In response to the growing risks of pluvial flooding due to climate change, this thesis presents a framework to assess the resilience of urban drainage systems and guide adaptation strategies using coupled 1D-2D modelling and economic flood risk assessments. The research begins by exploring methods in InfoWorks ICM to simulate interactions between surface and subsurface flows in urban environments, focusing on a simplified approach to model gully flow that reduces data requirements and computational load. Building on this, flood hazards from the simplified model are used to identify buildings at risk of internal flooding, estimate potential financial losses, and calculate expected annual damages under current and future climate conditions, accounting for climate change impacts. Subsequently, this research evaluates blue, green, and grey infrastructure measures, through cost-benefit analysis where benefits are quantified as reductions in expected damages.

A detailed case study from Spangen, a densely populated residential area in Rotterdam, applies the proposed framework, demonstrating that a simplified 1D-2D modelling approach without individual gully data can realistically estimate pluvial flood hazards and support economic flood risk assessments. The findings of the risk assessment suggest that existing infrastructure investments in the neighborhood have effectively reduced current pluvial flood risks. Looking ahead, for future climate conditions, a combination of green, blue, and grey infrastructure proves to be the most effective adaptation strategy as these measures synergistically enhance the resilience. Despite this, the cost-benefit analysis revealed a negative net present value when considering only flood damage reduction due to low flood risks under current climate conditions. Nonetheless, comprehensive decision-making should account for the additional benefits of green infrastructure, such as urban cooling and associated energy savings, improved air quality, and enhanced biodiversity.

Both globally and locally on the island of Curaçao, coral reef degradation is a pressing issue. These ecosystems are threatened by climate change and pollution due to human activities. The latter mostly occurs through pollution of groundwater, elevating the groundwater concentration of nutrients such as Nitrogen (N) and Phosphorus (P). A possible route of this polluted groundwater towards the coastal areas is through submarine groundwater discharge (SGD). One of the main groundwater polluting factors in Curaçao is the leakage of N and P from onsite sewage disposal systems (OSDS). Limited data is available on these leakage processes, and how the increased nutrient concentrations reach the sea through SGD. With the reef degradation furthering, it is of high importance to gain insight into this pollution process.

The goal of this thesis was to determine the behaviour of nutrient fluxes towards the sea and the bays through SGD on Curaçao. This was done by creating a numerical model in MODFLOW6, which first determined the groundwater head distribution and flow field on Curaçao based on a variable-density model. In this model, simplifications were done and fractured flow was ignored. A nutrient model was used to simulate the current state of the nutrient levels of N and P in the groundwater resulting from leakage from OSDS, and their progression towards the coastal area. The current state and three future scenarios were performed, consisting of a pollution increase due to population growth, a pollution stop and constant pollution similar to the current state.

The scenario simulations highlighted the immediate and delayed impacts of population growth and stopped pollution on nutrient fluxes. While N-fluxes responded quickly to changes in input, P, due to its sorptive behaviour, showed a delayed response. Although the SGD is equally distributed between the bays and the sea, the nutrient fluxes are relatively higher towards the bays for the current situation (83% for N and 61% for P). In both current and future states, N-concentrations were higher than P-concentrations, due to a higher N-input rate and the sorptive behaviour of P. If leakage from OSDS stops, N as decaying is almost completely flushed out within 25 years. For N with conservative behaviour, the N flux will be reduced by 75% in 2050. For P, it will take much longer to flush out, as after 30 years the outflow is still increasing. If current pollution increases due to population growth, the N-flux increase by 13% and 12% for respectively the conservative and decay simulations. In 2050, or quickly after, the flux will reach a new constant level. Contrarily, the P-flux will continue to increase for the foreseeable future, decreasing the N:P mass ratio.

The model results provided first insights into nutrient fluxes, current pollution, and future scenarios. However, the results are subject to uncertainties because fractured flow and dual-porosity were not included, requiring careful consideration of the results. In addition, future research should refine parameters and include an uncertainty analysis. Despite these limitations, the model offered valuable insights into nutrient behaviour and the model could be employed in more realistic simulations, allowing assessment of the future of groundwater pollution and its effect on Curaçao’s coral reefs.

Globally, there is an ongoing trend to improve the live-ability of cities. Furthermore, the importance of sufficient urban response systems for storm water is growing due to climate change and urbanization. Sustainable Urban Drainage Solutions (SUDSs) are seen as a key tool to tackle multiple urban challenges. This is as their design is multi-objective, focusing on water quantity, water quality, amenity, and biodiversity. However, currently knowledge is lacking amongst decision makers on how SUDS affect the urban environment. Therefore, this research aims to develop an assessment framework for SUDS-based storm water management in the urban landscape to help Dutch municipalities improve their decision making to improve the live-ability of the urban environment.

To evaluate the performance of SUDS, assessment frameworks include Key Performance Indicators (KPIs). KPIs are measurable indicators demonstrating how effective SUDS are in achieving their objectives. This research highlights that there is no universal or even country based standard assessment framework for SUDS. Furthermore, there are few examples of the translation of the scientific assessment methods of SUDS to engineering practice available. The assessment of the full effect of SUDS therefore remains unclear to practitioners.

This research proposes a new framework (”extended framework”) to assess the performance of SUDS, building on the existing framework (”conventional framework”) which assesses cost and water quantity currently used in engineering practice. The extended framework adds KPIs assessing the remaining three objectives of SUDS design. Firstly, water quality is assessed with the KPIs Site Pollution Index (SPI) and Pollutant Removal Capacity (PRC). Amenity with the KPIs Thermal Comfort Score (TCS) and impervious area. Thirdly, biodiversity is assessed with the KPI Biotope Area Factor (BAF). Furthermore, it improves the assessment of water quantity by replacing the currently used KPI with Expected Annual Damages (EAD). With the choice of KPIs in the extended framework, it is ensured that their assessment methodologies are suitable to engineering practice. Furthermore, by including KPIs that assess the multi-objectiveness of SUDS, the co-benefits are included in the extended framework.

With the application of both frameworks on the municipality of Alkmaar, this research substantiates the positive influence of SUDS on urban areas. The case study shows improving performance for water quantity, water quality, amenity and biodiversity if the number of SUDS increases.

To assess the effect of the extended framework on the decision making process, the MCDA type Compromise Programming (CP) is applied to the results of both frameworks. With the identification of the best choice of design based on the performance results of either the conventional or extended framework, the outcome of the CP method showed that using the extended framework as opposed to the conventional framework sometimes led to different design choices.

It is demonstrated that the extended framework indeed improves the decision making process to improve the live-ability of the urban environment. Even though the extended framework is more time consuming and may result in more costly designs, using this framework to base decision making on is likely to result in better quality of life for humans with a reduced negative impact on the associated natural environment. This framework better equips decision-makers to face
emerging urban challenges. However, both frameworks are of use in engineering practice. The ultimate choice of using either one of the frameworks is dependent on the goal of the project, the client, and the amount of time and money available.

In this study, the relationship between water quality and agriculture in the upstream region of the Brantas catchment has been investigated, with a focus on Electric Conductivity (EC), Dissolved Oxygen (DO), pH, nitrate, Biological Oxygen Demand (BOD), phosphate and ammonia concentrations. The EC concentrations ranged from 120 to 570 μS/cm, the DO concentrations from 3.15 to 8.57 mg/L, the nitrate concentrations from 0 to 20 ppm, the nitrite concentrations from 0 to 3 ppm, the BOD concentrations from 6.22 to 6.87 mg/L, the phosphate concentrations from 0.25 to 1 mg/L and the ammonia concentrations from 0 to 0.25 mg/L. Using detailed land use data, the correlation between land use classes and water quality parameters was analyzed. Nitrate concentrations of streams of which the catchment area consists of over 70% Ladang area ranged from 2.5 to 11 ppm, while catchment areas consisting of over 70% of Kebun area featured nitrate concentrations of up until 4 ppm. Regarding EC, this difference is 200 to 475 μS/cm versus 200 up until 375 μS/cm. Certain parameter concentrations, in particular BOD, raise potential concern. While this research provides some insights into water quality in the Brantas catchment, it also underlines the need for further investigations employing improved methodologies, increased sampling over a larger timescale and area, and comprehensive, multidisciplinary approaches. It is recommended that further studies in the area focus more on different parameters, in particular BOD.

Dunea’s drinking water treatment plants (DWTPs) want to reach the new arsenic (As) companytarget of < 1 µg/L, due to uncertainties on toxicity at the current WHO, European and Dutch guideline of 10 µg/L. The aim of this research was to lower the As concentration in Dunea’s effluent
to < 1 µg/L by improving our system understanding and exploring novel techniques for As(III) oxidation. Fieldwork was performed to assess whether each well section contributed to the elevated As concentrations. In order to enhance As(III) oxidation at Dunea’s DWTP, the use of electrochemical advanced oxidation processes (eAOPs) with a RuO2/IrO2-coated anode was examined during laboratory experiments. Fieldwork results showed that in each monitoring point the measured As concentration was > 1 µg/L, indicating that each well section contributed to the elevated As concentrations. The combination of strongly fluctuating groundwater tables, infiltration of oxygenated water, the observed pH decrease and synchronous mobilisation of several TEs, indicated that As was most probably mobilised by pyrite oxidation. It was observed that the As-bearing layer was present between -2.5 and -8.5 m NAP. With an average filter depth from -1.6 to -7.4 m, water was being extracted from the As-bearing layer. Laboratory results showed complete As(III) oxidation by eAOPs at a current density (i) of 7.5 A/m2, with a corresponding charge dosage (q) and hydraulic retention time (HRT) of 30 C/L and 1.4 min, respectively. At the aforementioned condition, the energy consumption of the eAOP cell was 0.066 kWh/m3 with operational costs of 0.04 e/m3. Free chlorine formation was minimized by reducing q, HRT and i. During the optimal anodic configuration of 7.5 A/m2, the estimated cathodic OH− production was sufficient to replace the dosed chemicals for pellet softening (PS). However, it was not sufficient to buffer for the anodic pH decrease. It was proposed to implement the eAOP cell at Dunea’s DWTP after PS and before aeration and rapid sand filtration.

The water quality of the Brantas river in Indonesia is of concern to several agencies on East Java. These agencies all measure its water quality in their own way in terms of locations, rhythms and parameters. The goal of this thesis is to find out if these agencies measure the same and if not, how these measurements differ. From these measurements, perspectives are constructed for each agency with the use of Principal Component Analysis. The agencies investigated are the Dinas Lingkungan Hidup Jawa Timur (DLH Jatim), Belai Besar Wilayah Sungai Brantas (BBWS) and Perum Jasa Tirta I (PJT). As an addition to the PCA, a neural network model is constructed and trained to recognize the measurement agency of a datapoint from the measurement values. It was found that the all three agencies recognized oxygen as a dominant driver in water quality processes. Secondary processes were mostly driven by rainfall, but the effect of this was seen differently by the agencies. DLH Jatim distinguishes surface waste runoff separately from rainfall, while Perum Jasa Tirta I will see them as inherently connected. BBWS will not recognize the surface waste runoff process as a significant factor in the water quality. These differences found in the representation of core processes in the Brantas outline how different agencies can have a different perspective on water quality. This was further underlined by the conclusions from the neural network analysis. Here it was found that the author could be recognized from the measurement values alone on 88% of agency data.

Saltwater intrusion in groundwater is a concern in many aquifers around the world. It results in deterioration of potable and irrigation water quality and degradation of ecosystems. The problem is exacerbated by fresh groundwater abstraction, drying climates and a rising seawater level.
Esperance is a small town situated on the south coast of Western Australia. The drinking water is supplied by a borefield located on the coastal plain in between the Southern Ocean and the saline lakes: Lake Warden and the terminal Pink Lake. Saltwater intrusion has been monitored for over two decades in this aquifer.
Managing Saltwater intrusion has been a priority for the local water company and the regulator for decades yet a numerical model of the aquifer capable of quantifying flows and salinity distributions does not exist.
In this study, a numerical flow model was developed as a first step towards a model that also includes saltwater movement, i.e. density-dependent flow. A site-specific literature review is documented in this report, as well as relevant saltwater intrusion studies.
A 3-dimensional hydrogeological model was created with a kriging geostatistical algorithm with data from Airborne Electromagnetic (AEM) surveys and borehole logs. A database including climatological fluxes, abstraction rates, groundwater heads, lake stages and lithographic data was created. The salinity distribution in the catchment was analysed using borehole observations and AEM data. Groundwater salinity is more prevalent in the east and northeast of the domain. Salts from inland sources are transported to the coastal lakes by a combination of groundwater and surface water.
The flow model was calibrated with PEST++ and a linear parameter error and sensitivity reduction was carried out with GENLINPRED from the PEST++ suite. The result of the study is a groundwater flow model that is able to quantify the approximate fluxes and heads within the catchment. However, it must be noted that the calibration can be improved. The relative error reduction for some parameters is large, for example groundwater recharge in areas with sparse and dense vegetation (0.91, 0.84 respectively), the runoff/quickflow factors towards the lakes (0.87, 0.95 and 0.88 for the Pink Lake, Lake Warden and Windabout/Woody lakes respectively) and reasonable for some of the hydraulic conductivities. The identifiability for other parameters (such as specific yields and vertical hydraulic conductivity) is low.
Zone budget calculations show that groundwater annual recharge and evaporation are the largest fluxes in the catchment and are equal in magnitude. The annual average evaporation rate over the entire catchment is 0.74 mm/d. The annual average groundwater abstraction is the same order of magnitude of the flow that enters the ocean, 5,656 m3/d vs. 8,169 m3/d respectively.
Modelling indicates that abstraction has a large effect on groundwater levels. The decline is the largest (> 1 m) a couple of kilometres west from the town area where abstraction decreases the water table. The effect is less south of the Pink Lake (~0.40 m).
(Hyper) salinity is the result of the net transport of saline groundwater entering into the lakes in combination with net evaporation. Water budget calculations show that the groundwater inflow in the hypersaline lakes exceeds groundwater outflow by a factor 8.1 for the Pink Lake and 1.7 for Lake Warden. Freshwater entering the lakes originates from direct precipitation and a calibrated runoff/quickflow component. This results in an effective lake area for precipitation of 1.6 times for the Pink Lake and 2 times for Lake Warden. In the lakes the evaporation exceeds the freshwater inflow by a factor of 1.5 and 1.1 for the terminal Pink Lake and Lake Warden respectively.
The low flow velocities towards the ocean in the eastern part of the catchment underline the risk of saltwater intrusion in this area. Flow field modelling suggests that groundwater abstracted in areas directly south of the Pink Lake is saline.
Finally, the current model is able to support recommendations for expansion of the borefield towards the area in the west of the catchment.

This study addresses the critical aspects of injection well clogging as part of an Aquifer Storage, Transfer and Recovery (ASTR) pilot infiltrating tile drainage water (TDW) from agricultural field into an anoxic brackish sandy aquifer for later re-use as irrigation water for flower bulbs. Two ASTR injection periods suffering from clogging were intensely monitored during several weeks in 2019 to 2020. The wells were rehabilitated by methods of backflushing and mechanical cleaning (high-pressure jetting) and sampled to obtain information on the kind of clogging material. The recharge water is nutrient rich (PO4: 2-18 mgL-1, NO3: 6-50 mgL-1, NH4: 0.1-0.6 mgL-1, DOC: 25-32 mgL-1) and attained significantly turbid conditions (usually between 5-20 NTU; up to 160 NTU) caused by the removal of resuspended biochemical material in the tile drainage network by extreme precipitation and extensive drain discharge events. Consequentially, the 40 µm spin Klin-disc filters as pre-treatment step experienced reduced functionality due to clogging when subjected to high turbid loads. Microbial processes within the ASTR piping system additionally caused fluctuations in turbidity by periodic on/off operation, indicating a high potential for (bio)physical and biological clogging in the injection wells. Microscopic and (hydro)geochemical analysis of injectant and backflushed suspended solids demonstrated a significant contribution of injected Fe-hydroxyapatite flocs and biochemical material incorporating siliceous clay and silt particles below 40 µm, while pyrite and possibly calcite precipitants were flushed from the aquifer matrix when removing suspended matter from the wells. The injection of suspended material caused clogging predominantly by physical mechanisms. During standstill, the hydrochemical environment in the well indicated substantial microbial activity by reduced redox conditions in the well and the mobilization of Fe(II), Mn(II), P, and Ca, indicating the vulnerability for biological clogging. Improving the feasibility of the ASTR system requires the high clogging potential of TDW to be reduced. It is recommended to adopt a settling tank, rapid sand filtration followed by slow sand filtration as pre-treatment steps to reduce the physical and biological clogging potential. Various other recommendations to reduce the clogging risks are discussed further. Regarding the well rehabilitation, methods of compressed-air ‘jutteren’ are recommended to recovery the well performance by effectively removing residual clogging material from the gravelpack and borehole wall.

Seawater intrusion modeling is challenging either because of a lack of many approaches' ability to cope with complex environments or significant computational expense. Seawater intrusion models also face issues with parameterization and validation due to problems with many parameters and also a lack of observational data. Bakker and Schaars (2013) proposed a method to solve for the steady-state interface using a single-density flow model (MODFLOW). In this thesis, this method was applied to 3 existing coastal flow models and shown to be able to compute the steady interface. The work also contains examples of applying critical pumping solutions to the models to demonstrate its applicability as a management tool. The research also contains an effort to solve for an interface when the saltwater is moving but was ineffective. Modifications may be made to resolve the issues with the latter approach that could lead to a advances in interface modeling methods.

Eternal aftercare for landfills is the standard in Dutch waste management policy after a law came into effect in 1996, meaning eternal waste management from potentially hazardous substances. A prescription of this policy is the application of watertight barriers on top of the wastebody. The policy also prescribes the renewal of the packing materials every 75 years. The wastebody is dried out, and the degradation has stopped so the wastebody does not change. The 'dry tomb' stays hazardous, thus eternal aftercare is implied.

The project 'introductie Duurzaam Stortbeheer (iDS) aims to create aftercare with an ending, or finite aftercare. It is looking for possibilities to stabilise the landfill mass, i.e. to eliminate the threat of pollutants by treating the wastebodies.

The goal of the CURE project is to develop fundamental insight into landfill processes in order to research the feasibility of wastebody stabilisation. To predict behaviour of landfills, and to monitor the processes, as much information as possible needs to be gathered through measurements. These consist of measurement of gas concentration and production rates together with the variation in leachate quality and volumes, as well as many more. This research, as part of the CURE project, presents the applicability of settlement as and addition to these measurements.

The main goal of waste body stabilisation is to actively reduce the amount of organic matter in a landfill. Uncontrolled landfills produce considerable methane emissions as well as high concentrations of nitrogen and heavy metals in the leachate, leading to groundwater hazards in the environment.

McDougall (2007) introduced the fundamental conceptual model upon which this research is based. This model is not publicly available, so one of the goals of this research is to provide a fundamental conceptual model. The relation between degradation and settlement has been studied and implemented in a 1D model which allows for hydrological systems, oxygen penetration, degradation and cell strain. The outcome is a relation between mechanics, biochemistry and hydrology. A few assumptions and simplifications were made to make the model versatile and adjustible, but also easy to read. For instance, the model uses oxygen as absolute limiting factor in degradation, neglecting all processes concerning anaerobic degradation. The model also assumes that at the beginning of the simulation, each cell has the same composition, because there is no conclusive data about the distribution of waste types. The model has been created in one dimension, thereby neglecting all multi-dimensional processes and limitations.

In the final scenario, the main limitation to degradation is the availability of dissolved oxygen. As irrigation provides infiltration of 5 mm water per day with 10 mg dissolved oxygen per liter, the daily reduction of oxygen demand is 50 mg. The total modelled oxygen demand of the landfill is over 9600 kg, which concludes that a different tactic needs to happen in order to stabilise the wastebody. To increase the degradation rate, more oxygen needs to be applied. An approximation of the effect of applying a partial vacuum above the water table in the landfill to attract air from the environment is modelled, giving the oxygen more transfer area into unsaturated water. An increase by a factor 10^{4} is applied to the effect of oxygen on organic matter to model this enhanced irrigation system. The results are modeled over 100 years, after which approximately 26.17% of the degradation has happened. This shows that aerobic degradation over a wastebody takes too long with conventional degradation, and the unsaturated voids might help the process.

The model shows credible results for an unspecified landfill with deterministic parameters. Settlement has been brought in relation to a simplified form of biodegradation. The need for further research, with a spatial fluctuation of these parameters and detailed multidimensional water flow is needed to predict landfill behaviour in more detail. \pagebreak

Due to the predicted impacts of climate change on the frequency of storm events, water managers are challenged to improve and adapt the current urban infrastructure. Cities need to be able to deal with the adverse effects due to more frequent and heavier rainfall. This implies the need for sustainable urban drainage systems (SUDS) that can deal with these challenges. SUDS can be seen as designs that can improve both, the quantitative as well as qualitative characteristics of stormwater. The study area in the south of Amsterdam will be equipped with a SUDS, namely a SediSubstrator L by Fränkische Rohrwerke. The objective is to remove particles from stormwater discharge to prevent clogging of the infiltration facility (AquaBASE) installed in sequence. Additionally, it can remove harmful pollutants which are adsorbed to the fine particles.
This research aims to investigate the characteristics of the sediments in stormwater in theory and develop an appropriate sampling strategy to monitor the relevant parameters in the field. The long-term objective hereby is to determine the removal efficiency of the SediSubstrator L using a finite amount of parameters. To do so, a threefold approach composed by a detailed literature review, stormwater sediment sampling as well as a model simulation was used.
Based on the identified parameters to be assessed, a specific monitoring and sampling setup is proposed to determine the removal efficiency of stormwater sediments in the study area. Along with the efficiency, the volume of sediments that are caught by the facility can be approximated. The latter needs to be removed once the entire storage volume of the sedimentation facility is filled. It is recommended that Waternet uses measured stormwater data to improve the model, while monitoring the efficiency under field conditions. Once the results of the model and the actual field measurements match, the model can be used to simulate the sediment removal for long time series. In this way the cleaning intervals can be predicted, while avoiding expensive long-term measurements to do so.

The Climate Risk Informed Decision Analysis (CRIDA) framework incorporates the uncertainties of climate change that impact project planning, socioeconomic justification, and engineering design into a step-wise and collaborative planning process to guide a technical analyst to low-regret risk- and cost-effective solutions; Research has been carried out to demonstrate and improve, through additional guidelines, the usability of CRIDA, in a pilot for the Limari basin in Chile. The added guidelines (1) offer the analyst numerically based justifications for analytical decisions to ensure a more structured application of CRIDA and (2) improves on co-design aspects by incorporating stakeholder risk perceptions and opinions explicitly in the process. The Limari Basin has experienced an increase in drought frequency and severity over the last decades. A strategic approach for adaptation is recommended through CRIDA based on an evaluation of the future risk to climate change and the confidence in this analysis and a subsequent systematic assessments of adaptation options. The resulting strategy requires the increase of water supply robustness by adding new water sources that can be implemented in combination with flexible measures for managing demand (i.e. implementing agricultural meshes and improving irrigation efficiency) in parallel or in series to create adaptation pathways. The study demonstrated the functionality of CRIDA. While the added guidelines required more processing time, subjectivity in the method is reduced thus also reducing possible bias introduced by the analyst. In addition, overall acceptability of the proposed strategies is improved by incorporating stakeholder risk perceptions and opinions explicitly in the process.

The Miombo woodlands are characterized by a transition period which is defined as the dry period in which grasses wither, trees shed and flush their leaves a few weeks before the rainy season. It is difficult to measure evaporation, due to the influence of the plant water storage on the water availability during the dry season. The seasonal variation in the plant water storage makes it even harder, as the time lag between the plant water storage and the terrestrial groundwater storage varies between the 0 to 90 days depending on the vegetation density. (Tian et al., 2018). It is unclear why the trees prefer this early flushing strategy and what is triggering the shedding of old leaves and flushing of new leaves. It is difficult to remotely sense the variation during this period. In this report, the outputs of several evaporation products and the vegetation indices are studied and compared to see how models follow the transition period. Three models, that are chosen for the comparison use different methods to indirectly calculate the evaporation flux. The first model is the Surface Energy Balance System (SEBS), which is based on the Surface Energy Balance as the name suggests and calculates the evaporation through land-atmosphere relationships. The second model is the Global Land Evaporation Amsterdam Model (GLEAM); this model uses the water balance model to calculate the water stress factor and in return the actual evaporation. And lastly, the MODIS Terrestrial Evapotranspiration (MOD16A2) which uses the Penman-Monteith equation as a basis to separately calculate the evaporative fluxes such as transpiration, soil evaporation, and interception. The outputs of the evaporation models differ quite a lot, especially during the transition period. This is among other things due to the input variable such as vegetation indices. There are several vegetation indices such as the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Infrared Index (NDII) and the Leaf Area Index (LAI). The difference in the indexes is minimal and only small timing differences can be found. This means that the output differences are not influenced by the vegetation indices. MODIS follows the trends found by the vegetation indices best as it does not have the shortcomings that GLEAM and SEBS display. GLEAM overestimates the water stress because the model doesn’t account for plant water storage. While SEBS responds well until the start of July in which the model starts to oscillate. The oscillations could be due to the slash and burn culture which happens around this time which could impact SEBS substantially due to its dependency on temperature and radiation. Even if the MODIS output is the most similar to the vegetation output, it is limited by the fact that it is average values and daily variations might be lost. As this research is based on mostly satellite images supplemented by field observations, no statements can be made about it how accurate the models are. But based on this research, the MODIS model seems to be the preferred evaporation output.

Urban sanitation in developing countries requires systems thinking as there is a plethora different variables which can impact the delivery of adequate sanitation for the people. In the traditional sense, sanitation planning in urban cities focuses on keeping people away from human-waste related pathogens. As cities in India and several developing countries are growing at exponential rates, government agencies are struggling to provide adequate safe sanitation in their cities. In recent years, due to a range of factors such as increasing water stress, recreational needs and biodiversity protection in an urban fabric, urban waterbodies are deemed worthy of conservation. The objective of this research was to systematically understand urban sanitation and how it relates to urban waterbody health. Having understood the system adequately, the aim of the thesis was to answer the research question, can “Citywide Inclusive Sanitation as a planning approach aid in the betterment of urban waterbodies?”. The study adopted a mixed method which comprises of quantitative water quality testing in Kommaghatta lake in Bengaluru city, India and a qualitative analysis at the Bengaluru city level. It included elements of qualitative social research methods such as field observations, informal conversations and semi-structured interviews to answer the research questions. Water quality results and qualitative analysis suggests that there are three significant pollution pathways into Bengaluru lakes, each carrying different wastewater characteristics and pollution load. The predominant pathway for the pollution of waterbodies in the city is through the stormwater drainage. Additionally, sewer pipes and desludging trucks which dispose faecal waste from on-site sanitation systems also contribute to pollutant load entering into the lakes in the city. From the semi-structured interviews, a conceptual model of urban sanitation in Bengaluru city and how it relates to waterbodies was developed. From conducting a qualitative analysis, six major system levers were identified. They levers influence the dynamics of urban sanitation in Bengaluru and forms the basis for the pollution pathways that enter into the lake. They six major system levers for Bengaluru urban sanitation are:
1.Rapid urbanization
2.Fragmentation of government entities
3.Sewer infrastructure
4.Feacal sludge management
5.Treated water reuse
6.Citizen group involvement The study shows that CWIS principles have a significant relevance for solving urban sanitation issues which were identified through the system levers. In addition to solving urban sanitation issues which centres on public health matters, the study also shows that there is also an environmental case for CWIS by arresting waterbody pollution through the identified pollution pathways. Findings from this research can help to improve decision making in terms of urban sanitation by paying close attention to the cause-effect relationships between variables in the urban sanitation sphere and improve waterbody health in their cities.

Resource recovery from waste streams is indispensable to shifting from a linear economy to a circular economy. Industrial concentrate is a waste stream that is actively researched to explore and expand the prospects of resource recovery. Strontium (Sr), an alkaline earth metal, while found regularly in concentrate streams has not been a focus for recovery. Through this study, the recovery of Sr as strontium carbonate (SrCO₃) via precipitation from concentrate streams has been investigated. The objective of this study is to characterize SrCO₃ precipitation in terms of factors that influence it. Specifically, the effect of multiple factors has been investigated on the amount of Sr precipitated (as % relative to the initial amount of Sr) as well as the purity of the corresponding SrCO₃ precipitate (%). Factors that could affect either the amount of Sr precipitated or the purity of the precipitated SrCO₃ were identified based on theoretical knowledge. Equilibrium-based simulations were performed using OLI studio to confirm their impact. The conditions associated with the identified influencing factors were investigated in concentrate from a reverse osmosis unit during drinking water production. A Box-Behnken Design was implemented to quantify the relationship between the identified factors and two responses (i) Amount of Sr precipitated and, (ii) Purity of SrCO₃ precipitated. The range of the factors in the design was established based on their ranges as observed in the concentrate. The value of pH and concentrations of strontium, inorganic carbon (C), calcium (Ca), barium (Ba) and inorganic sulfur (S) were hypothesized to have quantitative and qualitative effects on the SrCO₃ precipitated. Magnesium (Mg) was hypothesized to have a qualitative effect on the SrCO₃ precipitated. Direct SrCO₃ precipitation from concentrate was not practical due to considerably higher concentration of other ions. To facilitate SrCO₃ precipitation from concentrate, the concentration of the other ions was reduced by recovering them as precipitates. The recovery of these precipitates was investigated through variation of process conditions via OLI simulations. Theoretically, it is possible to recover 0.0014g of SrCO₃ (100% purity) per liter of concentrate along with 0.684g CaCO₃ (99.95% purity), 0.161g Mg(OH)₂ (96% purity), 0.0083g Ca(OH)₂ (99.99% purity) and  NaCl solution (4.65 M). Using Box-Behnken Design, the mathematical relationship between the amount of Sr precipitated (% relative to initial concentration) and purity of SrCO₃ precipitated (%) subject to the identified factors was established. The equations had a R² of 98.75% and 97.38% respectively. S was found to not have any significant impact on SrCO₃ precipitation while a positive interaction effect between Sr and Ca was also identified. %Sr precipitated=0.82098+0.01319(pH)-0.04004(Sr)+0.11581(C)-0.07343(Ca)-0.01314(pH*pH)-0.04299(Sr*Sr)-0.04073(C*C)-0.02041(Mg*Mg)+0.01818(pH*Ca)+0.05369(Sr*C)+0.07436(Sr*Ca)-0.05763(C*Ca)  SrCO₃ purity(%)=0.5155-0.20923(pH)+0.12593(Sr)-0.03178(C)-0.06115(Ca)-0.07187(Mg)+0.0617(pH*pH)-0.0388(Sr*Sr)-0.0295(C*C)+0.0456(Mg*Mg)-0.0485(pH*Sr)+0.0595(pH*C)+0.0405(pH*Ca)-0.0903(pH*Mg)+0.0481(Sr*C)+0.0614(Sr*Ca)-0.0453(C*Ca) The predictive R² of these equations are 93.45% and 86.32% respectively. This is representative of their prediction accuracy and hence their applicability to replace experiments and simulations. These equations, however, are built on outputs from OLI simulations. Therefore, their accuracy is subject to the predictive capability of OLI software. Experimental results based on the chosen Box-Behnken Design are needed to either replace the OLI simulations results entirely or account for the inaccuracy of OLI simulations.

According to the United Nations, eutrophication is the most prevalent water quality problem. Developing countries especially are struggling to manage the increasing volume of untreated wastewater. A preliminary study of a Dutch-Indian partnership, developing universal watermanagement (LOTUSHR), has shown some indication of ortho-phosphate removal by mineral wool. The objective of this research is to understand the ortho-phosphate removal mechanism of mineral wool used for wastewater treatment. It was hypothesized that mineral wool dissociates ions due to biologically mediated pH changes, which subsequently interact with ortho-phosphate, forming minerals and removing ortho-phosphate from wastewater. First of all, the chemical composition of mineral wool was determined. Secondly, the dissolution of mineral wool was quantified by batch experiments at different pH and phosphate concentrations. Furthermore, geochemical modeling with PHREEQC was used to analyze the thermodynamic potential of wastewaters to precipitation, not containing mineral wool. Additionally, the phosphate removal rates of a flow-through experiment, using mimicked Indian Drain Water and mineral wool, was compared with PHREEQC simulations. Results showed that based on chemical analysis mineral wool contains: 188.0 g/kg silicon, 187.6 g/kg calcium, 79.3 g/kg aluminum, 43.1 g/kg iron, among other elements. The mineral wool showed no significant dissolution of ions under different pH and phosphate concentrations. Therefore, the hypothesis was rejected, as the mineral wool did not release ions when stressed with different pH. Consequently, biological conversion will not facilitate ion release from the mineral wool either. The mineral wool did show a self-buffering effect, due to its alkaline properties. Furthermore, with use of PHREEQC, amorphous tricalcium phosphate was characterized as the major mineral phase. In conclusion, the hypothesis formulated was rejected. This research performed did not lead to the identification of the removal mechanism responsible for the ortho-phosphate removal from wastewater by mineral wool filters.

The temperature of drinking water is an important parameter, affecting physical, chemical, biological and aesthetic properties of the water. Currently, measurements exceeding the legal limit of 25ᵒC at the tap are exceptional. However, there are reasons to believe that the number of exceedances will increase due to climate change and urbanization. So far the effects of sunlight hours and soil coverage on drinking water temperature have already been quantified quite well. Still lacking is the exact effect of anthropogenic heat sources on these temperatures. In this study more insight is given in the extent of this effect for Rotterdam, and measures are discussed to mitigate or to prevent drinking water warming. First, potential anthropogenic heat sources are identified. By analyzing data on tap temperatures and old soil temperature measurements, several anthropogenic heat sources emerged. A map of the statistically warm drinking water temperatures in Rotterdam, appears to have a lot of resemblance to the city heating system whereabouts. Furthermore, smaller indications point at high voltage power cables and metro lines to be important anthropogenic heat sources. Soil temperature measurements around these potential heat sources confirm some of the expectations. Around high voltage power cables, a limited elevated temperature of 0.6ᵒC is found. Much more alarming results were encountered around the city heating mains. In autumn, primary heating mains warm-up the soil by 4.9 – 5.3ᵒC and secondary heating mains do so by 2.9ᵒC. A temperature elevation of 1ᵒC is measured to a distance of 3.8 - 5.25m and 2.3m, respectively. However, these results are highly dependent of several parameters, like the temperature differences between the air and soil, the thermal properties of the soil, and the depth and state of the anthropogenic heat sources themselves. Several strategies to mitigate the warming of drinking water in the distribution system are applicable. In a general sense, it is most sensible to create a distance between any heat source and the distribution system. By placing drinking water mains in the shade, below grass and away from anthropogenic heat sources, warming of the drinking water can be prevented in a relatively inexpensive manner. Measures targeted at temporary local hotspots can be focused on restraining the heat flux from the heat source to the soil, the heat flux through the soil, and the heat flux from the soil to the drinking water.

This study investigated the three possible main causes of injectivity reduction in geothermal wells (suspended solids, scaling, biological activity). That has been done by obtaining water samples at three operating geothermal doublet locations in the Netherlands. This paper contains new geothermal data and the interpretation of them. At the moment, injectivity reduction is the biggest and least understood issue in geothermal projects in the Netherlands. Investigating this problem is valuable for current and future geothermal injectors and essential for the upscaling of geothermal energy in the Netherlands.The three locations differ from each other in several aspects (reservoir, surface facilities, chemicals in use, injectivity reduction), which yields a good comparison. Water samples were taken at different moments in time, on different points in the geothermal systems and for different purposes: TSS, chemical composition and ATP concentrations. The data is obtained in the laboratory and used for scale analysis (using the Stream Analyzer software from OLI Studio®) and microbial kill tests to determine the influences on growth. Scientific quality and data reliability are guaranteed by multiple pre-experiments (e.g. to verify sterility of sample bottles) and extra measurements (e.g. duplo samples, oxygen concentrations). It has been found that TSS is reduced through the systems by filters (from 35-55 mg/L in production water to <8-16 mg/L in injection water). Also, scales can potentially form (calcite before- and barite after the heat exchanger). Furthermore, biological activity in the water is initially low, but can grow over time to high levels (>500.000 microbial equivalents). Microbial growth is site-specific and correlatable to injectivity reduction. When there is microbial growth, corrosion inhibitor (CI) enhances this growth. Scale formation is possible, but has a limited likelyhood to cause significant injectivity problems. Furthermore, there is no reason for TSS to be problematic, but it can also not be excluded as possible source for injectivity reduction. Mitigation of these issues can be done by using more injection filters in a geothermal system (for further TSS reduction). Scaling inhibitor can be used preventive and a CI without nutrients (in the solvent) should be used, or a biocide should be injected simultaneously with the CI. This report is interesting for geothermal operators, researchers and anybody else interested in geothermal operations in general or more specifically in injectivity reduction.

Additional master thesis

Freshwater biodiversity is in a state of crisis with an annual decline rate of 3.9% compared to 1.1% decline in terrestrial biodiversity (Living Planet Index). The actual decline rate may be higher than estimated as many of the species are data deficient or not yet assessed or became extinct before assessment. We have far surpassed the sustainable or natural limit of reductions in populations of freshwater species. With an unprecedented increase in global energy and water demand, planetaries boundaries for sustainable use of freshwater may be overstepped in the near future, as presently visible at a local scale. A staggering decline in freshwater biodiversity is a first warning signal of a looming global water crisis. With continued pressures like river fragmentation, flow regulation, overextraction of surface or groundwater, pollution, invasive species and climate change, on freshwater habitats, this crisis may shift one level higher and impact human species severely.

Environmental flows forms the link between ecological health of a river and the ecosystem services we derive from it. It can be a great tool to achieve twin objective of maintaining the ecosystem integrity of freshwater habitats and deciding trade-offs for ensuring sustainable water management in a river basin. This study focuses on developing a holistic methodology for preliminary assessment of ecosystem integrity or ecological health of a river basin, which can be easily adapted to other river basins using open source global datasets. The proposed methodology was applied to Kaveri basin to test its applicability and identify the limitations of available global datasets. A widely accepted regional environmental flow assessment framework, ELOHA (Ecological Limits of Hydrological Alteration) was adapted by using global datasets. A global river classification dataset was used to identify the river classes in Kaveri basin. Monthly hydrological alteration in magnitude at the location of gauge stations was calculated, using PCR-GLOBWB data as reference for natural flow conditions, in absence of records for natural flow in a highly modified Kaveri basin. An ecosystem integrity indicator framework was developed to assess the hydrologic, geomorphic and ecological modifications in the river basin. Indicators grouped under four main categories - Connectivity status, Land Use, Biodiversity, Water Quality were adopted using exiting global datasets and values for all the sub-basins of Kaveri basin were estimated.

Finally an attempt to derive flow alteration-ecological response was made. Threatened fish species percentage, quantified using IUCN spatial dataset, showed an increase in value with increase in alteration in flow magnitude. No clear relationship was observed when data for other taxonomic groups like plants, molluscs, odonata, shrimps and crabs were used. Hence, species of concern (IUCN red list category - CR, EN,VU) data can be useful in deriving preliminary flow alteration-ecological response relationship. An attempt to find linkage between flow alteration and floodplain gross primary productivity was also made. In dry season an inverse relationship was observed at few gauge stations but in general other climatic factors like rainfall and evapotranspiration had greater influence on gross primary productivity. Impact on gross primary productivity due to flow alteration could not be isolated using existing datasets because of coarse resolution.