CAL version 2.0 manual [online]. Available at http://portal.unesco.org/es/files/39388/11896110471WQMCALversion2_Description.doc/WQMCALversion2%2BDescription.doc [29-04-2009] Juba S., Samoladas V., Boretos N., Manakos I. and Karydas C. (2007). IMS: a Web-based Map Server for Spatial Decision Support. Neural, Parallel and Scientific Computations, 15(2), 2007, 207-220 Law G. (2009). Administrative Divisions of Countries ("Statoids"). McFarland & Company, Jefferson, North Carolina [online]. Available at http://www.statoids.com/yvn.html Le Cao Q. (2007). The development and sustainability of Shrimp Culture in Viet Nam. Species and System Selection for sustainable Aquaculture,chapter 19, pg 283-294

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Lupo F. (2007). Bilateral Coöperation – 2nd session of the S&T Mixed Commision with Vietnam period 2006 – 2008. AquaSID, Technical, Management & Financial Proposal. Reference. AquaSID-SPB-O-770 Melkote S. R., Steeves H. L. (2001). Communication for development in the Third World: theory and practice for empowerment [online]. Available at http://books.google.nl/books?hl=nl& lr=&id=8kBwya_2SmMC&oi=fnd&pg=PA9&dq=communication+in+development+projects&ots=UinHpsLbjw&sig=ltyP1_t3PW--X5Sv5dI3fKVa3c4#v=onepage&q=communication%20in%20development%20projects&f=false Mercury JA (2006). The official site of Ben Tre province [online]. Available at http://www.bentre.gov.vn/english/index.php?option=com_content&task=category&sectionid=2&id=16&Itemid=54 Mitchell T. (2005). Web Mapping Illustrated. O'Reilly, 368 p. Ninh Nguyen H., Kien Trung V., Xuan Niem N., (2007). Flooding in Mekong River Delta, Viet Nam. Human Development report 2007/2008 [online]. Available at http://hdr.undp.org/en/reports/global/hdr2007-2008/papers/Nguyen_Huu%20Ninh.pdf Rice M. A. (2008). Aquaculture in the north east. NRAC publications No. 105 Ti et al. (2003). Mekong case study, UNESCO/IHP, 56p. Vietnam General statistic office (2009). Population and labour: average population statistics [online]. Available at http://www.gso.gov.vn/default.aspx?tabid=387&idmid=3&ItemID=8636 Web Sawadee Public Company Limited (2009). Vietnam [online]. Available at http://vietnam.sawadee.com/bentre/index.htm