Determining the Critical Points of a Basin from the Point of View of Water Productivity and Water Consumption Using the WaPOR Database

Abstract

Actual evapotranspiration is one of the major components of the soil water balance equation. Several methods have been presented for estimating actual evapotranspiration, but the older methods are not practical because of their spatial and temporal dependence. Recently, the Food and Agriculture Organization of the United Nations (FAO) created the WaPOR open-access system on water productivity with the aim of covering countries experiencing water crises in Africa and the Middle East, and the estimation of actual evapotranspiration (ETa) is one of its main products. This portal makes it possible to determine water consumption and water productivity on a large scale with minimal time and cost, so it can be used to manage the agricultural sector. The Google Earth Engine System (GEE), introduced by Google in 2010, is an effective remote sensing instrument for gathering important data from satellite imagery. In this study, the actual evapotranspiration maps of the Maroon-Jarahi basin for 2017 were extracted using the methodology introduced by the FAO and provided in the WaPOR database, and the coding was performed in the GEE system. The results showed that the actual evapotranspiration during this period was highest in July and decreased with the onset of the fall season. Limited water resources are a major obstacle to ensuring food security. Considering that the agricultural sector consumes most of the water in Iran and worldwide, water management in the agricultural sector is of great importance. Water productivity is a key indicator in studying and improving agricultural water management as well as one of the Sustainable Development Goals. In this study, the actual evapotranspiration (AET), net primary production (NPP), and water productivity (WP) for the basin were estimated using the WaPOR portal and Google Earth Engine over a 10-day period with a spatial resolution of 250 m (decadal data). Based on the obtained results, areas with low water productivity were identified. By studying the existing cropping patterns, the type of irrigation system used, and the water and soil conditions in these areas, it was possible to investigate the reason for the low water productivity and propose solutions to improve it.

Keywords

• irrigation management
• water consumption
• WaPOR
• evapotranspiration