Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Supporting data for 'Hydrological drought forecasts outperform meteorological drought forecasts'
    Sutanto, Samuel - \ 2020
    Wageningen University & Research
    drought - forecasts - hydrology - meteorology
    This dataset was used in our paper with the title: Hydrological drought forecasts outperform meteorological drought forecasts. It contains drought indices analysis using proxy observed, re-forecasts, and ESP data.
    Rapid Assessment of Floating Macroplastic Transport in the Rhine
    Vriend, Paul ; Calcar, Caroline van; Kooi, Merel ; Landman, Harm ; Pikaar, Remco ; Emmerik, Tim van - \ 2020
    Frontiers in Marine Science 7 (2020). - ISSN 2296-7745
    flux measurements - hydrology - macroplastic - marine litter - passive sampling - riverine plastic - visual sampling

    Most marine litter pollution is assumed to originate from land-based sources, entering the marine environment through rivers. To better understand and quantify the risk that plastic pollution poses on aquatic ecosystems, and to develop effective prevention and mitigation methods, a better understanding of riverine plastic transport is needed. To achieve this, quantification of riverine plastic transport is crucial. Here, we demonstrate how established methods can be combined to provide a rapid and cost-effective characterization and quantification of floating macroplastic transport in the River Rhine. We combine visual observations with passive sampling to arrive at a first-order estimate of macroplastic transport, both in number (10–75 items per hour) and mass per unit of time (1.3–9.7 kg per day). Additionally, our assessment gives insight in the most abundant macroplastic polymer types the downstream reach of the River Rhine. Furthermore, we explore the spatial and temporal variation of plastic transport within the river, and discuss the benefits and drawbacks of current sampling methods. Finally, we present an outlook for future monitoring of major rivers, including several suggestions on how to expand the rapid assessment presented in this paper.

    Seine Plastic Debris Transport Tenfolded During Increased River Discharge
    Emmerik, Tim van; Tramoy, Romain ; Calcar, Caroline van; Alligant, Soline ; Treilles, Robin ; Tassin, Bruno ; Gasperi, Johnny - \ 2019
    Frontiers in Marine Science 6 (2019). - ISSN 2296-7745
    France - hydrology - marine plastic debris - plastic pollution - plastic pollution monitoring - river plastic - Seine

    Rivers transport land-based plastic waste into the ocean. Current efforts to quantify riverine plastic emission come with uncertainty as field observations are scarce. One of the challenging aspects is the lack of consistent measurement methods that allow for comparing rivers over space and time. Recent studies have shown that simple visual observations provide a robust first-order characterization of floating and superficially suspended plastic transport, both in quantity, spatiotemporal distribution and composition. For this study, we applied this method to the river Seine, France, to provide new insights in the spatiotemporal variation in riverine plastic transport. First, we studied the response of plastic flow to increased river discharge by comparing measurements taken during low flow and high flow periods. Second, we investigated the variation of riverine plastic transport over the river length to improve our understanding of the origin and fate of riverine plastics. We demonstrate that during a period with higher river discharge, plastic transport increased up to a factor ten at the observation point closest to the river mouth. This suggests that the plastic emission into the ocean from the Seine may also be considerably higher during increased discharge. Upstream of Paris plastic transport increased only with a factor 1.5, suggesting that most plastics originate from Paris or areas further downstream. With this paper we aim to shed additional light on the seasonal variation in riverine plastic transport and its distribution along the river length, which may benefit future long-term monitoring efforts and plastic pollution mitigation strategies.

    Riverine plastic emission from Jakarta into the ocean
    Emmerik, Tim Van; Loozen, Michelle ; Oeveren, Kees Van; Buschman, Frans ; Prinsen, Geert - \ 2019
    Environmental Research Letters 14 (2019)8. - ISSN 1748-9318
    anthropocene - hydrology - macroplastic - marine litter - urban river

    Plastic pollution in aquatic environments is an increasing global risk. In recent years, marine plastic pollution has been studied to a great extent, and it has been hypothesized that land-based plastics are its main source. Global modeling efforts have suggested that rivers in South East Asia are in fact the main contributors to plastic transport from land to the oceans. However, due to a lack of plastic transport observations, the origin and fate of riverine plastic waste is yet unclear. Here, we present results from a first assessment of riverine macroplastic emission from rivers and canals that run through a densely populated coastal urban city. Using a combination of field measurements, empirical relations and hydraulic modeling, we provide an estimate of total riverine plastic export originating from Jakarta, Indonesia, into the ocean. Furthermore, we provide insights in its composition, and variation in time and space. We found that most macroplastics in Jakarta consists of films and foils. We estimate that 2.1 103 tonnes of plastic waste, is transported from land to sea annually, equaling 3% of the total annual unsoundly disposed plastic waste in the Jakarta area.

    Twenty-three unsolved problems in hydrology (UPH)–a community perspective
    Blöschl, Günter ; Bierkens, Marc F.P. ; Chambel, Antonio ; Cudennec, Christophe ; Destouni, Georgia ; Fiori, Aldo ; Kirchner, James W. ; McDonnell, Jeffrey J. ; Savenije, Hubert H.G. ; Sivapalan, Murugesu ; Stumpp, Christine ; Toth, Elena ; Volpi, Elena ; Carr, Gemma ; Lupton, Claire ; Salinas, Josè ; Széles, Borbála ; Viglione, Alberto ; Aksoy, Hafzullah ; Allen, Scott T. ; Amin, Anam ; Andréassian, Vazken ; Arheimer, Berit ; Aryal, Santosh K. ; Baker, Victor ; Bardsley, Earl ; Barendrecht, Marlies H. ; Bartosova, Alena ; Batelaan, Okke ; Berghuijs, Wouter R. ; Beven, Keith ; Blume, Theresa ; Bogaard, Thom ; Borges de Amorim, Pablo ; Böttcher, Michael E. ; Boulet, Gilles ; Breinl, Korbinian ; Brilly, Mitja ; Brocca, Luca ; Buytaert, Wouter ; Castellarin, Attilio ; Castelletti, Andrea ; Chen, Xiaohong ; Chen, Yangbo ; Chen, Yuanfang ; Chifflard, Peter ; Claps, Pierluigi ; Clark, Martyn P. ; Collins, Adrian L. ; Croke, Barry ; Dathe, Annette ; David, Paula C. ; Barros, Felipe P.J. de; Rooij, Gerrit de; Baldassarre, Giuliano Di; Driscoll, Jessica M. ; Duethmann, Doris ; Dwivedi, Ravindra ; Eris, Ebru ; Farmer, William H. ; Feiccabrino, James ; Ferguson, Grant ; Ferrari, Ennio ; Ferraris, Stefano ; Fersch, Benjamin ; Finger, David ; Foglia, Laura ; Fowler, Keirnan ; Gartsman, Boris ; Gascoin, Simon ; Gaume, Eric ; Gelfan, Alexander ; Geris, Josie ; Gharari, Shervan ; Gleeson, Tom ; Glendell, Miriam ; Gonzalez Bevacqua, Alena ; González-Dugo, María P. ; Grimaldi, Salvatore ; Gupta, A.B. ; Guse, Björn ; Han, Dawei ; Hannah, David ; Harpold, Adrian ; Haun, Stefan ; Heal, Kate ; Helfricht, Kay ; Herrnegger, Mathew ; Hipsey, Matthew ; Hlaváčiková, Hana ; Hohmann, Clara ; Holko, Ladislav ; Hopkinson, Christopher ; Hrachowitz, Markus ; Illangasekare, Tissa H. ; Inam, Azhar ; Innocente, Camyla ; Istanbulluoglu, Erkan ; Jarihani, Ben ; Kalantari, Zahra ; Kalvans, Andis ; Khanal, Sonu ; Khatami, Sina ; Kiesel, Jens ; Kirkby, Mike ; Knoben, Wouter ; Kochanek, Krzysztof ; Kohnová, Silvia ; Kolechkina, Alla ; Krause, Stefan ; Kreamer, David ; Kreibich, Heidi ; Kunstmann, Harald ; Lange, Holger ; Liberato, Margarida L.R. ; Lindquist, Eric ; Link, Timothy ; Liu, Junguo ; Loucks, Daniel Peter ; Luce, Charles ; Mahé, Gil ; Makarieva, Olga ; Malard, Julien ; Mashtayeva, Shamshagul ; Maskey, Shreedhar ; Mas-Pla, Josep ; Mavrova-Guirguinova, Maria ; Mazzoleni, Maurizio ; Mernild, Sebastian ; Misstear, Bruce Dudley ; Montanari, Alberto ; Müller-Thomy, Hannes ; Nabizadeh, Alireza ; Nardi, Fernando ; Neale, Christopher ; Nesterova, Nataliia ; Nurtaev, Bakhram ; Odongo, Vincent O. ; Panda, Subhabrata ; Pande, Saket ; Pang, Zhonghe ; Papacharalampous, Georgia ; Perrin, Charles ; Pfister, Laurent ; Pimentel, Rafael ; Polo, María J. ; Post, David ; Prieto Sierra, Cristina ; Ramos, Maria Helena ; Renner, Maik ; Reynolds, José Eduardo ; Ridolfi, Elena ; Rigon, Riccardo ; Riva, Monica ; Robertson, David E. ; Rosso, Renzo ; Roy, Tirthankar ; Sá, João H.M. ; Salvadori, Gianfausto ; Sandells, Mel ; Schaefli, Bettina ; Schumann, Andreas ; Scolobig, Anna ; Seibert, Jan ; Servat, Eric ; Shafiei, Mojtaba ; Sharma, Ashish ; Sidibe, Moussa ; Sidle, Roy C. ; Skaugen, Thomas ; Smith, Hugh ; Spiessl, Sabine M. ; Stein, Lina ; Steinsland, Ingelin ; Strasser, Ulrich ; Su, Bob ; Szolgay, Jan ; Tarboton, David ; Tauro, Flavia ; Thirel, Guillaume ; Tian, Fuqiang ; Tong, Rui ; Tussupova, Kamshat ; Tyralis, Hristos ; Uijlenhoet, Remko ; Beek, Rens van; Ent, Ruud J. van der; Ploeg, Martine van der; Loon, Anne F. Van; Meerveld, Ilja van; Nooijen, Ronald van; Oel, Pieter R. van; Vidal, Jean Philippe ; Freyberg, Jana von; Vorogushyn, Sergiy ; Wachniew, Przemyslaw ; Wade, Andrew J. ; Ward, Philip ; Westerberg, Ida K. ; White, Christopher ; Wood, Eric F. ; Woods, Ross ; Xu, Zongxue ; Yilmaz, Koray K. ; Zhang, Yongqiang - \ 2019
    Hydrological Sciences Journal 64 (2019)10. - ISSN 0262-6667 - p. 1141 - 1158.
    hydrology - interdisciplinary - knowledge gaps - research agenda - science questions

    This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.

    Soil frost effects on streamflow recessions in a subarctic catchment
    Ploum, Stefan W. ; Lyon, Steve W. ; Teuling, Adriaan J. ; Laudon, Hjalmar ; Velde, Ype van der - \ 2019
    Hydrological Processes 33 (2019)9. - ISSN 0885-6087 - p. 1304 - 1316.
    Arctic - hydrology - permafrost - recession analysis - snowmelt - soil frost - thawing - warming
    The Arctic is warming rapidly. Changing seasonal freezing and thawing cycles of the soil are expected to affect river run-off substantially, but how soil frost influences river run-off at catchment scales is still largely unknown. We hypothesize that soil frost alters flow paths and therefore affects storage–discharge relations in subarctic catchments. To test this hypothesis, we used an approach that combines meteorological records and recession analysis. We studied streamflow data (1986–2015) of Abiskojokka, a river that drains a mountainous catchment (560 km2) in the north of Sweden (68° latitude). Recessions were separated into frost periods (spring) and no-frost periods (summer) and then compared. We observed a significant difference between recessions of the two periods: During spring, discharge was linearly related to storage, whereas storage–discharge relationships in summer were less linear. An analysis of explanatory factors showed that after winters with cold soil temperatures and low snowpack, storage–discharge relations approached linearity. On the other hand, relatively warm winter soil conditions resulted in storage–discharge relationships that were less linear. Even in summer, relatively cold antecedent winter soils and low snowpack levels had a propagating effect on streamflow. This could be an indication that soil frost controls recharge of deep groundwater flow paths, which affects storage–discharge relationships in summer. We interpret these findings as evidence for soil frost to have an important control over river run-off dynamics. To our knowledge, this is the first study showing significant catchment-integrated effects of soil frost on this spatiotemporal scale.
    Regional soil moisture monitoring network in the Raam catchment in the Netherlands - 2016-04 / 2017-04 (corrected)
    Benninga, H.F. ; Carranza, C.D. ; Pezij, M. ; Ploeg, M.J. van der; Augustijn, D.C.M. ; Velde, R. van der - \ 2018
    University of Twente
    agriculture - hydrology - soil moisture - soil temperature - unsaturated zone - water management
    Learn how to calculate the water balance. Part 2 | WURcast
    Dijksma, R. - \ 2017
    Wageningen : WURcast
    water balance - available water - hydrology
    Regional soil moisture monitoring network in the Raam catchment in the Netherlands - 2016-04 / 2017-04
    Benninga, H.F. ; Carranza, C.D. ; Pezij, M. ; Ploeg, M.J. van der; Augustijn, D.C.M. ; Velde, R. van der - \ 2017
    University of Twente
    agriculture - hydrology - soil moisture - soil temperature - unsaturated zone - water management
    The Raam soil moisture measurement network dataset contains soil moisture and soil temperature measurements for 15 locations in the Raam, which is a 223-km2 river catchment in the southeast of the Netherlands. The network monitors soil moisture in the unsaturated zone for different soil textures and land covers present in the area, and it covers the topographic gradient of the region. At each location we installed Decagon 5TM sensors at depths of 5 cm, 10 cm, 20 cm, 40 cm and 80 cm. The logging time interval is set on 15 minutes. The Raam network is operational since April 2016 and the measurements are on-going.
    Hydrological drought and wildfire in the humid tropics
    Taufik, Muh - \ 2017
    Wageningen University. Promotor(en): R. Uijlenhoet, co-promotor(en): Henny van Lanen. - Wageningen : Wageningen University - ISBN 9789463436359 - 99
    wildfires - drought - humid tropics - wetlands - hydrology - prediction - water management - natuurbranden - droogte - humide tropen - wetlands - hydrologie - voorspelling - waterbeheer

    Drought is a recurrent hazard, which has happened throughout human history, and it is anticipated to become more severe in multiple regions across the world. Drought occurs in all climate regimes from humid to dry and from hot to cold. Drought is often viewed through its impact on environment and society, including wildfire, which is the topic of this study. The nature of such impacts differs remarkably from region to region. Although drought does not directly cause wildfire, it provides favorable conditions for wildfire ignition and spread. When drought coincides with strong El Niño events in the humid tropics, e.g. Southeast Asia, the impacts worsen through uncontrolled forest fires affecting the global carbon cycle. These include reduction of the carbon stock, intensifying the haze hazard, and other severe socio-economic impacts in Southeast Asia, including areas far away from the burnt area, e.g. Singapore because of fires in Sumatra.

    There still remains a serious lack of scientific understanding about the fundamental role of drought in fire-generating processes. Most research, so far, suggests that climate controls wildfire occurrence in the humid tropics. However, this climate-centered approach, which is reflected in contemporary drought-fire related indices, overlooks soil and hydrological processes beneath the surface across the humid tropics. There is also uncertainty about the relative roles of climate variability and human activities in influencing the nature and distribution of drought-related wildfires. Hence, the general objective of this PhD research is to examine how characterization of hydrological drought under natural and human-modified conditions can improve understanding of wildfires in general in the humid tropics.

    Chapter 2 discusses the contribution of humans to an increase of hydrological drought severity in the tropical peatland of Southeast Asia. Climate variability induces drought in the region, however, human activities (human-modified drought) may increase its severity. Analyzing long time series of simulated historical groundwater levels from selected regions in Southeast Asia, which were validated against some years with observations, revealed that human interference (through canalization and land-use change) has amplified drought severity. The drought amplification due to human interference was at least double that of climate-induced drought. The amplification is even higher when peatland is converted into acacia plantation. Further, research findings suggest that even if the Paris Agreement target is met, drought risk of peatlands remains high unless sustainable water management receives top priority in the region.

    Chapter 3 deals with how an existing, well-known drought-fire related index, i.e. the Keetch-Byram Drought Index (KBDI), is modified to improve applicability in the humid climate environment of Southeast Asia. The improvement includes: (i) adjustment of the drought factor to the local climate, and (ii) addition of the water table depth as a dynamic factor to fine-tune the drought index. The results indicate that the modified Keetch-Byram Drought Index (mKBDI) performed well in predicting fire hazard. Furthermore, the research identified a critical water table depth, which represents maximum fire hazard (0.85 m for the wetland forest of South Sumatra). Below this value hazard does not increase anymore. The mKBDI could be more widely applied, if pedotransfer functions would be developed that link easily-obtainable soil properties to the parameters of the water table factor.

    Chapter 4 shows that wetland transformation (i.e. through canalization and land-use change) not only affects hydrological drought (Chapter 2), but also influences fire behaviour. In Southeast Asia, expansion of agricultural cropland and forest plantations has changed the landscape of wetlands. The findings showed that the transformation into acacia plantation has amplified the fire hazard from 4% (under natural conditions) to 17%. An even higher amplification (40% fire hazard) is expected under poor water management, that is, uncontrolled drainage. The findings derived from this observation-based modeling experiment suggest that improved water management (controlled drainage with higher dry season surface water levels) can minimize fire susceptibility.

    Chapter 5 explains the importance of hydrology for fire hazard studies. Borneo is selected to investigate the added value of including hydrological variables in fire hazard prediction approaches. More than 300 statistical models were tested, and the results showed that models that include hydrological variables better predict area burnt than those solely based on climate indicators/indices. Further, modelling evidence shows amplifying wildfires and greater area burnt in response to El Niño Southern Oscillation (ENSO) strength, when hydrology is considered. These results highlight the importance of considering hydrological drought for wildfire prediction. I recommend that hydrology should be considered in future studies of the impact of projected ENSO strength, including effects on tropical ecosystems and biodiversity conservation.

    The contributions of this thesis research to science are summarized and synthesized in Chapter 6. First, the research identified that fire hazard studies would benefit from adding hydrology, which is reflected in the improved model performance when hydrological variables are integrated. Next, the research revealed that humans play a substantial role in modifying groundwater drought characteristics, hence amplifying the fire hazard in Southeast Asia. Further, the chapter identified several relevant research findings, including the model choice, which should consider the simplicity and the applicability of the model. Another finding demonstrated that controlling canal water level through canal blocking is a practical water management tool to restore degraded wetland. This restored wetland would benefit some endemic species. However, the restored wetland still faces high drought severity. Hence they remain more fire-prone until the un-impacted hydrology condition is achieved. Finally, this research suggest that currently widely-used drought indices (such as FWI) require improvements in their model structure, which means integration of hydrological variables to increase their applicability for fire hazard studies in the humid tropics.

    Getting a grip on hydrological and sediment connectivity
    Masselink, Rens J.H. - \ 2017
    Wageningen University. Promotor(en): C.J. Ritsema; S.E.A.T.M. van der Zee, co-promotor(en): S.D. Keesstra; A.J.A.M. Temme. - Wageningen : Wageningen University - ISBN 9789463436342 - 158
    hydrology - sediment - land degradation - slopes - geological sedimentation - land management - soil physics - hydrologie - sediment - landdegradatie - hellingen - geologische sedimentatie - grondbeheer - bodemfysica

    Land degradation is a large problem worldwide, especially in agricultural areas. Between 1-6 billion ha of land worldwide is affected by land degradation. With an increasing world population, more food production is needed and, therefore, more land is converted into agricultural areas. This conversion of land to agricultural areas, in turn, leads to more land degradation. Some common forms of land degradation are desertification, salinization and soil erosion by water. The negative effects of soil erosion have been recognized for a long time. Since the early 20th century, researchers have tried to quantify soil displaced due to water, and to measure and model the efficiency of management strategies.

    The implications of problems with upscaling, wrong process representation and equifinality include the difficulty to properly predict sediment sources, pathways and sinks within catchments. These problems then can translate into the implementation of sub-optimal management strategies. To deal with these non-linear processes and the lack of proper representation of water and sediment sources, pathways and sinks, the concept of connectivity was developed. Currently, many definitions of connectivity have been proposed, although the definition most used is that of hydrological connectivity by Pringle (2003): ‘Hydrologic connectivity is the water-mediated transport of matter, energy and organisms within or between elements of the hydrologic cycle’.

    A unified theory on what constitutes connectivity and how connectivity should be measured or inferred remains one of the biggest challenges within catchment science. In addition, it is unclear whether connectivity should be an output or an input of a model and if an input, whether this should be added explicitly or implicitly. The main objective of this thesis was, therefore, to assess and quantify hydrological and sediment connectivity in a meaningful way, which can further our understanding of hydrological and sediment transport processes and catchment system dynamics.

    The study was carried out in three catchments in Navarre, northern Spain. Two catchments, ‘Latxaga’ and ‘La Tejeria’, are agricultural catchments with sizes of 2.07 km2 and 1.69 km2, respectively. The ‘Oskotz Forestal’ catchment is a (semi-)natural catchment, with a size of 5.05 km2. Land cover in the agricultural catchments is mainly winter wheat and barley, while in the Oskotz catchment it is grassland and forest. Latxaga and La Tejeria are mainly underlain by marls and within La Tejeria some sandstone is also present. The geology in Oskotz is characterised by an alternation of marls and sandy limestone.

    In chapter 2, I used networks (graph theory) to characterise and quantify overland flow connectivity dynamics on hillslopes in a humid sub-Mediterranean environment by using a combination of high-resolution digital-terrain models, overland flow sensors and a network approach. Results showed that there are significant differences between overland flow connectivity on agricultural areas and semi-natural shrubs areas. Significant positive correlations between connectivity and precipitation characteristics were found. Significant negative correlations between connectivity and soil moisture were found, most likely due to soil water repellency and/or soil surface crusting. The combination of structural networks and dynamic networks for determining potential connectivity and actual connectivity proved a powerful tool for analysing overland flow connectivity.

    In chapter 3, I determined the functioning of hillslope-channel connectivity and the continuation of transport of these sediments in the channel. To determine this functioning, I obtained data on sediment transport from the hillslopes to the channels while simultaneously looking at factors that influence sediment export out of the catchment. For measuring hillslope-channel sediment connectivity, Rare-Earth Oxide (REO) tracers were applied to a hillslope in the Latxaga catchment preceding the winter of 2014-2015. The results showed that during the winter there have been no sediments transported from the hillslope into the channel. Analysis of precipitation data showed that although total precipitation quantities did not differ much from the mean, the precipitation intensities were low. Using a Random Forest (RF) machine learning method, I showed that hillslope-channel connectivity in Latxaga is dominated by sediment mobilisation during large (high intensity) precipitation events. Sediments are for a large part exported during those events. Large events also leave behind large amounts of sediments in and near the channel, which is gradually removed by small events.

    In chapter 4 I demonstrated that existing data can be used to assess governing factors of connectivity, and how these factors change over time. Data from three catchments in Navarre, Northern Spain, were used to assess factors that influence hydrologic and sediment connectivity. These factors were used as components in a spatially-lumped linear model for discharge and suspended-sediment yield. Three components of connectivity were distinguished: topographical, biological and soil. Changes in the topographical component for the studied periods were considered relatively small, and, therefore, kept constant. Changes in the biological component were determined using the Normalised Difference Vegetation Index. Changes in the soil component were assessed using an Antecedent Precipitation Index. Nash-Sutcliffe model efficiency coefficients were between 0.49 through 0.62 for the discharge models and between 0.23 through 0.3 for the sediment-yield models. I recommended applying the model at smaller spatial scales than catchment scale to minimize the lumping of spatial variability in the components.

    In chapter 5, the objective was to better understand the implications of model calibration at different spatial scales on the simulation of hydrology and sediment dynamics of an agricultural catchment. I applied the LAPSUS-D model to the Latxaga catchment. The model was calibrated and validated (4 years: 2011-2015) using three datasets at varying spatial scales: hillslope, catchment and the combined dataset (combined-calibrated model). The hillslope-calibrated model showed mainly infiltration-excess overland flow, the catchment-calibrated mainly saturation-excess overland flow at the footslopes and the combined-calibrated model showed saturation-excess overland flow from the midslopes to the footslopes. For hydrology, the combined-calibrated model simulated the large discharge peaks best, while at the hillslope scale, the hillslope-calibrated model performed best. The hillslope-calibrated model produced the highest model efficiencies for sediments, for calibration (0.618) and validation (0.269). The hillslope-calibrated model was the only model that showed observed gully erosion on a high-resolution DEM and displayed channel sediment dynamics. However, absolute quantities of erosion and deposition within the catchment were too high. The results show that modellers need to be aware of problems associated with automatic calibration, over-calibration and not incorporating measured data at multiple spatial scales. We advocate incorporating runoff and sediment tracing data at multiple scales whenever this is possible and to, furthermore, carry out specific measuring campaigns towards this end, ultimately to get a more comprehensive view on hydrological and sediment connectivity within a catchment.

    The combination of chapters in this thesis showed that the connectivity concept is useful for a wide range of studies, from hillslope scale to catchment scale. Using the concept, I was able to determine sediment dynamics for a humid-Mediterranean catchment and show that this behaviour is different than previously thought.

    Depending of the aim of the study, various concepts of connectivity are useful. Different geologic and climatic settings cause large differences in catchment (sediment) dynamics. It might, therefore, not be necessary, or even possible, to strive for a single, unifying conceptual framework for connectivity. Instead, a collection of frameworks for different settings should be developed. These frameworks should, however, always aim at helping to understand which measurements need to be taken and which type of models and indices should be used for that particular setting.

    It is my honest opinion that connectivity is definitely a useful concept to advance our knowledge on water and sediment transport processes further. However, careful consideration is also required as this particular concept will not necessary provide the ultimate explanation and insights in dynamic behaviour within watersheds around the world. The gap between the different spatial and temporal scales is too complex to be bridged with a single concept like connectivity. However, the many studies about connectivity that will be published in the near future will be able to advance knowledge on water and sediment transport processes.

    Modelling the dynamic interactions between food production and ecosystem services : a case study in Benin
    Duku, C. - \ 2017
    Wageningen University. Promotor(en): L.G. Hein, co-promotor(en): S.J. Zwart. - Wageningen : Wageningen University - ISBN 9789463431613 - 141
    ecosystem services - modeling - food production - case studies - hydrology - irrigation - forests - woodlands - climatic change - nature conservation - food security - benin - ecosysteemdiensten - modelleren - voedselproductie - gevalsanalyse - hydrologie - irrigatie - bossen - bosgebieden - klimaatverandering - natuurbescherming - voedselzekerheid - benin

    Given the high levels of food insecurity and the loss of vital ecosystem services associated with deforestation, countries in sub-Saharan Africa (SSA) face a major dilemma. How can they produce enough food in a changing climate to feed an increasing population while protecting natural forests and woodlands that provide a wide array of ecosystem services beneficial to livelihoods? Thus, the objectives of this thesis are twofold. First, to further enhance the understanding of the dynamic interactions between food production, and natural and semi-natural ecosystems with a case study in Benin. Second, to further enhance the understanding of how hydrological ecosystem services can be captured in an accounting framework. Understanding hydrological ecosystem services is key to understanding the multi-directional relationship between food production and ecosystem services supply from natural and semi-natural ecosystems. First, I examine how a spatially explicit ecohydrological model can be used to analyse multiple hydrological ecosystem services in line with the ecosystem accounting framework. The hydrological ecosystem services include crop water supply for rainfed agriculture, household water supply (both groundwater supply and surface water supply), water purification, and soil erosion control. Second, I develop a general modelling approach for analysing the effects of deforestation on the availability of water for irrigation at the watershed level, and I apply the approach to the Upper Oueme watershed in Benin. Third, I analyse the impact of climate change on agricultural intensification options. Finally, I quantify trade-offs between per capita food availability and protecting forests and woodlands at different levels of yield increases taking into account climate change, population growth. This thesis shows that the integration of hydrological ecosystem services into an accounting framework can provide relevant information at appropriate scales suitable for decision-making. It is empirically feasible to distinguish between service capacity and service flow of hydrological ecosystem services. This requires appropriate decisions regarding physical and mathematical representation of ecohydrological processes, spatial heterogeneity of ecosystems, temporal resolution, and required model accuracy. This thesis also shows that opportunities for irrigation expansion depend on conservation of forests and woodlands in the headwaters of the rivers feeding the irrigation scheme. Opportunities for agricultural intensification in SSA are likely to diminish with climate change, hence increasing pressure to expand cultivated areas in order to meet increasing food demand. Climate change will lead to substantial reductions in; exploitable yield gaps for major food crops, rainfed cropland areas that can support the cultivation of two or more crops per year, and water availability for irrigation expansion. Furthermore, in the far future crop yields will have to increase at a faster rate than has been recorded over the past two and half decades in order to maintain current levels of per capita food availability. Failure to achieve the required levels of yield increases is likely to lead to the conversion of substantial areas of forests and woodlands for crop cultivation. Based on the results of this thesis, four main recommendations to help address the dual challenge of food security and ecosystem protection in Benin and the larger SSA region are made: (i) promote a precautionary approach to forest and woodland conservation, (ii) promote cross-sectoral policy coherence and consultations, (iii) promote the development of satellite ecosystem accounts consistent with national accounts, and (iv) identify, evaluate and implement adaptation and resilience measures to reduce agricultural vulnerability to climate change.

    Hydrological controls on salinity exposure and the effects on plants in lowland polders
    Stofberg, Sija F. - \ 2017
    Wageningen University. Promotor(en): S.E.A.T.M. van der Zee; J.P.M. Witte. - Wageningen : Wageningen University - ISBN 9789463431873 - 172
    hydrology - lowland areas - soil salinity - temperate climate - fens - surface water - vegetation - fen soils - salinization - polders - hydrologie - laaglandgebieden - bodemzoutgehalte - gematigd klimaat - laagveengebieden - oppervlaktewater - vegetatie - laagveengronden - verzilting - polders

    The Dutch lowlands may be subject to salinization, through saline upward seepage and increased salt concentrations in the surface water, which may affect agriculture and nature areas with floating fens.

    A simple approach was proposed to estimate root zone salinization in areas with fresh water lenses that float on upward seeping saline groundwater, based on analytical solutions and approximations, which could be used for prioritization.

    The hydrology of floating fens was investigated and important processes and parameters were identified, which could be used to estimate root zone exposure to salinity. The flow processes are mostly controlled by the root mat geometry, which determines which part of the root mat floats within the surface water.

    A greenhouse experiment showed that salinity may affect the growth of some plant species from floating fens, which implies that salinization may affect species composition in these nature areas.

    Preserving Urmia Lake in a changing world : reconciling anthropogenic and climate drivers by hydrological modelling and policy assessment
    Shadkam, Somayeh - \ 2017
    Wageningen University. Promotor(en): P. Kabat, co-promotor(en): F. Ludwig; P.R. van Oel. - Wageningen : Wageningen University - ISBN 9789463431866 - 140
    lakes - hydrology - climatic change - modeling - water resources - water management - environmental protection - iran - meren - hydrologie - klimaatverandering - modelleren - watervoorraden - waterbeheer - milieubescherming - iran

    Urmia Lake, in north-western Iran, is an important internationally recognized natural area designated as a RAMSAR site and UNESCO Biosphere Reserve. Over the last 20 years, the surface area of Urmia Lake has declined by 80%. As a result, the salinity of the lake has sharply increased which is disturbing the ecosystems, local agriculture and livelihoods, regional health, as well as tourism, which could amplify economic, political and ethnic tensions in this already volatile region. In response to that, Iranian government established the ten-year “Urmia Lake Restoration Program (ULRP)” proposing six approaches in terms of controlling, protecting, surveying, studying and supplying water from other sources. This study first assessed the main reasons for the decreased inflow using the Variable Infiltration Capacity (VIC) hydrological model, including reservoirs and irrigation modules. The results showed that climate change was the main contributor to this inflow reduction. However, water resources development, particularly water use for irrigation, has played a substantial role as well. In the second step assessed Urmia lake inflow under future climate change and irrigation scenarios. Then, the (VIC) model was forced with bias-corrected climate model outputs for both the lowest (RCP2.6) and highest (RCP8.5) greenhouse-gas concentration scenarios to estimate future water availability. The results showed that the water resources plans are not robust to changes in climate. In other words, if future climate change is limited due to rapid mitigation measures (RCP2.6) the new strategy of reduction of irrigation water use can contribute to preserve Urmia Lake.

    The next step of this study assessed the quantitative impacts of ULRP by introducing a constructive framework. The framework depicts real water saving by distinguishing between water withdrawals, depletion, and demand in the context of uncertainties in future demand and supply. The results showed that although the ULRP helps to increase inflow by up to 57% it is unlikely to fully reach its target for three main reasons. The first reason is decreasing return flows due to increasing irrigation efficiency. The second reason is increased depletion which is due to neglecting the fact that agricultural water demand is currently higher than available water for agriculture. The third reason is ignoring the potential impact of climate change. However, there still can be some additional none-quantifiable barriers and challenges that may cause the failure of the restoration plan. Therefore, in the last step, this study used two types of qualitative data to explore these aspects: first, the opinions from 40 experts and the in-situ observation of some of the ULRP implementation practices. The results indicate a number of challenges for the ULRP implementation including the water use regulations and the agricultural measures. In addition, (water) demand-side measures such as crop pattern changes were more supported, as opposed to supply-side measures.

    This thesis showed that the sustainable approach to preserve Urmia Lake should incorporate both demand management (considering socioeconomic complexity) and flexible supply management strategies (to deal with uncertainties in climate variability and change) in a participatory approach. To be prepared for the future, also scenarios with reduced inflow into Urmia Lake, either due to climate change or water resources development, need to be considered to deal with considerable amounts of variability in the current system and with future changes in climate and socioeconomic conditions.

    Effect of water harvesting techniques on hydrological processes and sediment yield in Northern Ethiopia
    Woldegiorgis, Berhane Grum - \ 2017
    Wageningen University. Promotor(en): V. Geissen; C.J. Ritsema, co-promotor(en): R. Hessel; C.A. Kessler. - Wageningen : Wageningen University - ISBN 9789463431682 - 156
    hydrology - water harvesting - arid zones - semiarid zones - water availability - ethiopia - hydrologie - regenwateropvang - aride klimaatzones - semi-aride klimaatzones - waterbeschikbaarheid - ethiopië

    The study was conducted in the semi-arid northern Ethiopia aimed at selecting appropriate water harvesting techniques (WHTs) for implementation. A plot-scale experiment was set up, in the Gule catchment, on a farmland to monitor the effect of in-situ WHTs such as tied ridges and straw mulch mainly on event-based runoff, soil-moisture, and soil and nutrient losses. The off-site effect of WHTs such as check dams and percolation ponds on catchment-scale event-based runoff and sediment yield was also monitored in the Gule catchment (~12 km2) and Misbar sub-catchment (~2.4 km2), northern Ethiopia. First, a decision support approach was developed to aid the selection of WHTs in arid and semi-arid areas. The decision support approach was validated with a case study for WHTs in the upper Geba watershed in northern Ethiopia. Using the decision support methodology, eight potential WHTs were pre-selected for implementation in the watershed. Next, using suitability indicators for WHTs and a GIS-based multi-criteria analysis, suitable areas were identified for three of these WHTs, namely check dams, percolation ponds and bench terraces and suitability maps were generated. The multi-criteria analysis was validated by comparing the predicted suitable areas with the already existing locations of WHTs in the watershed. The result was that 90% of the existing check dams and 93% of the percolation ponds in the upper Geba watershed were correctly identified by the approach. The field study showed runoff reduction by WHTs from farmland between 40 to 88% and soil loss between 60 to 90%. Nutrient loss reduction from farmland by WHTs also ranged between 52 and 86%. Soil-moisture also improved due to the use of the in-situ WHTs. Model-based simulation at the Gule and Misbar outlets using LISEM showed that the current WHTs applied in the catchment are able to decrease event-based runoff by 41 and 45%, respectively. Similarly, sediment yield was reduced at both the Gule outlet and Misbar sub-outlet, by 67 and 55%, respectively. This study has verified that in semi-arid areas, such as the northern Ethiopian highlands, in-situ and catchment-scale WHTs can be used to improve the efficiency of rainwater harvesting and water availability for agricultural uses. Furthermore, these WHTs help to mitigate land degradation by decreasing soil and nutrient losses from farmland and sediment yield from catchments.

    The Mekong’s future flows : quantifying hydrological changes and developing adaptation options
    Hoang, Long Phi - \ 2017
    Wageningen University. Promotor(en): P. Kabat; R. Leemans, co-promotor(en): F. Ludwig; M.T.H. van Vliet. - Wageningen : Wageningen University - ISBN 9789463431088 - 159
    hydrology - mekong river - modeling - climatic change - socioeconomics - water resources - water use - south east asia - hydrologie - mekong - modelleren - klimaatverandering - sociale economie - watervoorraden - watergebruik - zuidoost-azië

    This multidisciplinary study focuses on projecting and adapting to future hydrological changes in the Mekong – an international river of global significance in terms of rapidly increasing human pressures and climate-change vulnerability. A modelling framework was developed to project future changes in both the river flow regime and hydrological extremes (i.e. high/low flows and floods), under multiple scenarios of climate change, irrigation and hydropower developments. Furthermore, we developed a combined quantitative-qualitative approach to develop suitable adaptation measures and strategies to future floods in the Mekong Delta being a key vulnerability hotspot.

    Results show that the Mekong’s future flow regime is subjected to substantial changes under climate change and human developments. Climate change will intensify the hydrological cycle, resulting in increasing average river flows (between +5 % and +16%, annually), and more frequent and extreme high flows during the wet season. Flow regime shows substantial alterations in the seasonal flow distributions under the combined impacts of climate change, irrigation expansions and hydropower developments. While dry season flows increase strongly (monthly changes up to +150%), wet season flows show contrasting changes with reductions during June - October (up to -25%) and substantial increases during November – December (up to 36%). A follow-up modelling assessment for the Mekong Delta shows substantial increases in flood hazards under climate change and sea level rise, shown by higher flood frequencies and flood depths across the whole delta. Increasing flood hazards therefore represents a key issue to be addressed in terms of future adaptation. The adaptation appraisal study further shows that effective adaptation requires looking beyond sole infrastructural investments. Instead, technological innovations for flood risk management combined with improved governance and institutional capacities offer ample opportunities to adapt to future hydrological changes.

    This study projects substantial future hydrological changes under future climate change and accelerating socioeconomic developments and shows potentially serious consequences for water related safety and sustainable water resources uses and allocations. Furthermore, this study demonstrates amble opportunities to manage future changes through strategic development planning and through adaptive interventions. Insights from this study address the needs for quantified future hydrological changes and emphasize adequate adaptation to the associated risks in an important international river experiencing climate change and rapid socioeconomic developments.

    Ecohydrologische systeemanalyse Liefstinghsbroek
    Delft, S.P.J. van; Waal, R.W. de; Jansen, P.C. ; Bijlsma, R.J. ; Wegman, R.M.A. - \ 2017
    Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2790) - 133
    ecohydrologie - hydrologie - vegetatie - natura 2000 - bossen - graslanden - historische geografie - groningen - ecohydrology - hydrology - vegetation - natura 2000 - forests - grasslands - historical geography - groningen
    Het Lieftinghsbroek in Oost-Groningen bestaat uit gevarieerd loofbos met enkele schraalgraslandjes in het dal van de Ruiten Aa. Het gebied is aangewezen voor Natura 2000 habitattypen bos en schraalland en is tevens bosreservaat. Om meer inzicht te krijgen in het effect van vernattingsmaatregelen in de directe omgeving van het gebied is een ecohydrologisch onderzoek uitgevoerd, waarbij geologisch/bodemkundige, hydrologische en vegetatiekundige gegevens verzameld zijn (uit literatuur en in het veld) en het historisch grondgebruik is beschreven. Voor de bossen is het gebied te nat geworden, of te zuur door het ontbreken van kwelinvloed. Ook voor Blauwgraslanden zijn de mogelijkheden beperkt. Er wordt aanbevolen aanvullende maatregelen te treffen om de sterke vernatting te verminderen door minder neerslagwater vast te houden in het gebied.
    Bodemhydrofysische gegevens in BRO en BIS : update 2016
    Bakker, G. ; Heinen, M. ; Wesseling, J.G. ; Groot, W.J.M. de; Assinck, F.B.T. ; Hummelink, E.W.J. - \ 2017
    Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2789) - 77
    bodemfysica - hydrologie - water - bodem - soil physics - hydrology - water - soil
    Chemisch-fysische schematisering van de bodem voor NHI-waterkwaliteit : naar een nieuwe fysisch-chemische schematisering van de Nederlandse bodem
    Bolt, Frank van der; Walvoort, Dennis ; Vries, Folkert de; Hoogland, Tom ; Vroon, Henk ; Groenendijk, Piet ; Renaud, Leo ; Massop, Harry ; Veldhuizen, Ab ; Walsum, Paul van - \ 2016
    Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2753) - 34
    bodem - bodemkwaliteit - hydrologie - bodemeigenschappen - bodemkarteringen - soil - soil quality - hydrology - soil properties - soil surveys
    Voor de ontwikkeling van het Nationaal Hydrologisch Instrumentarium-waterkwaliteit is een aanpak opgesteld om de fysisch-chemische schematisering van de bodem in Nederland verder te ontwikkelen. Op korte termijn (2017-2018) is een pragmatische werkwijze nodig om de bodemchemische parameters met bijbehorende schematisering in representatieve eenheden voor de operationele toepassing voor landelijke beleidsstudies te actualiseren. Het gebruik van de huidige fysischchemische karakterisering voor de bodemkaart 1:50.000 vormt de geëigende methode. Op de langere termijn is het de wens om het Nationaal Hydrologisch Instrumentarium-waterkwaliteit ook te kunnen inzetten voor regionale toepassingen. Dit kan alleen als er een gedetailleerde geostatistisch gesimuleerde 3D-bodemkaart aan ten grondslag ligt die recht doen aan regionale variabiliteit van de bodem.
    Een nieuwe en handzame lysimeter: eerste stap naar een nationaal netwerk voor de werkelijke verdamping?
    Voortman, Bernard ; Witte, J.P. ; Rheenen, Hans van; Bosveld, F. ; Elbers, J.A. ; Bolt, F.J.E. van der; Heijkers, J. ; Hoogendoorn, Jan ; Bolman, A. ; Spek, T. ; Voogt, M. - \ 2016
    Stromingen : vakblad voor hydrologen 22 (2016)2. - ISSN 1382-6069 - p. 49 - 63.
    hydrologie - neerslag - waterbalans - grondwater - lysimeters - evaporatie - hydrology - precipitation - water balance - groundwater - lysimeters - evaporation
    Vrijwel overal op aarde verdampt meer dan de helft van het neerslagwater, ook in Nederland. Toch wordt deze grote verliespost in ons land slechts sporadisch gemeten. Door inspanningen van kennisinstituten, bedrijven en overheid is daarom een lysimeter ontwikkeld. Metingen in 2014 en 2015 op twee locaties vertonen opvallende verschillen, maar ook grote overeenkomsten, met eddy-correlatiemetingen. Schattingen van de verdamping via satellietdata zijn hoger dan de metingen. Tijd daarom, om metingen in het veld te combineren met modellen en waarnemingen vanuit de ruimte
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