Management of alternative water resources for variable rate irrigation - a Hungarian case study

Most of the climate scenarios predict increased water scarcity in arid areas, such as Hungary. However, the irrigated area in Hungary covers 2% of agricultural land, mostly with outdated irrigation technology. The aim of the research was to develop the basis of a variable rate irrigation for water-saving precision sprinkler irrigation system on an arable area (85 ha) which is located in the reference area of the Tisza Riven Basin. There is limited available water resources at the site, therefore alternative water sources utilization system was set up for irrigation to adapt to climate change and reduce fertilizers. The basis of the alternative water resources are excess water, treated wastewater, biogas fermentation sludge which is collected in a water reservoir with 114000 m³ capacity. For proper irrigation scheduling, heterogeneity of topography, hydrological, soil and crop conditions has to be explored and monitored. Therefore physically-based modelling of the water balance and remote sensing-based surplus water and  vegetation status surveying are tested to use for accurate irrigation scheduling.

Shallow groundwater and/or soil compaction can also contribute to excess inland water. This may occur even if there are drought periods in a year (e.g. in the Pannonian region), resulting in spots with a low crop yield. A LiDAR-based digital elevation model was found to provide appropriate data to identify sites affected by excess inland water. The spots identified can be used as spatial input data to compile a variable rate irrigation prescription map for imposing reduced (or zero) irrigation at areas more vulnerable to the occurrence of excess inland water. The water balance was also assessed for sites with physically-based models. Hydrus was used to model soil moisture changes at the Hungarian case study site.

A model concept for crop evapotranspiration estimation was also developed based on vegetation indices calculated from satellite imagery. Several combinations of sensors and remote sensing products were tested to use in ETc modelling potentially. This approach was tested both at the Hungarian case study sites. Remote sensing-based analysis of crop evapotranspiration, combined with physically-based modelling, appears to be a promising method in water balance modelling of maize fields, especially if these fields are in summer when the crop is fully developed. However, the remotely sensed information verification is essential for the proper utilization of the remote sensing data in ET_c modelling and predicting the spatio-temporal dynamics of crop yield, evapotranspiration, and irrigation demands.

There is a need further benchmark scenarios to improve both physically-based models and satellite-based crop evapotranspiration models to achieve more accurate and valid simulations.

The abstract was funded by European Union’s Horizon 2020 “WATERAGRI Water retention and nutrient recycling in soils and steams for improved agricultural production” research and innovation programme under Grant Agreement No. 858375. This research was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences.