Exploring pathways for sustainable water management in river deltas in a changing environment

Exploring adaptation pathways into an uncertain future can support decisionmaking in achieving sustainable water management in a changing environment. Our objective is to develop and test a method to identify such pathways by including dynamics from natural variability and the interaction between the water system and society. Present planning studies on long-term water management often use a few plausible futures for one or two projection years, ignoring the dynamic aspect of adaptation through the interaction between the water system and society. Our approach is to explore pathways using multiple realisations of transient scenarios with an Integrated Assessment Meta Model (IAMM). This paper presents the first application of the method using a hypothetical case study. The case study shows how to explore and evaluate adaptation pathways. With the pathways it is possible to identify opportunities, threats, timing and sequence of policy options, which can be used by policymakers to develop water management roadmaps into the future. By including the dynamics between the water system and society, the influence of uncertainties in both systems becomes clearer. The results show, among others, that climate variability rather than climate change appears to be important for taking decisions in water management

Effect analysis of transient scenarios for successful water management strategies

Recent scenario studies on water management focus on one or two projection years and the effects on the water system and functions. The future is however more complex and dynamic. Therefore, we analyse transient scenarios in order to evaluate the performance of water management strategies. Current available simulation tools are not suitable for this purpose. Therefore, we have developed and used a tool to simulate 50-100 year long time series and that is good and fast enough to simulate the effects of these scenarios and strategies on the water system and the interaction with the human system. We present the first step by means of a case study

Flexible Invariants Through Semantic Collaboration

Modular reasoning about class invariants is challenging in the presence of dependencies among collaborating objects that need to maintain global consistency. This paper presents semantic collaboration: a novel methodology to specify and reason about class invariants of sequential object-oriented programs, which models dependencies between collaborating objects by semantic means. Combined with a simple ownership mechanism and useful default schemes, semantic collaboration achieves the flexibility necessary to reason about complicated inter-object dependencies but requires limited annotation burden when applied to standard specification patterns. The methodology is implemented in AutoProof, our program verifier for the Eiffel programming language (but it is applicable to any language supporting some form of representation invariants). An evaluation on several challenge problems proposed in the literature demonstrates that it can handle a variety of idiomatic collaboration patterns, and is more widely applicable than the existing invariant methodologies.Comment: 22 page

Sediment management and the renewability of floodplain clay for structural ceramics

The Netherlands has vast resources of clay that are exploited for the fabrication of structural ceramic products such as bricks and roof tiles. Most clay is extracted from the so-called embanked floodplains along the rivers Rhine and Meuse, areas that are flooded during high-discharge conditions. Riverside clay extraction is-at least in theory-compensated by deposition. Based on a sediment balance (deposition versus extraction), we explore the extent to which clay can be regarded as a renewable resource, with potential for sustainable use. Beyond that, we discuss the implications for river and sediment management, especially for the large engineering works that are to be undertaken to increase the discharge capacities of the Rhine and Meuse. Extraction rates are based on production statistics for clay, as well as those for fired end-products. Deposition rates are estimated from published and unpublished geological data (clay volumes and thicknesses, datings, etc.) and from morphological modeling studies. Comparisons between extraction and deposition are made at three different time-space scales: (1) long term (post-1850)/large scale (all Dutch floodplains), (2) present/large scale, and (3) present/site scale. The year 1850 is relevant because it approximately marks the beginning of the current, fully engineered river systems, in which depositional processes are constrained by dikes and groynes. As the Industrial Revolution began in the same period, post-1850 sediments can be identified by their pollution with heavy metals. (1) We estimate the post-1850 clay volume in situ at about 0.20 km(3), and the total extracted volume in the same period at about 0.17 km(3). This puts the net long-term average deposition rate of clay at similar to 1.3 million m(3)/year and the corresponding extraction rate at similar to 1.1 million m(3)/year. (2) Current accumulation is approximately 0.4 million m(3)/year and expected to increase, and current extraction is about 0.7 million m(3)/year and expected to decrease. (3) Clay extraction creates a depression that has an increased sediment-trapping efficiency. This local effect is not considered explicitly in large-scale morphological modeling. Based on maximum observed sedimentation rates, we estimate that replenishment of a clay site takes in the order of 150 years. As clay extraction lowers some 0.5 km(2) of floodplain yearly, a surface area of approximately 75 km(2) would be required for sustainable clay extraction. This is about 1/6 of the total surface area of the embanked floodplains. On the long term, clay extraction from the embanked floodplain depositional environment has been sustainable. At strongly decreasing deposition rates, the ratio between extraction and replenishment seems to have shifted towards unsustainable. However, current sedimentation is estimated conservatively. The site-scale approach suggests that, even if extraction would currently exceed deposition, this could be resolved with sediment management, that is, with site restoration measures aimed at higher sediment-trapping efficiency. Our results have implications for river engineering, especially where substantial digging is involved (floodplain lowering, high-discharge bypass channels, obstacle removal). First, this inevitably affects the clay resources that we studied, while resource sterilization should be avoided. Secondly, the effect that any form of digging has on subsequent sedimentation-increased rates-relates to long-term river maintenance. We conclude that floodplain clay is a renewable resource, especially if managed accordingly. Beyond that, we established that clay extraction is a significant, lasting factor in floodplain evolution along the Rhine and Meuse Rivers. The interests of the extractive industry and river managers could be served jointly with sediment management plans that are based on sediment-budget analyse

Zitstokgebruik en beweeglijkheid

Naar aanleiding van de aanbevelingen van de Commissie Alders heeft het Praktijkcentrum 'Het Spelderholt' onderzoek uitgevoerd met drie soorten langzaam groeiende vleeskuikens. Naast het bepalen van de technische en slachterijresultaten is ook gekeken naar het gedrag van de dieren. In dit artikel wordt ingegaan op het zitstokgebruik en de mate van beweeglijkheid van die kuikens in vergelijking met een gangbaar soort vleeskuiken. Uit dit onderzoek kwam naar voren dat kuikens van de langzamer groeiende soorten meer gebruik maken van de zitstokken en actiever zijn dan het 'gangbare' vleeskuiken

Searching for Planets in the Hyades II: Some Implications of Stellar Magnetic Activity

The Hyades constitute a homogeneous sample of stars ideal for investigating the dependence of planet formation on the mass of the central star. Due to their youth, Hyades members are much more chromospherically active than stars traditionally surveyed for planets using high precision radial velocity (RV) techniques. Therefore, we have conducted a detailed investigation of whether magnetic activity of our Hyades target stars will interfere with our ability to make precise RV searches for substellar companions. We measure chromospheric activity (which we take as a proxy for magnetic activity) by computing the equivalent of the R'HK activity index from the Ca II K line. is not constant in the Hyades: we confirm that it decreases with increasing temperature in the F stars, and also find it decreases for stars cooler than mid-K. We examine correlations between simultaneously measured R'HK and RV using both a classical statistical test and a Bayesian odds ratio test. We find that there is a significant correlation between R'HK and the RV in only 5 of the 82 stars in this sample. Thus, simple Rprime HK-RV correlations will generally not be effective in correcting the measured RV values for the effects of magnetic activity in the Hyades. We argue that this implies long timescale activity variations (of order a few years; i.e., magnetic cycles or growth and decay of plage regions) will not significantly hinder our search for planets in the Hyades if the stars are closely monitored for chromospheric activity. The trends in the RV scatter (sigma'_v) with , vsini, and P_rot for our stars is generally consistent with those found in field stars in the Lick planet search data, with the notable exception of a shallower dependence of sigma'_v on for F stars.Comment: 15 pages, 7 figures, 3 tables; To appear in the July 2002 issue of The Astronomical Journa

Use of A Collagen/Elastin Matrix As Transport Carrier System to Transfer Proliferating Epidermal Cells to Human Dermis in Vitro

This in vitro study describes a novel cell culture, transport, and transfer protocol that may be highly suitable for delivering cultured proliferating keratinocytes and melanocytes to large open skin wounds (e.g., burns). We have taken into account previous limitations identified using other keratinocyte transfer techniques, such as regulatory issues, stability of keratinocytes during transport (single cell suspensions undergo terminal differentiation), ease of handling during application, and the degree of epidermal blistering resulting after transplantation (both related to transplanting keratinocyte sheets). Large numbers of proliferating epidermal cells (EC) (keratinocytes and melanocytes) were generated within 10-14 days and seeded onto a three-dimensional matrix composed of elastin and collagen types I, III, and V (Matriderm®), which enabled easy and stable transport of the EC for up to 24 h under ambient conditions. All culture conditions were in accordance with the regulations set by the Dutch Central Committee on Research Involving Human Subjects (CCMO). As an in vitro model system for clinical in vivo transfer, the EC were then transferred from Matriderm onto human acellular dermis during a period of 3 days. After transfer the EC maintained the ability to regenerate into a fully differentiated epidermis containing melanocytes on the human dermis. Proliferating keratinocytes were located in the basal layer and keratin-10 expression was located in differentiating suprabasal layers similar to that found in human epidermis. No blistering was observed (separation of the epidermis from the basement membrane). Keratin-6 expression was strongly upregulated in the regenerating epidermis similar to normal wound healing. In summary, we show that EC-Matriderm contains viable, metabolically active keratinocytes and melanocytes cultured in a manner that permits easy transportation and contains epidermal cells with the potential to form a pigmented reconstructed epidermis. This in vitro study has produced a robust protocol that is ready for clinical studies in the future