Search

Nik Verweel (24), master student Geografische Informatiesystemen (GIS) aan Wageningen University and Research (WUR), winnaar BSc Scriptieprijs KNW 2024.

Storage change in heat in the soil is one of the main components of the energy balance and is essential in studying the land-Atmosphere heat exchange. However, its measurement proves to be difficult due to (vertical) soil heterogeneity and sensors easily disturbing the soil. Improvements in the precision and resolution of distributed temperature sensing (DTS) equipment has resulted in its widespread use in geoscientific studies. Multiple studies have shown the added value of spatially distributed measurements of soil temperature and soil heat flux. However, due to the spatial resolution of DTS measurements (g1/430gcm), soil temperature measurements with DTS have generally been restricted to (horizontal) spatially distributed measurements. This paper presents a device which allows high-resolution measurements of (vertical) soil temperature profiles by making use of a 3D-printed screw-like structure. A 50gcm tall probe is created from segments manufactured with fused-filament 3D printing and has a helical groove to guide and protect a fiber-optic (FO) cable. This configuration increases the effective DTS measurement resolution and will inhibit preferential flow along the probe. The probe was tested in the field, where the results were in agreement with the reference sensors. The high vertical resolution of the DTS-measured soil temperature allowed determination of the thermal diffusivity of the soil at a resolution of 2.5gcm, many times better than what is feasible using discrete probes. A future improvement in the design could be the use of integrated reference temperature probes, which would remove the need for DTS calibration baths. This could, in turn, support making the probes "plug and play"into the shelf instruments without the need to splice cables or experience in DTS setup design. The design can also support the integration of an electrical conductor into the probe and allow heat tracer experiments to derive both the heat capacity and the thermal conducti, Atmospheric Remote Sensing, Water Resources

Wind machines have been increasingly used for frost damage mitigation in the agricultural community. During radiative frost nights, wind machines are used to erode near-surface thermal inversion by air mixing. The underlying mixing processes remain poorly understood. A full picture of warming effects caused by air mixing requires measurements with wide coverage and high resolution. Our study aimed to quantify the magnitude and area of warming by air mixing and identify the characteristic mixing processes downwind and upwind. We installed 9 km of fiber optic cables in a 6.75 ha orchard block, creating two horizontal planes and three vertical profiles. Quasi-3D temperature responses with spatial sampling and temporal resolution of 25 cm and 10 s, respectively, were obtained before and during machine operation. We found a 50% reduction of the local inversion strength (8 K) over 0.42 ha at 1 m and 0.46 ha at 2 m height. The warming area for a 30% reduction extends to 2.81 and 2.52 ha, respectively. As the propeller rotates 360°, the weak background wind substantially impacts the air mixing processes downwind and upwind. When jets blow along with background wind, the warming plumes arrive earlier than the jet due to horizontal advection from earlier warmed sections. The warming plumes consequently accumulate downwind and penetrate deep into the canopy. In contrast, in upwind direction, wind drag resistance causes warming plumes arrive later than the jet. Quadrant analysis reveals that flux transport during the machine operation is dominated by sweeping and ejection motions. Intermittent downdrafts of warm air and updrafts of cool air result in efficient vertical heat exchange. This feature makes wind machines highly effective in raising canopy airspace temperature to mitigate frost damage., Atmospheric Remote Sensing, Water Resources

We moeten af van het onderscheid tussen lager en hoger onderwijs, luidt, kort gezegd, de missie van onderwijsminister Robbert Dijkgraaf. Hij benadrukt dat beroepsonderwijs gelijkwaardig moet zijn aan hoger onderwijs. Goed voor de kansengelijkheid onder jongeren. Én goed voor bedrijven. Want in alle sectoren is grote behoefte aan mbo’ers. Dus ook in de watersector. Om die reden organiseert Koninklijk Nederlands Waternetwerk (KNW) nu voor de tweede keer een speciale mbo-studentendag tijdens de vakbeurs Aqua Nederland.

Waterschappen besluiten over zaken waarmee jongeren in de toekomst te maken krijgen. Terwijl de (meeste) mensen die nú die besluiten nemen, er dán niet meer zijn. Daarom willen Margot Kwee, Frank Huijgens en Mathijs van Eeuwijk zèlf gaan meebesturen.

The trend and magnitude of actual evaporation across the phenophases of miombo woodlands are unknown. This is because estimating evaporation in African woodland ecosystems continues to be a challenge, as flux observation towers are scant if not completely lacking in most ecosystems. Furthermore, significant phenophase-based discrepancies in both trend and magnitude exist among the satellitebased evaporation estimates (i.e. Global Land Evaporation Amsterdam Model (GLEAM), moderate resolution imaging spectroradiometer (MODIS), operational simplified surface energy balance (SSEBop), and water productivity through open-access remotely sensed derived data (WaPOR)), making it difficult to ascertain which of the estimates are close to field conditions. Despite the many limitations with estimation of evaporation in woodlands, the development and application of the distributed temperature system (DTS) is providing deepened insights and improved accuracy in woodland energy partitioning for evaporation assessment. In this study, the Bowen ratio distributed temperature sensing (BRDTS) approach is used to partition available energy and estimate actual evaporation across three canopy phenophases of the miombo woodland, covering the entire 2021 dry season (May–October) and early rain season (November– December) at a representative site in Mpika in Zambia, southern Africa. To complement the field experiment, four satellite-based evaporation estimates are compared to the field observations. Our results show that actual evaporation of the miombo woodland appears to follow the trend of the net radiation, with the lowest values observed during the phenophase with the lowest net radiation in the cool dry season and the highest values during the phenophase with peak net radiation in the early rainy season. It appears the continued transpiration during the driest period in the dormant phenophase (with lowest canopy cover and photosynthetic activities) may be influenced by the species-depe, Water Resources, Atmospheric Remote Sensing

To mitigate spring frost damage, fruit farmers use wind machines to mix warm overlying air down to the vegetation. Up to this point, studies on wind machine efficiency have focused on air temperatures. The temperature of different plant organs during operation remains unknown, while critical for the actual degree of frost damage. With Distributed Temperature Sensing we measured vertical in-canopy air temperature profiles in a pear orchard in the Netherlands and thermistors were installed to determine the plant tissue temperatures. We found that to optimize wind machine operation, it is important to consider two effects of a wind machine: (1) mixing of stratified air above and into the canopy layer and (2) erosion of the leaf boundary layer to facilitate plant–air heat exchange. We show how foliage reduces plume penetration to the ground with distance to the wind machine. Due to this blocking at least 15 rotations (∼ 75 min) are needed for optimal mixing. Leaf temperatures lag behind air temperatures, due to strong radiative cooling. We found that over the rotation cycle of a wind machine the temperature difference between leaf and air is variable as convective warming repeatedly dominates over radiative cooling. This is different for flowers and shoots due to different heat capacities. Thin flower petals store little heat and are almost in direct equilibrium with air temperature changes. Shoots, with their higher heat capacity and lower surface/volume ratio, store more heat during the day that is slowly released at night. This discrepancy between plant and air temperature should be considered for frost damage prediction., Water Resources, Atmospheric Remote Sensing

Despite the importance of forests in the water and carbon cycles, accurately measuring their contribution remains challenging, especially at night. During clear-sky nights current models and theories fail, as non-turbulent flows and spatial heterogeneity become more important. One of the standing issues is the ‘decoupling’ of the air masses in and above the canopy, where little turbulent exchange takes place, thus preventing proper measurement of atmospheric fluxes. Temperature inversions, where lower air is colder and thus more dense, can be both the cause and result of this decoupling. With Distributed Temperature Sensing (DTS) it is now possible to detect these temperature inversions, and increase our understanding of the decoupling mechanism. With DTS we detected strong inversions within the canopy of a tall Douglas Fir stand. The inversions formed in on clear-sky nights with low turbulence, and preferentially formed in the open understory. A second inversion regularly occurred above the canopy. Oscillations in this upper inversion transferred vertically through the canopy and induced oscillations in the lower inversion. We hypothesize that the inversions could form due to a local suppression of turbulent motions along the height of the canopy. This was supported by a 1-D conceptual model, which showed that a local inversion layer would always form within the canopy if the bulk inversion (over the full canopy) was strong enough. Due to the near-continuous vertical motion and specific height the inversions occur at, a very high measurement density (better than ∼2 m) and measurement frequency (>0.1 Hz) are required to detect them. Consequently, it could be possible that the observed inversions are a regular feature in similarly structured forests, but are generally not directly observed. With DTS it is possible to detect and describe these types of features, which will aid in improving our understanding of atmospheric flows over complex terrain such as fores, Atmospheric Remote Sensing, Water Resources

Forests cover a large part of the globe, and are responsible for a large amount of evaporation and the fixation of carbon. To be able to better understand this atmospheric exchange of forests, and how the forests will behave under future climate change, both accurate measurements as well as models are required. However, due to their height and heterogeneity they are difficult to model and measure. Standard theories do not apply well to forests, and as such more effort is required to understand the exchange between the forests and the atmosphere. However, precise measurements are made difficult due to a number of issues. The most prominent are the non-closure of the energy balance, and so-called ‘decoupling’ of the canopy. Non-closure of the energy balance is where all the measured inflows and outflows of energy do not add up to the measured change in energy storage in the forest system. The size and heterogeneity of forests makes this difficult to assess. Second is ‘decoupling’, where the vertical mixing of air within the canopy is hampered, and measurements performed above the canopy are not representative of what happens in the entire canopy down to the forest floor., Water Resources

The urban heat island, is a serious threat for the urban well-being, and can be determined by the local energy balance. The surface energy balance, with respect to incoming radiative energy and subsequent partitioning into reflected energy (albedo), absorbed energy and further partitioning of latter into convectional heat (QH), radiative heat (QR) and latent heat (QE) by using commonly applied urban materials and vegetation types, was therefore experimentally quantified in this study. In agreement with previous studies it was found that materials convert most of absorbed energy into convectional heat (>92%) while vegetation channels a substantial part of absorbed radiative energy into latent heat (27–50%). It is for the first time experimentally demonstrated that significant differences in thermal behaviour between different types of urban vegetation surfaces occur. Of the investigated vegetation types ivy and moss showed respectively the highest (0.10) and lowest (0.07) albedo, but sedum and moss channelled respectively lowest (27%) and highest (50%) percentage of the absorbed radiative energy into latent heat production. Of the four investigated plant types, moss appeared most effective in preventing UHI, converting only 50% of incoming radiative energy into convectional heat, while sedum was least effective converting 73% of incoming radiative energy into convectional heat. These quantitative measurements show that strategic use of specific types of urban vegetation surfaces, instead of commonly applied building materials, can be an effective measure for mitigation of UHI leading to improved climate resilient cities., Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public., Materials and Environment, Atmospheric Remote Sensing

Kan historisch water de waarde van de stad verhogen, was afgelopen zomer een vraag op de dertiende Waterconferentie in Gouda. Het antwoord in vele watersteden is: ja. Een historisch watersysteem kan een belangrijke rol spelen in het versterken van de vitaliteit, de klimaatbestendigheid en de cultuurhistorische waarde van de binnenstad.

Wie een blik werpt op de websites van verschillende waterschappen ziet het meteen: deze bestuurslaag bereidt zich voor op een ongewisse toekomst. En dat komt met name door invloeden van buitenaf. H2O onderzocht afgelopen zomer in een reeks artikelen voor de website de opgaven waar de waterschappen voor staan. “Ik zie veel lerend vermogen.”

Young waterprofessionals in the picture: een interview met Ruud Steenbeek (27), onderzoeker Chemische Waterkwaliteit en Gezondheid bij KWR.

Measurements of ice temperature provide crucial constraints on ice viscosity and the thermodynamic processes occurring within a glacier. However, such measurements are presently limited by a small number of relatively coarse-spatial-resolution borehole records, especially for ice sheets. Here, we advance our understanding of glacier thermodynamics with an exceptionally high-vertical-resolution (∼0.65 m), distributed-fiber-optic temperature-sensing profile from a 1043-m borehole drilled to the base of Sermeq Kujalleq (Store Glacier), Greenland. We report substantial but isolated strain heating within interglacial-phase ice at 208 to 242 m depth together with strongly heterogeneous ice deformation in glacial-phase ice below 889 m. We also observe a high-strain interface between glacial- and interglacial-phase ice and a 73-m-thick temperate basal layer, interpreted as locally formed and important for the glacier's fast motion. These findings demonstrate notable spatial heterogeneity, both vertically and at the catchment scale, in the conditions facilitating the fast motion of marine-terminating glaciers in Greenland., Water Resources, Geoscience and Remote Sensing

Forest evaporation exports a vast amount of water vapor from land ecosystems into the atmosphere. Meanwhile, evaporation during rain events is neglected or considered of minor importance in dense ecosystems. Air convection moves the water vapor upwards leading to the formation of large invisible vapor plumes, while the identification of visible vapor plumes has not yet been studied. This work describes the formation process of vapor plumes in a tropical wet forest as evidence of evaporation processes happening during rain events. In the dry season of 2018 at La Selva Biological Station (LSBS) in Costa Rica it was possible to spot visible vapor plumes within the forest canopy. The combination of time-lapse videos at the canopy top with conventional meteorological measurements along the canopy profile allowed us to identify the driver conditions required for this process to happen. This phenomenon happened only during rain events. Visible vapor plumes during the daytime occurred when the following three conditions are accomplished: presence of precipitation (P), air convection, and a lifting condensation level value smaller than 100 m at 43 m height (z lcl.43)., Water Resources

Het water weer terugbrengen in de historische stad. Daarvoor pleiten watergildes in Hollandse watersteden als Gouda en Leiden. Want meer water maakt de stad aantrekkelijker om te wonen en te bezoeken (wanneer dat weer steeds meer kan), versterkt (zodoende) de stedelijke economie én creëert meer waterberging om hoosbuien op te vangen. Een ‘win-win-winsituatie’ dus. En meer dan nostalgie.

Oude schetsen van 34 duizend aansluitingen controleren op de aanwezigheid van lood. Gebruikmaken van stille winkelstraten en uitgaansgebieden voor het vernieuwen van waterleidingen. Brandkranen voor bemonstering geschikt maken. Een pleidooi om het werk van mensen die ervoor zorgen dat ons afvalwater kan blijven wegstromen te beschouwen als vitaal. De bemonstering van rioolwater opschalen van twee naar zeven keer per week. Een greep uit de ervaringen van waterwerkers in coronatijd, die nu een jaar duurt.

In the picrure: Frederic Béen, onderzoeker bij KWR in de groep chemische waterkwaliteit en gezondheid.

Complex ecosystems such as forests make accurately measuring atmospheric energy and matter fluxes difficult. One of the issues that can arise is that parts of the canopy and overlying atmosphere can be turbulently decoupled from each other, meaning that the vertical exchange of energy and matter is reduced or hampered. This complicates flux measurements performed above the canopy. Wind above the canopy will induce vertical exchange. However, stable thermal stratification, when lower parts of the canopy are colder, will hamper vertical exchange. To study the effect of thermal stratification on decoupling, we analyze highresolution (0.3 m) vertical temperature profiles measured in a Douglas fir stand in the Netherlands using distributed temperature sensing (DTS). The forest has an open understory (0'20 m) and a dense overstory (20'34 m). The understory was often colder than the atmosphere above (80 % of the time during the night, > 99 % during the day). Based on the aerodynamic Richardson number the canopy was regularly decoupled from the atmosphere (50 % of the time at night). In particular, decoupling could occur when both u∗ < 0:4 m s-1 and the canopy was able to cool down through radiative cooling. With these conditions the understory could become strongly stably stratified at night. At higher values of the friction velocity the canopy was always well mixed. While the understory was nearly always stably stratified, convection just above the forest floor was common. However, this convection was limited in its vertical extent, not rising higher than 5 m at night and 15 m during the day. This points towards the understory layer acting as a kind of mechanical "blocking layer"between the forest floor and overstory. With the DTS temperature profiles we were able to study decoupling and stratification of the canopy in more detail and study processes which otherwise might be missed. These types of measurements can aid in describing the canopy' atmosphere interact, Water Resources, Atmospheric Remote Sensing

Near-surface wind speed is typically only measured by point observations. The actively heated fiber-optic (AHFO) technique, however, has the potential to provide high-resolution distributed observations of wind speeds, allowing for better spatial characterization of fine-scale processes. Before AHFO can be widely used, its performance needs to be tested in a range of settings. In this work, experimental results on this novel observational wind-probing technique are presented. We utilized a controlled wind tunnel setup to assess both the accuracy and the precision of AHFO under a range of operational conditions (wind speed, angles of attack and temperature difference). The technique allows for wind speed characterization with a spatial resolution of 0.3 m on a 1 s timescale. The flow in the wind tunnel was varied in a controlled manner such that the mean wind ranged between 1 and 17 m s-1. The AHFO measurements are compared to sonic anemometer measurements and show a high coefficient of determination (0.92–0.96) for all individual angles, after correcting the AHFO measurements for the angle of attack. Both the precision and accuracy of the AHFO measurements were also greater than 95 % for all conditions. We conclude that AHFO has the potential to measure wind speed, and we present a method to help choose the heating settings of AHFO. AHFO allows for the characterization of spatially varying fields of mean wind. In the future, the technique could potentially be combined with conventional distributed temperature sensing (DTS) for sensible heat flux estimation in micrometeorological and hydrological applications., Water Resources, Atmospheric Remote Sensing

Distributed temperature sensing (DTS) systems can be used to estimate the temperature along optic fibers of several kilometers at a sub-meter interval. DTS systems function by shooting laser pulses through a fiber and measuring its backscatter intensity at two distinct wavelengths in the Raman spectrum. The scattering-loss coefficients for these wavelengths are temperature-dependent, so that the temperature along the fiber can be estimated using calibration to fiber sections with a known temperature. A new calibration approach is developed that allows for an estimate of the uncertainty of the estimated temperature, which varies along the fiber and with time. The uncertainty is a result of the noise from the detectors and the uncertainty in the calibrated parameters that relate the backscatter intensity to temperature. Estimation of the confidence interval of the temperature requires an estimate of the distribution of the noise from the detectors and an estimate of the multi-variate distribution of the parameters. Both distributions are propagated with Monte Carlo sampling to approximate the probability density function of the estimated temperature, which is different at each point along the fiber and varies over time. Various summarizing statistics are computed from the approximate probability density function, such as the confidence intervals and the standard uncertainty (the estimated standard deviation) of the estimated temperature. An example is presented to demonstrate the approach and to assess the reasonableness of the estimated confidence intervals. The approach is implemented in the open-source Python package “dtscalibration”., Corrigendum: DOI 10.3390/s21030912. The original article has been updated., Water Resources

Wind machines are used in the agricultural sector to prevent or mitigate the adverse effects of night frost in spring. In this study we aim to quantify the impact of wind machine operation on the local temperature field in an orchard. To this end, a field experiment is conducted and experimental analysis is combined with numerical simulation studies in order to assess the functional relations between wind machine performance and the dominating physical processes occurring during radiative frost events. Experimental observations showed that the temperature response strongly depends on the radial distance to the fan and the height above the surface. In agreement with previous studies, the wind machine was able to achieve rotation-averaged temperature increases of up to 50% of the inversion strength ( ≈ 3 K) in an area of 3–5 ha at 1 m height. Furthermore, it was observed that even weak ambient winds (<1 m/s) already may cause strong upwind-downwind asymmetries in the protected area, the downwind area being larger. The numerical model, inspired by the field experiment, showed similar spatial temperature responses as compared to observations. Interestingly, it was found that slower rotation times of the wind machine (3 to 6 min) lead to a significant increase of affected area, while the temperature enhancement itself stayed relatively constant. Variation of the horizontal tilt angle showed that, in our model, temperature enhancement was maximized between 8∘ and 16∘. This nearly horizontal flow already facilitates efficient vertical mixing of momentum and heat, presumably due to generation of shear instabilities at the lower edge of the jet. Finally, like in the observations also the numerical result showed strong upwind-downwind asymmetry in the affected area due to background wind., Atmospheric Remote Sensing, Water Resources

The interception of precipitation by vegetation has important consequences for climate and water resources. Although canopy interception has been studied for centuries, many fundamental unknowns remain. We present persistent questions that reflect challenges in measuring, representing, and understanding how terrestrial ecosystems intercept, partition, and transport precipitation—down to soils or back to the atmosphere. In summary of this book, we outline future needs and simultaneously provide a primer for those interested in precipitation interception processes.

WML, producent van Limburgs drinkwater, is naarstig op zoek naar nieuwe medewerkers. Vanwege de vergrijzing en het samenstellen van een zogeheten saneringspool van monteurs om het vervangen van oude leidingen deels zelf te kunnen uitvoeren. In korte tijd kwamen er maar liefst zes in dienst, al had maar één van hen de gewenste papieren en ervaring.

Conventional in situ observations of visibility and other meteorological variables are restricted to a limited number of heights near the surface, with the lowest observation often made above 1 m. This can result in missed observations of shallow fog as well as the initial growth stage of thicker fog layers. At the same time, numerical experiments have demonstrated the need for high vertical grid resolution in the near-surface layer to accurately simulate the onset of fog; this requires correspondingly high-resolution observational data for validation. In November 2017, a field experiment was conducted at the Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands with the aim of observing the growth of shallow fog from the ground up, assessing the applicability of emerging high-resolution methods for observing shallow fog. Two innovative, high-resolution techniques were employed: distributed temperature sensing (DTS), providing temperature and relative humidity observations at vertical resolutions as fine as 1 cm, and a novel camera-LED method to observe near-surface visibility below the conventional sensor height of 2.0 m. These observations were supplemented by the existing observations at the site, including those along a 200-m tall tower. Comparison between the high-resolution observations and their conventional counterparts shows the errors to be small, giving confidence to the reliability of the techniques. The high resolution of the observations subse- quently allows for detailed investigations of near surface processes. The growth of fog layers from the ground up was observed with very strong temperature inversions in the lowest metre (up to 5 K), and corresponding region of (super)saturation where the fog formed and grew. Throughout the two-week observation period, fog was observed twice at the conventional sensor height of 2.0 m, but up to four times in the lowest 0-0.5 m using the camera estimates, with the shallow fog also forming u, Atmospheric Remote Sensing, Water Resources

Wie niet kan zweten, raakt oververhit. Dat geldt voor mensen én steden. Daarom pleit Anna Solcerova er in haar promotieonderzoek voor om steden in te richten met meer open water en meer groen. En ook de eeuwenoude Japanse traditie ‘uchimizu’ kan bij het bestrijden van de stedelijke hittestress goed van pas komen.

Water Resources

Iemand die een deuk in je auto schopt, je achterna zit door de straat, je bedreigt, je klem zet in een lift of voor een deur. Ook waterwerkers ervaren geregeld agressie tijdens het werk. Wat doet dat met de mensen die het meemaken?

Ze slieren langs je benen bij het zwemmen, draaien vast in de schroef van je boot of blijven hangen in je vishengel. Recreanten gruwen van waterplanten in open water. Maar dankzij die waterplanten is het water vaak helder, is de kwaliteit beter dan ooit en verdween de blauwalg. Toch, liever wegmaaien vinden veel recreanten. Goed beheren zeggen anderen. Wat te doen?

Hoe breng je schoon water naar het Zuiderpark, de waterparel van Rotterdam? Met een nieuwe waterweg die schoon water, extra waterberging en meer natuur en recreatie biedt. Een kunststukje. “De Blauwe Verbinding is hét voorbeeld van brede samenwerking.”

De kleinschalige wateraanvoer werd afgelopen zomer ingezet om tegendruk te bieden aan de oprukkende verzilting. Zoet tegen zout. Er wordt gewerkt aan KWA-plus: een aanvoercapaciteit van 15 m3 per seconde. Met in de verdere toekomst plannen voor 24 en mogelijk zelfs 30 m3 per seconde.

Rapid improvements in the precision and spatial resolution of Distributed Temperature Sensing (DTS) technology now allows its use in hydrological and atmospheric sciences. Introduced by Euser [Hydrol. Earth Syst. Sci., 18, 2021–2032 (2014)] is the use of DTS for measuring the Bowen ratio (BR-DTS), to estimate the sensible and latent heat flux. The Bowen ratio is derived from DTS measured vertical profiles of the air temperature and wet-bulb temperature. However, in previous research the measured temperatures were not validated, and the cables were not shielded from solar radiation. Additionally, the BR-DTS method has not been tested above a forest before, where temperature gradients are small and energy storage in the air column becomes important. In this paper the accuracy of the wet-bulb and air temperature measurements of the DTS are verified, and the resulting Bowen ratio and heat fluxes are compared to eddy covariance data. The performance of BR-DTS was tested on a 46 m high tower in a mixed forest in the centre of the Netherlands in August 2016. The average tree height is 26 to 30 m, and the temperatures are measured below, in, and above the canopy. Using the vertical temperature profiles the storage of latent and sensible heat in the air column was calculated. We found a significant effect of solar radiation on the temperature measurements, leading to a deviation of up to 3 K. By installing screens, the error caused by sunlight is reduced to under 1 K. Wind speed seems to have a minimal effect on the measured wet-bulb temperature, both below and above the canopy. After a simple quality control, the Bowen ratio measured by DTS correlates well with eddy covariance (EC) estimates (r2 = 0.59). The average energy balance closure between BR-DTS and EC is good, with a mean underestimation of 3.4 W m−2 by the BR-DTS method. However, during daytime the BR-DTS method overestimates the available energy, and during night-time the BR-DTS method estim, Water Resources

Gemeenten en waterschappen roepen mensen op om hun tuinen, daken en stoepen te vergroenen. Beter voor de wateropvang, beter voor de biodiversiteit en goed tegen de hitte. Maar: hoe krijg je iedereen zover?

Vier artikelen over het thema arbeid: 1) 'Water heeft een Freek Vonk nodig': jongeren vinden sector nog steeds niet sexy. 2) Personeelstekort in de watersector: tot 2020 bijna vijfduizend vacatures. 3) De waterprofessional m/v 2.5: een schaap met tien poten. 4) Welke gevolgen heeft 'ZZP-tijdperk' voor de watersector?: 'kennisvlucht vormt afbreukrisico'.

Wat moet de waterprofessional van morgen allemaal kunnen? Veel, zo leert een blik in de toekomst. Heel veel.

Aaf Verkade houdt van water. In haar stad Leiden maakte ze watertuinen. En op een mooie zomerdag dook ze de gracht in. Sindsdien is ze stadssnorkelaar.

Het regent prijzen in 2017. Van individuele onderscheidingen tot awards voor concepten en technieken. De prijzenparade is een staalkaart van de prestaties, betekenis en innovatieve kracht van de Nederlandse watersector. H2O zet ze op een rij en sprak met een aantal winnaars.

In hydrological models evaporation is often still quite uncertain. Potential evaporation is used as input, but the modelling of plant stresses is not always accurate enough to describe the behaviour in reality. In situ measured actual evaporation data is rare, and doing measurements is time consuming and expensive. With the advance of satellite technology, remote sensing products modelling actual evaporation have been developed. To see if models can be easily improved using this actual evaporation data, it will be directly imposed. As remote sensing data product, the LSA SAF actual evaporation product will be used. As input it uses most importantly Meteosat-10 data. As other sources it has ERA-interim and ECOCLIMAP. Accuracy is generally high when comparing it to in situ measurements (R2=0.90 when comparing it to eddy covariance at Cabauw), although a correction factor might be necessary for some locations. Three models were tested, WALRUS, SIMGRO and FLEX. Two sites in the Netherlands were studied (Cabauw and the Hupsel Brook) and two catchments in Spain (Ubierna and Ulzama). WALRUS was applied to the Cabauw Polder and the Hupsel Brook, SIMGRO was applied to Cabauw, and FLEX was used in Spain. SIMGRO did not perform well, and modelled water stress during summers at Cabauw, while in situ measurements showed that water stress was not an issue. The performance was too low for LSA SAF evaporation to make a difference. WALRUS performed well at Cabauw, although there was no difference between the performance of the model when using actual evaporation instead of Makkink evaporation (NS=0.693 and NS=0.673 respectively), as the catchment does not suffer from water stress. In the Hupsel Brook water stress does occur, and the model performs slightly better when using actual evaporation instead of Makkink evaporation (NS=0.762 and NS=0.733 respectively). In Spain the uncertainty of the input data was high, and some corrections were necessary. For the Ubierna catchment, the per, Civil Engineering and Geosciences, Water Management, Hydrology

Mannen kunnen er hun baard laten verzorgen. Wie verdrietig is, kan zich er een troostgedicht laten voorlezen. Je kunt er ook terecht voor een expositie of muziekoptreden. Of binnenkort misschien zelfs voor een overnachting. Nu steeds meer brugwachters naar centrale meldkamers verhuizen, krijgen hun huisjes nieuwe bestemmingen.

Duurzaamheid is wat haar bezighoudt bij drinkwaterbedrijf Oasen. Hoofdtaak van Nicole Zantkuijl is het ontwikkelen van een visie op duurzaamheid, het aanbrengen van samenhang in al bestaande projecten en activiteiten èn het starten van nieuwe projecten...

Corné van der Westen experimenteerde als kind al met een eigen laboratoriumsetje. Voor scheikunde had hij altijd goede cijfers. Hij volgde een beroepsopleiding aan de laboratoriumschool en haalde later zijn bachelor in chemische technologie. Zijn werkzame leven bracht hij bij de Amercentrale door, later switchte hij naar de locatie Moerdijk. "In feite doen wij niets anders dan water rondpompen".

Henk Schobben is verantwoordelijk voor de regionale invulling van het landelijke Deltaprogramma, in samenwerking met alle bij het water betrokken partijen. Deltaprogrammeur heet die functie. "Mijn grote passie is verschillende belangen bij elkaar brengen. Dat is in onze netwerksamenleving de enige manier om iets voor elkaar te krijgen".

Waarom verruilden ze een baan voor het onzekere ondernemerschap? Hoe komen ze aan opdrachten in tijden van crisis? Hoe houden ze hun kennis op peil. Ook de watersector telt steeds meer zelfstandigen (zonder personeel). H2O portretteert er vijf.

Barry Scholten kwam op het idee van de Smart Polder. In de Amerfoortse nieuwbouwwijk Vathorst werd zijn idee werkelijkheid: "In de Smart Polder wordt oppervlaktewater een energiebron. Een oer-Hollandse uitvinding, maar in elke delta, waar ook ter wereld, toepasbaar."

Peter-Jules van Overloop, universitair hoofddocent Operationeel Waterbeheer aan de TU Delft wil ICT in dienst stellen van waterbeheer. Dat kan slim met je smartphone, zoals blijkt uit een praktijkvoorbeeld.

Een waterleidingbedrijf dat kalkkorrels produceert? Dat gebeurt o.a. bij Brabant Water in het waterwingebied Seppe. Olaf van der Kolk is commercieel manager van Reststoffenunie Drinkwaterleidingbedrijven, een samenwerkingsverband binnen drinkwatersector.

Jan van Bruchem (42) is beheerder Grondzaken bij het hoogheemraadschap de Stichtse Rijnlanden. Een nieuwe functie, die hij sinds 1 januari 2012 bekleedt. "Als we bijvoorbeeld een kade of dijk moeten versterken en verbreden is meer grond nodig. Dan ga ik onderhandelen met boeren. Om de grond, die wij willen hebben, te ruilen voor een ander stuk waar zij weer hun voordeel mee kunnen doen. Ik werk bij het waterschap, maar doe in grond." Lachend: "Dat is soms lastig uit te leggen."