R. Uijlenhoet | TU Delft Repository

Numerical Rainfall Prediction for Ghana Using the Weather Research and Forecasting Model

A Model Performance Evaluation

Master thesis (2024) - S.C. Verheugd (author), N.C. van de Giesen (mentor), R. Uijlenhoet (graduation committee member), Louise Nuijens (graduation committee member), S. Ligtenberg (mentor), L. Occelli (mentor)

Agricultural businesses in Ghana heavily depend on rain-fed farming, but they are facing increasing challenges due to climate change and population growth. Accurate weather forecasts providing useful information on the onset of the rainy season are therefore of utmost importance. ...

Precipitation Nowcasting using a Generative Adversarial Network

Master thesis (2024) - S. van Os (author), M.A. Schleiss (mentor), R. Taormina (graduation committee member), R. Uijlenhoet (graduation committee member), Mattijn van Hoek (graduation committee member), Dorien Lugt (graduation committee member)

Nowcasting high-intensity precipitation is crucial for emergency services and municipalities when making weather-dependent decisions. This research implements and trains a deep generative model for nowcasting using a cleaned precipitation radar composite dataset spanning 15 years ...

Physics-informed machine learning for nowcasting extreme rainfall

Master thesis (2024) - J. Yin (author), Justin Dauwels (mentor), L. Abelmann (graduation committee member), R. Uijlenhoet (graduation committee member)

The thesis explores an innovative technique for enhancing the precision of short-term weather forecasts, particularly in predicting extreme weather phenomena, which present a notable challenge for existing models such as PySTEPS due to their volatile behavior. Leveraging precipit ...

Separation of fresh and brackish water in polder water canals

Master thesis (2023) - I. de Vries (author), O.A.C. Hoes (mentor), Anne van der Heijden (graduation committee member), R. Uijlenhoet (graduation committee member), W.S.J. Uijttewaal (graduation committee member)

Polders water canals are sometimes exposed to brackish seepage from the nearby saline sea (salinization). This is a problem because the canal water is used to irrigate crops. A characteristic of water is that less dense (fresh) water floats on top of dense (saline) water. In lake ...

Polders water canals are sometimes exposed to brackish seepage from the nearby saline sea (salinization). This is a problem because the canal water is used to irrigate crops. A characteristic of water is that less dense (fresh) water floats on top of dense (saline) water. In lakes and oceans, it is common that water layers with various densities flow on top of each other (stratification). However, this has not been observed yet on a small scale, such as in polder water canals. It is assumed that, with a traditional weir, fresh water is discharged, and saline water stays behind. To encounter this, a modified weir is developed. It uses an underflow gate in front of the traditional weir to discharge the bottom water out of the canal. This research aimed to investigate if stratification happens in polder water canals and to explore how a modified weir can be implemented. The Negenboerenpolder in Groningen (the Netherlands) served as an example. Multiple methods are used because of the broad and practical nature of the problem. First, field measurements in the Negenboerenpolder demonstrated stratification in polder water canals. At multiple locations in the polder, the Electrical Conductivity (EC) is measured over the depth or continuously measured at two depths. Secondly, flume experiments gave information about the experimental procedure and implementation of a modified weir. Thirdly, 2D simulations of a modified weir are done in ANSYS Fluent, a Computation Fluid Dynamics (CFD) software. The simulations suggest that a modified weir works as expected, but the model is not completely representative. Observations are that such a weir is more effective in discharging brackish water with a low flow velocity and a larger distance between the underflow gate and the weir. Implementation advice for a modified weir is also included in this research. To conclude, this research implies that a modified weir can be used to discharge brackish water, but the design and implementation need to be done carefully. Recommendations for future research are to experiment with a modified weir in a polder and to build a 3D CFD model to investigate the flow around the underflow gate.

Towards Water Availability Predictions with Earth-Observed Open Data in Man-Made Reservoirs Worldwide

Master thesis (2023) - E.A.M. Klein Holkenborg (author), H.C. Winsemius (mentor), R. Uijlenhoet (graduation committee member), Marc van den Homberg (graduation committee member), Tina Comes (graduation committee member)

Small to medium-sized man-made freshwater reservoir are a reliable source for drinking water supply, hydropower generation and irrigation purposes worldwide. However, water volumes in these reservoirs can be significantly affected by prolonged droughts, resulting in severe impact ...

Small to medium-sized man-made freshwater reservoir are a reliable source for drinking water supply, hydropower generation and irrigation purposes worldwide. However, water volumes in these reservoirs can be significantly affected by prolonged droughts, resulting in severe impacts on society (Kozacek, 2014; Mahr, 2018). To mitigate the impact of such events it is crucial for decision makers to know when the available water resources are lacking. Although many reservoirs are closely monitored, this data is not always readily available. Inadequate information sharing, inaccessibility, and a lack of tools to predict future reservoir storages contribute to this problem.

Remote sensing has the potential to address this problem. The Global Water Watch is a platform that and provides earth-observed surface area dynamics that can be used to monitor small to medium-sized reservoirs worldwide and detect trends in water availability. While this method serves as a valuable indicator of water availability, it falls short in providing decision-makers with the necessary absolute volume time series and volume predictions. Currently, no platform exists beyond in-situ measurements to meet this essential need.

This thesis presents a novel method for retrieving near real-time volume time series in small to medium-sized man-made reservoirs worldwide using remotely sensed open data. The method utilises the MERIT-Hydro digital elevation model, HydroMT and stream flow methods by Eilander et al. (2023), and literature by Messager et al. (2016) to reconstruct reservoir bathymetry. This novel approach in reconstructing reservoir bathymetry enables the conversion of available reservoir area time series into volume time series. These were employed in autoregressive and multi-linear regression models to predict water availability up to six months in advance. The models incorporate ERA5 precipitation data by Hersbach's (2020) and the Standardised Precipitation and Evaporation Index (SPEI) by Beguería et al. (2021) to improve the accuracy of the volume predictions.

When comparing the novel method to the method proposed by Messager et al. (2016), the novel method yielded more accurate reservoir volume estimations. The method successfully obtained bathymetries and accurate volume estimations when validating using 2 reservoirs in Zambia and 48 in India, demonstrating the potential of this novel approach. However, some reservoirs with complex shapes faced initial delineation challenges, resulting in inaccurate volume predictions. These issues could be resolved by manually delineating the area for bathymetry reconstruction. Moreover, regression models were applied to case study reservoirs in Eswatini and Lesotho, demonstrating reasonable predictive capabilities with the Heidke Skill Scores ranging from 0.77 to 1 for up to 2 months ahead. However, precise prediction of extreme decreases in reservoir levels requires a physically based approach that incorporates the volumetric time series provided by this novel method. The study emphasises the necessity of considering the volume time series’ memory to predict water availability and provides a valuable foundation for volume time series analysis using remotely sensed data.

Waterschaarste

Hoe de beleidsontwikkelingen aangevuld kunnen worden om aan te sluiten op de veranderingen die optreden tot en met 2050

Master thesis (2023) - M. Verdaasdonk (author), E. Mostert (mentor), R. Uijlenhoet (graduation committee member), Marjolein van Zuilekom (coach), Marloes Dignum (coach)

In dit onderzoek is onderzocht welke aanvullingen in het waterschaarstebeleid ervoor kunnen zorgen dat de beleidsontwikkelingen in Nederland aansluiten op de optredende verandering tot en met 2050. Hierbij is enerzijds in kaart gebracht hoe het beleid, met betrekking tot watersch ...

Prediction of Discharges from Polders to ‘Boezem’ Canals with a Random Forest and an LSTM Model

Improving Inputs of the Decision Support System of the Hoogheemraadschap van Delfland

Master thesis (2023) - J. van Marrewijk (author), R. Taormina (mentor), R. Uijlenhoet (graduation committee member), M.A. Schleiss (graduation committee member), Sjoerd Gnodde (graduation committee member), J. Driebergen (graduation committee member)

In this research the possibilities of the application of machine learning models at ‘Hoogheemraadschap van Delfland’ are studied. A random forest (RF) and an LSTM model are used for the prediction of the sum of the discharge in the next 2, 8 and 12 hours from the polders to the b ...

The Hydrological Effect of Urban Nature-based Solutions on Catchment Scale

A Case Study in the Geul Catchment

Master thesis (2023) - C.E. Muishout (author), M.M. Rutten (mentor), R. Uijlenhoet (graduation committee member), Joost Buitink (graduation committee member), Reinder Brolsma (graduation committee member)

Climate change imposes an increasingly big challenge worldwide regarding floods and droughts. The Netherlands is no exception to this, as it has been increasingly hit by these phenomena in recent years, especially in the south of the country. The July 2021 flood in the Geul catch ...

Climate change imposes an increasingly big challenge worldwide regarding floods and droughts. The Netherlands is no exception to this, as it has been increasingly hit by these phenomena in recent years, especially in the south of the country. The July 2021 flood in the Geul catchment intensified discussions on climate resilience. It prompts consideration of transforming the Dutch landscape into a more sponge-like system. Urban areas, identified as both problem areas and potential solutions within the catchment, stand out, since these areas are highly vulnerable and amplify climate change effects. Implementing Urban Nature-Based Solutions (UNBSs) emerges as a promising approach to address these challenges, potentially offering a solution to enhance climate resilience and mitigate the vulnerabilities of urban areas.
This research addressed the challenge of flood protection in the Geul catchment. It focuses on studying the impact of UNbSs and developing a methodology to select, model, and assess their performance in the catchment. This has been done by answering the following questions:

Which Urban Nature-based Solutions are suitable for the Geul catchment?
What is the hydrological effect of these Urban Nature-based Solutions locally?
What is the hydrological effect of Urban Nature-based Solutions at catchment scale?

This research followed a three-step workflow in line with the research questions. Firstly, the study focused on an assessment of neighbourhood types in the catchment and selecting suitable UNbSs for the Geul catchment. Based on this assessment, UNbS measures were chosen for their compatibility with these neighbourhoods. Next, this research analyzed the local effects of the implementation of these measures into the chosen neighbourhoods using the Climate Resilient City Tool. The final step involved an assessment of the hydrological impact of UNbSs on catchment scale. This was achieved by converting the previous results to wflow parameters.
The research succeeded in establishing a workflow for modeling UNbS impact at the catchment scale. It involved selecting UNbSs for three neighborhood types, resulting in the selection and implementation of green roofs, water roofs, permeable pavement, retention ponds, removing pavement to plant green and bioswales.
Locally, the study found that permeable pavement and bioswales were most effective for increasing storage capacity, evapotranspiration, and groundwater recharge. However, the overall order of magnitude for all measures remained consistent across neighbourhoods. Considering the total storage capacity increase, the order of magnitude was found to be between 34- and 39-mm storage equivalent over the total surface area of the neighbourhoods.
On a catchment scale, UNbS implementation resulted in a discharge reduction ranging from 1.71% to 3.10%, with a more pronounced effect upstream. Three neighbourhood scenarios exhibited minimal differences, all below 0.1%, which is considered insignificant. Absolute discharge reduction consistently followed patterns across low and high discharge periods, with more substantial reductions during peak discharges. However, the percentage difference between original and altered discharge was found to be similar across all periods, making this trend less evident.
Based on these results, the research proposed the following five recommendations regarding future research and implementation: 1) improve model transparency and sensitivity analysis, 2) consider practical implementation challenges, 3) refine typology mapping and data, 4) evaluate Nature-based Solutions in diverse landscapes and 5) promote the role of UNbSs in climate resilience.

Investigating the potential role of pumped hydro storage in the Ethiopian energy system using OSeMOSYS

Master thesis (2023) - D.H.X. de Vries (author), E. Abraham (mentor), R. Uijlenhoet (graduation committee member), F.O. Annor (coach), N.C. van de Giesen (coach), Viktoria Martin (coach)

Ethiopia’s energy demand is expected to increase sevenfold in the coming 30 years, resulting in increased variable renewable electricity (VRE) production by solar PV and wind. Energy storage acts as a buffer that mitigates the effects of over- or under-capacity in production by V ...

Ethiopia’s energy demand is expected to increase sevenfold in the coming 30 years, resulting in increased variable renewable electricity (VRE) production by solar PV and wind. Energy storage acts as a buffer that mitigates the effects of over- or under-capacity in production by VRE. With 97% of global bulk energy storage, pumped hydro storage is the most widely used and mature energy storage method. With its long operational life, high round-trip efficiency (80%) and stable cost trajectory, it is a beneficial option for many energy systems. However, drawbacks of pumped storage include heavy technical, site-specific restrictions, long construction times and high initial capital investment requirements.

This study investigates if Ethiopia’s energy pathways benefit from adding pumped storage, where to build it, and if storage increases system resilience. The long-term energy planning tool OSeMOSYS is used, which allows for detailed investigation into system dynamics whilst parallelly minimising costs. OSeMOSYS enables the investigation into Ethiopia by looking at an extensive host of techno-economic
specifications and supply and demand dynamics from the electrification of transport and integration of variable renewables to residential cooking demands.

This report discusses thirteen scenarios which are separated into three main categories: Base Case (3), Emission Penalty (EMI) (6) and Varying Wind Capacity and Seasonality (WND) (6). The base case introduces pumped storage to the energy pathways. The EMI scenario characterises three pathways for carbon pricing. In the WND scenario, wind power’s capacity factor and seasonality are altered to
investigate the potential effects of using more accurate local data or prioritising some supply zones on the energy system configuration. Additionally, the most favourable locations for solar PV and wind are combined with potential PHS locations to find optimal sites for storage construction.

The results of the research show that pumped hydro storage is adopted into the energy system in all scenarios, following both a diurnal and seasonal (dis)charge pattern. Variable renewable integration increases by an average of 10% from the addition of storage (78 GWh). The emission penalty increases the electrification of residential cooking demand and boosts VRE penetration but does not integrate
storage integration further than the base case due to reaching the upper limit of the storage capacity set in the planning experiments. Lastly, the changes in capacity factor and seasonality have a marginal effect on the energy pathways.

Pumped hydro storage increases the energy system’s resilience to climate-driven seasonal uncertainties and prices due to fossil fuel and carbon price uncertainties by making it less dependent on fossil fuels, decreasing vulnerability for potential emission penalties and seasonal capacity fluctuations. The introduction of PHS does not increase overall system costs, making it a prime candidate for large-scale energy storage in Ethiopia, combined with the stable levelised cost of storage and high maturity

Investigation of the Impacts of Climate Variability and Land Use Changes on the Hydrology of the Geul River Catchment

Master thesis (2022) - A. TSIOKANOS (author), M.M. Rutten (mentor), R. Uijlenhoet (graduation committee member), R. Velner (graduation committee member), K.F. Jansen (graduation committee member)

The Geul river, a tributary of the Meuse located in the south Netherlands, Belgium, and part of Germany, is vulnerable to extreme hydrological events, such as floods, droughts, and erosion. There is evidence that these conditions are exacerbated by land use and climate changes. T ...

The Geul river, a tributary of the Meuse located in the south Netherlands, Belgium, and part of Germany, is vulnerable to extreme hydrological events, such as floods, droughts, and erosion. There is evidence that these conditions are exacerbated by land use and climate changes. This thesis focuses on investigating the temporal variability and trends of hydrometeorological variables, as well as the main land use changes in the Geul river catchment. Accordingly, this thesis aims to improve understanding of the impacts of climate change and human intervention on the hydrological response of the Geul. In the first part of the thesis, temporal changes in (extreme) precipitation regimes for the period 1951-2021 and potential evaporation for the period 1965-2021, are identified by calculating trends for each 30-year moving period within the available time frames. The main land use changes are evaluated using CORINE annual land cover maps for the period 1990-2018. Changes in discharge regimes are investigated using a multi-temporal approach in which trends are evaluated in every possible combination of start and end years. In the second part of the thesis, the effects of climate variability and land use changes on the variability of runoff patterns are assessed. This is achieved by correlating the rates of change between extreme precipitation and maximum discharges all over the moving periods. The work also includes the use of a water balance separation framework to estimate the attribution of alterations in mean stream flows to land use and climate changes. A statistically significant increase in very wet days is reported in the area that mainly derives from the winter period. The extreme summer precipitation
shows a relatively strong increase since the 1980s. The trend analysis in the potential evaporation time series suggests a very strong and stable increase. The main land use changes dominated before the 1970s, while there do not appear to be significant changes in the catchment from 1990 to 2018. Extreme annual discharges show an increasing insignificant tendency, while mean stream flows are decreasing. Results suggest that the variability of extreme and mean flows is mainly driven by climate variability, while at the same time the effects of land use changes on runoff patterns are not visible for the period 1970-2021. This study emphasizes that climate change should be incorporated into flood designs and climate adaptation strategies should be provided.

Hydrological Response of the Geul Catchment to the Rainfall in July 2021

Master thesis (2022) - A.C. Klein (author), M.M. Rutten (mentor), R. Uijlenhoet (graduation committee member), Roel Velner (coach), Koen Jansen (coach)

Flash floods are a major concern in hydrology and natural hazard science due to their high potential of causing fatalities and damages. They are caused by short, high-intensity rainfall and characterized by a flood event happening within six hours of the onset of precipitation.

Flash floods are a major concern in hydrology and natural hazard science due to their high potential of causing fatalities and damages. They are caused by short, high-intensity rainfall and characterized by a flood event happening within six hours of the onset of precipitation.
In July 2021 an extremely large rainfall event took place in the mid mountain area of Belgium (Ardennes), Germany (Eifel), Luxembourg and the Netherlands (South Limburg). Precipitation amounts of up to 250 mm in 48 hours were recorded in the core of the rainfall area in Belgium. In the Netherlands the Geul catchment was affected the most as the high precipitation resulted in a flash flood hitting the villages and cities along the rivers.

This research is aimed at understanding the hydrological response of the Geul catchment to this extreme rainfall event. To begin with, the catchment and its hydrological behaviour is studied in detail, followed by an event analysis including rainfall, discharge and groundwater data. Furthermore, the antecedent wetness conditions prior to the event are assessed. Next to the data analysis, a wflow model was set up and adjusted to reproduce the event, to evaluate the event contributions of the different tributaries, and to test the impact of different antecedent conditions, rainfall amounts and infiltration capacities on the discharge response. By adjusting three parameters in the model (soil thickness, maximum leakage and a horizontal conductivity parameter), the model was able to reproduce the floods and the different responses of the subcatchments.

In July 2021 the Geul catchment received on average 128 mm precipitation in 48 hours. The highest rainfall sums were recorded in the Belgian part of the catchment and around Ubachsberg. The high rainfall quantities led to high discharges in the catchment. Based on model results, the peak discharge in the central part of the catchment at Gulpen was approximately 124 m3/s. The discharge response of the catchment differed strongly between the subcatchments, especially between the tributaries and the Belgian upstream part of the catchment. The Belgian part contributed about 60% to the flow in Gulpen,
although its contributing area is only 45%. The event run-off coefficient in the Belgian area was approximately 41%, while the event runoff coefficients of the tributaries Gulp and Eyserbeek were 21 and 23%, respectively. The differences in hydrologic responses within the catchment can be linked back to the geology. While the upstream part is characterized by thin soils and impermeable carboniferous rocks at the riverbed, the central and lower part of the catchment consist of a thick unsaturated chalk layer acting as major storage areas. In general, the overall run-off coefficient of 32% is fairly small for such an extreme event. The floodplains and the thick unsaturated zone at the chalk plateaus stored much water, and considerably delayed and dampened the peak. Based on the simulation approximately 75mm of water was stored in the catchment area upstream of Gulpen. 30-days prior to the event the catchment received 50% more rain than the long-term average. Assuming average July wetness conditions, according to the simulation the event peak and cumulative discharges would have been 20-35% lower, and an additional 4.8 x 106 m3 water could have been stored in the catchment upstream of Valkenburg. Consequently, the wetter-than-usual antecedent wetness conditions increased the severity of the flood from being minor (under normal conditions) to the major flooding which was experienced in the downstream catchment areas. However due to climate change, wetter summers are projected to become more frequent in the future and consequently the role of antecedent wetness will become even more important.

In the Geul catchment the geology is a dominant control on the runoff response of the (sub)catchments. The impact of flood mitigation measures can be maximized by taking the role of geology and its interaction with the effect of land-use changes into account in the selection process. Flood mitigation measures are especially required in the Belgian upstream part of the catchment. Retaining water already there, will attenuate and delay peak discharges at the villages and cities downstream.

Strategies to decrease water shortage in South-East Brabant

A groundwater model case-study

Master thesis (2022) - A.J. van Osnabrugge (author), O.A.C. Hoes (mentor), J.S. Timmermans (graduation committee member), R. Uijlenhoet (graduation committee member), Louis Broersma (coach)

The Netherlands has suffered form three successive dry summers resulting in a lowering of the groundwater table, causing water shortage. Also in the area of Water BoardDe Dommel, locatedwithin the province of Brabant, water shortage is a common problem. This results in water abst ...

The Netherlands has suffered form three successive dry summers resulting in a lowering of the groundwater table, causing water shortage. Also in the area of Water BoardDe Dommel, locatedwithin the province of Brabant, water shortage is a common problem. This results in water abstraction restrictions for farmers in the crop season every year. With climate change the precipitation pattern in the Netherlands will change, resulting in longer dry periods during summertime. Water Board De Dommel is searching for strategies to decrease this water shortage. These strategies need to be tested for future climate scenarios. This research tests different interventions for two specific areas within De Dommel. These areas differ in land-use, location in the catchment, geo(hydro)logy and infrastructure. This research answers the following research question: How does the groundwater of two different areas within Waterschap De Dommel react to different interventions
to prevent water shortage in long-termfuture scenarios?
To find the answer to this research question a stationary groundwater model (iMOD) is used. In this model
the different interventions are tested with four climate scenarios from the KNMI. These interventions take place in the top layers of the subsoil. Next to these interventions also three abstraction scenarios are modeled, to see the effect of changes in deeper aquifer layers. The interventions are tested with three signals from the model: 1) the head of the first aquifer layer, 2) the water balance for both areas for the first aquifer layer as well as the first four aquifer layers combined and 3) the flow paths. Because models include uncertainties and assumptions, expert judgement is included to test the interventions. The expert judgment is based on historical maps and the location of the interventions. At the end of the research a non-stationary model is used to test the "Brook swamp" intervention. This result is compared to the results of the stationary model of this intervention. The results show that changes in the top layers of the subsoil have almost no effect on the groundwater in the deeper layers for De Pielis area. More downstream in the catchment, at the Landschotse Heide area, this effect is bigger, because of changes in the upstream area. In the top soil layers the groundwater reacts positive for most interventions for both areas resulting in more water availability. Also in the top layers the effect is bigger at the Landschotse Heide area than at De Pielis area. With the non-stationary model results the groundwater reacts more positive to the "Brook swamp" intervention than for the stationary model. A non-stationary model is therefore better to see how the groundwater reacts to seasonal dependent interventions. The groundwater reacts differently per areas as well as per intervention. In both areas the groundwater does react positively to most interventions. For the Landschotse Heide area the groundwater reacts more positive than for De Pielis area. For both areas the "higher water level" and "closed ditches" interventions show the most positive reactions of the groundwater. Based on these results the Water Board is advised to research the effect of enriching the top layer of De Pielis, to see if these top layers can then hold more water. For the Landschotse Heide the Water Board is advised to decide if agriculture or nature is more important in that area, because these cannot coincide, and reach all demands, in the way it is set-up now.

Precipitation and its extremes: a study into the hydro-climatological controls of extreme precipitation

Master thesis (2022) - I.E. van der Veer (author), R.J. van der Ent (mentor), R. Uijlenhoet (graduation committee member), A.P. Siebesma (graduation committee member)

Extreme precipitation can be characterized by the tail behavior of precipitation probability distributions.The tail contains the most extreme precipitation events and tells something about both the magnitude and frequency of these events. Here the heaviness amplification factor i ...

Extreme precipitation can be characterized by the tail behavior of precipitation probability distributions.The tail contains the most extreme precipitation events and tells something about both the magnitude and frequency of these events. Here the heaviness amplification factor is used to represent the tail behavior. This research determines the most important hydro-climatological controls of the heaviness amplification factor. The study area is the entire world, where Antarctica and the oceans are not taken into account. A pre-defined set of 17 controls divided into four groups is used. The four groups are: general climate condition, geography, land cover and climate variability. The relation between the heaviness and the controls is determined with multiple linear regression, where the standardized controls are used. Since multiple linear regression is applied, multicollinearity might be a problem. This term refers to the occasion where independent variables are correlated to another independent variable or a linear combination of variables. This could lead to erroneous and unreliable results. To deal with this problem, three elimination methods are applied. This first method consists of a correlation analysis, where two controls are highly correlated if their correlation coefficient is higher than 0.9. The control with the lowest regression coefficient is eliminated. This is followed by another regression analysis with all the remaining controls, where controls with a low regression coefficient are also eliminated. The second method applies an iterative regression procedure, where in each iteration the control with the lowest coefficient is eliminated until three controls remain. The last method calculates the variance inflation factor, which is a measure for multicollinearity. It removes the controls with the highest variance inflation factor if higher than 10, until none of the controls has a score above this limit. The described analysis is done for the entire world, but also for 44 IPCC climate reference regions. The conclusion of the analysis is that the most important controls for the heaviness belong to the general climate condition and the climate variability. In total, 13 of the 17 controls occur in a top three for at least one region in one or more of the elimination methods. The most important control is precipitation variability which is in 57% of the regions in the top three based on the results of methods 1, 2 and 3. Each region gives a different top three or at least a different order of controls. The heaviness is calculated based on the outcomes of the multiple linear regression. The R-squared ranges from 0.2 to 0.8, with an average value around 0.3. This suggests that the controls explain about 30% of the variance. The average error for the world between the data and the calculation of the heaviness is 0.11. When the heaviness of a single region is calculated, the absolute error between the data and the calculation of the heaviness reduces from 0.12 to 0.10 when using regional coefficients. This result leads to the conclusion that regional processes do play a role in the behavior of extreme precipitation. This makes it less appropriate to define a global set of most important controls. None of the three elimination methods is able to solve the problem of multicollinearity completely. On average, 35% of the controls have a opposite sign between the correlation and regression coefficient.

Delft Meet Regen

Onderzoek naar de dagelijkse neerslagspreiding in Delft op basis van de neerslagdata van Delft Meet Regen

Bachelor thesis (2021) - R.J.W. van Beek (author), J.A.E. ten Veldhuis (mentor), R. Uijlenhoet (graduation committee member), S. de Vries (coach)

In dit rapport zal er onderzocht worden wat de dagelijkse ruimtelijke spreiding van regen in Delft is op basis van de neerslagdata van het Delft Meet Regen project. In totaal hebben er 90 vrijwilligers meegedaan aan dit project en zijn er dus ook 90 meetpunten. De neerslagdata di ...

In dit rapport zal er onderzocht worden wat de dagelijkse ruimtelijke spreiding van regen in Delft is op basis van de neerslagdata van het Delft Meet Regen project. In totaal hebben er 90 vrijwilligers meegedaan aan dit project en zijn er dus ook 90 meetpunten. De neerslagdata die gebruikt is voor dit onderzoek is de neerslagdata in de periode van 1 augustus 2021 tot en met 17 september 2021. De neerslagdata is vervolgens vergeleken met de data van KNMI station 449, door de dagelijkse gemiddelden normaal en cumulatief met elkaar te vergelijken. De KNMI data heeft een goede overeenkomst met de neerslagdata van het Delft Meet Regen project.
Hierna is het onderzoeksgebied ingedeeld in de volgende vier gebieden: noordwest, noordoost, zuidwest en zuidoost. Van deze gebieden zijn de dagelijkse gemiddelden, aantal metingen, standaard afwijkingen en de dagelijkse gemiddelden cumulatief met elkaar vergeleken. Dit is gedaan doormiddel van grafieken, staafdiagrammen en ruimtelijke plots. Hieruit is geconcludeerd dat er sprake is van gemiddelde dagelijkse neerslagverschillen tussen de gebieden, maar dat er geen sprake is van een patroon. Het aantal metingen per gebied verschilt per dag en dit heeft invloed op de nauwkeurigheid van de resultaten. Hoe meer metingen er beschikbaar zijn, hoe nauwkeuriger de resultaten zullen zijn...

Delft Meet Regen: Vergelijking van de regenmeters van Delft Meet Regen met andere regenmeters

Bachelor thesis (2021) - K. Chen (author), J.A.E. ten Veldhuis (mentor), R. Uijlenhoet (graduation committee member)

In het project Delft Meet Regen zijn er ongeveer 90 inwoners in Delft die een eigen handmatige regenmeter hebben gekregen en elke ochtend het aantal millimeters regen meten dat gedurende de ongeveer 24 uur daaraan voorafgaand is gevallen. De data van deze regenmeters gedurende ee ...

In het project Delft Meet Regen zijn er ongeveer 90 inwoners in Delft die een eigen handmatige regenmeter hebben gekregen en elke ochtend het aantal millimeters regen meten dat gedurende de ongeveer 24 uur daaraan voorafgaand is gevallen. De data van deze regenmeters gedurende een periode van ongeveer 6 weken zijn vergeleken met die van het automatische weerstation van het KNMI bij Rotterdam Airport, de regenmeter van het vrijwilligersnetwerk van het KNMI bij de Botanische tuin in Delft, en de automatische weerstations die verbonden zijn met het WOW-NL netwerk. De data van het automatische weerstation van het KNMI bij Rotterdam Airport zijn vergeleken met de gemiddelde waarden van de data van het Delft Meet Regen project, waarbij de verschillen te inconsistent zijn om dit aan een systematische fout te wijten. De buien in Delft verschillen van de buien in Rotterdam. De neerslagdata van de regenmeter van het vrijwilligersnetwerk van het KNMI volgen bijna dezelfde patronen als de regenmeter van het Delft Meet Regen project, met een afwijking van enkele millimeters. Er zijn vijf meetpunten waar de handmatige regenmeters van het Delft Meet Regen project zijn vergeleken met de automatische weerstations die zijn verbonden met het WOW-NL netwerk die op dezelfde locatie staan. Op een na, volgden de data van de handmatige regenmeter bijna dezelfde patronen als het automatische weerstation. Hierbij was er in de meeste gevallen een afwijking van enkele millimeters, waarbij sommige regenmeters een grotere afwijking vertoonden dan andere.

Performance of nonlinear time series models to simulate synthetic groundwater table time series from an unsaturated zone model

Master thesis (2021) - M.A. Vonk (author), M. Bakker (mentor), Raoul A. Collenteur (graduation committee member), Frans Schaars (graduation committee member), R. Uijlenhoet (graduation committee member), E. Abraham (graduation committee member)

Transfer function noise (TFN) modelling is a form of time series analysis which regularly uses the recharge as a stress to explain the groundwater table fluctuations. Often the recharge flux is estimated as a linear combination of the precipitation and the (potential) evaporation ...

Transfer function noise (TFN) modelling is a form of time series analysis which regularly uses the recharge as a stress to explain the groundwater table fluctuations. Often the recharge flux is estimated as a linear combination of the precipitation and the (potential) evaporation. However, this is a simplification of the actual hydrological processes in the unsaturated zone. This is tried to be overcome by implementing a nonlinear recharge model in TFN time series models. Additionally, TFN models can use different impulse response functions, where some of them account for dispersion and retardation due to the unsaturated zone.

In this report the performance of a linear and nonlinear recharge model, inside the TFN model, are tested against synthetic time series of the groundwater table. These time series for the groundwater table are created with the unsaturated/saturated zone model HYDRUS-1D. With HYDRUS-1D, thirty-five synthetic time series are created for five different soil types and seven different unsaturated zone thicknesses (up to 5 m). The three most commonly used response functions, exponential, gamma and four-parameters are also tested for these thirty-five time series.

The results show that TFN models using the nonlinear recharge model are almost always better in estimating the groundwater table time series than the linear recharge model. This is confirmed in both the calibration and validation period. The common disadvantage of the linear recharge model, undershooting the groundwater table in (dry) summers, is not observed for the nonlinear recharge model. This can improve the forecasting abilities of TFN models during droughts.

Additionally, the nonlinear recharge model gives a more realistic representation of the fluxes in the root zone. This is confirmed goodness-of-fit parameters when comparing of the recharge flux and evaporation reduction calculated by HYDRUS-1D and the nonlinear recharge model. Especially when using the exponential response function, the recharge flux can be estimated quite well by the nonlinear recharge model. However, the nonlinear recharge model is currently not able to estimate groundwater uptake (upwards recharge) while it is observed in the HYDRUS-1D simulations.

The linear model does perform decently for shallow groundwater tables down to a depth of 150 cm since that is where large groundwater fluctuations and more days with groundwater uptake (upward recharge) are observed. The use of the gamma and four-parameter response functions significantly improves the performance of the linear recharge model. This can be explained by the compensation of these response functions for dispersion and retardation in the root zone. Nevertheless, when performing groundwater table time series analysis on synthetic time series created with HYDRUS-1D, the nonlinear recharge model is preferred to simulate the groundwater table.