University of Twente Student Theses


Modeling the impacts of conservation agriculture on hydrological processes and crop yield using the swat model : a study case in the Hupsel Catchment, East Netherlands

Aflah, Wiyanda Naufal (2022) Modeling the impacts of conservation agriculture on hydrological processes and crop yield using the swat model : a study case in the Hupsel Catchment, East Netherlands.

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Abstract:Drought is a severe issue that may have various adverse effects on agriculture. The types of droughts, such as hydrological and agricultural, are caused by a lack of precipitation. Additionally, as global warming levels rise, the frequency and severity of droughts will continue to rise on both a continental and worldwide scale. Poor rainwater partitioning contributes significantly to drought because it results in less productive rainfall (used by the plants) and less soil moisture, which could also lead to agricultural drought. An alternative agricultural practice might be utilized to deal with the droughts by improving rainwater partitioning. Alternative agricultural practices such as residue management (mulching), minimal soil disturbance (tillage), and crop rotation are all included in conservation agriculture (CA). In order to overcome inadequate rainfall partitioning, conservation agriculture focuses on minimizing runoff, soil evaporation and increasing soil water content or soil moisture. There is still minimal research on conservation agriculture as a potential drought solution, and there is even less research on how agricultural conservation methods affect crop productivity, hydrology, and the response to climate change. In order to address drought, the purpose of this thesis is to model the effects of conservation agriculture practices on hydrology and agricultural productivity of a rainfed agriculture area, which in this case is the Hupsel catchment located in the East of the Netherlands since this location experience droughts conditions in recent years. To accomplish the study's goal, a baseline scenario is first created using a crop-water model that covers both crop growth and hydrological model. This study used the Soil and Water Assessment Tool (SWAT) model to simulate the baseline scenario using historical climate data to match the agricultural practices practised in the study area. It is crucial for the CA impact assessment because it allows comparisons between the baseline and the various CA practice scenarios. Additionally, the accuracy of the baseline scenario is evaluated by comparing the model's output with the readily accessible observed data related to hydrology and agricultural productivity. Next, the CA practices are modelled individually and combined to assess their impacts on hydrology (surface runoff, percolation, evapotranspiration, and soil moisture) and agricultural productivity (crop yield). These practices were compared to the baseline scenario under the same historical climate condition to see the effects further. Similarly, the last part of this study aims to model the CA practices under future climate change scenarios provided by The Royal Netherlands Meteorological Institute (KNMI’14), specifically for the Netherlands. Thus, the results of this step will be compared to the baseline scenario (under the historical climate condition) to see the response of CA practices toward the future climate change condition. The result of the first step following conventional agriculture, the agriculture currently practised in the Hupsel watershed, was adequately modelled using the SWAT+ model. The model was calibrated and tested using daily observed streamflow, and then the model's performance was then assessed using a performance metric, Nash-Sutcliffe Efficiency (NSE). The model performed both quantitatively (NSE>0.65) and qualitatively performed well. In addition, the model predicted a yearly crop output comparable to the observed data from the Netherlands. Therefore, the model can be accurate enough to simulate agricultural yield and hydrology in the study area. Next, the results of the second step indicate that generally speaking, the CA practices have little influence on agricultural productivity (crop yield) and hydrological fluxes. The hydrological fluxes connected to the system's water loss (such as surface runoff, baseflow, and soil evaporation) are most significantly increased by crop rotation practices, whereas mulching has the reverse effect. On the other hand, it was found that the no-tillage method only affected surface runoff while barely showing any change for the other hydrological fluxes. Furthermore, mulching is observed to have the highest reduction in hydrological drought severity, while crop rotation and combination of CA practices scenarios favour lowering the agricultural drought severity. As for the last part, it was found that future climate conditions increased all hydrological fluxes in general, except for a slight decrease in soil water relative to the baseline scenario under the historical climatic condition. The practice of mulching significantly affects plant transpiration, having the most significant effect compared to the other scenarios under the future climate condition represented by the WL scenario (warm and low influence of air circulation). It also exhibits the most significant decrease in soil evaporation but little change in percolation or surface runoff. Contrarily, the practice of crop rotation has a different effect on evapotranspiration than the practice of mulching while simultaneously having the most significant rise in surface runoff and percolation compared to the other activities. Regarding crop yield, mulching and a combination of CA practices scenarios increased corn yield under future climate conditions. In contrast, the other practices have almost no effects. On the other hand, CA practices have no effect on the amount of grass yield under the conditions of future climate change, whether they are used individually or together as one scenario. Similarly, mulching was still observed to have the most positive effect on reducing the hydrological drought severity. At the same time, crop rotation and a combination of CA practice scenarios provide less agricultural drought severity. There are several limitations to the study. For instance, the unavailable parameters within the SWAT+ toolbox, values of the variables (such as Manning value) and databases (e.g., plants, soil, tillage) are less accurate in representing the actual condition in the Netherlands, and no specific mulching operation. The methodology and results of this study can be used as a reference for further study but still needs improvements to get proper output. The recommendations to improve this study vary, such as choosing the Green & Ampt method to get an accurate output of infiltration that is essential for modelling the CA practices, using licensed software to help the calibration and sensitivity analysis, and exploring other cropping systems along with other possible best management practice such as strip cropping and contouring.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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