Analysis of the impact of different irrigation scenarios on the water balance of the Ebro River Basin by means of a LSM and remote sensing irrigation estimations

Irrigation consumes around 70% of the world’s freshwater and has a significant impact on the continental water and energy cycles of the basins where it is present. Despite the clear benefits of irrigation, it has a strong impact on the continental water cycle, which must be evaluated to improve water resources management. Land-Surface Models (LSM) and remote sensing data can be used to analyse and quantify how irrigation affects the continental water cycle.

The Ebro basin is located in the Iberian Peninsula and is a representative Mediterranean basin. It is therefore characterised by a variety of different landscapes, as well as an uneven distribution of precipitation. This leads to the construction of a large network of dams and canals to supply water to agricultural irrigated districts. In fact, irrigated agriculture and farming represent 92% of the basin's total water consumption, according to the Ebro Hydrographic Confederation.

This work presents studies using datasets developed at the Ebro Observatory to simulate irrigation related processes over the Ebro basin with a LSM. It is provided at 1 km spatial resolution and contains meteorological and physiographical data, namely vegetation classes, actual irrigated areas, irrigation methods per area, and a new version of the SAFRAN meteorological forcing. All of the simulations used in the work presented here are carried out using the SURFEX LSM v9 version, which has an irrigation scheme implemented.

In the first place, we evaluate how the new physiographic datasets impact irrigation simulation in the area. Then, the datasets are used to perform simulations to analyse the impact of different irrigation scenarios (defined by different model parameters) on irrigation, evaporation, streamflow, and drainage. The scenarios defined are the default configuration of SURFEX’s irrigation scheme, a realistic simulation based on a survey to farmers from several irrigation districts from the Ebro basin, and further scenarios modifying the irrigation event’s frequency and amount of water. For this analysis, the simulations are carried out from 2008 to 2019. 

In the second place, a comparison of our simulation results to remote sensing irrigation estimations from the ESA funded IRRIGATION+ project is performed. For this, the irrigation estimation is added to the precipitation of the SAFRAN forcing, which is then used to force SURFEX simulations. The irrigation products span different periods ranging from 2015 to 2021 and are based on different techniques: data assimilation (Sentinel-1), SM-based DELTA algorithm (Sentinel-1), SM-based inversion algorithm (Sentinel-1, ERA5-Land, GLEAM product), and the Hydrological Similar Pixels (HSP) algorithm.

This work is a contribution to the LIAISE campaign, through the IDEWA project (PCI2020-112043), as well as to the IRRIGATION+ (4000129870/20/I-NB) project.