The south of Portugal is a region where extreme climatic conditions and insufficiently fertile land limit the development of a competitive agriculture. With its long dry and hot season, is a water-stressed area, with a limited and variable stock of water resources, facing strong environmental vulnerability. In this region, the decrease of water availability can have exponential negative effects on the human population well-being. In fact, in this region, irrigation cannot be seen as a way to increase and improve agricultural productivity.
Here, irrigation is crucial to ensure agricultural productivity. In the framework of the highest water consumption sector, agriculture activities have strong responsibilities in the water preservation in Portugal. These are dependent on the soil occupation extent, the type of land use, the cultures and the fertilizers and pesticides applied, and the geomorphologic conditions, soil type and climatic conditions. Furthermore, in many cases the agriculture areas are located in regions with high infiltration rates and vulnerability where recharge of aquifers take place, which together with bad practices of irrigation and fertilization, leads to the presence of nitrates and pesticides above the limits in the downgradient waters.
The region can benefit from the proposed project since the approach to the problem of integrated water management and policy making can have significant positive effects on the sustainable use of water resources. Moreover, it will endorse participatory processes of stakeholders, which will be involved in the discussions, analyses and assessment of scenarios and of local strategies for sustainable irrigation management.
Spain: Cuenca del Júcar (Valencia)
The basin of the river Júcar is made up of 21,578 km2 distributed between the autonomous regions of Castilla-La Mancha (the provinces of Albacete and Cuenca) and the Valencian Community (the province of Valencia), in Eastern Spain. This watershed could be divided in four sectors with different physical conditions. The first one, the Serranía de Cuenca, encompasses the northern mountainous area, where headwaters sub-basins of Cabriel and Júcar tributaries are placed. To the South, the second sector, The Plateau of La Mancha, is the western part of the Castilian highlands, a plain or tabular relief, badly drained and recently irrigated with groundwater, which presents several endorheic and semi-endorheic areas. To the East, third, an arc of calcareous mountain ranges –strongly karstified— establishes a transition between the high and low sectors and acts as a groundwater reservoir. Finally, the Low Júcar Valley, known as the Ribera del Xúquer, is an alluvial plain historically and intensively irrigated, flanked to the coast by two protected wetlands, the Marjal de Corbera and the Albufera of Valencia.
There is also a great contrast, from a socio-economical point of view, between the High and the Low Júcar. Whilst La Ribera del Xúquer is a densely populated area, highly urbanized and industrialized, the high lands of this basin are a rural depressed area, where only the functional axis Albacete-Almansa presents an important economic dynamism. Population density reflects this contrast. It reaches values extremely higher in the Xúquer floodplain –210 hab/km in the Ribera Alta and 250 hab/km in the Ribera Baixa– if we compare them with the rest of the basin: 10 hab/km in the mountain ranges (Province of Cuenca or Caroig Massif) an 27 hab/km in Albacete plain.
Italy: Venice Lagoon Watershed
The Venice Lagoon Watershed (VLW) is located in the North Eastern part of Italy and consists of several hydrographical sub-basins discharging into the Venice Lagoon. In the past years the nutrient discharge of the VLW has been widely studied because of the critical effect on the eutrophication of the Venice Lagoon and the intensive agricultural land use was identified as one of the main pollution sources. A recent monitoring activity indicated a total nitrogen load discharged into the VL of about 5000-6000 tN y-1, versus a maximum nitrogen load allowed by the local environmental legislation of 3000 tN y-1.
The Venice Lagoon Watershed has a surface area of 2038 km2 and consists of 8 main sub-basins (which cover about 90% of the whole VLW area) and 7 minor subbasins. The average annual volume discharged into the Venice Lagoon is of about 109 m3. In the northern part of the watershed, groundwaters recharge the surface waters, significantly contributing to the hydraulic and nutrient load discharged into the Venice Lagoon. Moreover, due to the intensive agricultural landuse, the VLW is characterised by a very complex network of irrigation channels which very often receives also direct sewage discharges.
Irrigation is a common practice with different methods and varying efficiency and it is very relevant for determining both the volumes of water flowing across the watershed and the quality of water bodies, in particular for what concerns the content of nutrients which may significantly contribute to the eutrophication of the Venice Lagoon.
The main challenges that the agriculture of the VLW will face over the coming year are therefore related to the maintenance of profitable farming activities while facing increasing environmental constraints related to unstable and decreasing rainfall, increasing conflicts for water resources and also increasing constraints in terms of environmental protection norms.