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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2010.07.041 Byline: Diego Valbuena (a)(b), Arnold K. Bregt (a), Clive McAlpine (c), Peter H. Verburg (a)(d), Leonie Seabrook (c) Abstract: In rural regions, land use changes (LUC) are often the result of the decision-making of individual farmers. To influence this decision-making, compulsory and voluntary mechanisms are implemented. However, farmers' decision-making is a heterogeneous process that depends on their ability and willingness to take certain decisions. Discrepancies between farmers' ability and willingness and the design of voluntary mechanisms occur frequently. This makes it necessary to understand how farmers' participation in these mechanisms can affect LUC. The aim of this paper was to demonstrate an agent-based approach to analyse and explore how voluntary mechanisms can influence LUC processes in rural regions. This approach was applied to a rural region in Australia, where clearing of native vegetation has occurred for agricultural development. Historical land cover data and semi-structured interviews were used to parameterise an agent-based model. Factors that influence farmers' ability and willingness to participate in these mechanisms were identified. Three scenarios were simulated with the model to explore how the implementation of different voluntary mechanisms can affect the landscape structure of the region. This paper identifies how the diversity of farmers' decision-making can influence the landscape structure in the region. The advantages and limitations of an agent-based approach in relation to LUC research and policy are discussed. Author Affiliation: (a) Wageningen University, Department of Environmental Sciences, PO Box 47, 6700 AA Wageningen, The Netherlands (b) International Livestock Research Institute, System-wide Livestock Programme, P.O. Box 5689, Addis Ababa, Ethiopia (c) The University of Queensland, School of Geography, Planning & Environmental Management, Brisbane 4072, Qld, Australia (d) Institute for Environmental Studies, VU University Amsterdam, de Boelelaan 1087, 1081 HV Amsterdam, The Netherlands Article History: Received 28 December 2009; Revised 27 June 2010; Accepted 19 July 2010

Multi-agent Systems (MAS) that consist of agents representing organizations and interest groups involved in an urban allocation problem during a land use planning process are demonstrated. The potential and limitations of the MAS to build models that enable spatial planners to include the 'actor factor' in their analysis and design of spatial scenarios are discussed.

Environmental sensing data provide crucial information for environment-related decision-making. Formal data are provided by official environmental institutes. Beyond those, however, there is a growing body of so-called informal sensing data, which are contributed by citizens using low-cost sensors. How good are these informal data, and how might they be applied, next to formal environmental sensing data? Could both types of sensing data be gainfully integrated? This paper presents the results of an online survey investigating perceptions within citizen science communities, environmental institutes and their networks of formal and informal environmental sensing data. The results show that citizens and experts had different views of formal and informal environmental sensing data, particularly on measurement frequency and the data information provision power. However, there was agreement, too, for example, on the accuracy of formal environmental sensing data. Furthermore, both agreed that the integration of formal and informal environmental sensing data offered potential for improvements on several aspects, particularly spatial coverage, data quantity and measurement frequency. Interestingly, the accuracy of informal environmental sensing data was largely unknown to both experts and citizens. This suggests the need for further investigation of informal environmental sensing data and the potential for its effective integration with formal environmental sensing data, if hurdles like standardisation can be overcome. [ABSTRACT FROM AUTHOR]

Policies supporting rice production and investments in water infrastructure enabled intensification and diversification of farming systems in the Vietnamese Mekong Delta (VMD) over the past 20 years. Yet, demands of food security, economic development, and climate change continue to pose diverging and often conflicting challenges for water resources management in the upper, central, and coastal zones of the delta. The major changes effected in the VMD’s hydrological regime and land-use patterns are acknowledged in the literature, but few studies have examined the interplay between these dynamics at the delta scale. Based on time-series maps and statistical data on land-use, flooding, and salinity intrusion, we investigated the interrelations between land-use dynamics and changes in hydrological regime across the VMD in three representative periods. Land-use was found to be highly variable, changing by 14.94% annually between 2001 and 2012. Rice cropping underwent the greatest change, evolving from single cropping of traditional varieties towards double and triple cropping of high-yielding varieties. Aquaculture remained stable after rapid expansion in the 1990s and early 2000s. Meanwhile, flooding and salinity intrusion were increasingly controlled by hydrological infrastructure erected to supply freshwater for agriculture. Effects of this infrastructure became particularly evident from 2001 to 2012. During this period, spatial and temporal impacts on flooding and salinity intrusion were found, which extended beyond the rice fields to affect adjacent lands and livelihood activities. Unforeseen effects will likely be aggravated by climate change, suggesting a need to rethink the scale of planning towards a more integrated hydrologic approach. [ABSTRACT FROM AUTHOR]

Spatial decision support systems (SDSS) represent a step forward in efforts to account for the spatial dimension in environmental decision-making. The aim of SDSS is to help policymakers and practitioners access, interpret and understand information from data, analyses and models, and guide them in identifying possible actions during a decision-making process. Researchers, however, report difficulties in up-take of SDSS by the intended users. Some suggest that this field would benefit from investigation of the social aspects involved in SDSS design, development, testing and use. Borrowing insights from the literature on science-policy interactions, we explore two key social processes: knowledge integration and learning. Using a sample of 36 scientific papers concerning SDSS in relation to environmental issues, we surveyed whether and how the selected papers reported on knowledge integration and learning. We found that while many of the papers mentioned communication and collaboration with prospective user groups or stakeholders, this was seldom underpinned by a coherent methodology for enabling knowledge integration and learning to surface. This appears to have hindered SDSS development and later adoption by intended users. [ABSTRACT FROM AUTHOR]

Land-change models are increasingly used to explore land-change dynamics, as well as for policy analyses and scenario studies. In this paper we review calibration and validation approaches adopted for recently published applications of land-change models. We found that statistical analyses and automated procedures are the two most common calibration approaches, while expert knowledge, manual calibration, and transfer of parameters from other applications are less frequently used. Validation of model results is predominantly based on locational accuracy assessment, while a small fraction of the applications assessed the accuracy of the generated land-use or land-cover patterns. Of the reviewed model applications, thirty-one percent did not report any validation. We argue that to mature as a scientific tool, and to gain credibility for scenario studies and policy assessments, the validation of land-change models requires consideration of challenges posed by uncertainty, complexity, and non-stationarity of land-change processes, and equifinality and multifinality of land-change models. [ABSTRACT FROM AUTHOR]

The development of shrimp farming in Vietnam has eroded the social-ecological resilience of the coastal ecosystem. Recent literature supports the idea that integrated mangrove-shrimp production systems can contribute to rebuilding this resilience in the Mekong Delta. Two experts panels, international and Vietnamese, were consulted to validate and weight drivers identified from literature that enable or constraint farmers to shift from extensive production system to integrated mangrove-shrimp system or to continue such integrated system. Though a combination of drivers is needed to enhance changes, two sets of drivers were given the highest weight. Experts considered the ecosystem function of the mangrove an enabling driver pushing farmers to plant mangrove in order to improve the pond's water quality and limit disease outbreaks. They perceived the drivers related to the current regulatory framework as constraining because these limit the financial return associated with integrated mangrove-shrimp systems. The analysis indicates that the adoption of these integrated systems requires more equitable distribution of benefits from shrimp and timber production between farmers and other stakeholder in these value chains. We recommend to develop a regulatory framework that can optimize the financial benefits of the integrated mangrove-shrimp production systems for farmers. [ABSTRACT FROM AUTHOR]

Abstract: GPS technology is widely used to produce detailed data on the movement of people. Analysing massive amounts of GPS data, however, can be cumbersome. We present a novel approach to processing such data to aid interpretation and understanding of the aggregated movement of visitors in natural recreational areas. It involves the combined analysis of two kinds of movement patterns: ‘Movement Suspension Patterns’ (MSPs) and ‘Generalized Sequential Patterns’ (GSPs). MSPs denote the suspension of movement when walkers stop at a place, and are used to discover places of interest to visitors. GSPs represent the generalized sequence in which the places are visited, regardless of the trajectory followed, and are used to uncover commonalities in the way that people visit the area. Both patterns were analysed in a geographical context to characterise the aggregated flow of people and provide insights into visitors’ preferences and their interactions with the environment. We demonstrate the application of the approach in the Dwingelderveld National Park (The Netherlands). [Copyright &y& Elsevier]

Land-use change models are typically calibrated to reproduce known historic changes. Calibration results can then be assessed by comparing two datasets: the simulated land-use map and the actual land-use map at the same time. A common method for this is the Kappa statistic, which expresses the agreement between two categorical datasets corrected for the expected agreement. This expected agreement is based on a stochastic model of random allocation given the distribution of class sizes. However, when a model starts from an initial land-use map and makes changes to it, that stochastic model does not pose a meaningful reference level. This paper introduces K Simulation, a statistic that is identical in form to the Kappa statistic but instead applies a more appropriate stochastic model of random allocation of class transitions relative to the initial map. The new method is illustrated on a simple example and then the results of the Kappa statistic and K Simulation are compared using the results of a land-use model. It is found that only K Simulation truly tests models in their capacity to explain land-use changes over time, and unlike Kappa it does not inflate results for simulations where little change takes place over time. [Copyright &y& Elsevier]

Abstract: In land administration (LA), the right to exercising property/ownership rights on land is based on cadastral processes of adjudication, survey and rights registration. Private ownership rights are now being taken up in pastoral areas, where they must contend with pastoralists’ land rights. Pastoral land use requires seasonal migrations determined by climatic conditions. This study aimed to find out how well the existing land laws and property rights in LA are able to serve the requirements of pastoralists land use, identify mismatches and put forward possible solutions. A case study was carried out in the Samburu–Laikipia–Isiolo–Meru landscape in Kenya. Data on the degree of livestock dependency among pastoralist communities, the spatial extent and patterns of dry season migrations, the resulting encounters between herders’ and non-pastoralist land use actors, and the perceptions of land rights held by actors were collected through a variety of methods and analysed. The results show that pastoralism is still active. The migration corridors reveal that herders maintain extensive dry season mobility, even though some of the corridors currently overlap with areas where land is privately owned by non-pastoralist land use actors. Moreover, the results show that most non-pastoralist land use actors have their land rights registered, but seasonal encounters with migrating pastoralists persist as pastoralists continue to exercise customary rights of communal use. We conclude that existing land laws and property rights in LA are suitable for sedentary land use, but do not address how to serve pastoralists land rights in time and space. The pastoralist''s migration routes and patterns obtained indicated that it is possible to predict where pastoralists will be at a given time/drought period. This information could be used by decision makers and land administrators to identify where and when pastoralists’ land rights apply. This could provide the foundation for including pastoralists’ spatiotemporal land rights in LA. Arguments emphasize that adjudication, surveys and registration of rights should focus not only on ownership and full control of land, but also on defined periods when spatiotemporal mobility and access rights could be granted to pastoralists. [Copyright &y& Elsevier]

This paper presents an extension to the Constrained Cellular Automata (CCA) land use model of White et al. [White, R., Engelen, G., Uljee, I., 1997. The use of constrained cellular automata for high-resolution modelling of urban land-use dynamics. Environment and Planning B: Planning and Design 24(3), 323–343] to make it better suited for modelling the dynamics of shifting cultivation. In the extended model the time passed since the last land use transition of a location is a factor of its land use potential. The model can now account for the gradual decrease in soil fertility after an area of forest has been cleared for cultivation and also capture the process of regeneration once the plot is fallowed. The model is applied for the Ruhunupura area of Sri Lanka where chena, a particular practice of shifting cultivation, is a common land use that dominates the landscape dynamics. The model is calibrated for the period 1985–2001 and the results are assessed in terms of location to location overlap as well as structural similarity at multiple scales. These results give confidence in the representation of land use dynamics for the main land use classes. On the basis of a long term scenario run for the period 2001–2030, it is verified that the model captures stylized facts related to chena dynamics, in particular shortening fallow periods and increasingly long cultivation periods of chena, as a result of increasing land use pressure. We conclude that the model extension is crucial for regions with substantial areas of shifting cultivation. The extension affects not only the land use class shifting cultivation, but also through spatio-temporal interactions that are already present in the original CCA model the whole land use system is better represented. [Copyright &y& Elsevier]

Abstract: Incomplete information is one of the main constraints for decision-making, which are then by definition risky. In this study, formal risk concepts were introduced in decision-makers’ meetings according to local demands and following a participatory approach, as a first step towards integrating risk assessment into rural decision-making in Santa Catarina, Brazil. Semi-structured interviews and meetings were conducted with extensionists and farmers. The following information was presented and discussed: (1) the time series and frequency distribution of maize yield predictions, simulated by the GAPS computer program for 16 feasible planting dates, representing climatic risks, both within and between years; and (2) a simple economic analysis (gross margin) and income probabilities for seven land-use options over a recent five-year period, followed by an interactive exercise where probabilities of achieving user-supplied target gross margins were calculated according to participants’ actual information, using the computer program @RISK. This paper also investigates decision-makers’ attitudes towards risk, and how these were influenced by objective information. Although results from a study such as this are not definitive, considering that the effects of the information on actual decision-making require some time to become evident, it was already possible to conclude that the risk-orientated information presented according to local demands and following a participatory approach had a positive impact on decision-makers’ understanding and perceptions. This approach should be further explored to effectively integrate risk assessment into rural decision-making. [Copyright &y& Elsevier]

• We proposed a framework of resilience in the context of coupled Social-Ecological Systems (SES). • A stylized agent-based model of a land use system was implemented as an example of SES to investigate system resilience. • Internal mechanisms increased the ability of the system to recover from external shocks. • Feedbacks resulted in different regimes of crop cultivation, each with a distinctive set of functions. • Resilience is not a generic system property, but strongly depends on what system function is considered. Dynamics of coupled Social-Ecological Systems (SES) result from the interplay of society and ecology. To assess SES resilience, we constructed an Agent-Based Model (ABM) of a land use system as a stereotypical example of SES and investigated how resilience of the represented system is affected by both external disturbances and internal dynamics. The model explicitly considered different aspects of resilience in a framework derived from literature, which includes "resilience to", "resilience of", "resilience at", "resilience due to", and "indicators of resilience". External disturbances were implemented as shocks in crop yields. Internal dynamics comprised of two types of social interaction between agents (learning and cooperation), an ecological feedback of soil depletion and an economic feedback of agglomeration benefits. We systematically varied these mechanisms and measured indicators that reflected spatial, social, and economic resilience. Results showed that (1) internal mechanisms increased the ability of the system to recover from external shocks, (2) feedbacks resulted in different regimes of crop cultivation, each with a distinctive set of functions, and (3) resilience is not a generic system property, but strongly depends on what system function is considered. We recommend future studies to include internal dynamics, especially feedbacks, and to systematically assess them across different aspects of resilience. [ABSTRACT FROM AUTHOR]

Abstract: Wireless sensor networks (WSNs) play a vital role in environmental monitoring. Advances in mobile sensors offer new opportunities to improve phenomenon predictions by adapting spatial sampling to local variability. Two issues are relevant: which location should be sampled and which mobile sensor should move to do it? This paper proposes a form of adaptive sampling by mobile sensors according to the expected value of information (EVoI) and mobility constraints. EVoI allows decisions to be made about the location to observe. It minimises the expected costs of wrong predictions about a phenomenon using a spatially aggregated EVoI criterion. Mobility constraints allow decisions to be made about which sensor to move. A cost-distance criterion is used to minimise unwanted effects of sensor mobility on the WSN itself, such as energy depletion. We implemented our approach using a synthetic data set, representing a typical monitoring scenario with heterogeneous mobile sensors. To assess the method, it was compared with a random selection of sample locations. The results demonstrate that EVoI enables selecting the most informative locations, while mobility constraints provide the needed context for sensor selection. This paper therefore provides insights about how sensor mobility can be efficiently managed to improve knowledge about a monitored phenomenon. [Copyright &y& Elsevier]

Abstract: Wireless sensor networks (WSNs) play an important role in forest fire risk monitoring. Various applications are in operation. However, the use of mobile sensors in forest risk monitoring remains largely unexplored. Our research contributes to fill this gap by designing a model which abstracts mobility constraints within different types of contexts for the inference of mobile sensor behaviour. This behaviour is focused on achieving a suitable spatial coverage of the WSN when monitoring forest fire risk. The proposed mobility constraint model makes use of a Bayesian network approach and consists of three components: (1) a context typology describing different contexts in which a WSN monitors a dynamic phenomenon; (2) a context graph encoding probabilistic dependencies among variables of interest; and (3) contextual rules encoding expert knowledge and application requirements needed for the inference of sensor behaviour. As an illustration, the model is used to simulate the behaviour of a mobile WSN to obtain a suitable spatial coverage in low and high fire risk scenarios. It is shown that the implemented Bayesian network within the mobility constraint model can successfully infer behaviour such as sleeping sensors, moving sensors, or deploying more sensors to enhance spatial coverage. Furthermore, the mobility constraint model contributes towards mobile sensing in which the mobile sensor behaviour is driven by constraints on the state of the phenomenon and the sensing system. [Copyright &y& Elsevier]

Abstract: This paper discusses the validation of an agent-based model for simulating a multi-actor spatial planning process. After a general discussion about the pitfalls of validating agent-based models that simulate complex spatial systems, we briefly present a validation method based on role playing. The method is designed to generate insights that can improve our understanding of the behaviour of socio-spatial systems in a planning context. The method was tested by carrying out an experimental role play to validate individual agent tasks, focusing on the ability of agents to generate beliefs and preferences about their environment. We conclude that using role play as a validation technique can provide valuable information about the performance of the model. The insights gained aid identification and understanding of those parts of a multi-actor spatial planning system that are currently poorly understood and poorly represented by the agents. [ABSTRACT FROM AUTHOR]

Soil salinity increase is a serious and global threat to agricultural production. The only database that currently provides soil salinity data with global coverage is the Harmonized World Soil Database, but it has several limitations when it comes to soil salinity assessment. Therefore, a new assessment is required. We hypothesized that combining soil properties maps with thermal infrared imagery and a large set of field observations within a machine learning framework will yield a global soil salinity map. The thermal infrared imagery acts as a dynamic variable and allows us to characterize the soil salinity change. For this purpose we used Google Earth Engine computational environment. The random forest classifier was trained using 7 soil properties maps, thermal infrared imagery and the ECe point data from the WoSIS database. In total, six maps were produced for 1986, 2000, 2002, 2005, 2009, 2016. The validation accuracy of the resulting maps was in the range of 67–70%. The total area of salt affected lands by our assessment is around 1 billion hectares, with a clear increasing trend. Comparison with 3 studies investigating local trends of soil salinity change showed that our assessment was in correspondence with 2 of these studies. The global map of soil salinity change between 1986 and 2016 was produced to characterize the spatial distribution of the change. We conclude that combining soil properties maps and thermal infrared imagery allows mapping of soil salinity development in space and time on a global scale. • Soil properties maps combined with thermal imagery can be used to map soil salinity. • Thermal imagery can act as a dynamic variable. • Soil salinisation is increasing on global scale. [ABSTRACT FROM AUTHOR]

In the Mekong Delta coastal zone, decision makers must weigh trade-offs between sustaining the shrimp sector and thus ensuring economic development, while also promoting sustainable, environmentally friendly practices and planning for climate change adaptation. This study investigates future scenarios for development of shrimp aquaculture using a spatially explicit, agent-based model (ABM) simulating farmers' production system choices. A role playing game (RPG) with farmers was used to calibrate and validate the model. Four scenarios, representing different visions of aquaculture in the next 15 years, were elaborated with decision makers before discussing the different outputs of the model. Iterative consultation with farmers helped to fine-tune the model and identify key parameters and drivers in farmers' decision-making. The recursive process allowed us to construct a model that validly represents reality. Participants stated that use of the RPG improved their insight for planning. Results of the scenarios indicate that (i) intensification of production is unsustainable, (ii) market-based incentives are too limited to stimulate development of an integrated mangrove–shrimp production system and (iii) climate change will cause rapid decline of production in the absence of adaptation measures. RPG appeared to be a valuable method for formalizing local farmers' knowledge and integrating it into the planning approaches used by decision makers. The ABM, thus, can also be considered a medium or communication tool facilitating knowledge-sharing between farmers and decision makers. [ABSTRACT FROM AUTHOR]

Highlights: [•] We used modified enrichment factors to measure the neighbourhood effect. [•] Measurements confirm the existence of a neighbourhood effect, especially for urban land uses. [•] Modified enrichment factors can be used to improve the calibration of neighbourhood rules in land use models. [ABSTRACT FROM AUTHOR]

Abstract: Spatial Data Infrastructures (SDIs) have been developed over the last decades all over the world. They are the subject of periodic assessments in order to give account of past developments, to steer future developments or to better understand their functioning. Most assessment methods are analysing the SDI as a whole which does not allow understanding their internal dynamics. In this research we analyse SDIs from a network perspective and focus on the work processes that take place within these networks. The paper elaborates a series of indicators to assess the SDI performance from the perspective of the process owners and the users of spatial data within those processes. Three indicators are proposed to measure the performance related to the access, use and sharing of spatial data, and three indicators related to the contribution of SDIs to improve the work processes. The methodology is applied to a particular case, i.e. the process of the development of land use plans in Flanders (Belgium). The results show that the methodology and the indicators are applicable in the context of work processes. The proposed process-oriented methodology is complementary to approaches that assess SDIs as a whole. It helps to detect and understand differences in SDI performance between (parts of) organisations that are actively involved in the processes studied. The paper argues that the proposed indicators provide a good basis for analysing the degree to which organisations integrate SDI components in their work processes. [Copyright &y& Elsevier]

Abstract: The motives for constructing Spatial Data Infrastructures (SDIs) are often based on their anticipated benefits for society, economy, and environment. According to those widely articulated but rarely proven benefits, SDI coordinators have been defining more specific objectives to be achieved by their SDIs. However, there is a limited number of assessment approaches that are able to demonstrate whether SDIs indeed realize the intended goals. In this article we develop, apply and evaluate an assessment view for evaluating the extent to which SDIs realize their goals. The assessment view has been developed stepwise using the Multi-view SDI assessment framework as a guideline. The application of the proposed view in the Dutch SDI demonstrates its potential. In addition, the evaluation of the proposed view by the potential users confirms to a certain extent its usability. The results also show that the ease of determining assessment indicators depends on the precision with which the SDI goals are formulated. [Copyright &y& Elsevier]

Abstract: We use the Li-Strahler geometric-optical model combined with a scaling-based approach to detect forest structural changes in the Three Gorges region of China. The physical-based Li-Strahler model can be inverted to retrieve forest structural properties. One of the main input variables for the inverted model is the fractional component of sunlit background, which is calculated by using pure reflectance spectra (endmembers) of surface components. In this study, we extract these endmembers from moderate spatial resolution MODIS data using two scaling-based methods (namely, a regional based linear unmixing and a purest-pixel approach) relying on corresponding high spatial resolution Landsat TM images. Then, the forest structural property crown closure (CC) is estimated by inverting the Li-Strahler model based on the extracted endmembers. Changes in CC are mapped using MODIS mosaics dated 2002 and 2004 for the whole Three Gorges region. Validation of the estimated CC using 25 sample sites indicates that the regional scaling-based endmembers extracted using linear unmixing are more suitable to be used in combination with the inverted Li-Strahler model for monitoring the forest CC than the purest-pixel approach, and results in significantly better estimates in both years (R 2 2002 =0.614, RMSE2002 =6%, R 2 2004 =0.631 and RMSE2004 =5.2%). A change detection map of the model derived CC in 2002 and 2004 shows a decrease in CC in the eastern counties of the Three Gorges region located close to the Three Gorges Dam. An increase in CC has been observed in other counties of the Three Gorges region, implying a preliminary positive feedback on certain policy measures taken safeguarding forest structure. [Copyright &y& Elsevier]

Abstract: The relationship between landscape pattern and the function of nutrient reduction in the natural reed marsh of Liaohe Delta is studied with the help of some landscape metrics. The results discovered that not all the metrics selected are explanative in representing the function of nutrient reduction. Network connectivity, area size, and source to centre metrics are closely related to the simulation results from different pattern scenarios, while other metrics like area-weighted mean shape, fractal, contagion and aggregation are not related with the reduction process at all. Different metrics should be chosen according to the purpose of the study, based on the criteria of simplicity, generality and ecological meaning. [Copyright &y& Elsevier]

There is a great potential to use the estuary wetland as a final filter for nutrient enriched river water, and reduce the possibility of coastal water eutrophication. Based upon field data, spatial models were designed on a stepwise basis to simulate the nutrient reduction function of the wetland in the Liaohe Delta. The model contained two major subsystems: the canal system and the reed field. In the preliminary model, a non-linear regression model was established for the nutrient reduction in the canal system, while a percentage-based reduction model was used for the reed fields. It was first tested in one of the irrigation areas and finally extrapolated into the whole study area. Validation against field data indicated that the preliminary model was robust enough to simulate the nutrient removal process in the system. But the process model used for the reed field was much too simple compared to the model for the canal system. A more sophisticated linear regression model based on Maunder and Mauring’s work was finally adopted for the reed system. According to the simulation results, more than 3200 tonnes of total nitrogen (TN) and 77 tonnes of soluble reactive phosphorous (SRP) could be removed by the reed–canal system during the irrigation period in 1998, which was only one tenth of its total reduction capacity. [Copyright &y& Elsevier]