Lomellina (Northern Italy)
Italy is the leading rice producer in Europe, with more than half of the total production and a high quality level. By far, the most important rice-growing area is the portion of the Padana plain located on the left bank of the Po river and along the Ticino River, straddling the regions of Lombardy and Piedmont in northern Italy (more than 200,000 hectares, 92% of the Italian rice surface).
The irrigation systems in the rice territories of eastern Piedmont and western Lombardy have unique characteristics, mainly due to the following aspects:
- large prevalence of rice cultivation, even if occasionally alternated with other crops in rotation;
- historical abundance of water resource availability, through diversions from rivers;
- peculiarity of gravity irrigation systems, characterized by extensive networks of unlined irrigation and drainage canals and traditional irrigation methods (flooding);
- strong interactions between irrigation and groundwater dynamics, due to large percolations from paddies and channel networks and shallow aquifers in large portions of the irrigated areas;
- use and reuse of irrigation waters, since water losses from fields and canals are partially reused downstream within the area;
- multi-functionality and ecosystem services provided by the irrigation systems;
- use of a relevant amount of chemicals (fertilizers and plant protection products), which can lead to surface water and groundwater pollution;
- limited availability of flow discharge measurements in the irrigation and drainage canals;
- lack of studies on the role of rice cultivation in surface water and groundwater pollution, especially at scales larger than the single field;
- changed environmental and economic conditions in recent years, leading to the need to re-discuss rice cultivation methods in many areas.
Study aims and expected results
The study aims to enhance the understanding of water quantity and environmental issues in the rice cropping systems of the largest rice area in Europe, facing these problems both at the farm scale and at the district scale.
At the farm scale, experimental/demo fields are set up to compare different irrigation management options. Two Pilot Farms are involved in the study: in the first farm, wet seeding and traditional flooding, dry seeding and delayed flooding, wet seeding and alternated wetting and drying are compared; in the second farm, the current system of manually opened sluice gates for the wet seeding and traditional flooding irrigation management is compared with electro-mechanically controlled gates allowing a more accurate water management. Water use efficiency (WUE), yield and quality of the production, and environmental impacts on surface water and groundwater for each irrigation treatment are quantified.
The irrigation district scale (103-104 hectares) is crucial when the goal is to support decisions of authorities that deal with water resource planning and management at the regional scale, since rice fields are often not isolated units but part of large and homogenous areas where strong intra-field interactions may occur, particularly when flooding is the irrigation method adopted. From the perspective of the entire irrigation system, amounts of the so-called ‘water losses’ at the field scale (i.e., percolation below the root zone, surface or sub-surface drainage to ditches or other fields placed downslope in a field toposequence) are reused. Consequently, when water use efficiency (WUE) is computed at the irrigation district scale, water reuses must be taken into account, and may significantly increase the WUE value. To upscale the results measured at the farm level, agro-hydrological models are used.