Agricultural land use changes and water quality: A case study in the watershed of the Lagoon of Venice

The effects of alternative agricultural land use scenarios in terms of envi ronmental impact assessment on surface and ground water were simulated by m eans of combined socio-economic and environmental models. The economic mode l produced and evaluated alternative farming systems, defined in terms of l and use (in farm crop allocations and regional statistics of crop distribut ions) and cultivation practices as influenced by different macro-economic s cenarios of agricultural policies. These scenarios were defined on the basi s of the present Common Agricultural Policy of the European Union and possi ble future measures for reducing the impact of current agricultural systems on the environment. The farmers' decisional process has been simulated wit h multi-objective functions aimed at maximising profits and minimising risk The methodology for the environmental impact assessment of farming systems is based an a simulation model for non-point source agricultural pollution which determines the impact of agriculture on a single field basis as infl uenced by environmental variables (soil and climate) and farmers' decisions (crop, soil management, fertilisation, etc.). The results obtained from th is model were used to calculate a series of comparative indices capable of describing the effects of the use of fertilisers and pesticides on surface and ground waters. A geographical information system supported the spatial data management in particular for: a) the definition of simulation environm ents; b) the integration of physical and statistical geographical informati on; c) the cartographic presentation of results and the comparison of alter native scenarios. The model has been applied in the area of the Watershed o f the Lagoon of Venice (WLV), located in northern Italy and has demonstrate d how alternative policy scenarios determine not only significant variation s in the overall environmental impacts in the study area, but also remarkab le differences in their spatial distribution. (C) 1999 IAWQ Published by El sevier Science Ltd. All rights reserved.