Controlled drainage under two climate change scenarios in a flat high-latitude field

This simulation study focused on the hydrological effects of climate change and controlled drainage operated with subsurface drains and an open collector ditch in an agricultural field. The objective was to understand the potential of controlled drainage and open ditch schemes for managing groundwater levels and field water balance in climate conditions projected to take place in Finland during the 21st century with representative concentration pathways 8.5 and 2.6. A methodological aim was to find ways to condense hourly hydrological results to understand future changes in field hydrology. During the historical reference interval (1970–2005), controlled drainage caused 17–36 cm higher mean groundwater levels and decreased the mean annual drain discharge by 11–23% compared to conventional subsurface drainage. Controlled drainage was projected to increase groundwater levels by additional 1–4 cm in the future compared to its effect on drainage during the reference interval. The effect on annual drain discharge did not change significantly. The open collector ditch lowered groundwater tables and diminished the effect of controlled drainage on groundwater levels in the vicinity of the ditch. Controlled drainage was shown to remain an effective method for countering early summer drought and reducing drain discharge.

Seasonal effects of controlled drainage on field water balance and groundwater levels

Adaptive water management solutions such as controlled drainage have raised interest in Nordic areas due to climate variability. It is not fully known how controlled drainage affects seasonal field water balance or can help in preventing water scarcity during dry growing seasons (GSs). The objective was to simulate the effects of controlled drainage on field hydrology using a well-tested, process-based hydrological model. The FLUSH model was calibrated and validated to an experimental field. The model performance with non-local input data was moderate but acceptable for running the controlled drainage scenarios to test the response of the water management method to meteorological forcing. Simulation results showed that controlled drainage reduced drain discharge while increasing surface layer runoff and shallow groundwater outflow. Groundwater depths from the scenario simulations demonstrated that controlled drainage could keep the depth closer to the soil surface, but the effect diminished during the dry conditions. Controlled drainage can be used to change the water flow pathways but has a secondary effect compared with the primary meteorological drivers. The field data set and FLUSH formed a novel computational platform to study the impacts of different water management options on the whole water balance and spatial variability of groundwater depths.

Estimating evapotranspiration and irrigation water requirement in phonology stages of grape (VitisVinifera) using agro-hydrological model and remote sensing techniques

This study aims to compare the remote sensing (RS) approach and an agro-hydrological model to estimate evapotranspiration (ET) and irrigation water requirement (IWR) in semi-arid region, and the effect of vineyards management and their ages on these parameters. In the study region, after vineyards were classified into three main scenarios based on three vineyards ages (12-15, 15-18 and 18-21 years) and two management approaches (proper and improper management), ET and IWR were determined in each scenario using the Soil-Water-Atmosphere–Plant (SWAP) Model and Surface Energy Balance Algorithm for Land (SEBAL) for the year of 2019-2020 with Landsat8 images. While the accumulated ET calculated with SEBAL was compared with a field water balance, the results showed that without calibration or parameter optimization, the accumulated ET estimated with SEBAL exceeded that computed with SWAP. According to the findings, the most and least RMSE was related to August (1.32) and June (1.26). Analyses of scenarios showed that at the first stage of phonology (bud-break to bloom), the S3 scenario has the most IWR for each pixel (900 m2) by 2.7 m3, and at the second stage (bloom to ripening) and the third stage (ripening), the S1 scenario by 229.5 m3 and 78 m3 has the highest IWR, respectively.

Field monitoring and model predicted water balance of monolithic cover

The use of the evapotranspiration cover for landfill is increasing because of its long-term enhanced performance. However, the performance of evapotranspiration cover primarily depends on the onsite geo-climatic conditions. Therefore, field verification of cover performance through constructed test plots is required before actual implementation. Additionally, numerical modeling and comparison with field results are necessary for future performance prediction. The objective of this study was to simulate the water balance hydrology of evapotranspiration cover using the code SEEP/W. Drainage lysimeter was constructed with fine-grained soil and native vegetation. Field water balance data from the lysimeter were obtained through instrumentation. Onsite climatological data, laboratory and field investigated soil parameters and actual field studied plant parameters were used as model input. Based on one year’s simulation, it was observed that the code nearly captured the seasonal variations in the water balance quantities measured in the field. Surface runoff was reasonably predicted in the model where precipitation intensity appeared to be responsible to some extent. Evapotranspiration was slightly overpredicted and the fluctuation in soil water storage was similar to the field results. The model predicted annual percolation was approximately 45 mm, which is under-predicted than the actual field measured annual percolation of 62 mm.