Predicting evaporative loss at an Argentinian vineyard using a coupled water, vapor and heat flow model

Water resources in arid regions around the world are under a lot of strain due to extremely low precipitation rates and very high evaporation. In addition to water scarcity, irrigation methods can be inefficient. For example, over-irrigation beyond soil saturation can cause many problems, such as an increase in soil salinity and a decrease in productive soil capacity. This research aims to design a water content and soil temperature prediction system for an automated sensor monitoring system installed at the vineyard Ecohumus in San Juan province, Argentina. Short-term predictions of the water balance have the potential in delivering a useful tool to farmers for optimizing their irrigation water consumption.

For modeling soil water dynamics with evaporation and root water uptake losses, we use a coupled water, vapor, and heat flow model implemented in DRUtES software, Kuraz and Blöcher (2020). The model's top boundary condition solves the surface energy balance. For that we use weather forecast data and solar radiation as an input. The weather forecast is obtained from Norwegian meteorological institute (yr.no) using their API for developers which is provided as a free service. The solar radiation is computed based on equations suggested in the FAO Irrigation and Drainage guideline No. 56 and by Saito et al. (2006). Due to the lack of measurement data on the study site, soil hydraulic and thermal properties are estimated. We neglect the effect of soil organic matter in the water retention model and assume a homogeneous type of soil for the thermodynamic model. We establish communication with sensors installed in the soil for estimating initial conditions as well as with weather forecast service for estimating boundary conditions using our R script.

The result is output records that simulate pressure heads and water content distribution across the flow field over the simulated period. We present a system that describes the flow field allowing us to calculate evaporation rate changes with time, thereby optimizing the irrigation process according to soil and plant needs. This can be a helpful decision-making tool for farmers.