A modelling approach for the assessment of irrigation water requirements spatial and temporal distribution in Greece

Agriculture is an essential driving force in the management of water resources in Mediterranean countries as it has a dominant role in sustaining the growth of rural areas and at the same time represents by far the major water consumer. However, detailed assessment of the irrigation water requirements spatial and temporal distribution is challenging in the case of poorly gauged regions and especially in countries characterized by vast spatial and temporal variability like Greece, as water absractions in agriculture are spatially scattered, various water sources are used in each field, and the corresponding monitoring infrastructure is scarce.

This study presents a modelling approach for the assessment of irrigation water requirements spatial and temporal distribution in Greece on the basis of farm structure survey data, annual crop statistics and meteorological data. The proposed methodology is using an entirely spatially distributed, continuous hydrological model, in order to estimate the spatial distribution of the hydrological balance components at every point of the studied region as well as plants water deficit, and irrigation water requirements in a daily time step for the entire country. The developed approach is directly relevant to agricultural water policies design and evaluation. A special algorithm that is able to link each farm parcel polygon (over 6,000,000 polygons) of the spatial database of the Integrated Administration and Control System (IACS) with the nearest corresponding grid cell of the model was also developed. In this way, the developed approach utilizes all the information included in the IACS database (e.g. irrigation system, water source, applied agri-environmental measures) and provides very precise information at farm parcel level facilitating further analysis. Remote sensing data (Sentinel-Copernicus) and methods were also used for the validation of the crop patterns and of the irrigated fields in IACS database. The model was applied for 34 years reference period (1971-2004) at a daily time step. The obtained results were analyzed to identify spatial patterns and relationships, to investigate the temporal variability and the presence of trends and to provide detailed information on the water requirements of various crops and regions providing valuable information concerning agricultural water management.