Spatial exploration of the relationships between agricultural land use and water quality measures

Agricultural land-use and effects on water quality (surface and groundwater) is a well known issue and actions are needed to reduce the impacts of farm inputs management. Direct and indirect links can be found with some of the SDGs such as SDG 6 - Clean water and sanitation and SDG 15 Life on land. Assessing these impacts can support the definition of sustainable management practices for agricultural production.

In this work we performed an analysis of the relationship between agricultural land-use and pesticides found in surface water monitoring stations located in South Italy (Foggia province).

Land-use data were produced with a complex data integration process based on the use of geospatial data from the Italian agricultural paying agency. These administrative data support the process for assigning European agricultural subsidies to farms and are made up of land-use maps and farm crops declaration at parcel level. The geospatial administrative data were integrated ensuring a consistent definition of the geometric and nomenclature characteristics (e.g. topology checks, semantic harmonisation of crops and land use classes).

A subset of 26 monitoring stations located in the main watershed of the study area were acquired from the georeferenced database on water quality from the Italian environmental agency. Among the active substances monitored, only those commonly related to farm inputs products were extracted. Specifically, we selected Isoproturon, a plant protection chemical, present in surface waters.

This methodology was followed: polygons within a 5km buffer area around the monitoring station were selected, rasterized and assigned to the respective Isoproturon concentration level. Then, the raster was converted into point data and the frequency matrix of land-use and concentration was used to perform a Correspondence Analysis.

The results, plotted in a symmetric map, show the variation of concentration level among the different land-uses. Specifically, low concentration levels are usually associated with agricultural polygons located within ecological focus areas as defined by the European policies.