Exploiting High-Resolution Remote Sensing Soil Moisture to Estimate Irrigation Water Amounts over a Mediterranean Region

Jacopo Dari,Renato Morbidelli,Vivien Stefan,Pere Quintana-Seguí,Luca Brocca,María José Escorihuela

doi:10.3390/rs12162593

Abstract

Despite irrigation being one of the main sources of anthropogenic water consumption, detailed information about water amounts destined for this purpose are often lacking worldwide. In this study, a methodology which can be used to estimate irrigation amounts over a pilot area in Spain by exploiting remotely sensed soil moisture is proposed. Two high-resolution DISPATCH (DISaggregation based on Physical And Theoretical scale CHange) downscaled soil moisture products have been used: SMAP (Soil Moisture Active Passive) and SMOS (Soil Moisture and Ocean Salinity) at 1 km. The irrigation estimates have been obtained through the SM2RAIN algorithm, in which the evapotranspiration term has been improved to adequately reproduce the crop evapotranspiration over irrigated areas according to the FAO (Food and Agriculture Organization) model. The experiment exploiting the SMAP data at 1 km represents the main work analyzed in this study and covered the period from January 2016 to September 2017. The experiment with the SMOS data at 1 km, for which a longer time series is available, allowed the irrigation estimates to be extended back to 2011. For both of the experiments carried out, the proposed method performed well in reproducing the magnitudes of the irrigation amounts that actually occurred in four of the five pilot irrigation districts. The SMAP experiment, for which a more detailed analysis was performed, also provided satisfactory results in representing the spatial distribution and the timing of the irrigation events. In addition, the investigation into which term of the SM2RAIN algorithm plays the leading role in determining the amount of water entering into the soil highlights the importance of correct representation of the evapotranspiration process.

Highlights

Human interventions into the natural circulation of water on the Earth’s surface can no longer be neglected in the global economy of the hydrological cycle
All the remotely sensed and meteorological data sets used have been resampled to the same 1 km grid; this procedure allowed us to perform the analyses described in this study with spatially coherent data
In the experiment exploiting SMAP at 1 km soil moisture, the amounts of irrigation water feeding the pilot districts during a 20-month period, from the beginning of 2016 to September 2017, were estimated and compared with benchmark data

Summary

Introduction

Human interventions into the natural circulation of water on the Earth’s surface can no longer be neglected in the global economy of the hydrological cycle. Abbot et al [1] suggest that even the traditional representations of the cycle need to be adapted by involving anthropic water uses. It is estimated that over 70% of water withdrawals from lakes, rivers, and groundwater resources are destined for use in irrigation practices [2,3]. The continuous growth of the global population and the ever-rising living standards are expected to bring to an intensification of water depletion for improving agricultural production through irrigation practices, with higher impacts over areas already experiencing water stress conditions [4,5,6]. Irrigation practices need to be adequately managed [7,8]. Irrigation amounts often represent the missing information to adequately solve the water balance at several spatial scales [9,10]

Methods

Results

Discussion

Conclusion