Estimating water balance components in irrigated agriculture using a combined approach of soil moisture and energy balance monitoring, and numerical modelling

Abstract

Information on water balance components such as evapotranspiration and groundwater recharge are crucial for water management. Due to differences in physical conditions, but also due to limited budgets, there is not one universal best practice, but a wide range of different methods with specific advantages and disadvantages. In this study, we propose an approach to quantify actual evapotranspiration, groundwater recharge and water inflow, i.e. precipitation and irrigation, that considers the specific conditions of irrigated agriculture in warm, arid environments. This approach does not require direct measurements of precipitation or irrigation quantities and is therefore suitable for sites with an uncertain data basis. For this purpose, we combine soil moisture and energy balance monitoring, remote sensing data analysis and numerical modelling using Hydrus. Energy balance data and routine weather data serve to estimate ET 0. Surface reflectance data from satellite images (Sentinel-2) are used to derive leaf area indices, which help to partition ET 0 into energy limited evaporation and transpiration. Subsequently, first approximations of water inflow are derived based on observed soil moisture changes. These inflow estimates are used in a series of forward simulations that produce initial estimates of drainage and ET act , which in turn help improve the estimate of water inflow. Finally, the improved inflow estimates are incorporated into the model and then a parameter optimization is performed using the observed soil moisture as the reference figure. Forward simulations with calibrated soil parameters result in final estimates for ET act and groundwater recharge. The presented method is applied to an agricultural test site with a crop rotation of cotton and wheat in Punjab, Pakistan. The final model results, with an RMSE of 2.2% in volumetric water content, suggest a cumulative ET act and groundwater recharge of 769 and 297 mm over a period of 281 days, respectively. The total estimated water inflow accounts for 946 mm, of which 77% originates from irrigation.

Simulating Water Balance and Crop Yield for Sugarcane Plantation in Pasuruan Using Aquacrop Model

“…A. Water Balance Information on water balance is important for agricultural use (Schulz, et al, 2021). There are many water balance components can be measured in field by direct and indirect measurements.…”

Soil Moisture Estimation for Winter-Wheat Waterlogging Monitoring by Assimilating Remote Sensing Inversion Data into the Distributed Hydrology Soil Vegetation Model

“…Therefore, as shown in Figure 6, the measured soil moisture content is far less than the simulated soil moisture content after heavy rain. Schulz et al also found that the decrease of soil moisture content using artificial drainage is faster than that under natural drainage conditions [47]. Eekhout et al [48] indicate that the uncertainty of the DHSVM model increases with extreme precipitation and runoff.…”

Allowing the Actual Evapotranspiration Uncertainty in Hydrological Models: Coupling of Interval-Based Water Balance and METRIC Models

“…Earth Observation (EO) approach is of key signi cance in estimating ET due to its appropriate estimation accuracy, economical, and widely spatiotemporal coverage (Zhang et al, 2016;Taghvaeian and Neale, 2011;Schulz et al, 2021). EO-based ET estimation models can vary from entirely empirical methods to physically-based models.…”