Regional data sets of high-resolution (1 and 6 km) irrigation estimates from space

Abstract

Abstract. Irrigation water use represents the primary source of freshwater consumption by humans. The amount of water withdrawals for agricultural purposes is expected to further increase in the upcoming years to face the rising world population and higher living standards. Hence, effective plans for enacting a rational management of agricultural water use are urgent, but they are limited by knowledge gaps about irrigation. Detailed information on irrigation dynamics (i.e., extents, timing, and amounts) is generally lacking worldwide, but satellite observations can be used to fill this gap. This paper describes the first regional-scale and high-resolution (1 and 6 km) irrigation water data sets obtained from satellite observations. The products are developed over three major river basins characterized by varying irrigation extents and methodologies, as well as by different climatic conditions. The data sets are an outcome of the European Space Agency (ESA) Irrigation+ project. The irrigation amounts have been estimated through the SM-based (Soil-Moisture-based) inversion approach over the Ebro river basin (North-eastern Spain), the Po valley (Northern Italy), and the Murray-Darling basin (South-eastern Australia). The satellite-derived irrigation products referring to the case studies in Europe have a spatial resolution of 1 km, and they are retrieved by exploiting Sentinel-1 soil moisture data obtained through the RT1 (first-order Radiative Transfer) model. A spatial sampling of 6 km is instead used for the Australian pilot area, since in this case the soil moisture information comes from CYGNSS (Cyclone Global Navigation Satellite System) observations. All the irrigation products are delivered with a weekly temporal aggregation. The 1 km data sets over the two European regions cover a period ranging from January 2016 to July 2020, while the irrigation estimates over the Murray-Darling basin are available for the time span April 2017 – July 2020. The retrieved irrigation amounts have been compared with benchmark rates collected over selected agricultural districts. Results highlight satisfactory performances over the major part of the pilot sites falling within the two regions characterized by a semi-arid climate, namely the Ebro and the Murray-Darling basins, quantified by median values of RMSE, Pearson correlation, r, and BIAS equal to 12.4 mm/14-day, 0.66, and -4.62 mm/14-day, respectively, for the Ebro basin and to 10.54 mm/month, 0.77, and -3.07 mm/month, respectively, for the Murray-Darling basin. The assessment of the performances over the Po valley is affected by the limited availability of in situ reference data for irrigation.

Quantifying the Hydrological Impacts of Irrigation on a Mediterranean Agricultural Context Through Explicit Satellite‐Derived Irrigation Estimates

“…The maximum differences in drainage fluxes detected in winter can be explained by irrigation occurring outside the main watering season to feed fruit trees and greenhouses (Dari et al., 2020). Such irrigation amounts, even though much lower than those delivered to the crops during summer (Dari et al., 2023), produce a surplus of water when the consumption due to evapotranspiration is lower and the soil moisture is closer to saturation. This condition reasonably leads to higher groundwater recharge rates (Jasechko et al., 2014).…”

“…Such irrigation schemes proved to be useful tools to investigate irrigation impacts on both water and energy balances at the regional scale (Modanesi et al., 2022). Recent exploitation of remotely sensed data to estimate irrigation amounts has led to the development of the first spatially distributed irrigation water data sets at different scales (Dari et al., 2020, 2023; Zhang et al., 2022). More in detail, Dari et al.…”

“…Later on, Dari et al. (2023) implemented the methodology to develop high‐resolution and regional‐scale irrigation data sets for three major basins: the Ebro basin (in Spain), the Po river valley (in Italy), and the Murray‐Darling basin (in Australia). In this case, the SM‐based inversion approach was forced with Sentinel‐1 soil moisture data obtained through the RT1 (first‐order Radiative Transfer) model (Quast et al., 2019, 2023) for the European sites and with CYGNSS (Cyclone Global Navigation Satellite System) soil moisture (Freeman et al., 2020) for the Australian pilot area.…”

Irrigation Quantification Through Backscatter Data Assimilation With a Buddy Check Approach

“…The first regional datasets of high resolution irrigation water use, based on S1 data, have been released by Dari et al. (2023) using the soil moisture‐based inversion approach. While the backscatter itself has already been used in irrigation mapping and timing studies at the local scale (Bazzi, Baghdadi, Fayad, Charron, et al., 2020; Bazzi, Baghdadi, Fayad, Zribi, et al., 2020), the direct use of S1 data to quantify irrigation is only in its infancy, as changes in backscatter are affected by the water in the topsoil, but also by the vegetation (water, volume, density, and geometry), and terrain roughness (McNairn & Shang, 2016).…”

Drainage assessment of irrigation districts: on the precision and accuracy of four parsimonious models

“…It is hence crucial to develop tools to retrieve the irrigation practices, notably at the integrated spatial scales of sub-basin or irrigation district. To this end, many recent works seek to assimilate satellite products of soil moisture or ET in crop water 590 balance models at a range of scales (e.g., Ouaadi et al, 2021;Massari et al, 2021;Dari et al, 2022;Olivera-Guerra et al, 2020). The coupling of such remote sensing approaches with surface and subsurface models is likely to improve the predictive capabilities of drainage on irrigated areas.…”