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

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

Stormwater quality characteristics in (Dutch) urban areas and performance of settlement basins

Stormwaters, flowing into storm sewers, are known to significantly increase the annual pollutant loads entering urban receiving waters and this results in significant degradation of the receiving water quality. Knowledge of the characteristics of stormwater pollution enables urban planners to incorporate the most appropriate stormwater management strategies to mitigate the effects of stormwater pollution on downstream receiving waters. This requires detailed information on stormwater quality, such as pollutant types, sediment particle size distributions, and how soluble pollutants and heavy metals attach themselves to sediment particles. This study monitored stormwater pollution levels at over 150 locations throughout the Netherlands. The monitoring has been ongoing for nearly 15 years and a total of 7,652 individual events have been monitored to date. This makes the database the largest stormwater quality database in Europe. The study compared the results to those presented in contemporary international stormwater quality research literature. The study found that the pollution levels at many of the Dutch test sites did not meet the requirements of the European Water Framework Directive (WFD) and Dutch Water Quality Standards. Results of the study are presented and recommendations are made on how to improve water quality with the implementation of Sustainable Urban Drainage Systems (SUDS) devices

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

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,

Do green roofs cool the air?

AbstractRapid urbanization and an increasing number and duration of heat waves poses a need to mitigate extremely high temperatures. One of the repeatedly suggested measures to moderate the so called urban heat island are green roofs. This study investigates several extensive sedum-covered green roofs in Utrecht (NL) and their effect on air temperature right above the roof surface. The air temperature was measured 15 and 30 cm above the roof surface and also in the substrate. We showed that under well-watered conditions, the air above the green roof, compared to the white gravel roof, was colder at night and warmer during the day. This suggests that extensive sedum-covered green roofs might help decrease air temperatures at night, when the urban heat island is strongest, but possibly contribute to high daytime temperatures. The average 24 h effect of sedum-covered green roof was a 0.2 °C increase of air temperature 15 cm above the ground. During a dry year the examined green roof exhibited behavior similar to conventional white gravel roof even exhibited slight cooling effect in late afternoon. Interestingly, the pattern of soil temperature remained almost the same for both dry and well-prospering green roofs, colder during the day and warmer at night