Due to the climate change the efficient use of fresh water has become a hot issue. One of the ways to collect water that could otherwise be wasted, is the water harvesting technique. These techniques have been known for centuries and widely applied in the Middle East. This paper presents a simple and easy-to-use water-balance based rainwater harvesting model called WHCatch. It has been designed to investigate the effects of water harvesting on the catchment scale. The catchment is divided into several sub-catchments which can store water for the purpose of water harvesting. The model has been created as a simple Excel workbook with some VBA-code for the computations. Results are presented in the same workbook as separate worksheets. Graphical presentations are created automatically. The capabilities of the workbook are presented and examples of in-and output are shown. Due to its flexibility, the model is suitable to show the effects of climate change as well. It is especially suitable to visualize the effects of measures.

Oscillating reactions are one of the most interesting topics in chemistry and analytical chemistry. Fluctuations in concentrations of one the reacting species (usually a reaction intermediate) create an oscillating chemical reaction. In oscillating systems, the reaction is far from thermodynamic equilibrium. In these systems, at least one autocatalytic step is required. Developing an instinctive feeling for how oscillating reactions work will be invaluable to future generations of chemists. Some software programs have been released for simulating oscillating systems; however, the algorithm details of such software are not transparent to chemists. In contrast, function of spreadsheet tools, like Microsoft Excel, is well understood, and the software is nearly universally available. In this work, the simulation and visualization of different oscillating systems are performed using Microsoft excel. The simple repetitive solving of the ordinary differential equation of an autocatalytic reaction (a spreadsheet row) followed by time, easily automated by a subroutine (a “ Macro” in Excel), readily simulates an oscillating reaction. This permits the simulation of some oscillating systems such as Belousov-Zhabotinsky. The versatility of an easily understandable computational platform further enables the simulation of the effects of linear and nonlinear parameters such as concentrations of reactants and catalyst, and kinetic constants. These parameters are readily changed to examine their effects.

Demographic parameters such as intrinsic rate of increase estimates are of main interest in a wide range of ecological researches. Two widely used uncertainty estimate techniques are bootstrap and jackknife methods.Bootstrap estimates are time-consuming processes that are impossible to use without a computer program. Unfortunately few programs, if any, have been developed for this task. In this study a guideline was offered to prepare a program in Microsoft Excel environment to carry out time-consuming calculations of reproductive life table data in a minute or two by repeatedly pressing a shortcut key.

The length of the steady Gradually Varied Flow (G.V.F) profile in a circular gravity pipe section is computed using the Graphical Integration Method. The equations used for the solution are: a) the dynamic equation of Gradually Varied Flow in a prismatic channels, b) the hydraulic exponents M and N equation derived by Chow [2], and c) the Varied hydraulic exponents M (y/do) and N(y/do) equation modified by Zaghloul [15]. The results of the calculated G.V.F profile length using the modified hydraulic exponents M(y/do) and N(y/do) equation are closer to the G.V.F length calculated based on the exact formulation of the G.V.F dynamic equation. The percentage difference ranges from 0.67% to 8.72% for various bed slopes and G.V.F depth limits. The calculated G.V.F profile length using the Chow hydraulic exponents M and N resulted in wider values with percentage difference ranges from 0.16 to 25.59%. Hence, a remarkable improvement of the computation of G.V.F profile is achieved using the modified M(y/do) and N(y/do) hydraulic exponents.The unsteady Gradually Varied Flow wave propagation in circular gravity pipe section is simulated using the Explicit Method. The Extended Transport block (EXTRAN) of the latest Storm Water Management Model (PCSWMM2000) was used to route the wave through a circular gravity pipe section. The resulting routed hydrographs by the Explicit Method and the EXTRAN Block of the PCSWMM 2000, provided similar flow peak and lag time in both cases.A computer package was developed for the Steady G.V.F length calculation for gravity pipes using the Microsoft Excel spreadsheet. The results are plotted using the Excel graphics capabilities.A second computer package using Microsoft Excel was developed for the Unsteady G.V.F simulation based on the Explicit Method. The routed hydrographs arc plotted by the Excel graphics capabilities.The Excel packages for the Steady and Unsteady G.V.F are user friendly and are posted on the Internet Website location http://briefcase.yahoo.com/civil engineering2001.ARead me File is provided for each Excel package and is used as a users guide.