Streamflow Simulation by SWAT Using Different Precipitation Sources in Large Arid Basins with Scarce Raingauges

Streamflow from the mountains is the main source of water for the lower plain in arid regions. Accurate simulation of streamflow is of great importance to the arid ecosystem. However, many large arid drainage basins in northwestern China have low density of precipitation stations, which makes the streamflow modeling and prediction very difficult. Based on raingauge data and Tropical Rainfall Measuring Mission (TRMM) data combined with raingauge data, different approaches were explored for spatializing precipitation in large area with scarce raingauges. Spatialized precipitation was then input into Soil and Water Assessment Tool (SWAT), a semi-distributed hydrological model, to simulate streamflow. Results from a case study in the Manas river basin showed that simulated hydrographs using both the approaches are able to reproduce the watershed hydrological behavior. Moreover, statistical assessment indicated that hydrological model driven by the spatialized precipitation based on radar combined with raingauge data performed better than that based on gauge data. Radar precipitation estimator can provide a practical data source for hydrological modeling at a basin scale where the raingauge network is sparse.     

The living company

What can explain the longevity gap between a company that survives for centuries--the Swedish company Stora, for example, which is more than 700 years old--and the average corporation, which does not last 20 years? A team at Royal Dutch/Shell Group explored that question. Arie de Geus, a retired Shell executive, writes about the team's findings and describes what he calls living companies-organizations that have beaten the high mortality rate of the average corporation. Many companies die young, de Geus argues, because their policies and practices are based too heavily on the thinking and language of economics. Their managers focus on producing goods and services and forget that the organization is a community of human beings that is in business--any business--to stay alive. In contrast, managers of living companies consider themselves to be stewards of a long-standing enterprise. Their priorities reflect their commitment to the organization's long-term survival in an unpredictable world. Like careful gardeners, they encourage growth and renewal without endangering the plant they are tending. They value profits the same way most people value oxygen: as necessary for life but not the purpose of it. They scuttle assets when necessary to make a dramatic change in the business portfolio. And they constantly search for new ideas. These managers also focus on developing people. They create opportunities for employees to learn from one another. Such organizations are suited for survival in a world in which success depends on the ability to learn, to adapt, and to evolve.     

Water network cost optimization in a paper mill based on a new library of mathematical models

The increasing costs associated with water supply and the disposal of wastewater has stimulated industries to seek more efficient water management systems. Mathematical modelling and simulation can be a very valuable tool for the study of the multiple alternatives available whilst assessing optimum solutions for water management in industry. This study introduces a new steady state model library able to reproduce industrial water circuits. It has been implemented in a novel software framework for the representation, simulation and optimization of industrial water networks. A water circuit representing a paper mill has been modelled and simulated showing the capability to reproduce real case studies. Alternative scenarios for the water network have also been tested to assess the capability of the models to optimize water circuits minimizing total cost.     

A groundwater perspective on the river basin management plan for central Portugal - developing a methodology to assess the potential impact of N fertilizers on groundwater bodies

The Water Framework Directive establishes that the river basin management plans must have a summary of the pressures and impacts of human activities, such as agriculture, on the chemical and quantitative status of groundwater bodies. In order to identify those areas where a potential impact from agricultural activities on groundwater bodies exists, but currently lacking groundwater monitoring data, a methodology was developed that combines the use of gross nitrogen balance values with the results of a specific vulnerability assessment index. A farm management efficiency parameter is added, to identify the factors that contribute to nitrogen use efficiency and to assess the near-future scenarios. This methodology allows the identification of significant pressures that may be responsible for a groundwater body failing good status where there is no representative monitoring network.     

Evaluation of Crop Models for Simulating and Optimizing Deficit Irrigation Systems in Arid and Semi-arid Countries Under Climate Variability

The variability of fresh water availability in arid and semi-arid countries poses a serious challenge to farmers to cope with when depending on irrigation for crop growing. This has shifted the focus onto improving irrigation management and water productivity (WP) through controlled deficit irrigation (DI). DI can be conceived as a strategy to deal with these challenges but more knowledge on risks and chances of this strategy is urgently needed. The availability of simulation models that can reliably predict crop yield under the influence of soil, atmosphere, irrigation, and agricultural management practices is a prerequisite for deriving reliable and effective deficit irrigation strategies. In this context, this article discusses the performance of the crop models CropWat, PILOTE, Daisy, and APSIM when being part of a stochastic simulation-based approach to improve WP by focusing primarily on the impact of climate variability. The stochastic framework consists of: (i) a weather generator for simulating regional impacts of climate variability; (ii) a tailor-made evolutionary optimization algorithm for optimal irrigation scheduling with limited water supply; and (iii) the above mentioned models for simulating water transport and crop growth in a sound manner. The results present stochastic crop water production functions (SCWPFs) that can be used as basic tools for assessing the impact on the risk for the potential yield due to water stress and climate variability. Example simulations from India, Malawi, France and Oman are presented and the suitability of these crop models to be employed in a framework for optimizing WP is evaluated.     

Plant algae method for arsenic removal from arsenic contaminated groundwater

Field studies were carried out in Urumqi River Basin in Northwest China. The study focused on experimentation on a plant algae method that was tested by taking various water chemistries into consideration. The results from a greenhouse experiment evaluated for four doses of P (0, 100, 200, and 300 μmol/L) using two ferns (30 and 60 day old) on 15 L of contaminated groundwater per plant revealed that the biomass of 30-day old ferns gained was higher than 60-day fern. As solution-P increased from 0 to 450 μmol/L, Phosphorus concentration in the fronds increased from 1.9 to 3.9 mg/kg and 1.95 to 4.0 mg/kg for 30-d and 60-d ferns respectively. This study showed that the plant algae method may be a good solution to maximize arsenic uptake in the short term under normal climatic conditions.     

Volatilization of hydrogen sulfide from a quiescent surface

Air-water mass transfer of hydrogen sulfide from a shallow tank with a quiescent surface under the influence of weak wind stress on the water surface was studied numerically using a two-dimensional model. The flow field in the tank was investigated using a computational code based on a finite volume, which is used to numerically solve momentum, mass and continuity conservation equations. The results show that water phase flow field is strongly dependent on the wind-induced surface velocity and the aspect ratio of the tank. Based on the numerical study, the liquid-side mass transfer coefficient is correlated with Reynolds number (R(e)), tank aspect ratio (AR) and Schmidt number (S(c)). Overall mass transfer coefficient (K(L)) values extend further downstream as the R(e) number increases.     

Announcement effects of bank mergers in Europe and the US

We investigate the announcement effect of large bank mergers in the European and US stock market. Cumulative abnormal returns are calculated on the basis of the performance vis-à-vis the market and a sector index. Mergers result in small positive abnormal returns. Target banks realize significantly higher returns than bidders. In many respects, there is a difference between the announcement effects of European bank mergers compared to those in the US.