Venice Lagoon Watershed Research Articles

SWAT meta-modeling as support of the management scenario analysis in large watersheds.

In the last two decades, numerous models and modeling techniques have been developed to simulate nonpoint source pollution effects. Most models simulate the hydrological, chemical, and physical processes involved in the entrainment and transport of sediment, nutrients, and pesticides. Very often these models require a distributed modeling approach and are limited in scope by the requirement of homogeneity and by the need to manipulate extensive data sets. Physically based models are extensively used in this field as a decision support for managing the nonpoint source emissions. A common characteristic of this type of model is a demanding input of several state variables that makes the calibration and effort-costing in implementing any simulation scenario more difficult. In this study the USDA Soil and Water Assessment Tool (SWAT) was used to model the Venice Lagoon Watershed (VLW), Northern Italy. A Multi-Layer Perceptron (MLP) network was trained on SWAT simulations and used as a meta-model for scenario analysis. The MLP meta-model was successfully trained and showed an overall accuracy higher than 70% both on the training and on the evaluation set, allowing a significant simplification in conducting scenario analysis.

Multi-agent agro-economic simulation of irrigation water demand with climate services for climate change adaptation

Farmers’ irrigation practices play a crucial role in the sustainability of crop production and water consumption, and in the way they deal with the current and future effects of climate change. In this study, a system dynamic multi-agent model adopting the soil water balance provided by the Food and Agriculture Organization (FAO) Irrigation and Drainage Paper 56 was developed to explore how farmers’ decision making may affect future water needs and use with a focus on the role of climate services, i.e. forecasts and insurance. A climatic projection record representing the down-scaled A1B market scenario ( a balance across all sources ) of the assessment report of the Intergovernmental Panel on Climate Change (IPCC) is used to produce future daily data about relative humidity, precipitation, temperature and wind speed. Two types of meteorological services are made available: i) a bi-weekly bulletin; and ii) seasonal forecasts. The precision of these services was altered to represent different conditions, from perfect knowledge to poor forecasts. Using the available forecasts, farming agents take adaptation decisions concerning crop allocation and irrigation management on the basis of their own risk attitudes. Farmers’ attitudes are characterized by fuzzy classifications depending on age, relative income and crop profitability. Farming agents’ adaptation decisions directly affect the crop and irrigation parameters, which in turn affect future water needs on a territorial level. By incorporating available and future meteorological services, the model allows the farmer’s decision making-process to be explored together with the consequent future irrigation water demand for the period 2015 to 2030. The model prototype is applied to a data set of the Venice Lagoon Watershed, an area of 2038 km 2 in north-east Italy, for a preliminary test of its performance and to design future development objectives.

Managing the nutrient loads of the Venice Lagoon Watershed: are the loads external to the watershed relevant under the WFD River Basin District framework?

Azzellino A., Carpani M., Çevirgen S., Giupponi C., Parati P., Ragusa F., Salvetti R. 2013. Managing the nutrient loads of the Venice Lagoon Watershed: are the loads external to the watershed relevant under the WFD River Basin District framework?Water policy in the EU needs to be increasingly coordinated under the integrated management structure required by Water Framework Directive. In the WFD framework, all river catchments are assigned to administrative River Basin Districts (RBDs) that produce river basin management plans (RBMPs). RBMPs need to define appropriate Program of Measures (PoMs) based on the knowledge of the pressures and impacts affecting the water environments. However, pressures may also be external to the administrative RBDs, and still play a significant role. This study presents the case of the Venice Lagoon Watershed (VLW) and analyses the apportionment of the nutrient loads discharged to the lagoon by apportioning the external and the internal nutrient sources. VLW is included in the River Basin District of the Eastern Alps, although due to the complex framework of legislations and authorities that have managed the watershed to date, it is the object of a separate planning. The source apportionment assessment is assessed at the watershed scale by combining direct measurements and modeling results. The US Soil and Water Assessment Tool is used to simulate the expected improvements due to the application of “within watershed” measures. Model simulations pointed out the significant contribution of the loads external to the watershed, which seriously affect the effectiveness of the “within watershed” PoMs which are revealed largely ineffective if not coordinated with PoMs of boundary RBDs.

Construction of a Bayesian Network for the Assessment of Agri-Environmental Measures – The Case Study of the Venice Lagoon Watershed

A methodological framework was designed to assess the effectiveness of agri-environmental policy measures adopted by the Veneto Region to reduce diffuse water pollution of agricultural origin. Two already existing methodologies were combined in a new flexible approach for policy assessment: Conceptual Modelling and Bayesian Networks (BNs). The former supported the development of a shared conceptual model (a cognitive map) of the agro-ecosystem of the study area; while the latter allowed the development of a probabilistic model coherent with the cognitive map. BNs were selected because they allow analyses with scarce data; they can be updated when further information becomes available, and are easily understandable by layperson. The paper reports the results obtained in the Venice Lagoon Watershed (VLW) case study, where the current agri-environmental measures were assessed in order to identify their effectiveness in terms of reduction of nitrogen releases in water bodies connected to the lagoon ecosystem. Preliminary results obtained by implementing expert opinions in the BN pointed out the likely limited effects of the measures on the declared objective of

Evaluation of Agri-Environmental Measures in the Venice Lagoon Watershed. Nitrogen Budgets and Surplus Indicators

One of the main concerns of the environmental scientists and policy makers is related to the environmental compatibility of current agricultural systems and, in particular, to the losses of chemical fertilizers and manure in surface and ground-waters, as a consequence of run-off and leaching phenomena. In most cases European recent agrienvironmental schemes envisaged specific measures for the reduction of fertilizer rates and the control of manure applications, in order to limit the releases of nutrients in surface and ground-waters. Substantial financial resources are invested in those measures and therefore the issue raises interest in monitoring and evaluating their effectiveness. Nutrient balance indicators are often used for quantitative assessment of the effectiveness of the measures in limiting the environmental impact of farming activities. N-surplus is one of the most commonly used indicators. The paper refers the results of a research project aimed at assessing the outcomes of agri-environmental measures implemented in the Venice Lagoon Watershed with an approach based upon the gross nitrogen balance, called “Nboxes”. The results of applying the Nboxes procedure to a sample of 550 farms set are presented, evidencing the expectations of greater effectiveness in terms of nitrogen surplus reduction from the measure C.5.1.3a and C.5.1.3b (low input farming and buffer strips). Measures supporting improved irrigation systems, controlled drainage and more rational livestock nutritional programmes and technologies, showed instead only limited potential for tangible contributions to the reduction of nitrogen surplus in cultivated soils.

Evaluation of Agri-Environmental Measures in the Venice Lagoon Watershed. Expert Knowledge Elicitation and Multi-Criteria Analysis

Various tools and approaches have been experimented worldwide to address the externalities arising from agricultural activities, among which the design of agri-environmental policies and the introduction of specific measures to cope with the environmental impacts of agricultural origin. The mechanisms adopted within the Common Agricultural Policy with such aim fall within the category of Agri-Environmental Schemes (AESs), which are market-based policy schemes aimed at providing farmers with the right incentives to adopt farming practices yielding positive environmental externalities and are based on voluntary participation. Given the intrinsic complexity of agro-ecosystems and the effects of farmers’ behaviour, the assessment of the effectiveness and cost-effectiveness of AESs is always challenging, and often both the environmental and economic effectiveness of AESs are questionable. The main objective of this paper is to present a framework for assessing the effectiveness of AESs in promoting social and environmental sustainability in Europe, based on experts’ knowledge. Experts’ knowledge, acquired through adequate elicitation strategies and managed with robust and transparent methodologies, can help building a system of information that can then be used to infer the effectiveness of agri-environmental measures, at least in comparative terms, if not in terms of quantitative absolute estimations. In the present study, the NetSyMoD framework approach has been adopted. First, a short introduction of the policy evaluation framework, the role of monitoring and performance indicators and of experts’ opinion is provided. Subsequently the methodology used to identify experts and to elicit their assessment on the effectiveness of AES schemes is presented. Finally, the paper provides a concrete example in which experts’ opinions have been used for the assessment exercise, and presents a framework for collecting, managing and integrating different opinions in a coherent framework and with quantitative indicators.

Modelling the point and non-point nitrogen loads to the Venice Lagoon (Italy): the application of water quality models to the Dese-Zero basin

The study analyzes the source apportionment of a river basin, the Dese-Zero river, located within the North-Eastern part of the Venice Lagoon Watershed (VLW), Italy. The Dese-Zero river basin is characterised by a very intensive agriculture and landfarming system. To assess the source apportionment, two different models have been applied: the QUAL2E model for the simulation of the dry weather scenario and the BASINS-SWAT model for the simulation of the wet weather scenario. Out of a total nitrogen load of 512 t N y −1, for a surface of 293 km 2, in dry weather conditions the apportionment was found as follows: 20% point sources (i.e. WWTP and industrial discharge and direct sewer discharge into surface waters) and about 80% attributed to not rain-driven diffuse loads (i.e. groundwater/spring recharge and tributary/irrigation channels coming from bordering watersheds). As far as rainy events are concerned, the surface runoff load was of about 200 t N y −1, over a total annual nitrogen load of about 700 t N y −1. Therefore, on an annual basis, the total source apportionment was found as follows: about 30% surface runoff loads, about 15% point sources and about 55% of the total annual load was found to be constituted by not rain-driven diffuse sources.

A method for the remote sensing identification of uncontrolled landfills: formulation and validation

The identification of uncontrolled landfills is a central environmental problem in all developed and developing countries, where several illegal waste deposits exist as a result of rapid industrial growth over the past century. Remote sensing can potentially provide crucial information for the identification of contaminated sites, but surprisingly there is a marked lack of rigorously validated approaches. In this paper we introduce and validate a method that uses remotely sensed information and a geographic information system (GIS) to identify unknown landfills over large areas. The method is applied to a study area located in NE Italy (part of the Venice lagoon watershed) using IKONOS satellite data. Soil contamination effects on the radiometric properties of vegetation, calibrated using spectral signatures of stressed vegetation from known illegal landfill sites, were used to define numerous candidate sites that are most likely to host waste materials. Distributed geographical information, such as the position of the road network, the population density, and historical aerial photographs, have then been used to select the most likely contaminated sites among the candidates identified through remote sensing. The importance of the integration of GIS and remote sensing is highlighted and represents a key instrument for environmental management and for the spatially distributed characterization of possible uncontrolled landfill sites.

Practical results of a water budget estimation for a constructed wetland

An experimental water treatment plant was established to verify the effectiveness of constructed wetlands to improve water quality in the Venice Lagoon watershed. The wetland comprised three different subsystems, ranging from a riparian swamp to a marsh ecosystem. As a first step, monitoring was conducted over three years to evaluate the efficacy and efficiency of the system. Here, we report an analysis of the water budget resulting from routinely collected hydraulic and meteorological data. We used independent estimates of the water-budget terms, rather than budgetary residual estimation, because we wanted to estimate the water-budget error. Surface-water inflow, surface-water outflow, and direct precipitation were measured. Daily potential evapotranspiration values were estimated using the FAO Penman Monteith equation; runoff was estimated using the USDA Soil Conservation Service curve number model; indirect precipitation that flows toward the wetland via subsurface flow was estimated from the soils field capacity; and seepage was estimated using Darcy's law. The objectives of the research were to establish the best way to develop a water budget useful for application and design purposes, to determine the term that most influences the water-budget error, and to perform a sensitivity analysis on the parameters affecting this term. Surface flow dominated the wetland system, precipitation and evapotranspiration contributed about 10% to the water budget, and changes in water storage and the seepage flow contributed less than 5% to the water budget. The seepage flow term had the highest uncertainty, and the frequency of ground-water level measurements had the greatest impact on the water-budget error (ranging from 10.0%-28.6%). Therefore, in a free-water surface wetland with a shallow ground-water system, the main effort in field measurement should be to ensure a measurement frequency of less than five days.

Heavy Metal Behaviour in an Experimental Free Water Surface Wetland in the Venice Lagoon Watershed

Wetlands are effective in the treatment of polluted surface water. A semi-natural wetland pilot plant was established to verify the pollutant abatement effectiveness of the Venice Lagoon inlet water. The unique conditions of this brackish environmental site are: (1) a high concentration of carbonate and low concentrations of sulphides, and (2) the abundance of organic matter in sediments. The goal of this study was to examine how these characteristics influence the metal mobility in the wetland and to compare our results to published literature. The data collected were limited with respect to statistical analysis because the metal concentrations were often below the detection limits. Therefore, we chose to perform non-parametric analyses. To analyse the relationships among heavy metal concentrations and the physical and chemical wetland variables, and to investigate the processes of metal removal, we performed a multivariate statistical analysis and a Spearman correlation analysis. The results indicated that the reduced and basic conditions of the sediments seen in the Venice Lagoon environment facilitated the removal of metals due to the formation of insoluble compounds with sulphides and carbonates.

Accumulation of nutrients and heavy metals in Phragmites australis (Cav.) Trin. ex Steudel and Bolboschoenus maritimus (L.) Palla in a constructed wetland of the Venice lagoon watershed

A recently constructed wetland, located in the Venice lagoon watershed, was monitored to investigate growth dynamics, nutrient and heavy metal shoot accumulation of the two dominating macrophytes: Phragmites australis and Bolboschoenus maritimus. Investigations were conducted over a vegetative season at three locations with different distance to the inlet point to assess effects on vegetation. The distance from the inlet did not affect either shoot biomass or nutrients (N, P, K and Na) and heavy metals (Cr, Ni, Cu and Zn) shoot content. With the exception of Na, nutrient and heavy metal concentrations were higher in shoots of P. australis than in B. maritimus. Heavy metal concentration in the incoming water and in the soil was not correlated to the plant content of either species. Shoot heavy metal concentrations were similar to those reported in the current literature, but accumulation generally increased towards the end of the growing season.

A multicriteria approach for mapping risks of agricultural pollution for water resources: The Venice Lagoon watershed case study

A multicriteria analysis system was developed for producing risk maps of agricultural pollution due to alternative cultivation systems in the Watershed of the Lagoon of Venice (WLV) in Italy. Results of a field-scale simulation model for agricultural diffuse pollution were used to compile a matrix of environmental impacts, in terms of pollution indices. The most widespread combinations of typical environments (as defined by combinations of soil and climate variables) and alternative land uses (types of crops and cultivation systems) were described in the impact matrix. Land use in terms of crop distribution was based on census data. Two alternative cultivation systems were defined on the basis of the recent changes to the European Common Agricultural Policy: ordinary and eco-compatible. The effects of alternative scenarios were evaluated in terms of pollution risks for water resources. The evaluation procedure was built into the framework of a geographical information system to take into account the spatial features of pollution phenomena, vulnerability of the land and risk for water resources. The results demonstrated the great potential of eco-compatible practices for reducing the risks for surface and groundwater (−15 and −50%, respectively).