How to account for irrigation withdrawals in a watershed model

Abstract

Abstract. In agricultural areas, the downstream flow can be highly influenced by human activities during low-flow periods, especially during dam releases and irrigation withdrawals. Irrigation is indeed the major use of freshwater in the world. This study aims at precisely taking these factors into account in a watershed model. The Soil and Water Assessment Tool (SWAT+) agro-hydrological model was chosen for its capacity to model crop dynamics and management. Two different crop models were compared in terms of their ability to estimate water needs and actual irrigation. The first crop model is based on air temperature as the main determining factor for growth, whereas the second relies on high-resolution data from the Sentinel-2 satellite to monitor plant growth. Both are applied at the plot scale in a watershed of 800 km2 that is characterized by irrigation withdrawals. Results show that including remote sensing data leads to more realistic modeled emergence dates for summer crops. However, both approaches have proven to be able to reproduce the evolution of daily irrigation withdrawals throughout the year. As a result, both approaches allowed us to simulate the downstream flow with a good daily accuracy, especially during low-flow periods.

Can adaptations of crop and soil management prevent yield losses during water scarcity? – A modelling study

“…The restriction of water use is often not considered in models, which Winter et al (2017) identified as a limitation of the state-of-the-art models. (Brochet et al, 2024) used SWAT to integrate irrigation water withdrawals into their streamflow predictions to account for the significant anthropogenic influence in low-flow periods. In their study area, daily irrigation water withdrawal was measured and used for calibration and validation.…”

“…They found that future water levels in the reservoirs are insufficient to meet the increase in irrigation water demand under future climate change (Gorguner and Kavvas, 2020). Such efforts to quantify current or future irrigation water demand and shortage have either been made globally (Wada et al, 2014;Müller Schmied et al, 2021;Joseph et al, 2020), in semi-arid catchments (Gorguner and Kavvas, 2020) or without considering water restrictions (Brochet et al, 2024;Masia et al, 2021).…”