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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Propagation of tides along a river with a sloping bed
Kästner, K. ; Hoitink, A.J.F. ; Torfs, P.J.J.F. ; Deleersnijder, E. ; Ningsih, N.S. - \ 2019
Journal of Fluid Mechanics 872 (2019). - ISSN 0022-1120 - p. 39 - 73.
river dynamics - shallow water flows - topographic effects

Conceptually, tidal rivers are seen as narrow channels along which the cross-section geometry remains constant and the bed is horizontal. As tidal waves propagate along such a channel, they decrease exponentially in height. The more rapid the decrease, the stronger the river flow. Near the coast, the tidally averaged width and depth change little throughout the year, even if the river discharge varies strongly between the seasons. However, further upstream, the water depth varies considerably with the river discharge. Recent observations from the Kapuas River, Indonesia, show that the water surface forms a backwater profile when the river flow is low. In this case, the depth converges, i.e. it gradually decreases between the river mouth and the point where the bed reaches sea level. This effect distinctly influences how tidal waves propagate up river so that their wave height does not decrease exponentially any more. We present a theoretical analysis of this phenomenon, which reveals several so far overlooked aspects of river tides. These aspects are particularly relevant to low river flow. Along the downstream part of the tidal river, depth convergence counteracts frictional damping so that the tidal range is higher than expected. Along the upstream parts of the tidal river, the low depth increases the damping so that the tide more rapidly attenuates. The point where the bed reaches sea level effectively limits the tidal intrusion, which carries over to the overtide and the subtidal water level set-up.

Prerequisites for Accurate Monitoring of River Discharge Based on Fixed-Location Velocity Measurements
Kästner, K. ; Hoitink, A.J.F. ; Torfs, P.J.J.F. ; Vermeulen, B. ; Ningsih, N.S. ; Pramulya, M. - \ 2018
Water Resources Research 54 (2018)2. - ISSN 0043-1397 - p. 1058 - 1076.
discharge - index velocity - Indonesia - Kapuas River - rating curve - velocity profile
River discharge has to be monitored reliably for effective water management. As river discharge cannot be measured directly, it is usually inferred from the water level. This practice is unreliable at places where the relation between water level and flow velocity is ambiguous. In such a case, the continuous measurement of the flow velocity can improve the discharge prediction. The emergence of horizontal acoustic Doppler current profilers (HADCPs) has made it possible to continuously measure the flow velocity. However, the profiling range of HADCPs is limited, so that a single instrument can only partially cover a wide cross section. The total discharge still has to be determined with a model. While the limitations of rating curves are well understood, there is not yet a comprehensive theory to assess the accuracy of discharge predicted from velocity measurements. Such a theory is necessary to discriminate which factors influence the measurements, and to improve instrument deployment as well as discharge prediction. This paper presents a generic method to assess the uncertainty of discharge predicted from range-limited velocity profiles. The theory shows that a major source of error is the variation of the ratio between the local and cross-section-averaged velocity. This variation is large near the banks, where HADCPs are usually deployed and can limit the advantage gained from the velocity measurement. We apply our theory at two gauging stations situated in the Kapuas River, Indonesia. We find that at one of the two stations the index velocity does not outperform a simple rating curve.
Hydrology of inland tropical lowlands : The Kapuas and Mahakam wetlands
Hidayat, Hidayat ; Teuling, Ryan ; Vermeulen, Bart ; Muh, Taufik ; Kastner, Karl ; Geertsema, Tjitske J. ; Bol, Dinja C.C. ; Hoekman, Dirk H. ; Sri Haryani, Gadis ; Lanen, Henny A.J. van; Delinom, Robert M. ; Dijksma, Roel ; Anshari, Gusti Z. ; Ningsih, Nining S. ; Uijlenhoet, Remko ; Hoitink, Ton - \ 2017
Hydrology and Earth System Sciences 21 (2017)5. - ISSN 1027-5606 - p. 2579 - 2594.

Wetlands are important reservoirs of water, carbon and biodiversity. They are typical landscapes of lowland regions that have high potential for water retention. However, the hydrology of these wetlands in tropical regions is often studied in isolation from the processes taking place at the catchment scale. Our main objective is to study the hydrological dynamics of one of the largest tropical rainforest regions on an island using a combination of satellite remote sensing and novel observations from dedicated field campaigns. This contribution offers a comprehensive analysis of the hydrological dynamics of two neighbouring poorly gauged tropical basins; the Kapuas basin (98g700gkm2) in West Kalimantan and the Mahakam basin (77g100gkm2) in East Kalimantan, Indonesia. Both basins are characterised by vast areas of inland lowlands. Hereby, we put specific emphasis on key hydrological variables and indicators such as discharge and flood extent. The hydroclimatological data described herein were obtained during fieldwork campaigns carried out in the Kapuas over the period 2013-2015 and in the Mahakam over the period 2008-2010. Additionally, we used the Tropical Rainfall Measuring Mission (TRMM) rainfall estimates over the period 1998-2015 to analyse the distribution of rainfall and the influence of El-Niño - Southern Oscillation. Flood occurrence maps were obtained from the analysis of the Phase Array type L-band Synthetic Aperture Radar (PALSAR) images from 2007 to 2010. Drought events were derived from time series of simulated groundwater recharge using time series of TRMM rainfall estimates, potential evapotranspiration estimates and the threshold level approach. The Kapuas and the Mahakam lake regions are vast reservoirs of water of about 1000 and 1500gkm2 that can store as much as 3 and 6.5 billiongm3 of water, respectively. These storage capacity values can be doubled considering the area of flooding under vegetation cover. Discharge time series show that backwater effects are highly influential in the wetland regions, which can be partly explained by inundation dynamics shown by flood occurrence maps obtained from PALSAR images. In contrast to their nature as wetlands, both lowland areas have frequent periods with low soil moisture conditions and low groundwater recharge. The Mahakam wetland area regularly exhibits low groundwater recharge, which may lead to prolonged drought events that can last up to 13 months. It appears that the Mahakam lowland is more vulnerable to hydrological drought, leading to more frequent fire occurrences than in the Kapuas basin.

Distributary channels in the fluvial to tidal transition zone
Kästner, K. ; Hoitink, A.J.F. ; Vermeulen, B. ; Geertsema, T.J. ; Ningsih, N.S. - \ 2017
Journal of Geophysical Research: Earth Surface 122 (2017)3. - ISSN 2169-9003 - p. 696 - 710.
Delta - Distributary - Grain size - Hydraulic geometry - Kapuas River - River
Coastal lowland plains under mixed fluvial-tidal influence may form complex, composite channel networks, where distributaries blend the characteristics of mouth bar channels, avulsion channels, and tidal creeks. The Kapuas coastal plain exemplifies such a coastal plain, where several narrow distributaries branch off the Kapuas River at highly asymmetric bifurcations. A comprehensive geomorphological analysis shows that trends in the channel geometry of all Kapuas distributaries are similar. They consist of a short, converging reach near the sea and a nonconverging reach upstream. The two parts are separated by a clear break in scaling of geometrical properties. Such a break in scaling was previously established in the Mahakam Delta, which suggests that this may be a general characteristic in the fluvial to tidal transition zone. In contrast to the geometrical trend similarities, a clear difference in bed material between the main and side distributaries is found. In the main distributary, a continuous trend of downstream fining is established, similar to what is often found in lowland rivers. In the side distributaries, bed material coarsens in the downstream direction. This indicates an undersupply of sediment to the side distributaries, which may contribute to their long-term stability as established from historical maps. Tides may be the main agent preventing fine sediment to settle, promoting residual transport of fine material to the coastal ocean.
Aboveground carbon stocks in oil palm plantations and the threshold for carbon-neutral vegetation conversion on mineral soils
Khasanah, N. ; Noordwijk, M. van; Ningsih, H. - \ 2015
Cogent Environmental Science 1 (2015). - ISSN 2331-1843 - 18 p.
The carbon (C) footprint of palm oil production is needed to judge emissions from potential biofuel use. Relevance includes wider sustainable palm oil debates. Within life cycle analysis, aboveground C debt is incurred if the vegetation replaced had a higher C stock than oil palm plantations. Our study included 25 plantations across Indonesia, in a stratified study design representing the range of conditions in which oil palm is grown. From allometric equations for palm biomass and observed growth rates, we estimated the time-averaged aboveground C stock for 25-year rotation and 95%-confidence interval to be 42.07 (42.04–42.10) Mg C ha−1 for plantations managed by company on mineral soils, 40.03 (39.75–40.30) Mg C ha−1 for plantations managed by company on peat, and 37.76 (37.42–38.09) Mg C ha−1 for smallholder oil palm on mineral soils. Oil palm can be established C debt-free on mineral soils with aboveground C stocks below these values; neutrality of mineral soil C pools was documented in a parallel study. Acknowledging variation in shoot:root ratios, the types of vegetation that can be converted debt-free to oil palm include grasslands and shrub, but not monocultural rubber plantations, rubber agroforest, and similar secondary or logged-over forests of higher C stock.
Klaver, D.C. ; Kusters, C.S.L. ; Pradhan, M. ; Vigh, M. ; Groot Bruinderink, M. ; Rossum, I. van; Böhnke, L. ; Wallaart, K. ; Malamas, S. ; Berkhout, E. ; Ni Wayan Suriasatini, ; Sikoki, B. ; Ginting, M.B. ; Mulia, M. ; Ningsih, K. ; Pujiastuti, S. ; Dwi Andari, B. ; Suprobo, N. ; Priyahita, W. ; Sihombing, R.R. ; Rokhmatulloh, S.W. ; Rosita, I. ; Wieriks, M. ; Smidt, H. ; Nugroho, K. ; Prasetyo, K. ; Larastiti, C. ; Amir, S. ; Sutikno, - \ 2015
Wageningen : Centre for Development Innovation, Wageningen UR (CDI rapporten )
This report on Indonesia is one of a series of evaluation reports, consisting of ten reports in total, reflecting the results of the jointly-organised MFS II evaluation: - eight country reports (India, Bangladesh, Ethiopia, Uganda, Indonesia, DR Congo, Liberia, Pakistan); - a synthesis report (covering the eight country studies); and - a report with the results of the international lobbying and advocacy programmes. This series of reports assessed the 2011-2015 contribution of the Dutch Co-Financing System (MFS II) towards achieving the Millennium Development Goals, strengthening international civil society, setting the international agenda and changing decision-makers’ policy and practice, with the ultimate goal of reducing structural poverty. On July 2nd, 2015, the reports were approved by the independent steering committee (see below), which concluded that they meet the quality standards of validity, reliability and usefulness set by the Ministry of Foreign Affairs.
Carbon neutral? No change in mineral soil carbon stock under oil palm plantations derived from forest or non-forest in Indonesia
Khasanah, N. ; Noordwijk, M. van; Ningsih, H. ; Rahayu, S. - \ 2015
Agriculture, Ecosystems and Environment 211 (2015). - ISSN 0167-8809 - p. 195 - 206.
Sustainability criteria for palm oil production guide new planting toward non-forest land cover on mineral soil, avoiding carbon debts caused by forest and peat conversion. Effects on soil carbon stock (soil Cstock) of land use change trajectories from forest and non-forest to oil palm on mineral soils include initial decline and subsequent recovery, however modeling efforts and life-cycle accounting are constrained by lack of comprehensive data sets; only few case studies underpin current debate. We analyzed soil Cstock (Mgha-1), soil bulk density (BD, gcm-3) and soil organic carbon concentration (Corg, %) from 155 plots in 20 oil palm plantations across the major production areas of Indonesia, identifying trends during a production cycle on 6 plantations with sufficient spread in plot age. Plots were sampled in four management zones: weeded circle (WC), interrow (IR), frond stacks (FS), and harvest paths (HP); three depth intervals 0-5, 5-15 and 15-30cm were sampled in each zone. Compared to the initial condition, increases in Corg (16.2%) and reduction in BD (8.9%) in the FS zone, was compensated by decrease in Corg (21.4%) and increase in BD (6.6%) in the HP zone, with intermediate results elsewhere. For a weighted average of the four management zones and after correction for equal mineral soil basis, the net temporal trend in soil Cstock in the top 30cm of soil across all data was not significantly different from zero in both forest- and non-forest-derived oil palm plantations. Individual plantations experienced net decline, net increase or U-shaped trajectories. The 2% difference in mean soil Cstock in forest and non-forest derived oil palm plantations was statistically significant (p
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