University of Twente Student Theses
Estimating current and possible future irrigation water requirements : an approach for the Rhine basin during the growing season in periods of drought
Schoot, F.H.E. van (2021) Estimating current and possible future irrigation water requirements : an approach for the Rhine basin during the growing season in periods of drought.
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| Abstract: | The year 2018 turned out to be an extremely dry year in the Rhine basin (Wilkes and Parkin, 2020), with the same trend continuing in the years 2019 and 2020 during the growing season or summer period (KNMI, 2020a). This has led to alarming low water levels in main rivers such as the Rhine, which has negatively impacted sectors dependent on these water flows. The agricultural sector, which is the largest water consuming sector in the world, is one of these sectors. Especially in dry years, crops are dependent on irrigation water from surface water (e.g. rivers). The goal of this study is to estimate the current and possible future irrigation water requirements of the agricultural sector in the Rhine basin and consequently, its impacts on the Rhine river flow during growing seasons. With the help of the Aqua21 water footprint accounting model and the Delft-Agri water demand and allocation model, water requirements are quantified, compared with historic data for validation, and assessed for future scenarios. Since irrigation water is mostly applied during dry years, these years are considered in this study. The four most important irrigated crops in terms of irrigation water use (m3) – sugar beet, potatoes, maize and oats - are used for the estimation of current and future water requirements. The Delft-Agri model can calculate the gross water requirement (m3) for any time at any location, and the model package RiBaSIM is able to show the river discharge (m3/s) of various stations. In this study, agricultural input data for the Delft-Agri model for the Rhine basin were taken from Aqua21. Therefore, first the model performance of Aqua21 is tested against small scale (NUTS-1 level) validation data. The model turns out to perform good on the variables production (tonne) and yield (tonne/ha) for both average, as well as dry years. Afterwards, the performance of the Delft-Agri model is tested against Aqua21 results. The model turns out to perform good on the net water requirement (m3) variable. However, the Delft-Agri model for the Rhine basin does not account for drought damage in the production (tonne) variable. The performance of the river discharge (m3/s) variable is rather low for low flows, which limits the analysis on estimating the impact of changing river flow under various scenarios. To scope possible future irrigation water use in the Rhine basin, four scenarios are designed with the help of the story-and-simulation approach (Alcamo, 2001): modest global warming – intensive agriculture, modest global warming – sustainable agriculture, much global warming – intensive agriculture, much global warming – sustainable agriculture. This study shows that the current irrigation water requirement of the agricultural sector in the Rhine basin during the growing season in periods of drought can go up to 9.4*107 m3/month. The possible IV future irrigation water requirement of the agricultural sector in the Rhine basin during the growing season in periods of drought varies per scenario. For the intensive agricultural scenarios an increase of 96% (modest global warming) to 130% (much global warming) can be expected during the growing season for the year 2050. The sustainable agriculture scenarios show an increase of 12% (modest global warming) to 33% (under much global warming) compared to the current scenario. The impact of the irrigation water requirement (m3) on river discharge (m3/s) is rather low: changes in river flow relative to the reference scenario remain below 1% for both the main river as the side rivers. This estimation only considers the impact of the scenarios, not the decrease in river flow due to climate change. This study has sought a methodology to estimate the current and future irrigation water requirement of the Rhine basin. While this study has given new insights, some challenges still remain to be solved in future research. It is recommended to expand the Delft-Agri model with a dynamic crop plan, so crop ratios can be set per year, resulting in more precise water requirement estimations per sub-basin. The possibility to insert dynamic potential crop yield (Ym) values would also increase the model’s accuracy on yield estimations. Furthermore, the collection and use of irrigation data on small scales (NUTS-1 level) would improve the model results of both Aqua21 and Delft-Agri. Especially when the sub-basin resolution of the Delft-Agri model is increased. |
| Item Type: | Essay (Master) |
| Faculty: | ET: Engineering Technology |
| Programme: | Civil Engineering and Management MSc (60026) |
| Link to this item: | https://purl.utwente.nl/essays/85890 |
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