Short-Term Evaporation Estimating From Complex Small Lakes In Arid And Semi-Arid Regions

In many parts of the world, the available water resources are now being used close to their limits. Global climate change, the increasing population of the earth and ever-increasing standards of living and consequent growing demand of water are bringing water sustainability into sharp focus. Evaporation as a major component of the hydrologic cycle, is the largest one of water loss from lakes especially in arid and semi-arid regions. Because of lacking of understanding of the thermodynamics of atmospheric boundary layer(ABL) and heat exchange between the water surface and atmosphere, an accurate estimation of evaporation from water surfaces is almost unknown. It is thus of major importance to have precise estimation of the amount of this undesirable, unrecoverable and unproductive water loss from water body for a good management of available water resources. However, most of the models so far described in the literature are one-dimensional with areal homogeneity assumption and can be used for long-term estimations. In the framework of this study, a numerical approach was developed to predict evaporation from shallow and small lakes in (semi-) arid regions considering the heat and water vapor exchanges process between the air-water surface . The model takes into account advection, oasis effect and stability conditions of ABL in the heat exchange process. To have a precise estimation of evaporation the effects of the terrain surrounding the water body, the water body size and the effects of the available fetch of water body were implemented in the model. The governing equations of the model have been solved by OpenFOAM ; an open source, freely available CFD toolbox and easily extended to run in parallel. The estimated evaporation values were compared against the field measurements and they showed reasonable agreement

Dambo Farming In Zimbabwe: Water Management, Cropping and Soil Potentials for Smallholder Farming in the Wetlands

A conference paper on water management in Africa.Rising population pressures in Africa have caused the agricultural use of wetlands to become increasingly important. Developing large surface irrigation infrastructures, as Asia did during the sixties and seventies, often proves to be too costly for Africa. This makes wetlands, with their relatively good water availability and high soil fertility, an interesting alternative for increasing food production. Wetland use offers economic advantages as well. Farming on wetlands is a labor-intensive process, while surface irrigation is capital- intensive

Step fluctuations and random walks

The probability distribution p(l) of an atom to return to a step at distance l from the detachment site, with a random walk in between, is exactly enumerated. In particular, we study the dependence of p(l) on step roughness, presence of other reflecting or absorbing steps, interaction between steps and diffusing atom, as well as concentration of defects on the terrace neighbouring the step. Applying Monte Carlo techniques, the time evolution of equilibrium step fluctuations is computed for specific forms of return probabilities. Results are compared to previous theoretical and experimental findings.Comment: 16 pages, 6 figure

General practice cooperatives: long waiting times for home visits due to long distances?

BACKGROUND: The introduction of large-scale out-of-hours GP cooperatives has led to questions about increased distances between the GP cooperatives and the homes of patients and the increasing waiting times for home visits in urgent cases. We studied the relationship between the patient's waiting time for a home visit and the distance to the GP cooperative. Further, we investigated if other factors (traffic intensity, home visit intensity, time of day, and degree of urgency) influenced waiting times. METHODS: Cross-sectional study at four GP cooperatives. We used variance analysis to calculate waiting times for various categories of traffic intensity, home visit intensity, time of day, and degree of urgency. We used multiple logistic regression analysis to calculate to what degree these factors affected the ability to meet targets in urgent cases. RESULTS: The average waiting time for 5827 consultations was 30.5 min. Traffic intensity, home visit intensity, time of day and urgency of the complaint all seemed to affect waiting times significantly. A total of 88.7% of all patients were seen within 1 hour. In the case of life-threatening complaints (U1), 68.8% of the patients were seen within 15 min, and 95.6% of those with acute complaints (U2) were seen within 1 hour. For patients with life-threatening complaints (U1) the percentage of visits that met the time target of 15 minuts decreased from 86.5% (less than 2.5 km) to 16.7% (equals or more than 20 km). DISCUSSION AND CONCLUSION: Although home visits waiting times increase with increasing distance from the GP cooperative, it appears that traffic intensity, home visit intensity, and urgency also influence waiting times. For patients with life-threatening complaints waiting times increase sharply with the distance

Van Nederlands naar 'Europees' onrechtmatige daadsrecht

In deze bijdrage gaat het om de vraag hoeveel invloed het Europese, in de zin van: van de Europese Unie (EU) afkomstige, recht op het Nederlandse buitencontractuele aansprakelijkheidsrecht heeft. Die invloed is niet zo heel groot, zoals wij aan de hand van een korte schets van de huidige stand van zaken zullen laten zien (§2). Dat betekent tevens dat onze (Nederlandse) omgang met het (nog steeds Nederlandse) aansprakelijkheidsrecht niet fundamenteel gewijzigd is door de toenemende stroom van regelgeving vanuit Europa. Er gebeurt wel van alles op het terrein van het aansprakelijkheidsrecht, maar die gebeurtenissen spelen eerder op wat wij maar ‘particulier terrein’ noemen. Er zijn sinds de jaren ’90 namelijk een aantal groepen van wetenschappers die zich voorgenomen hebben het voortouw te nemen bij de harmonisatie van het buitencontractuele aansprakelijkheidsrecht. Juist omdat de EU tot op heden veel ruimte overlaat voor particulier initiatief, zullen wij die particuliere ontwikkelingen, met name de ontwerpen voor zogenaamde ‘Principles’, beschrijven (§3). Vervolgens wordt de vraag besproken of het eigenlijk zinvol is om te streven naar een geharmoniseerd aansprakelijkheidsrecht binnen de EU en of we beter af zijn met dit soort ‘Principles’ (§4). Ons antwoord luidt dat zulks slechts in beperkte mate het geval is. We concluderen in die paragraaf verder nog dat de rol van de EU waarschijnlijk gering zal blijven omdat de eenmaking op het gebied van het onrechtmatige daadsrecht tegen een aantal concrete hindernissen oploopt en de politieke noodzaak tot harmonisatie van algemene basisregels ontbreekt

Using a spatio-temporal dynamic state-space model with the EM algorithm to patch gaps in daily riverflow series, with examples from the Volta Basin, West Africa

International audienceA spatio-temporal linear dynamic model has been developed for patching short gaps in daily river runoff series. The model was cast in a state-space form in which the state variable was estimated using the Kalman smoother (RTS smoother). The EM algorithm was used to concurrently estimate both parameter and missing runoff values. Application of the model to daily runoff series in the Volta Basin of West Africa showed that the model was capable of providing good estimates of missing runoff values at a gauging station from the remaining series at the station and at spatially correlated stations in the same sub-basin

An LP-Model to Analyse Economic and Ecological Sustainability in Dutch Dairy Farming

Since the enactment of the Economic Growth and Tax Relief Reconciliation Act of 2001, owners and operators of farms and ranches have opportunities to evaluate new estate planning strategies for the transfer of farm businesses to subsequent generations. However, with provisions of the Act to be phased in over several years, consideration must be given to having a "staged" estate plan. Under provisions of the current law, estate tax is repealed in the year 2010, but if Congress does not act, the legislation sunsets and returns to prior law January 1, 2011. This fact provides planning challenges for owners and operators of farms and ranches as the phase-in of provisions, the repeal in 2010, and the return to prior law relative to estate planning and business inter-generational transfer of property. This paper investigates the planning process and options available as they relate to a family-owned property in North Carolina, USA. Plans made must take into consideration the dynamics of a changing legislative environment, special-use valuation of land, opportunity cost of alternative uses for land, and off-farm heirs.Environmental Economics and Policy, Livestock Production/Industries,

Effect of seasonal dynamics of vegetation cover on land surface models: a case study of NOAH LSM over a savanna farm land in eastern Burkina Faso, West Africa

International audienceThe sensitivity of the land surface model of the National Centers for Environmental Prediction (NCEP), the Oregon State University, the Air Force and the Hydrologic Research Lab (NOAH LSM) was evaluated with respect to the seasonal dynamics of the vegetation cover in the savanna area under intensive agriculture in the eastern part of Burkina Faso, West Africa. The data collected during the first long-term measurement of the surface fluxes in this mentioned region was used for this purpose. The choice of NOAH LSM was motivated by the fact that it has already been tested in different environments in West Africa, especially in Ghana. The sensitivity was tested by comparing the simulated surfaces fluxes using a fixed values of the roughness length for momentum as a standard in the model and the true seasonal value of this variable. The results show that NOAH LSM was not sensitive to the change of the roughness length for momentum neither on a seasonal basis nor on a daily basis, which was found to be abnormal. The formulation of the coefficient (Bc) coupling the dry canopy transpiration to the atmosphere was found to be the main reason for this. An improved formulation for this coefficient was given to solve this insensitivity and to improve the performance of the model. Recommendations are also given to enhance the performance of the model in the West African savanna environment