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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    Thermal regime, predation danger and the early marine exit of sockeye salmon Oncorhynchus nerka
    Katinic, P.J. ; Patterson, D.A. ; Ydenberg, R.C. - \ 2015
    Journal of Fish Biology 86 (2015)1. - ISSN 0022-1112 - p. 276 - 287.
    british-columbia - atlantic salmon - temperature - water - river - populations - mortality - migration - pacific - energetics
    Marine exit timing of sockeye salmon Oncorhynchus nerka populations on the Haida Gwaii Archipelago, British Columbia, Canada, is described, with specific focus on Copper Creek. Marine exit in Copper Creek occurs¿>¿130¿days prior to spawning, one of the longest adult freshwater residence periods recorded for any O. nerka population. Copper Creek presents an easy upstream migration, with mild water temperatures (7 to 14°¿ C), short distance (13·1¿km) and low elevation gain (41¿m) to the lake where fish hold prior to spawning. An energetic model estimates that
    Sustainable hydraulic engineering through building with nature
    Vriend, H.J. de; Koningsveld, M. van; Aarninkhof, S.G.J. ; Vries, M.B. de; Baptist, M.J. - \ 2015
    Journal of Hydro-environment Research 9 (2015)2. - ISSN 1570-6443 - p. 159 - 171.
    sea-level rise - intertidal habitats - river - protection - wetlands - coastal
    Hydraulic engineering infrastructures are of concern to many people and are likely to interfere with the environment. Moreover, they are supposed to keep on functioning for many years. In times of rapid societal and environmental change this implies that sustainability and adaptability are important attributes. These are central to Building with Nature (BwN), an innovative approach to hydraulic engineering infrastructure development and operation. Starting from the natural system and making use of nature's ecosystem services, BwN attempts to meet society's needs for infrastructural functionality, and to create room for nature development at the same time. By including natural components in infrastructure designs, flexibility, adaptability to changing environmental conditions and extra functionalities and ecosystem services can be achieved, often at lower costs on a life-cycle basis than ‘traditional’ engineering solutions. The paper shows by a number of examples that this requires a different way of thinking, acting and interacting.
    Iron oxidation kinetics and phosphate immobilization along the flow-path from groundwater into surface water
    Grift, B. van der; Rozemeijer, J.C. ; Griffioen, J. ; Velde, Y. van der - \ 2014
    Hydrology and Earth System Sciences 18 (2014)11. - ISSN 1027-5606 - p. 4687 - 4702.
    suspended sediment - ferrous iron - fresh-water - phosphorus limitation - nutrient dynamics - fe(ii) oxidation - arsenic removal - natural-waters - riparian zone - river
    The retention of phosphorus in surface waters through co-precipitation of phosphate with Fe-oxyhydroxides during exfiltration of anaerobic Fe(II) rich groundwater is not well understood. We developed an experimental field set-up to study Fe(II) oxidation and P immobilization along the flow-path from groundwater into surface water in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and surface water, we investigated Fe(II) oxidation kinetics and P immobilization processes. The oxidation rate inferred from our field measurements closely agreed with the general rate law for abiotic oxidation of Fe(II) by O-2. Seasonal changes in climatic conditions affected the Fe(II) oxidation process. Lower pH and lower temperatures in winter (compared to summer) resulted in low Fe oxidation rates. After exfiltration to the surface water, it took a couple of days to more than a week before complete oxidation of Fe(II) is reached. In summer time, Fe oxidation rates were much higher. The Fe concentrations in the exfiltrated groundwater were low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into a ditch. While the Fe oxidation rates reduce drastically from summer to winter, P concentrations remained high in the groundwater and an order of magnitude lower in the surface water throughout the year. This study shows very fast immobilization of dissolved P during the initial stage of the Fe(II) oxidation process which results in P-depleted water before Fe(II) is completely depleted. This cannot be explained by surface complexation of phosphate to freshly formed Fe-oxyhydroxides but indicates the formation of Fe(III)-phosphate precipitates. The formation of Fe(III)-phosphates at redox gradients seems an important geochemical mechanism in the transformation of dissolved phosphate to structural phosphate and, therefore, a major control on the P retention in natural waters that drain anaerobic aquifers.
    Spatial and temporal variation in rainfall erosivity in a Himalayan watershed
    Ma, X. ; Noordwijk, M. van; Xu, J. ; Lu, X. - \ 2014
    Catena 121 (2014). - ISSN 0341-8162 - p. 248 - 259.
    land-cover - r-factor - climate - china - variability - catchment - river
    Global climate change can modify rainfall patterns, leading to more extremes with associated erosion events. Rainfall erosivity, or the R-factor based on the Revised Universal Soil Loss Equation (RUSLE), indicates the potential water erosion risk and it plays an important role in water and soil conservation assessments. However, calculation of the R-factor requires high resolution data series, and thus we present an alternative model that can be used to accurately calculate the R-factor. Our erosivity model uses daily rainfall with advised regression parameters to estimate the R-factor in the watershed, which was selected by comparing the actual R-factor with 10 min high resolution rainfall data and the estimated R-factor with daily rainfall data from 1998 to 2002. The mean annual R-factor map was derived in the study using cokriging. The annual R-factor in the Kejie watershed was classified as medium and medium-strong erosivity, with a mean value of 3264 MJ.mm.ha- 1.h- 1.yr- 1 which represented a range from 2505 to 5538 MJ.mm.ha- 1.h- 1.yr- 1. A simple power relation between annual R-factor and annual rainfall was derived. The long-term change trend analysis showed no significant increasing or decreasing trend observed for the region; however, there was a significant increasing trend observed in two stations in September, one station in March. The annual R-factor with a coefficient of variation of 0.30 indicated inter-annual variation of the R-factor in the watershed was not so apparent. The intra-annual R-factor analysis illustrated the apparent seasonal and monthly distribution, about 65% from the summer season, and the maximum monthly R-factor occurring in July, followed by August and June. Consequently, the adjusted daily model can be applied in this Himalayan mountain area when high-resolution rainfall data is unavailable. The R-factor map and the simple power relation provided a useful tool for land-use planner and agriculture management in the Kejie watershed.
    Improved flow velocity estmates from oving-boat ADCO measurements
    Vermeulen, B. ; Sassi, M.G. ; Hoitink, A.J.F. - \ 2014
    Water Resources Research 50 (2014)5. - ISSN 0043-1397 - p. 4186 - 4196.
    doppler current profiler - suspended sediment - turbulence measurements - acoustic measurement - river - discharge - transport - division - channel - vessel
    Acoustic Doppler current profilers (ADCPs) are the current standard for flow measurements in large-scale open water systems. Existing techniques to process vessel-mounted ADCP data assume homogeneous or linearly changing flow between the acoustic beams. This assumption is likely to fail but is nevertheless widely applied. We introduce a new methodology that abandons the standard assumption of uniform flow in the area between the beams and evaluate the drawbacks of the standard approach. The proposed method strongly reduces the extent over which homogeneity is assumed. The method is applied to two field sites: a mildly curved bend near a junction featuring a typical bend flow and a sharply curved bend that features a more complex sheared flow. In both cases, differences are found between the proposed method and the conventional method. The proposed technique yields different results for secondary flow patterns compared with the conventional method. The velocity components estimated with the conventional method can differ over 0.2 m/s in regions of strong shear. We investigate the number of repeat transects necessary to isolate the mean flow velocity vector from the raw ADCP signal, discarding the influences of noise, positioning and projection errors, and turbulence. Results show that several repeat transects are necessary. The minimum number of repeat measurements needed for robust mean velocity estimates is reduced when applying the proposed method
    Inter-Laboratory trial of a standardized sediment contact test with the aquatic plant myriophyllum aquaticum (ISO 16191)
    Feiler, U. ; Ratte, M. ; Arts, G.H.P. ; Bazin, C. ; Brauer, F. ; Casado, C. - \ 2014
    Environmental Toxicology and Chemistry 33 (2014)3. - ISSN 0730-7268 - p. 662 - 670.
    fresh-water sediments - ecotoxicological assessment - toxicity - quality - assay - variability - river
    A whole-sediment toxicity test with Myriophyllum aquaticum has been developed by the German Federal Institute of Hydrology and standardized within the International Organization for Standardization (ISO; ISO 16191). An international ring-test was performed to evaluate the precision of the test method. Four sediments (artificial, natural) were tested. Test duration was 10 d, and test endpoint was inhibition of growth rate (r) based on fresh weight data. Eighteen of 21 laboratories met the validity criterion of r = 0.09 d(-1) in the control. Results from 4 tests that did not conform to test-performance criteria were excluded from statistical evaluation. The inter-laboratory variability of growth rates (20.6%-25.0%) and inhibition (26.6%-39.9%) was comparable with the variability of other standardized bioassays. The mean test-internal variability of the controls was low (7% [control], 9.7% [solvent control]), yielding a high discriminatory power of the given test design (median minimum detectable differences [MDD] 13% to 15%). To ensure these MDDs, an additional validity criterion of CV = 15% of the growth rate in the controls was recommended. As a positive control, 90 mg 3,5-dichlorophenol/kg sediment dry mass was tested. The range of the expected growth inhibition was proposed to be 35 ± 15%. The ring test results demonstrated the reliability of the ISO 16191 toxicity test and its suitability as a tool to assess the toxicity of sediment and dredged material
    Use, fate and ecological risks of antibiotics applied in tilapia cage farming in Thailand
    Rico, A. ; Oliveira, R. ; McDonough, S. ; Matser, A. ; Khatikarn, J. ; Satapornvanit, K. ; Nogueira, A.J.A. ; Soares, A.M.V.M. ; Domingues, I. ; Brink, P.J. van den - \ 2014
    Environmental Pollution 191 (2014). - ISSN 0269-7491 - p. 8 - 16.
    fluoroquinolone antibiotics - veterinary antibiotics - ubiquitous occurrence - asian aquaculture - sediments - china - water - river - oxytetracycline - tetracyclines
    The use, environmental fate and ecological risks of antibiotics applied in tilapia cage farming were investigated in the Tha Chin and Mun rivers in Thailand. Information on antibiotic use was collected through interviewing 29 farmers, and the concentrations of the most commonly used antibiotics, oxytetracycline (OTC) and enrofloxacin (ENR), were monitored in river water and sediment samples. Moreover, we assessed the toxicity of OTC and ENR on tropical freshwater invertebrates and performed a risk assessment for aquatic ecosystems. All interviewed tilapia farmers reported to routinely use antibiotics. Peak water concentrations for OTC and ENR were 49 and 1.6 µg/L, respectively. Antibiotics were most frequently detected in sediments with concentrations up to 6908 µg/kg d.w. for OTC, and 2339 µg/kg d.w. for ENR. The results of this study indicate insignificant short-term risks for primary producers and invertebrates, but suggest that the studied aquaculture farms constitute an important source of antibiotic pollution.
    Evaluation of solid polymeric organic materials for use in bioreactive sediment capping to stimulate the degradation of chlorinated aliphatic hydrocarbons
    Atashgahi, S. ; Maphosa, F. ; Vrieze, J. de; Haest, P.J. ; Boon, N. ; Smidt, H. ; Springael, D. ; Dejonghe, W. - \ 2014
    Applied Microbiology and Biotechnology 98 (2014)5. - ISSN 0175-7598 - p. 2255 - 2266.
    reductive dechlorination - trichloroethylene tce - natural attenuation - groundwater plume - vinyl-chloride - hydrogen - tetrachloroethene - river - contaminants - communities
    In situ bioreactive capping is a promising technology for mitigation of surface water contamination by discharging polluted groundwater. Organohalide respiration (OHR) of chlorinated ethenes in bioreactive caps can be stimulated through incorporation of solid polymeric organic materials (SPOMs) that provide a sustainable electron source for organohalide respiring bacteria. In this study, wood chips, hay, straw, tree bark and shrimp waste, were assessed for their long term applicability as an electron donor for OHR of cis-dichloroethene (cDCE) and vinyl chloride (VC) in sediment microcosms. The initial release of fermentation products, such as acetate, propionate and butyrate led to the onset of extensive methane production especially in microcosms amended with shrimp waste, straw and hay, while no considerable stimulation of VC dechlorination was obtained in any of the SPOM amended microcosms. However, in the longer term, short chain fatty acids accumulation decreased as well as methanogenesis, whereas high dechlorination rates of VC and cDCE were established with concomitant increase of Dehalococcoides mccartyi and vcrA and bvcA gene numbers both in the sediment and on the SPOMs. A numeric simulation indicated that a capping layer of 40 cm with hay, straw, tree bark or shrimp waste is suffice to reduce the groundwater VC concentration below the threshold level of 5 µg/l before discharging into the Zenne River, Belgium. Of all SPOMs, the persistent colonization of tree bark by D. mccartyi combined with the lowest stimulation of methanogenesis singled out tree bark as a long-term electron donor for OHR of cDCE/VC in bioreactive caps
    Influence of climate variables on the concentration of Escherichia coli in the Rhine, Meuse, and Drentse Aa during 1985–2010
    Vermeulen, L.C. ; Hofstra, N. - \ 2014
    Regional Environmental Change 14 (2014)1. - ISSN 1436-3798 - p. 307 - 319.
    fecal-indicator concentrations - land-use change - water-quality - air-temperature - risk-assessment - e. coil - disease - survival - river - cryptosporidium
    This study evaluates the relationship between the climate variables temperature and precipitation and the concentration of Escherichia coli bacteria in the Rhine, Meuse, and Drentse Aa for the period 1985–2010. Data from 4,679 E. coli concentration measurements spread over a total of 13 locations in these three river systems were used in this study. The variables water temperature, precipitation, and river discharge were correlated with E. coli measurements. Water temperature was found to correlate negatively, and this is in line with expectations that higher temperature increases microorganism die-off. Precipitation and discharge were found to correlate positively, and this is in line with expectations that runoff from agricultural lands brings along pathogens from manure and increases the chance of sewer overflows. The data of the Meuse were fit to a linear model that explained E. coli concentrations from a time component, the climate variables and a locations dummy variable, in order to assess the relative contribution of the different variables. This model had an R2 of 0.49, meaning that climate variables and location can account for nearly half of the observed variation in E. coli concentrations in surface water, even when other factors, such as land-use variables, are not taken into account. The effect of the different climate variables was found to differ with scale, with temperature being relatively important at a local scale, and discharge being mainly of importance at larger scales. From our results, we expect that climate change, mainly the projected increased precipitation, may increase E. coli concentrations overall. Other waterborne pathogens that follow similar transmission pathways as E. coli may be similarly impacted by climate change
    Tipping from the Holocene to the Anthropocene: How threatened are major world deltas?
    Renaud, F.G. ; Syvitski, J.P.M. ; Werners, S.E. ; Kremer, H. ; Kuenzer, C. ; Ramesh, R. ; Jeuken, A. - \ 2013
    Current Opinion in Environmental Sustainability 5 (2013)6. - ISSN 1877-3435 - p. 644 - 654.
    social-ecological systems - sea-level rise - climate-change - mississippi delta - northern india - river - thresholds - discharge - sediment - impact
    Coastal deltas are landforms that typically offer a wide variety of benefits to society including highly fertile soils for agricultural development, freshwater resources, and rich biodiversity. For these reasons, many deltas are densely populated, are important economic hubs, and have been transformed by human interventions such as agricultural intensification, modification of water and sediment fluxes, as well as urbanization and industrialization. Additionally, deltas are increasingly affected by the consequences of climate change including sea level rise, and by other natural hazards such as cyclones and storm surges. Five examples of major deltas (Rhine-Meuse, Ganges, Indus, Mekong, and Danube) illustrate the force of human interventions in shaping and transforming deltas and in inducing shifts between four different social-ecological system (SES) states: Holocene, modified Holocene, Anthropocene and ‘collapsed’. The three Asian deltas are rapidly changing but whereas SES in the Ganges and Indus deltas are in danger of tipping into a ‘collapsed’ state, SES in the Mekong delta, which is at the crossroads of various development pathways, could increase in resilience in the future. The Rhine-Meuse and Danube delta examples show that highly managed states may allow, under specific conditions, for interventions leading to increasingly resilient systems. However, little is known about the long-term effects of rapid human interventions in deltas. It is therefore critical to increase the knowledge-base related to SES dynamics and to better characterize social tipping points or turning points in order to avoid unacceptable changes.
    Making the distinction between water scarcity and drought using an observation-modeling framework
    Loon, A.F. van; Lanen, H.A.J. van - \ 2013
    Water Resources Research 49 (2013)3. - ISSN 0043-1397 - p. 1483 - 1502.
    decision-support-system - climate-change - hydrological drought - resource-management - central spain - runoff model - forcing data - groundwater - river - basin
    Drought and water scarcity are keywords for river basin management in water-stressed regions. “Drought” is a natural hazard, caused by large-scale climatic variability, and cannot be prevented by local water management. “Water scarcity” refers to the long-term unsustainable use of water resources, which water managers can influence. Making the distinction between drought and water scarcity is not trivial, because they often occur simultaneously. In this paper, we propose an observation-modeling framework to separate natural (drought) and human (water scarcity) effects on the hydrological system. The basis of the framework is simulation of the situation that would have occurred without human influence, the “naturalized” situation, using a hydrological model. The resulting time series of naturalized state variables and fluxes are then compared to observed time series. As second, more important and novel step, anomalies (i.e., deviations from a threshold) are determined from both time series and compared. We demonstrate the use of the proposed observation-modeling framework in the Upper-Guadiana catchment in Spain. Application of the framework to the period 1980–2000 shows that the impact of groundwater abstraction on the hydrological system was, on average, four times as high as the impact of drought. Water scarcity resulted in disappearance of the winter high-flow period, even in relatively wet years, and a nonlinear response of groundwater. The proposed observation-modeling framework helps water managers in water-stressed regions to quantify the relative impact of drought and water scarcity on a transient basis and, consequently, to make decisions regarding adaptation to drought and combating water scarcity.
    Changing monsoon patterns, snow and glacial melt, its impacts and adaptation options in northern India: Setting the stage
    Moors, E.J. ; Stoffel, M. - \ 2013
    Science of the Total Environment 468-469 (2013)Suppl.. - ISSN 0048-9697 - p. S1 - S3.
    climate-change - water - river - state - asia - dam
    To set the stage of this special issue this paper gives a short introduction to the sensitivity to climate change of the main bio-physical processes in the Hindukush–Karakoram–Himalayas. It also describes the socio-economic setting of the Ganges basin in northern India as the main focal point of the impact and adaptation studies in this special issue.
    Probabilistic analysis of hydrological drought characteristics using meteorological drought
    Wong, G. ; Lanen, H.A.J. van; Torfs, P.J.J.F. - \ 2013
    Hydrological Sciences Journal 58 (2013)2. - ISSN 0262-6667 - p. 253 - 270.
    frequency-analysis - streamflow droughts - severity - copulas - duration - europe - river - propagation - groundwater - risk
    Droughts are an inevitable consequence of climate variability and are pervasive across many regions. Their effects can vary on an extensive scale, depending on the type of drought and people’s vulnerability. Crucial characteristics of both hydrological (groundwater, streamflow) and meteorological (precipitation) droughts are related to their durations and severities, and these characteristics are typically correlated. While many studies have addressed the dependencies between these characteristics for either the meteorological or hydrological drought, the cross-dependence between meteorological and hydrological drought characteristics is barely investigated. The development of meteorological drought characteristics to hydrological drought characteristics is often hard to model and their connection is not definitively established. In order to better understand and explain this relationship, this study seeks to apply statistical tools and models. Drought characteristics data from areas in Europe with different climates are analysed. Two approaches of identifying related meteorological and hydrological drought are explored and compared. Classical linear correlation techniques do not provide promising results, indicating that any statistic of a hydrological drought is not a straightforward function of a preceding meteorological drought. Subsequently, the application of the concept of copulas to explore this dependence between meteorological and hydrological drought characteristics is investigated. The more comprehensive approach of copulas shows that the meteorological drought contains probability information of the successive hydrological drought.
    Daily reference evapotranspiration modeling by using genetic programming approach in the Basque Country (Northern Spain)
    Shiri, J. ; Kisi, O. ; Landeras, G. ; Lopez, J.J. ; Nazemi, A.H. ; Stuyt, L.C.P.M. - \ 2012
    Journal of Hydrology 414-415 (2012). - ISSN 0022-1694 - p. 302 - 316.
    daily pan evaporation - artificial neural-networks - fuzzy inference system - computing technique - climatic data - intelligence - prediction - parameters - anfis - river
    Evapotranspiration, as a major component of the hydrological cycle, is of importance for water resources management and development, as well as for estimating the water budget of irrigation schemes. This study presents a Gene Expression Programming (GEP) approach, for estimating daily reference evapotranspiration (ET0) in four weather stations in Basque Country (Northern Spain), for a 5-year period (1999-2003). The data set comprising air temperature, relative humidity, wind speed and solar radiation was employed for modeling ET0 using FAO-56 Penman Monteith equation as the reference. The GEP results were compared with the Adaptive Neuro-Fuzzy Inference System (ANFIS), Priestley-Taylor and Hargreaves-Samani models. Based on the comparisons, the GEP was found to perform better than the ANFIS, Priestley-Taylor and Hargreaves-Samani models. The ANFIS model is ranked as the second best model.
    Mount Kenya volcanic activity and the Late Cenozoic landscape reorganisation in the upper Tana fluvial system
    Veldkamp, A. ; Schoorl, J.M. ; Wijbrans, J.R. ; Claessens, L.F.G. - \ 2012
    Geomorphology 145-146 (2012). - ISSN 0169-555X - p. 19 - 31.
    african climate-change - western turkey - sediment yield - gregory rift - debris flows - east-africa - pleistocene - evolution - river - uplift
    Volcanic–fluvial landscape interaction of the late Cenozoic Mt Kenya region in the upper Tana catchment has been reconstructed. The oldest newly dated phonolite flow is 5.78 Ma (40Ar/39Ar), placing the initiation of Mt Kenya volcanic activity within the Late Miocene, much earlier than reported before, 3–3.5 Ma (K/Ar). The main body of the stratovolcano was already in existence around 4.22–5.27 Ma (40Ar/39Ar) supplying lahars to its lower footslopes. The final recorded volcanic main vent phase in the study area produced multiple phonolitic flows and lahars around 2.8 Ma (40Ar/39Ar). There is evidence of at least two major Pliocene drainage blocking events between 3.89 and 2.81 Ma (40Ar/39Ar) causing lava dammed lakes in which volcanic tuff deposits accumulated. Around this time the river Tana did not incise much and shaped an extensive fluvial plain, whose remnants can now be found around 1150 m altitude. This fluvial plain has been incising during the last 2.8 Ma, whereby the incision rate changed in time due to changing uplift rate and volcanic events. A flood basalt eruption covering 1150 km2, estimated to be 5 km3, on the south flank of Mt Kenya of the Thiba basalts at 0.80 Ma (40Ar/39Ar) plugged the Upper Tana basin and caused significant drainage reorganisation. The Tana was diverted southwards abandoning its former valley. The terrace record in the Tana valley downstream the Thiba basalts appears to register this event as a post 0.8 Ma accelerated incision. Current Thiba valley morphology is relatively young and appears to register uplift controlled terraces with interbedded lahars for the last 300 ka only, indicating a delayed fluvial response of approximately 0.5 Ma. The landscape reconstruction demonstrates that the Tana was well able to compensate for many volcanic events such as lahars and lava flows. Only the build-up of a stratovolcano body and a large flood basalt caused prolonged impact on fluvial landscape development
    Preliminary results of a finite-element, multi-scale model of the Mahakam Delta (Indonesia)
    Brye, B. de; Schellen, S. ; Sassi, M.G. ; Vermeulen, B. ; Karna, T. ; Deleersnijder, E. ; Hoitink, A.J.F. - \ 2011
    Ocean Dynamics 61 (2011)8. - ISSN 1616-7341 - p. 1107 - 1120.
    mesh generation - makassar strait - circulation - estuary - ocean - river - rofi - sea
    The Mahakam is a 980-km-long tropical river flowing in the East Kalimantan province (Borneo Island, Indonesia). A significant fraction of this river is influenced by tides, the modelling of which is the main subject of this study. Various physical and numerical issues must be addressed. In the upstream part of the domain, the river flows through a region of three lakes surrounded by peat swamps. In the lowland regions, the river is meandering and its hydrodynamics is mostly influenced by tides. The latter propagate upstream of the delta, in the main river and its tributaries. Finally, the mouth of the Mahakam is a delta exhibiting a high number of channels connected to the Makassar Strait. This article focusses on the flow in the delta channels, which is characterised by a wide range of time and space scales. To capture most of them, the depth-integrated and the section-integrated versions of the unstructured mesh, finite-element model Second-Generation Louvain-la-Neuve Ice-Ocean Model are used. Unstructured grids allow for a refinement of the mesh in the narrowest channels and also an extension of the domain upstream and downstream of the delta in order to prescribe the open-boundary conditions. The Makassar Strait, the Mahakam Delta and the three lakes are modelled with 2D elements. The rivers, from the upstream limit of the delta to the lakes and the upstream limit of the domain, are modelled in 1D. The calibration of the tidal elevation simulated in the Mahakam Delta is presented. Preliminary results on the division of the Eulerian residual discharge through the channels of the delta are also presented. Finally, as a first-order description of the long-term transport, the age of the water originating from the upstream limit of the delta is computed. It is seen that for May and June 2008, the time taken by the water parcel to cross the estuary varies from 4 to 7 days depending on the channel under consideration.
    Watch: Current knowledge of the terrestrial Global Water Cycle"
    Harding, R. ; Best, M. ; Hagemann, S. ; Kabat, P. ; Tallaksen, L.M. ; Warnaars, T. ; Wiberg, D. ; Weedon, G.P. ; Lanen, H.A.J. van; Ludwig, F. ; Haddeland, I. - \ 2011
    Journal of Hydrometeorology 12 (2011)6. - ISSN 1525-755X - p. 1149 - 1156.
    climate-change projections - rainfall-runoff model - river - precipitation - trends - requirements - availability - streamflow - dataset - surface
    Water-related impacts are among the most important consequences of increasing greenhouse gas concentrations. Changes in the global water cycle will also impact the carbon and nutrient cycles and vegetation patterns. There is already some evidence of increasing severity of floods and droughts and increasing water scarcity linked to increasing greenhouse gases. So far, however, the most important impacts on water resources are the direct interventions by humans, such as dams, water extractions, and river channel modifications. The Water and Global Change (WATCH) project is a major international initiative to bring together climate and water scientists to better understand the current and future water cycle. This paper summarizes the underlying motivation for the WATCH project and the major results from a series of papers published or soon to be published in the Journal of Hydrometeorology WATCH special collection. At its core is the Water Model Intercomparison Project (WaterMIP), which brings together a wide range of global hydrological and land surface models run with consistent driving data. It is clear that we still have considerable uncertainties in the future climate drivers and in how the river systems will respond to these changes. There is a grand challenge to the hydrological and climate communities to both reduce these uncertainties and communicate them to a wider society
    Opportunities and Constraints for Climate Adaptation in Regional Water and Land Use Planning
    Werners, S.E. ; West, J. ; Leemans, R. ; Tabara, J.D. ; Dai, X. ; Flachner, Z. ; Neufeldt, H. ; McEvoy, D. ; Cots, F. ; Trombi, G. - \ 2011
    In: The Economic, Social and Political Elements of Climate Change / Leal Filho, W., Berlin : Springer Verlag - ISBN 9783642147753 - p. 669 - 692.
    inner-mongolia - resilience - management - science - river - china
    Whereas the literature on adaptation is rich in detail on the impacts of, vulnerability to, and constraints of climate adaptation, less is known about the conditions that facilitate adaptation in practice. We examined the constraints and opportunities for adaptation in water and land use planning in three regions: the Guadiana River Basin in Spain and Portugal, the Tisza River Basin in Hungary and western Inner Mongolia in China. We analysed the conditions that either facilitate or constrain adaptation in relation to (1) adaptation actors, (2) adaptation strategies, and (3) adaptation objectives. Many adaptation assessments concentrate on climate impacts and the potential of adaptation strategies. The conditions that enable people to act on adaptation are less studied. Yet these have been identified as particularly important for successfully implementing adaptation. We find that adaptation is enhanced by pilot projects that test and debate new ideas through collaboration between recognized actors from civil society, policy, and science. Promising for adaptation is the integration of (traditional) agro-environmental land use systems that regulate regional climate impacts with new technologies, organizational responsibilities and financial instruments. A key challenge is to create flexible and equitable financial instruments that facilitate benefit and burden sharing, social learning, and that support a diverse set of potentially better adapted new activities rather than compensate for climate impacts on existing activities
    Applicability of adapted reservoir operation for water stress mitigation under dry year conditions
    Olsson, O. ; Ikramova, M. ; Bauer, M. ; Froebrich, J. - \ 2010
    Water Resources Management 24 (2010)2. - ISSN 0920-4741 - p. 277 - 297.
    quality - system - management - quantity - river
    This paper introduces the conjunctive use of a deterministic water quality model and water balance criteria for supporting the assessment of simulation and to evaluate the effectiveness of proposed operation strategies. By this, the applicability of enhanced reservoir operation strategies addressing both water quality as well as water quantity aspects under water deficit conditions in dry years can be shown. Arguments will be developed to address stakeholders and decision makers in the context of a more conservative past operation regime. Results are presented for the Kaparas reservoir, which is located in the lower Amu Darya River, on the border of Turkmenistan and Uzbekistan. As being one out of four large reservoirs of the Tuyamuyun Hydro Complex (THC), the Kaparas reservoir could be increasingly used for drinking water supply for the lower Amu Darya region. The results for the dry year 2001 indicates that the combination of simulation together with practical assessment criteria confirm the applicability of adapted operation rules for THC reservoirs and ways can be found to supply the local population (of the lower Amu Darya region) with more potable water of higher quality even subject to a parallel reduction of water deficits. Future aggravation of water stress due to increasing population growth and water quality deterioration will require a more comprehensive consideration of water quality aspects in many arid and semi arid regions. The experience gained during this study emphasizes the fact that classical deterministic water quality models provide effective tools to address even more complex water quality problems under water stressed conditions, provided processing of results is performed, to support the decision making process.
    Abundance, distribution, and population trends of hippopotamus in Gonarezhou National Park, Zimbabwe
    Zisadza, P. ; Gandiwa, E. ; Westhuizen, H. van der; Westhuizen, E. van der; Bodzo, V. - \ 2010
    South African Journal of Wildlife Research 40 (2010)2. - ISSN 0379-4369 - p. 149 - 157.
    amphibius - behavior - zambia - river
    To understand the abundance, distribution, and population trends of the common hippopotamus (Hippopotamus amphibius) in the Gonarezhou National Park (GNP), Zimbabwe, we (i) carried out an aerial survey along sections of major perennial rivers, namely Runde, Save and Mwenezi and other inland water pans, and (ii) analysed the long-term aerial survey data (1965–2008). For the aerial survey, a Piper PA-18 Super Cub aircraft was flown once along each of the three major rivers and associated pans in November 2008. We recorded a total of 187 hippos and 19 groups in the GNP. All sightings were in Runde River, Tambohata Pan and Massasanya Dam (density = 2.4 hippos/km). We found three trends in hippo populations in the GNP for the period 1965–2008. First, the period 1965–1982 was characterized by a significant increase in the hippo population (simple linear regression: loge[hippo population estimate] = 0.05[year] - 89.01; F1,13 = 56.26, P <0.001, R2 = 0.81; average annual exponential rate of increase [r] = 0.05, 95% confidence interval [CI] for r = 0.03–0.06); second, the period 1983–1997 was characterized by a significant hippo population decline (simple linear regression: loge[hippo population estimate] = 355.87–0.18[year]; F1,10 = 10.44, P <0.001, R2 = 0.51; r = -0.18, 95% CI for r = -0.30 to -0.05) and thirdly, r between two survey counts in 1997 and 2008 was 0.06. We attributed the overall decline in hippo abundance, the disappearance of the hippos in the Mwenezi River, and their huge decline in the Save River in the GNP primarily to past droughts, siltation and persecution in adjacent communal areas. We recommend collaborative efforts by the relevant authorities to ensure a continuous flow of water in the Mwenezi River. This will allow for the maintenance of hippo habitats downstream of the Manyuchi Dam, thus creating conducive environment for the re-establishment of the hippos in the Mwenezi River section in GNP. We also recommend that GNP's management should continue to monitor the hippo population and distribution in the park's major rivers and natural pans.
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